Medicine

HYGIENE OF SOIL AND AIR

HYGIENE OF WATER AND WATER SUPPLY OF POPULATED AREAS. EVALUATION OF THE QUALITY OF DRINKING WATER. METHODS OF IMPROVING THE QUALITY OF DRINKING WATER.HYGIENE OF SOIL AND CLEANING INHABITED PLACES

Water is vital to humans. It is needed for food preparation, drinking, washing, and irrigation. In addition, massive quantities are used daily in industrial processes. Yet, it is a limited resource that must be collected and distributed with increasing care. The most important source of water is rain, which may be collected directly in cisterns and reservoirs or indirectly through a watershed system or well. A watershed is the network of rivulets, streams, and rivers by which entire areas are watered. Ground water is rain that has trickled through rock layers, forming pools after many years. If it is under pressure, groundwater may bubble to the surface as a spring. Irrigation canals, reservoirs, wells, and water towers are man-made devices for diverting and collecting water from these natural sources. Because of contamination concerns, water from reservoirs, wells, and rivers is usually processed in a treatment plant before distribution.

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Functions of Water in the Body

The ultimate source of all natural potable water on the earth is rain, which is rarely used as a direct source except on islands in salt water, such as Bermuda, where the rain is collected and led into cisterns to serve as the only available water supply. When rain falls, it runs off into streams, in the case of heavy rains, or soaks into the ground, percolating through porous strata until it reaches an impervious stratum, upon which it collects, forming groundwater. Groundwater is the source of wells and of the springs that feed streams, rivers, and lakes. In its course, groundwater dissolves soluble mineral matter, and often the surface waters of rivers and lakes are polluted by the influx of sewage or industrial wastes (see Sewage Disposal; Water Pollution). In modern water-supply systems, an entire watershed is usually made into a reservation to control pollution. The waters are impounded by a system of dams, and flow by gravity, or are pumped, to the local distribution system.

Water is Essential for Life

It covers 71% of the earth's surface and makes up 65 % of our bodies. Everyone wants clean water-- to drink, for recreation, and just to enjoy looking at. If water becomes polluted, its loses its value to us economically and aesthetically, and can become a threat to our health and to the survival of the fish living in it and the wildlife that depends on it.

Hygienic significance of water

Water physiological functions:

-       flexibility – about 65 % of body mass of adult person consists of water. 70 % of water is the intracellular water, 30 % - extracellular water (in blood), (7%) - lymph and 23 % - intertissue fluid. Water makes up 20 % of the bone mass, 75 %, of the muscle mass, 80% of the connective tissue mass, 20% of blood plasma mass, 99% of vitreous body of an eye. Major part of water is a component of macromolecular complexes of proteins, carbohydrates and fats, forming the jelly-like colloid cells and extracellular structures together with them. The smaller part of it is in a free state;

-       participation in metabolism and interchange of energy – all assimilation and dissimilation processes in organism occur in water solutions;

-       role in support of osmotic pressure and acid-base balance;

-       participation in heat exchange and thermoregulation – at evaporation of 1 g of moisture from lungs’ surface, mucous membranes and skin (latent heat of evaporation) organism loses 2.43 kJ (0.6 kcal) of heat;

-       transportation function – delivery of nutrients to cells with blood and lymph, removal of waste products from the organism with urine and sweat;

-       as a component of dietary intake and a source of macro- and microelements supply to organism;

-       there are neuropsychic disorders that are resulted from impossibility to satisfy thirst if water is not available or if it is of bad organoleptic characteristics. According to I.P. Pavlov’s doctrine on higher nervous activity, odour, taste, after-taste, water appearance, clarity (transparency) and colour are irritators that influence the whole organism through central nervous system. Worsening of organoleptic characteristics of water causes the reflex effect on water intake schedule and some physiological functions, for example it oppresses the secretory function of stomach. Drinking of such water causes the defence reaction in human organism – the feeling of aversion, which makes a person to refuse such water irrespective of thirst.

 

Epidemiological and toxicological role of water

 

Water can participate in spread of infections in the following ways:

-       as transfer factor of pathogens with the fecal-oral transfer mechanism: enteric infections of bacterial and viral origin (typhoid, paratyphoid А, В, cholera, dysentery, salmonellosis, coli-entheritis, tularaemia /deep-fly or rabbit fever/, viral and epidemic hepatitis А, or Botkin disease, viral hepatitis E, poliomyelitis and other enterovirus diseases, such as Coxsakie, EСНО etc.); geohelminthosis (ascaridiasis, trichocephaliasis, ankylostomiasis); biohelminthosis (echinococcosis, hymenolepiasis); of protozoal etiology (amebic dysentery (amebiasis), lambliasis); zooanthroponosis (tularemia, leptospirosis and brucellosis);

-       as a transfer factor of pathogens of the skin and mucous membrane diseases (when swimming or having another contact with water): trachoma, leprosy, anthrax, contagious molluscum, fungous diseases (i.e., epidermophytosis);

-       as the habitat of disease carriers – anopheles mosquitoes, which transfer malarial haemamoeba and others (open water reservoirs).

Symptoms of water epidemics:

-       simultaneous appearance of big number of enteric infected people, i.e. jump of population morbidity – so-called epidemic outburst;

-       people who used the same water source, the same pipeline of water supply network, the same water-pump, shaft well etc. will suffer from diseases;

-       morbidity level will stay high for the long period of time to the extent of water contamination and consumption;

-       morbidity curve will have one, two, three, or more peaks. First of all those diseases that have short incubation period will be registered (coli-entheritis, salmonellosis - 1-3 days, cholera – 1-5 days, typhoid – 14-21 days and at last - those with the longest period: virus and epidemic hepatitis А and Е – 30 days and more);

-       after the taking of antiepidemic measures (liquidation of the contamination source, disinfection of water supply network, sanitation of wells) the outburst fades away and morbidity goes down drastically;

-       still, for some time morbidity remains above the sporadic level – so-called epidemic tail. This is caused by the appearance of big amount of new potential sources of infection (sick people and infection carriers) during the epidemic outburst and activation of other ways of the pathogenic microorganisms spreading from these sources – domestic contact (through dirty hands, dishes, children toys, personal hygiene articles), through food or by living carriers (flies) etc.

Toxicological role of water consists in it containing chemical agents that may negatively influence people health causing different diseases. They are divided into chemical agents of natural origin, those, which are added to water as reagents and chemical agents, which come into the water as the result of industrial, agricultural and domestic pollution of water supply sources. Insufficient or non-effective treatment of such waters at waterworks procures the continuous toxic effect of small concentrations of chemical agents, or, rarely, in cases of accidents and other emergency situations – acute poisonings.

Balneal role of water

 Water is used in medicinal purpose for rehabilitation of convalescents (drinking of mineral waters, medicinal baths), and also as tempering factor (bathing, swimming, rub-down).

Domestic and economic role of water

 Sanitary-hygienic and domestic functions of water include:

-       water usage for cooking and as a part of dietary intake;

-       usage of water as means of keeping body, clothes, utensil, residential and public premises and industrial areas, settlements clean;

-       watering of the green areas within settlements;

-       sanitary-transport and disinfection functions of water – disposal of residential and industrial waste through sewer system, waste processing on plants, self-purification of water reservoirs;

-       fire fighting, atmospheric pollution clearing (rain, snow).

Economical functions of water:

-       usage in agriculture (irrigation in crop and gardening, greenhouses, poultry and cattle breeding farms);

-       industry (food, chemical, metallurgy etc.);

-       as the route of passenger and cargo transportation.

 

Classification of water supply sources

 Water supply sources are divided into ground and surface:

-      middle waters with pressure (artesian) and without pressure that lie in aquifers (water-bearing horizons,) (sandy, gravelled, cracked) between impermeable to water layers of soil (clay, granites), therefore safely protected from penetration of pollutants from the surface. Middle water replenishes in feeding zones – places, where the auriferous stratum pinches out onto the surface, located considerably far away from the water take point. Middle waters are characterized by not very high, stable temperature (5-12°С), constant physical and chemical composition, steady level and considerable flow; they contain almost no microorganisms, especially pathogenic. Such waters are epidemically safe and don’t require disinfection;

-      underground waters that are located in aquifers above the first impermeable layer of soil and therefore, in case of them lying not very deep, they are insufficiently protected from penetration of pollutants from the surface. They are characterized by seasonal fluctuations of chemical and bacteriological composition and level, flow that depends on frequency and number of precipitations, availability of open-air water reservoirs, depth and soil type. Getting filtrated through the 5-6 m or bigger layer of clean fine-grained soil ground waters become clear, colourless, contain almost no pathogenic microorganisms. Supplies of ground water are small, therefore, in order to use them as a source of centralized water supply, the artificial recharge (replenishment) of them using special technical facilities is required;

-      spring water, flowing out from aquifers that pinch out onto the surface due to descending relief, e. g. on the hill slope, in deep ravine.

- perched groundwater, lying next to the ground surface, is formed as a result of atmospheric precipitates filtration within a small area. Very small supplies and bad water quality do not allow recommending perched groundwater as the source of domestic and drinking water supply.

Surface waters are divided into flowing (running) waters (rivers, waterfalls, glaciers), stagnant (dead-water, still water) (lakes, ponds, artificial open water reservoirs). Their water composition depends much on the soil at the territory of water intake, hydrometeorological conditions, and varies sufficiently during the year depending on the season or even on the weather. Compared to ground waters, surface water sources are characterized by big amount of suspended substances, low clarity, higher colour due to humic substances that are washed away from the soil, higher content of organic compounds, presence of autochthonic microflora and dissolved oxygen. Open-air reservoirs can easily be polluted from outside, therefore, from epidemiological point of view they are potentially unsafe.

In some water-poor or arid areas, the imported and precipitation (atmospheric) water (rain, snow), which is stored in indoor water reservoirs or artificially filled wells, is used.

The best is the situation when quality of water in the source of water supply completely meets the contemporary criteria of the good water quality. Such water doesn’t require any treatment and the only concern is not to spoil its quality at the stages of its take from the source and delivery to consumers. But disinfection of such water is the part of sanitary requirements anyway. Only some underground middle waters are like this, mostly – artesian (pressure) waters. In all other cases water in the source, especially the surface water, requires quality improvement: lowering of suspended materials concentration (clearing) and colour (decolouration), getting rid of pathogenic and conditionally pathogenic microorganisms (disinfection), sometimes chemical composition improvement using special treatment techniques (desalination, softening, defluorination, fluorination, deferrization etc.). Hygienic requirements to water quality in sources of centralized water supply are given in appendix 4.

 

Sources of the surface water reservoirs pollution

 

The main source of pollution of surface water reservoirs are sewage waters (especially untreated or insufficiently treated water) that are created as the result of the water use in private life, industry, poultry and cattle factories etc. Partial pollution of water reservoirs occurs in the result of surface drainage of rain, storm waters and waters that appear during snow melting. Sewage waters and surface drainage add a big amount of suspended solids and organic compounds to water of reservoirs that results in more colour and water turbidity increase, clarity (transparency) lowering, oxidation and biochemical oxygen demand (BOD) increase, amount of dissolve oxygen lowers, concentration of nitrogen-containing substances and chlorides increases, bacterial insemination grows. Together with industrial wastewaters and sewage from farmlands, as it was mentioned before, various hazardous toxic chemical substances get into water reservoirs.

Water in open reservoirs may be polluted in the result of its use for transport purposes (passenger, freight shipping, timber floating), when working near river-beds (e.g., extraction of river sand), during watering animals, at sports competitions, recreation of population.

 

Self-purification (natural purification) of open-air water reservoirs

 

Self-purification (natural purification) of open air water reservoirs takes place in the result of various factors’ effect: а) hydraulic(mixing and dilution of pollutants by water of water reservoir); b) mechanical (precipitation/sedimentation of suspended solids); c) physical(solar radiation and temperature effect); d) biological (interaction of water plant organisms and microorganisms with sewage organisms that got into reservoir); e) chemical (elimination of contaminants as the result of hydrolysis); f) biochemical (conversion of some substances into other due to biological elimination, mineralization of organic substances as the result of biochemical oxidation caused by water autochthonic microflora). Natural purification with pathogenic microorganisms occurs due to their death as the result of antagonistic action of water saprophytic organisms, antibiotic substances, bacteriophages etc. In case of pollution of water reservoirs by domestic and industrial wastewaters, processes of natural purification may be stopped. Water in reservoirs becomes overgrown (vegetation burst of aquatic plants, plankton), putretaction of water.

 

Selection of the source of centralized domestic and drinking water-supply

 

It is based on two theses:

-       consumer supply with adequate amount of good quality drinking water (water quality in reservoir must be suitable for conversion using up-to-date water treatment methods into potable water of good quality that would meet all requirements of State Standard (2874-82, SSRandN 136/1940) currently in force);

-       control of the highest sanitary reliability of the source (selection of the source is based on assessment and prognosis of its possible pollution).

The source of centralized domestic and drinking water-supply is to be selected as follows: 1) middle water (artesian) aquifers; 2) middle water (not-artesian) aquifer; 3) underground waters, which are refilled artificially; 4) surface waters (rivers, water reservoirs, lakes, canals).

When selecting the source, water amount sufficiency for covering all needs of the built-up area is considered, water supply points (water intakes) are defined and organizational opportunities for sanitary protection zones are assessed.

Hygienic principles are assumed as the basis of selection of water- supply source; water quality requirements of ground and surface sources, selection procedure are represented in SS 2761-84 “Centralized domestic and drinking water supply sources. Hygienic, technical requirements and selection guidelines” (Appendix 4).

  

Technique of sanitary inspection of water-supply sources

 Sanitary inspection includes three main stages:

-         sanitary-topographic inspection of water source environment;

-         sanitary-technical inspection of condition of water source equipment;

-         sanitary-epidemiological inspection of area of water source location.

 

Main task of sanitary-topographic inspection of water source is to discover possible sources of water pollution (dumps, refuse pits, lavatories, livestock farms, cemeteries etc.), distances from them to water source, topography of the locality, (drain direction of rain and snow waters towards water source or in another direction, flow direction of ground waters, overflows). On the basis of sanitary-topographic inspection a map – layout of positional relationship of water source and listed objects with marks of distances and direction of locality slope is created.

In most cases relationship between water source and source of pollution may be determined by research. For this purpose a saturated solution of sodium chloride or solution of fluoresceine is poured into the source of pollution (at least one bucket of mixture for every 10 m of distance towards water source), and every 3-4 hours during one or two days chlorides (or fluoresceines) are sampled in the water source.

The purpose of sanitary-technical inspection is to give a hygienic assessment of condition of technical equipment of hydraulic works at water source. Thus, in case of decentralized (local) water-supply, accuracy of allocation and exploitation of the mineshaft (availability and condition of log cabin, awning, riprap, devices for water lifting, “loamy key trench”); in case of centralized water-supply from ground middle water source – accuracy of arrangement and condition of artesian well, water lifting pumps; in case of surface water source – of diversion scoop and coastal sink. In case of centralized water-supply, sanitary-technical condition of main facilities of water-pipe, water supply network and constructions on it (namely, water-pumps).

It is of practical importance to determine the amount of water in the source of water and its discharge (output). E.g. amount of water in the well made of concrete rings with log cabin is determined by the formula:

V = π×R2×h,

where:    V – amount of water in the well, m3;

p - 3.14;

R – radius of log cabin ring, m;

h – water layer height, m.

Water height is determined by cord with weight, which is pulled down till the touch of the bottom and then a wet part of the cord is measured.

To find out discharge (output) of the well, 30-40 buckets of water are pumped out (scooped out) then the change in the level of water is marked and the time during which the previous level of water restores is fixed. Discharge (output) is calculated by formula:

D = 

            where: D – discharge of the well, l/hour;

      V – volume of pumped out water, l;

       t – time, during which the level of water restores and time of water pumping, minutes.

River discharge is the amount or volume of water that flows through a given cross-section of a river in a given unit of time (m/sec)

Discharge (output) of a brook or a small river is calculated by formula:

D = 0.5×b×h×v,

            where:  D – output (productivity), m3/sec;

       b – water flow width, m;

       h – water flow depth at the deepest point, m;

       v – flow velocity, m/sec (is determined using a float and stop-watch).

Sanitary-epidemiological inspection is aimed to discover and consider the following:

-       presence of intestinal infectious diseases (cholera, typhoid, paratyphoid А, В, dysenteries, virus hepatitis etc.) among population, which uses water from this source or lives close to it;

-         presence of epizootic diseases (tularemia, brucellosis, anthrax, murrain, mad cow disease (BSE) etc.) among rodents, domestic animals;

-       sanitary condition of the settlement (pollution of the territory, methods of collection and disinfection of liquid and solid domestic and industrial waste etc.).

During sanitary inspection water samples from open water reservoir, well or artesian well for further laboratory analysis are taken.

 

 

Technique of water sampling for laboratory analyses

 

During water sampling from open reservoir or a well the temperature of water is measured by a special thermometer (Fig. 16.1.) or by an ordinary chemical thermometer, the vessel of which is wrapped up with some layers of gauze bandage. Temperature is taken directly in the water source. Thermometer is put down into the water for 5-8 min., then it is quickly drawn up and temperature is read.

Fig. 1 Thermometer for taking temperature of water in reservoirs and wells (а), bathometers for water sampling for analysis (b).

 

Water sampling from open reservoirs and wells is carried out using bathometers of different design and supplied by double cord for putting the instrument down to specified depth and for opening the cork of the vessel at that depth (Fig. 1-b).

For water sampling from flowing water reservoirs (river, brook) there is a design of bathometer with stabilizer that directs a neck of the vessel against the stream.

Water sampling from water tap or equipped catchment is carried out:

-      for bacteriological analysis. Sample is put into a sterile bottle of 0.5 l volume, with bulky cork, wrapped with paper cap from above after preliminary singeing of outlet port of the tap or catchment by spirit flame and letting water out from the tap during at least 10 min. In order to avoid bulky cork wetting, only three quarters of the bottle is filled with water to leave at least 5-6 cm of air space under the cork. The bottle with bulky cork is preliminary sterilized in drying box at 1600 С during one hour;

-      for short sanitary-chemical analysis (organoleptic criteria, main indices of chemical compound and water pollution). About 1 liter of water is taken into a chemically clean glassware, which was preliminary rinsed with water to be sampled (for complete sanitary-chemical analysis 3-5 l of water are taken off).

During sampling a covering letter is written down. This letter indicates: type, name, location, address of the water source (surface water reservoir, artesian well, mineshaft, catchment, water tap, water-pump); its short specification, weather state during sampling and during last 10 days; reason and goal of sampling (regular inspection, adverse epidemic situation, population complaints about deterioration of water organoleptical properties); laboratory, to which the sample is sent; required extent of examinations (short, full sanitary-chemical analysis, bacteriological analysis, determination of pathogenic microorganisms); date and hour of sampling; research result received during sampling (temperature); who tested (surname, position, institution); signature of an official person, who took the sample.

Samples must be delivered to the laboratory as quickly as possible. Bacteriological analyses must be started during 2 hours since taking samples or in case of keeping samples in refrigerator at 1-8°С at the latest 6 hours. Physical and chemical analysis is made during 4 hours after taking a sample or in case of keeping a sample in refrigerator at 1-8°С at the latest 48 hours. In case of inability to perform the analysis during specified terms, sample must be preserved (except samples for physical-and-organoleptical and bacteriological analyses, and for BOD determination that must be necessarily made during terms specified above). Samples are preserved by 25% of H2SO4 - solution on the basis of 2 ml for 1 l of water or by another method depending on factors to be determined.

Taken sample comes with accompanying form, in which one indicates address details, kind of water source, where samples are directed, aim of the analysis, date and time of taking a sample, signature of an official person, which took this sample.

 

How does water pollution occur?

Although some kinds of water pollution can occur through natural processes, it is mostly a result of human activities. We use water daily in our homes and industries, about 150 gallons per day per person in the United States. The water we use is taken from lakes and rivers, and from underground (groundwater); and after we have used it-- and contaminated it-- most of it returns to these locations. The used water of a community is called wastewater, or sewage. If it is not treated before being discharged into waterways, serious pollution is the result. Historically, it has taken humanity quite a bit of time to come to grips with this problem. Water pollution also occurs when rain water runoff from urban and industrial areas and from agricultural land and mining operations makes its way back to receiving waters (river, lake or ocean) and into the ground.

What are some different types of water pollution?

Microbiological

Disease-causing (pathogenic) microorganisms, like bacteria, viruses and protozoa can cause swimmers to get sick. Fish and shellfish can become contaminated and people who eat them can become ill. Some serious diseases like polio and cholera are waterborne.

Chemical

A whole variety of chemicals from industry, such as metals and solvents, and even chemicals which are formed from the breakdown of natural wastes (ammonia, for instance) are poisonous to fish and other aquatic life. Pesticides used in agriculture and around the home-- insecticides for controlling insects and herbicides for controlling weeds-- are another type of toxic chemical. Some of these can accumulate in fish and shellfish and poison people, animals, and birds that eat them. Materials like detergents and oils float and spoil the appearance of a water body, as well as being toxic; and many chemical pollutants have unpleasant odors. The Niagara River, between the US and Canada, even caught fire at one time because of flammable chemical wastes discharged into the water.

Oxygen-depleting Substances

Many wastes are biodegradable, that is, they can be broken down and used as food by microorganisms like bacteria. We tend to think of biodegradable wastes as being preferable to non-biodegradable ones, because they will be broken down and not remain in the environment for very long times. Too much biodegradable material, though, can cause the serious problem of oxygen depletion in receiving waters.

Like fish, aerobic bacteria that live in water use oxygen gas which is dissolved in the water when they consume their "food". (The oxygen in the compound H2O, water, is chemically bound, and is not available for respiration (breathing)). But, oxygen is not very soluble in water. Even when the water is saturated with dissolved oxygen, it contains only about 1/25 the concentration that is present in air. So if there is too much "food" in the water, the bacteria that are consuming it can easily use up all of the dissolved oxygen, leaving none for the fish, which will die of suffocation.

Once the oxygen is gone (depleted), other bacteria that do not need dissolved oxygen take over. But whileaerobic microorganisms-- those which use dissolved oxygen-- convert the nitrogen, sulfur, and carbon compounds that are present in the wastewater into odorless-- and relatively harmless-- oxygenated forms like nitrates, sulfates and carbonates, these anaerobic microorganisms produce toxic and smelly ammonia, amines, and sulfides, and flammable methane (swamp gas). Add in the dead fish, and you see why we don't want large amounts of biodegradable materials entering lakes and streams.

Nutrients

The elements phosphorus and nitrogen are necessary for plant growth, and are plentiful in untreated wastwater. Added to lakes and streams, they cause nuisance growth of aquatic weeds, as well as "blooms" of algae, which are microscopic plants. This can cause several problems. Weeds can make a lake unsuitable for swimming and boating. Algae and weeds die and become biodegrable material, which can cause the problems mentioned above (and below). If the water is used as a drinking water source, algae can clog filters and impart unpleasant tastes and odors to the finished water.

Suspended matter

Some pollutants are dissolved in wastewater, meaning that the individual molecules or ions (electrically charged atoms or molecules) of the substance are mixed directly in between the molecules of water. Other pollutants, referred to as particulate matter, consist of much larger-- but still very small-- particles which are just suspended in the water. Although they may be kept in suspension by turbulence, once in the receiving water, they will eventually settle out and form silt or mud at the bottom. These sediments can decrease the depth of the body of water. If there is a lot of biodegradable organic material in the sediment, it will become anaerobic and contribute to problems mentioned above. Toxic materials can also accumulate in the sediment and affect the organisms which live there and can build up in fish that feed on them, and so be passed up the food chain, causing problems all along the way . Also, some of the particulate matter may be grease-- or be coated with grease, which is lighter than water, and float to the top, creating an aesthetic nuisance.

 

Water is the main substance of biosphere, without which the existence of organic nature is impossible. Water is vital to humans. It is needed for food preparation, drinking, washing, and irrigation. In addition, massive quantities are used daily in industrial processes. Any vital process cannot be performed without water, and any cell cannot exist in anhydrous environment. Water has the importance not only for drinking and meal, and also for normal existence of the human. Yet, it is a limited resource that must be collected and distributed with increasing care.

The most important source of water is rain, which may be collected directly in cisterns and reservoirs or indirectly through a watershed system or well. A watershed is the network of rivulets, streams, and rivers by which entire areas are watered. Ground water is rain that has trickled through rock layers, forming pools after many years. If it is under pressure, groundwater may bubble to the surface as a spring. Irrigation canals, reservoirs, wells, and water towers are man-made devices for diverting and collecting water from these natural sources. Because of contamination concerns, water from reservoirs, wells, and rivers is usually processed in a treatment plant before distribution.

Because of enlargement of cities, villages, development of economy and raising of cultural inquiries of the population the consumption of water increases with each year. While choosing a water source for water supply its output and quality of water, and, also stability of parameters, which characterize its reliability that is determined by its origin and conditions of formation of water quality, and also character and intensity of its pollution are taken into consideration

The pollution of water sources represents the important ecological problem. Depending on type of pollution there are: chemical, physical (radioactive substances, hot water), bacterial, virus and biological. Industrial wastewater is characterized by considerable quantity of components.

It is a lot of chemical substances, which come at reservoir, worsen biological and organoleptic properties of water (smell, smack, color, turbidity, formation of a pellicle, foams etc) that not favorably influences on water usage and population’s health. 

The output of industries, agriculture, and urban commu­nities generally exceeds the biologic capacities of aquatic systems, causing waters to become choked with an excess of organic substances and organisms to be poisoned by toxic materials. When organic matter exceeds the capacity of those microorganisms in water that break it down and recycle it. the excess of nutrients in such matter encourages rapid growth, or blooms, of algae. When they die, the remains of the dead algae add further to the organic wastes already in the water; eventually, the water becomes deficient in oxygen. Anaerobic organisms (those that do not require oxygen to live) then attack the organic wastes, releasing gases such as methane and hydrogen sulfide. which are harmful to the oxygen-requiring (aerobic) forms of life. The result is a foul-smelling, waste-filled body of water, a situation that has already occurred in such places as Lake Erie and the Baltic Sea and is a growing prob­lem in freshwater lakes of Europeand North America. The process by which a lake or any other body of water changes from a clean, clear condition—with a relatively low concentration of dissolved nutrients and a balanced aquatic community to a nutrient-rich, algae-filled body and thence to an oxygen-deficient, waste-filled condition is known as accelerated eutrophication.

SOURCES OF WATER.

 As a matter of fact all water is primarily derived from oceans. In tropical regions, evaporation of water into air is so great that it has been estimated that about 700 gallons (3182.20 litresof water is evaporated every minute from each square mile (2.59 square kilometres) of ocean surface.

Water reaches earth in the form of rain, hail, snow, dew or mist, from water vapour in the atmosphere, derived mainly from evaporation of the sea, from lakes, rivers and other waters of the land. Sea water contains sodium chloride and land water contains lot of dissolved and suspended impurities, but it evaporates in the form of pure distilled water which reaches earth again in the form of rain, snow or hail. This condensed water from the air, which is the ultimate source of all our natural water supply, is pure except for a few impurities that are absorbed from the atmosphere.

A part of rain water on reaching earth is evaporated again into the atmosphere and a part of it percolates into the earth. Some part of it gets col­lected in the form of lakes, ponds etc. But a major portion of it runs away at once in the direction of natural slope of ground and gets collected in the form of small streams, which forms rivers and finally it runs again to the sea and thus the cycle goes on repeating. This phenomenon is known asHydrolog-cal Cycle.

Sources of Water Supply.

The chief sources of water supply are:

(a)Rain water or snow water,

(b)Surface water i.e., streams, canals, rivers, lakes, tanks and ponds.

(c)Upland surface water and natural/artificial lakes.

(d)Ground water, i.e., wells and springs.

(e)Sea water.

 

Ground Water. It is superior to surface water, because the ground provides water an effective filtering medium. Water gets filtered and purified, while passing through it. Wells and springs constitute important sources of ground water.

Wells. These are artificial holes or pits dug into the earth to reach the underground water level. They constitute a very important source of water supply in Indian villages. There are four varieties of wells:

(1) Shallow   Wells   are   those   which   do   not penetrate an impermeable stratum. They simply tap the subsoil water, i.e., ground water lying between the surface and first impermeable stratum. The water of these wells gets pollut zd, cither from surface water or from contamination of subsoil water. Their water is moderately hard.

(2) Deep Wells are those which tap some water bearing layer below the first impermeable stratum. They may pass through one or more impermeable layers. They yield comparatively safer water for drinking purposes than shallow wells on account of efficient filtration, because their water travels a greater distance through the eai (h and also gets bet­ter protection from surface contamination by the impermeable strata above. They yield as a rule,more permanent supplies than shallow wells. The water is usually pure and germ free, but is often hard.

(3)Artesian Wells are a variety of deep wells in which water under great pressure comes out to the surface automatically. To accomplish this, the strata, which the well penetrates, must be cup shaped and the upper level of the ground water tapped between the two impervious strata must be higher than the surface of the earth, where the well lies. Thus in such a case the water shoots up. They are named after Artois province in France where they have been in use for a very long time.

 Norton's Abyssinian Tube Wells are really shallow wells which are bored by simply driving iron pipes 1 1/2" to 2" (3.8 to 5 cm.) in diameter and 20-25 ft. (6.096 to 7.62 metres) deep to tap the ground water. A pump is attached to the pipe to draw the water. Chiefly they were used temporarily in the Abyssinian Campaign. Nowadays these are used where the ground water is not many feet deep below the surface of earth. These wells are of use only when a temporary water supply is required. Since water is drawn out by means of pumps, their water is free from most of the dangers manifested in open wells.

Requirements of a Sanitary Well.

Wells

A well is a hole in the earth from which a fluid is withdrawn. Water wells are the most common type. Oil and natural gas wells are also common. Mining companies also pump steam and hot water down wells to remove salt and sulphur from deep in the ground (Gunning.)

Water Wells

The underground water that flows into wells is called ground water. Most of this water comes from rain that soaks into the ground and slowly moves down to the ground water reservoir, an area of soil and rock saturated with water. The top of this zone is the water table, the level at which water stands in a well that is not being pumped (Taylor.)

In damp places, the water table may lie just below the surface. It is easily reached by digging. A dug well is usually lined with bricks, stone, or porous concrete to keep the sides from caving in. In drier places, the water table may be hundreds of feet or meters down. It may be necessary to drill the well and sink pipes. Power-driven pumps usually draw the water out of deep wells (Berger, Cossi, Taylor.)

In some areas, underground water moving down from the slopes of hills and mountains becomes trapped under watertight layers of clay or shale. Wells drilled through these layers in valleys and plains run into water under pressure. Such wells are called flowing artesian wells (Eliav, Weiss.)

Many people depend on wells for their water supply, especially in rural areas. Underground water is usually pure, because soil makes a good filter. This water generally contains dissolved minerals. A well that taps water with a high mineral content is called a mineral well (Taylor.)

Water wells should be located so that they do not collect poisons or disease germs. A well should be at least100 feet (30 meters) from a cesspool and should never be located so that sewage drains toward it. Water from a well sunk through limestone may be dangerous because water runs through crevices and caves in limestone without being filtered. It is also important that surface water does not drain into a well.

(1) It should be tapped in a good soil and should be at least 50 ft. (15.24 metres) away from any possible source of contamination like a leaking cesspool, insanitary privy etc. The distance between the well and the houses of the users should be kept in view. If the well is situated far away, people may not use the well at all.

(2)The site should be sufficiently high to prevent entrance of water from outside into the well.

(3)It should be a deep well, i.e., sunk below the first impermeable stratum.

(4)It should be properly steined, i.e., built with bricks and lined with cement about 1 inch (2.54 cm.) thick or a watertight casting of concrete or bricks set in cement or having a metal wall, reaching below the water level, below which the joints are open to admit the water to the well. The water should only come from the bottom and not through the surface.

(5)Roots of trees should not be allowed to sprout from the linings of the wall.

(6)The space between the well wall and the lining should be sealed by cement grouting.

(7)It should be properly covered to prevent leaves and dust from blowing into it and also to prevent sparrows and pigeons making their nests in the crevices of the well wall.

(8)Around the top of the well, a parapet wall ft. (0.91 metre) high should be provided, so as to prevent the surface water entering the well. The top of this well should be sloping and not horizontal to discourage people sitting on it for washing clothes thereupon and thus contaminating the well water.

(9)There should be a cemented area at least feet (1.83 metres) with a fall away from the well, so that the surface washings may run away from it and not into it.

(10) It is best that no washing of clothes, utensils and bathing of persons be allowed near a well, as it is not uncommon for a well to get infected by washing clothes, etc., of patients suffering from cholera and other diseases. The best way to avoid this practice is to provide a proper washing and bathing place at a distance from the well to which water can be pumped by means of channels.

(11)All hollows, rat holes, foul tanks, cesspits etc. near the well should be filled up and useless trees and vegetation cut down.

(12)It is best to have a hand-pump or any other mechanical contrivance for drawing up the water in a sanitary manner, which should be discharged by a pipe ending at some distance from the well, so that no water after any possible contamination, can run back to the well. In the absence of any provision — of such a mechanical contrivance, it is desirable that a bucket and a chain for public use should be attached to the well permanently.

 



Fig.. A properly protected well.

1. Cemented brick work.

2. Puddled clay.

3. Platform

4. Cover

5. Channelled drain.

 

Qualities of Well Water. For all intents and purposes it is an excellent water. The bacterial count is very low. It is generally free from pathogenic agents. It is cool and sparkling due to the dissolved carbon dioxide of the ground air.

Cleansing of Well. This is done at the close of hot weather, when the water is at its lowest level. The well must be dewatered.

The sides of the well are scraped and all mud, silt, stones or pieces of bricks, which block the pores of bottom of the well, are removed. Subsequently, the well is treated with a solution of 1 part of freshly prepared

slaked lime to 4 parts of water or bleaching powder, or potassium permanganate solution.

Examination of Wells.

The following points should be borne in mind while examining a well:

(1)Size and depth of the well.

(2)Depth of water in the well.

(3)Nature of soil in which the well is sunk.

(4)Any possible sources of pollution within 200 to 350 ft(60.96 to 106.68 metres) of the well. Practical aspects are discussed subsequently.

(5)Average quantity of water which is daily drawn out.

(6)The way in which water is disposed off.

(7)Mechanical contrivance, with which water is drawn put, e.g., pump, rope and bucket etc.

(8)Whether there are cracks and fissures on the sides or not.

(9)Whether the mouth of the well is closed or open.

Varieties of Springs.

(1)   Surface Springs or Shallow or Land Springs. These  are  outlets of limited collection of ground water resting on the superficial impervious strata. .They are of intermittent nature, supplying water when the level of subsoil water is high, as during rains, and ceasing to flow in summer season (May-June) and starting again in autumn on commencement of percolation. They are an unsatisfactory source of water supply.

(2)   Deep or Main Springs. They derive their water supply from extensive water bearing strata. The water of these springs is clear, sparkling and is generally  safe,  having been  filtered in  its passage through the earth, and the flow is also constant. The water is often hard. These springs have no surface outlets but issue through a fissure or a crack in the soil.

Ordinarily spring water is pure and less liable to contamination, since there is no mechanical means to draw out the water. It is generally cool and palatable, but is highly charged with carbonic acid gas, which it absorbs from the ground. Moreover, on account of passing under pressure, it dissolves out lime and various other mineral salts contained in the soil through which it passes. Consequently, it gets hard and becomes unsuitable for washing andcooking purposes, although it may be valuable from the medicinal point of view.

(3) Hot or Tliennal Springs. These result from continuance of high internal temperature after a volcanic eruption has ceased. They continue to maintain their heat even for centuries. These springs may arise in places even hundreds of miles away from the actual volcanic vent. As examples   may   be   mentioned   springs   ofSitakoond (in Chittagong), Rajgir (in BiharVajreswari (50 milesi.e. 80.47 kilometres from Bombay) in India, springs of Bath and Buxton in England, and Yellowstone Park in U.S.A.

(4) Mineral Springs. The water of mineral springs is highly charged with minerafsalts and so used for medicinal or therapeutic purposes. There are also Sulphur Springs which contain sulphuretted hydrogen and various sulphides in solution. Water containing iron or magnesium in solution is known as Chalaybeate or Magnesia Water.

Yield of a SpringIt can be determined by:

(1)    Finding out the time, which it takes to fill a vessel of known capacity. The output of water in one hour can thus be determined.

(2)    By leading the entire flow of spring over a V or a rectangular notch and measuring the depth of flow over the side of notch. The yield of a spring can be calculated from charts and different formulae.

Safeguards against Pollution of Springs.

 The sources of pollution such as leaking cesspits, insanitary privies, latrines and stables etc., should not besituated near the springs. The springs should be protected by a masonry structure, which should extend deep into the ground to protect against surface contamination.

(e) Sea Water.

       Distilled sea water is used for drink­ing purposes, on board ships and in places like Aden, where wells happen to be brackish and rain does not fall even for several years. Dis­tilled water is flat to taste as all gases are drivenout of it by boiling and it is consequently un­palatable. So aeration of water should be done by allowing it to trickle down through a long column of wood charcoal, if it is required for drinking purposes. As sea water acts on lead, copper, zinc and iron, none of these metals should be exposed to its action in the condensing apparatus. Silver and tin linings are the best choice for pipes and vessels used for making distillation apparatus.

 

Hygienic standards of drinking water quality

 

Index

CIS (ГОСТ 2874-82) of Ukraine

Highest desirable level

WHO (1986)

Highest desirable level

Transparency

30 cm and more for reading of Snellen's print

-

Smell and taste

< 2 number

1-2 number

Colourity

not more than 20 (35) degrees

15 units of the colority

General hardness

7 mg eq/l (to 10 mg eq/l for some cases)

2 mg-eq/l (100 mg/l Ca CO3)

(MAC is 10 mg-eq/1 (500 mg/l Ca CO3))

Turbidity

not more than 0,5 (1,5) nephelometrical units

5 nephelomeric units of turbidity

pH

6,0 – 9,0

7,0 to 8,5 (MAC 6,5 to 9,2)

Dry residuum

100 mg/dm3 to 1000 mg/dm3

1000 mg/l

Chloride    (as Cl)

not more than 250 (300) mg/dm3

250 mg/l

Sulphates    (as  SO)

not more than 250 (500) mg/dm3

400 mg/l

Iron  ( total as Fe)

0,3 mg/dm3

0,3 (1.0) mg/l

Fluorine F

0,7-1,5 mg/dm3

1,5 mg/l

Nitrates     NO3-

45 mg/dm3

10 (by the nitrogen)

NH4

0,1 mg/dm3

 

NO2-

0,002 mg/dm3

-

Oxidizability

< 4 mg O2/dm3

-

Radioactivity:

General α-activity

General β-activity

 

0,1 Bq/l (Becquerel/dm3)

1,0 Bq/l

 

3 pCi/l

30 pCi/l

Index coliform bacteria

not more 3 CFU/dm3

 

General microbe index

Not more 100 CFU/ cm3

 

Number of stable to temperature intestinal rods

miss     CFU/100cm3

 

Number of the pathogenic microorganism

miss     CFU/dm3

 

Number of coliphages

miss      CFU/dm3

 

 

Sampling of water

                   For physical and chemical examination, about 2 litres water is essential. It must be collected in a clean glass stoppered bottle made of neutral glass. Before collecting the sample rinse the bottle well three times with the water filling it each time, about 1/3 full. For bacteriological examination about 300 ml water is required. It must be collected in clean sterilized bottle made of neutral glass, provided with a ground glass stopper having an overlapping rim. If the water to be sampled contains or is likely to contain chlorine, a small quantity of sodium thiosulphate  is added to bottle before sterilization.

A.      Sampling from Tap

                   If sample is taken from a tap in regular use, the tap should be opened fully and the water run to waste at least for 2 minutes in order to flush the stagnant water in nozzle and pipe. If sample is taken from tap not in regular use, the tap should be sterilized by heating it till it is red hot. Then allow water to run to waste for one minute and then collect sample.

B.      Sampling from a well:

                   Tie a sample bottle with a rope. Use a stone or piece of metal weighing about 500 gm as "the weight and attach the tube bottle just above it. After removing the cap aseptically, lower the bottle into the well into the well to a depth of 1m. When no more air bubbles rise to the surface, raise the bottle out of the well and carefully replace the cap.

C.      Sampling from stream.

                   Water is taken from middle of a stream, with the mouth of the bottle facing upstream, lower the bottle into the stream and allow filling. Tilt bottle upwards to fill completely. The cap is carefully screwed back, taking care not to touch the screw thread at the top of the bottle.

 

After taking sample following information must be given with bottle.

a.       Source of water supply

b.      Date, place and time of sampling

c.       Geological formation of soil, if available.

d.      In case of well, its depth, diameter and how it is used.

e.       Recent rainfall if there.

f.       Any suspected source of pollution in vicinity

g.       Whether any method of purification is used.

 

PURIFICATION OF WATER

Three main steps in purification of water on large scale:

Storage, Filtration, Chlorination

1. Storage:

Water is drawn out from source and impounded in natural or artificial reservoirs. Storage provides a reserve of water from which further pollution is excluded.

Advantages
a.       Physical — About 90% of suspended impurities settle down in 24 hours by gravity.

b        Chemical — The aerobic bacteria oxidize the organic matter present in water with the aid of dissolved oxygen. As a result the content of free ammonia is reduced and a rise in nitrates occur.

c.       Biological — 90% of total bacterial count drops in first 5 - 7 days.

2. Filtration

Filtration is important because 98 - 99% of bacteria are removed by filtration, a part from other impurities. Two types of filters are in use, they are:

a.       Slow sand filters (biological filters)

b.       Rapid sand filters (Mechanical filters)

a. Slow Sand Filter.  

ADVANTAGES OF filter.doc

Following are the elements of a slow sand filter.

*        Supernatant (raw) water:

Supernatant water is present above sand bed, its depth varies from (1 – 1,5 m). It serves 2 important functions.

i.        It serves as a constant supply of water,

ii.       It provides waiting period of some hours and there is partial purification by sedimentation & oxidation

*        Sand bed:

It is most important part of the filter; its thickness is about (1,2 m). The sand grains are of diameter between (0,15 – 0,35 mm). Sand bed is supported by a layer of graded gravel. Water percolates through the sand bed very slowly and during this it is subjected to number of purification processes — mechanical straining, sedimentation, adsorption, oxidation and bacterial action.

Vital Layer

Few days (3 to 5 days) after laying the filter, surface of sand bed gets covered with a slimy, green coloured growth made of fungi, algae, bacteria, diatoms and plankton. The formation of vital is known as "ripening of the filter". The growth present on sand bed is called as "Schmutzdecke". It removes organic matter, holds bacteria and oxidizes ammoniacal nitrogen into nitrates and helps in yielding a bacteria - free water.

 Under - drainage system

It consists of porous or perforated pipes lying at the bottom of the filter bed and provides an outlet for filtered water and also provides support to the filter medium above.

Slow filters clear water well only after they’re "ripening": the diameter of pores in the sand decreases, owing to the keeping of suspended matters in the highest layer. So, small particles, worm eggs and larvae and to 99.9% of bacteria can be detained. The clean sand does not absorb viruses. But after the "ripening", about 50-99% viruses are kept in the slow filters. If such filters are used correctly they free water from cercaria. At the same time the series of biological processes proceed in the ripped highest layer - biological film: the mineralization of organic matters and the death of bacteria. The contaminated highest layer of the sand is changed in 30-60 days.Slow filters are used when water turbidity doesn't exceed 200 mg/l in the small country water-pipes. They are always used after the preceding aeration to remove surplus iron and manganese.

 

Filter control valves:

The filter is equipped with certain valves and devices which are incorporated in the outlet pipe system maintaining a steady rate of filtration.

When the vital layer becomes dense and resistance to the passage of water is increased the supernatant water is drained off Sand bed is cleaned by scrapping of the top portion of the sand layer to a depth of 1 - 2 cms. Scrapping is done 20 - 30 times. The process is known as Filter Cleaning.

b. Rapid Sand Filter

Rapid sand filters are of two types, the gravity type and the pressure type. Both the types are in use. The following steps are involved in the purification of water by rapid sand filters.

 i. Coagulation:

Raw water is treated with a chemical coagulant such as alum. The dose required is usually 5 - 40 mg/liter.

ii. Rapid mixing:

The treated water is subjected to rapid mixing for few minutes. This allows a quick and thorough dissemination of alum throughout the bulk of water.

iii. Flocculation:

Treated water is gently stirred in a "flocculation chamber" for about 30 minutes. In chamber there are paddles which act as flocculator. They rotate at speed of  rate per minute. This slow and gentle stirring results in the formation of a thick, copious, white flocculent precipitate of aluminum hydroxide. The thicker the precipitate or flock diameter, the greater the settling velocity.

iv. Sedimentation:  

The coagulated water is now led into sedimentation tanks where it is detained for periods varying from 2 - 6 hours.

v. Filtration:

The partly clarified water now subjected to rapid and filtration.

 

 Filter Beds:

Each unit of filter bed has a surface of about 80 - 90 m2. Sand is filtering medium. The effective size of sand particles is between 0.6 - 2.0 mm. The depth of sand bed is usually about 1 m.  Below the sand bed is a layer of graded gravel 30 - 40 cm. The gravel supports the sand bed and the filtered water to move freely towards the under drains. The rate of filtration is 5 - 15 m3m2/hour.

Back - Washing:

Rapid sand filters need frequent washing daily or weekly. Washing is accomplished by reversing the flow of water through the sand bed, which is called "back-washing". Back - washing dislodges the impurities and cleans up the sand bed.

 

 

The disinfection is one of the most usable methods of water improvement. Usually it is a concluding and very important stage. The most spread methods of disinfection are different methods of chlorination. Sometimes ozonization and UV-irradiation use also.

3. CHLORINATION

Chlorination is the process in  which chlorine is added to water for purification. Chlorination-is more effective when pH of water is around 7.

 Effects of Chlorine:

a.       Chlorine kills pathogenic bacteria, it has no effect on spores and certain viruses.

b.       It has germicidal effects.

c.       It oxidizes iron, manganese and Hydrogen sulphide

d.       If destroys some taste and odour producing constituents.

e.       It controls algae and slim organisms

f.        It aids coagulation

Action of Chlorine.

When Chlorine is added to water, there is formation of hypochlorous and hydrochloric acid. The hydrochloric acid is neutralised by alkalinity of the water. The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions as follows.

H2O + CI2     ►      HCI--+HOCI

HOCI            ►         H++OCI"

The disinfecting action of-chlorine is mainly due to hypochlorous acid and to a small extent due to hypochloriteon.

The chlorination of water is one of the most spread methods and it is of great importance for the prophylaxis of water epidemics. It is explained by the reliable disinfection, accessability and cheapness.

The principle of chlorination is based on the treatment by chlorine or the chemical compounds, containing active chlorine and able to oxidize and provoke bactericidal action. Chlorine is subjected to hydrolysis in water:

Cl2+HOH → HOCl+HCl, so hydrochloric and chloricious acids are formed. Chloricious acid takes the central place in the mechanisms of bactericidal action. It was thought earlier that the latter was destroyed in water and discharged out atomic oxygen (HOCl → HCl+O·), which was the main bactericidal agent. Now, such explaination is considered insufficient. Chlorine in the structure of chloricious acid and hypochlorite-ion (HOCl→H +OCl ) free active chlorine, which determines bactericidal action in water. Not large molecules and electric neutrality let chloricious acid penetrate quickly through the bacterial membrane and influence upon the cellular enzymes, important for the metabolism and reproduction. It is assumed, that it reacts with SH-groups of enzymes, which become oxidized.

The reliable bactericidal effect of chlorine is achieved, if about 0,3 – 0,5 mg/l of free chlorine or 0,8 – 1,2 mg/l of connected chlorine are left in water after 30 - 60 min. of exposure.

Sanitary control of water pipes includes the determination of the remaining chlorine in water every hour, and the bacteriological investigation - not rare than once a day. Long-term experience of using such method in almost all countries of the world is evidence of chlorinated water safety for use.

Simple chlorination (by chlorine request). Right choice of the dose is of great importance for the reliable disinfection. Only about 1 – 2 % active chlorine are spent on the bactericidal action during the disinfection. The rest part is spent on oxidation of organic and inorganic matters in water. All these connected forms of chlorine form such a notion as "chlorine-absorbability of water". Different natural waters have different chlorine-absorbability. To disinfect water by such a method, they introduce such amount of chlorine, that the remaining free chlorine should be 0,3 - 0,5 mg/l and the remaining chlorammoniac chlorine – 0,8 - 1,0 mg/l. In such a case the organoleptic features of water do not become worse.

The number of active chlorine (mg), necessary for the disinfection of 1 liter of water, is called chlorine’s need of water (chlorine-request). It is determined by the experimental chlorination of certain volume of water, subjected to disinfection.

Besides the correct dose, good mixture and sufficient contact of chlorine with water are necessary for the effective disinfection.

The presence of suspended matters, gumines and other organic compounds in water lowers the action of chlorine. That's why it is necessary to light and decolourize turbid and colored waters before disinfection.

The chlorination of water by chlorine-request reliably disinfects water from the intestinal infections (typhoid fever, dysentery, cholera, patogenous strains of E.coli, salmonellas), brucellosis, tularemia, leptospirosis. There are some disputes about the polio virus. Many scientists consider, that this virus is inactivated by the chlorination for an hour. Water, containing Berket's rikketsia, amoebic cysts, worm eggs and the spores of some types of anthrax, cannot be disinfected by this method.

At chlorination of water under action of active chlorine oxidize the microorganisms, organic and inorganic substances, which are in water; the part of chlorine is absorbed by the substances, which have hanged in water, that is denoted as the chlorine absorption of water.

For reliable decontamination of water its contact with chlorine must be last: in summer - not less than 30 minutes, and in winter - not less than 1 hour. The residual chlorine (chlorine, which has remained in water after its decontamination) is the criterion of complete satisfaction of the chlorine absorption of water and also of the epidemic safety of water. Water which was correctly chlorinated must contain 0,3-0,5 mg/l of residual chlorine, as water, which contains more than 0,5 mg/l of residual chlorine, has specific unpleasant taste and smell. The sum of the chlorine absorption of water and the quantity of residual chlorine (0,3-0,5 mg/l) makes the chlorine’s need of water for chlorinate.

The chlorination by the post-break doses. By the results of some investigations the water can be disinfected by 2 doses of chlorine: 1mg/l (before-break dose) and 5,2 mg/l (post-break doses), as the concentration of the rest chlorine makes 0,5 mg/l in both cases.

However, by before-break dose the remaining chlorine is determined as chloramin, and by post-break doses - as free chlorine. The bactericidal action of such method is very effective. At the same time we improve water organoleptic features at the expense of oxidation of organic substances with the bad smell. It is necessary to use this method in hot countries widely.

The chlorination with the preammonization (chlorammination).

First, they introduse ammoniac solution and than, in 0.5-1 min, chlorine to the water. As a result chloramins are formed in water: NH2Cl - monochloramin and NHCl2 - dichloramin. The last one has the most expressed bactericidal action. The effectiveness of such method depends on the ratio NH3:Cl. That's why they use the doses of reagents in the following ratios: 1:3, 1:4, 1:6, 1:8. The ratio should be chosen for certain reservoirs individually.

This method prevents bad smells, which can appear by the chlorination of water, containing phenol and the matters from its group (as chlorphenols are formed). Chlorphenols impart medicinal smell and smack to the water even in the small quantities.

The speed of disinfection by this method is lower than that by chlorine. The exposure time should be not less than 2 hours.

If the water of reservoirs contains ammonium salts, chloramines are also formed. This fact decelerates disinfection. So, it is necessary to define free and connected chlorine separately to determine the reliability of disinfection. Obviously, the presence of only free chlorine is evidence of reliable disinfection.

Double chlorination. In many river water-pipes chlorine is given before the settling and than after the filtration as usual. The introduction of chlorine before the settling improves the coagulation and decolorization of water, inhibits the development of microorganisms in the settling tanks, increases the reliability of disinfection. However, the possibility of chlororganic compounds formation increases too.

The ozonization of water. It is widespread in the industrial countries. Ozone is destroyed in water, forming atomic oxygen: O3 → O2  → O. Now, it is proved, that this mechanism is more complicated: there are many intermediate reactions with the formation of free radicals (for example, HO2), which also have oxidizing features. Ozone oxidizing potential (+1.9) is higher than that one of chlorine (+1.36). From the hygienic point of view, ozonization is one of the best methods of disinfection: water is well disinfected, organic admixtures become destroyed, organoleptic features are improved. Water becomes blue and it is equated with spring water.

Ozone dose is 0,5 - 6 mg/l. Sometimes, higher doses are necessary for the lighting of water and improving other organoleptic features. The time of disinfection is 3-5 min. The remaining ozone should make up 0,1 – 0,3 mg/l. The concentration of the remaining ozone 0.4 mg/l provides the reliable inactivation of 99 % viruses for 5 min.

 

Advanced Water Purification System

 

UV-irradiation.

The maximal bactericidal effect is achieved by the waves 250-260 nm, which pass even through the 25 cmlayer of transparent and decolorized water.

The disinfection proceeds very quickly: vegetative forms of microorganisms die in 1-2 min. The turbidity, colour and iron salts decelerate the disinfection, decreasing the transparence of water. Consequently, it is necessary to light and decolorize water before the disinfection.

There are some advantages of UV-irradiation over the chlorination: bactericidal rays don't denaturate the water and don't change its organoleptic features, they have wider biological action. Their bactericidal action is spread over the spores, viruses and worm eggs, resistant to chlorine. Many investigators consider this method the best for the disinfection.

PURIFICATION OF WATER ON SMALL SCALE

The boiling.

It is the simplest method of disinfection. Vegetative forms of pathogenous microorganisms die in 20-40 sec. at the temperature -  80 °C. The water is almost disinfected until it begins to boil. 5 minutes of boiling provides reliable safety even in the very strong pollution by suspended matters, viruses and other pathological agents. During 30 min. of boiling most of spores die too. The spores of anthrax, worm eggs and larvae are inactivated. Protozoa die too. This method is often used in the everyday life, in hospitals, child welfare institutions, in the manufactures, railway stations. It is necessary to clean tanks before filling them with the boiled water and change water every day, as the microorganisms multiply here very quickly.

Chemical tablet methods. The use of tablets and solutions are widely used for the disinfection in the expeditions and hikes. Tablets "Halazone" contain chloramin, stable during the storage. The tablet is introduced to a certain volume of water (usually it is 1 liter), water and stirred every 3-5 min. It can be used in 30 min. But this tablet cannot be enough for the very contaminated water.

In these cases we can use tablets "Chlor-dechlor", which contain more chlorine and dechlorinated agent in the middle of the tablet (sodium hyposulphite). They introduce one tablet to the water and stir it every 2-3 min. thoroughly. After dissolving of the external part of the tablet its central part inactivates the surplus chlorine. If the water is very shady introduce 2-3 tablets at once. In Ukraine, we use tablets "Aquasept" and "Aquacide", which contain steady chlorine-containing preparations. One tablet (3,5 mg of active chlorine) is introduced to the 1 liter of water. Water becomes desinfected in 30 min.

 

Terminator

Iodine-containing preparations are widespread in tropical countries. They disinfect water from bacteria, many viruses and cysts. The simplest method is the disinfection by 10 % solution of iodine: 2 drops of such solution are introduced in 1 liter of very contaminated water. The water is usable in 20-30 min. Tablets "Globaline", "Potable", containing sodium tetraglycerate triiodate, disinfect water from bacteria, amoebic cysts, many viruses. They are the best disinfectant matters for the torrid zinc. They are safe for humans. Large tanks for the preservation of water must have sturdy cover and a tap.

EXPRESS METHODS OF WATER QUALITY IMPROVING.

Deodorization - elimination of smack and odour of water by aeration, usage of oxidants (ozonization, dioxide of chlorine, large doses of chlorine, potassium permanganate), filtrating through a layer of absorbent coal, by introduction in water to sedimentation of absorbent coal.

Deironation is carried out by spraying water with the purpose of aeration in graduation towers. Thus, bivalent iron is oxydated in ferric hydroxide, which sediments in settling tank, or delays on the filter.

Softening. By an aged method of water softening is soda calcareous, at which calcium and magnesium settle in a settling tank as unsolvable salts. Today is used filtrating water through filters, which are completed by ion exchangers. Ion exchangers are firm, unsolvable, acinose stuffs, which have property to exchange their ions on ions of salts, which are solved in water.

Desalting - the sequential filtrating of water through kationite, and then through anion exchanger permits to liberate it from solvable salts and consequently use with the purpose of desalting. For desalting water on water pipes, sea courts thermal method is used which bases on evaporation of water with the following condensation of steams. Also is used electro dialysis with usage of selective diaphragms, freezing and other methods.

Decontamination - at coagulation, settling and filtrating of water on waterpipes contents of radioactive substances in it is reduced only on 70-80%. For more penetrating decontamination water is filtrated through ionic exchanger of resin.

Fluoridation of water - synthetic adding of fluorine bonds with the purpose of decrease of its rate by caries of teeth.

The protective effect of fluoride occurs primarily during infancy and early childhood when the teeth are developing, but its caries-preventive action is carried over into adulthood as long as one has access to fluoridated water.

WATER PURIFICATION

Suspended and dissolved impurities present in naturally occurring water make it unsuitable for many purposes. Objectionable organic and inorganic materials are removed by such methods as screening and sedimentation to eliminate suspended materials; treatment with such compounds as activated carbon to remove tastes and odors; filtration; and chlorination or irradiation to kill infective microorganisms.

In aeration, or the saturation of water with air, water is brought into contact with air in such a manner as to produce maximum diffusion, usually by spraying water into the air in fountains. Aeration removes odors and taste caused by decomposing organic matter, and also industrial wastes such as phenols and volatile gases such as chlorine. It also converts dissolved iron and manganese compounds into insoluble hydrated oxides of the metals, which may then be readily settled out.

Hardness of natural waters is caused largely by calcium and magnesium salts and to a small extent by iron, aluminum, and other metals. Hardness resulting from the bicarbonates and carbonates of calcium and magnesium is called temporary hardness and can be removed by boiling, which also sterilizes the water. The residual hardness is known as noncarbonate, or permanent, hardness. The methods of softening noncarbonate hardness include the addition of sodium carbonate and lime and filtration through natural or artificial zeolites, which absorb the hardness-producing metallic ions and release sodium ions to the water. Sequestering agents in detergents serve to inactivate the substances that make water hard.

Iron, which causes an unpleasant taste in drinking water, may be removed by aeration and sedimentation or by passing the water through iron-removing zeolite filters, or the iron may be stabilized by addition of such salts as polyphosphates. For use in laboratory applications, water is either distilled or demineralized by passing it through ion-absorbing compounds.

WATER DESALINIZATION

Water Desalinization Technique Flash evaporation is the most widely used method of water desalinization. The seawater is heated and then pumped into a low-pressure tank, where the water is partially vaporized. The water vapor is then condensed and removed as pure water. This process is repeated many times (three stages are shown). The remaining liquid, called brine, contains a large amount of salt and is removed and often processed for minerals. Note that the incoming seawater is used to cool the condensers in each evaporator. This design conserves energy since the heat released when the vapor condenses is used to heat the next batch of seawater. 

         To meet the ever-increasing demands for fresh water, especially in arid and semiarid areas, much research has gone into finding efficient methods of removing salt from seawater and brackish waters. Several processes are being developed to produce fresh water cheaply.

Three of the processes involve evaporation followed by condensation of the resultant steam and are known as multiple-effect evaporation, vapor-compression distillation, and flash evaporation. The last-named method, the most widely used, involves heating seawater and pumping it into lower-pressure tanks, where the water abruptly vaporizes (flashes) into steam. The steam then condenses and is drawn off as pure water.

Freezing is an alternate method, based on the different freezing points of fresh and salt water. The ice crystals are separated from the brine, washed free of salt, and melted into fresh water. In another process, called reverse osmosis, pressure is used to force fresh water through a thin membrane that does not allow the minerals to pass. Reverse osmosis is still undergoing intensive development. Electrodialysis is being used to desalt brackish waters. When salt dissolves in water, it splits into positive and negative ions, which are then removed by electric current through anion and cation membranes, thus depleting the salt in the product water. Although developmental work on electrodialysis is continuing, a number of commercial plants are in operation.

library.thinkquest.org/C0115522/article.php?q...

COAGULATION

The coagulation is used to accelerate the sedimentation of suspended matters, filtration and lightening of water. They add the following coagulators to water: Al2(SO4)3, FeCl3, FeSO4 and so on. They form unsoluble compounds with the dissolved electrolytes, which are quickly sedimented as flocks. These flocks have a large active surface and positive electric charge. That's why they absorb even the smallest negative microbe particles and colloidal gumines, taking them to the bottom of the settling tank. The transparent and uncolored filtrate is formed after the sedimentation of flocks and the next filtration of water. The use of coagulators allows decolorizing water, to shorten the time of settling to 2-3 hours and to use fast filters. 95% worm eggs, 90% and more bacteria and viruses are left water after the coagulation and settling. Coagulation belongs to the most effective methods of water clearing from viruses. The best cleaning is realized by the combined coagulator (Al2(SO4)3 and iron salts).

Aluminium sulpfate Al2(SO4)3*18H2O is often used as a coagulator. It reacts with the calcium bicarbonate and forms Al(OH)3, which is bad-dissoluble and sediments as flocks. The dose of coagulators is 30-200mg/l, it depends on the color, turbidity, pH of water and many other conditions. It is determined by the experi ment for the certain water. Lately they have been used large-molecular matters - flocculators (activated silicic acid), which are active in very small doses (0,2 – 2,0 mg/l), to accelerate coagulation and economize the coagulator. 5% solution of coagulator is given to the mixer with the help of special dosator, where it is quickly mixed with water. Then, the water enters the reaction chamber, where the formation of flocks completes in 10-20 min. Such water passes to the settling tank, where the flocks are sedimented. The size of settling tank corresponds to the settling for 2 – 3 hours.

Then the water is given to the fast filters, where the layer of sand is 0,8 – 1,2 m and the granules - from 0,5 -1 mm. The speed of filtration is 5 - 8 m/h (it is automatically regulated). Soon after the beginning of the work, the filtrating film, consisting of the flocks of coagulator and unsedimented particles, is formed in the highest layer. It improves the detain of microorganisms and admixtures. In 8-12 hours the film becomes denser and the speed of filtration decreases. That's why the work is stopped and the filter is cleaned for 10-15 min. by the stream of clean water, directed upwards, to remove the film.

A complete system of water supply


HYGIENE OF SOIL AND CLEANING INHABITED PLACES

Soil may be defined as the fine earth covering land surfaces that has the important function of serving as a substratum of plain, animal, and human life. Soil acts as a reservoir of nutrients and water and absorbs and oxidises the injurious waste substances that plant growth accumulates in the rhizosphere (i.e.. the root zone). These functions of soil are possible because it contains clay minerals and organic substances (clay and humus form the finer part of soil) that absorb both ions (electrically charged atoms) and water.

Average Composition of Soil

Soils are composed of mineral matter, air, water, organic matter, and organisms. There are two general types of soils, mineral soils and organic soils. Mineral soils form from decomposed rocks or sediment derived from rocks. Organic soils form from the accumulation of plant material, usually in water-saturated, anaerobic conditions that retard decomposition. Mineral matter is described as texture and comprises half the volume of mineral soils. The other half of the soil volume is composed of voids or holes. These voids fill with water as the soil soaks up rain or flood waters, then are displaced with air as the water drains away, evaporates, or is absorbed by roots.

 

Both plants and animals help to create a soil. As they die, organic matter incorporates with the weathered parent material and becomes part of the soil.

         Living animals such as moles, earthworms, bacteria, fungi and nematodes are all busy moving through or digesting food found in the soil. All of these actions mix and enrich the soil. Here is a creature from each major group of soil organisms.

Basic physical properties and texture of soil

Lithosphere (the earth's crust) mineral and organic covering of the Earth, which extends from its surface to magma. It consists of lithosphere itself, which is formed from magma rocks destroyed by physical, physicochemical and chemical processes before beginnings of life on Earth, and soil.

Soil is a surface layer of lithosphere (from few millimeters in mountains and up to 10 kilometers in lowlands), which was formed after beginnings of life on Earth as the result of climate, flora and life (microorganisms and roots of higher plants) influence. Soil consists of the surface or fertile layer (0-25 cm) or humus layer, which is characterized by fertility and which is cultivated at growing plants, and of soil itself.

Soils are very different depending on conditions of their formation, first of all on climate and flora. In Ukraine most common are chernozem (black earth soils) (54.0% of territory), then –– grey forest soils (18.2% of territory) and sod-podsol soils (7.8% of territory).

Basic physical properties of soil:

- texture percentage of soil particles according to their sizes. It is determined by screening through Knopf sieves. There are 7 types (called “numbers”) of such sieves with apertures of different diameters from 0.25 to 10.0 mm (fig. 18.1). Soil texture consists of the following elements: stones and gravel (size > 3 mm); coarse sand (3-1 mm), medium (1-0.25 mm), fine (0.25-0.05 mm); coarse dust (0.05-0.01 mm), medium (0.01-0.005 mm), fine (0.005-0.001 mm); silt (< 0.001 mm). According to texture, soils are classified based on specific weight of physical sand (particles of size > 0.01 mm) and of physical clays (particles of size < 0.01 mm).  (Appendix 3);

- porositytotal volume of pores in the unit of soil volume, which is expressed in percents. The bigger is the size of some elements of soil tissue, i.e. its granularity, the bigger is the size of pores in homogeneous soil. The biggest pores are in rocky soil, smaller ones are in sandy soil, very small pores are in clay soil, and the smallest ones – in peat soil. At that total volume of pores, expressed in percents, increases, i.e. soil porosity is as higher as smaller is the size of some elements of soil tissue. Thus, porosity of sandy soil is 40%, and peat soil - 82%;

Fig. Knopf sieves for soil texture analysis

- air permeabilitysoil ability to let air through its thickness. It increases when size of pores is bigger and doesn’t depend on their total volume (porosity);

- water permeabilitysoil ability to absorb surface water and to let it pass through. Permeability consists of two stages: imbibition, when free pores gradually get filled with water till total saturation of soil and filtration, when, in the result of total water saturation of soil, water starts moving in soil pores because of gravity;

- moisture capacity amount of moisture, which soil is capable to retain due to sorptive and capillar powers. The smaller is the size of pores and the bigger is their total volume, i. e. porosity – the bigger is the moisture capacity. The finer is soil texture, the higher is its moisture capacity;

- soil capillaritysoil ability to lift water via capillaries from the bottom layers up. The smaller is the size of soil texture particles - the bigger is soil capillarity, but in such soil water goes up higher and slower.

In soils of light texture (sandy, clay sandy, light loamy) compared to heavy soils (clays, heavy loams) physical sand prevails, pores are of the larger size, porosity isnt high, air and water permeability, filtration capacity are considerable, capillarity and moisture capacity are low. On the one hand, processes of soil bio-decontamination run rather quickly in such soils, on the other hand, migration of chemical substances from soil into ground and surface water reservoirs, ambient air and plants is more considerable.

Physical Properties of Soil

Permeability (the rate at which water moves through the soil) and Water-Holding Capacity(WHC; the ability of a soils micropores to hold water for plant use) are affected by

  • The amount, size and arrangement of pores

  • Macropores control a soil’s permeability and aeration.

  • Micropores are responsible for a soil’s WHC

Porosity is in turn affected by

  • Soil texture

  • Soil structure

  • Compaction

  • Organic matter

Soil texture (the relative proportions of sand, silt, and clay) is important in determining the water-holding capacity of soil:

1.     Fine-textured soils hold more water than coarse-textured soils but may not be ideal

2.     Medium-textured soils (loam family) are most suitable for plant growth

-        Sands are the largest particles and feel gritty
- Silts are medium-sized and feel soft, silky, or floury
- Clays are the smallest sized particles and feel sticky and are hard to squeeze. 
- Relative size perspective: Sand (house) > Silt > Clay (penny)

soil texture triangle

n types of soil structure (the arrangement of aggregates in a soil):

  • Platy - common with puddling or ponding of soils

  • Prismatic (columnar) – common in subsoils in arid and semi-arid regions

  • Blocky – common in subsoils especially in humid regions

  • Granular (crumb) – common in surface soils with high organic matter content

Properties of soil particle size

 

Sand

Silt

Clay

Porosity

mostly large pores

small pores predominate

small pores predominate

Permeability

rapid

low to moderate

slow

Water holding capacity

limited

medium

very large

Soil particle surface

small

medium

very large

Soil Compaction destoys the quality of the soil because it restricts rooting depth and decreases pore size. The effects are more water-filled pores less able to absorb water, increasing runoff and erosion, and lower soil temperatures. To reduce compaction:

  • Add organic matter

  • Make fewer trips across area

  • Practice reduced-till or no-till systems

  • Harvest when soils are not wet

 

Soil consists of biotic (soil microorganisms) and abiotic components. Abiotic components include hard substance of soil (mineral and organic compounds and organomineral complexes), soil moisture and soil air.

60––80% of mineral (non-organic) substances of soil are represented by crystalline silica or quartz. The important place among mineral compounds is occupied by alumina-silicates, i.e. feldspar and mica. Also to alumina-silicates belong secondary clayey minerals, i.e. of montmorilonite group (montmorilonite, notronite, beidelite, saconite, hectorite, stevensite). Their hygienic importance is them being the cause of absorbing capacity and volume of cations’ absorption (i.e. heavy metals) by soil.

Beside silica and alumina-silicates, almost all elements of Mendeleyevs table appear in mineral compound of soil.

Organic substances of soil are represented both by soil organic (humic acids, fulvic acids etc.) compounds, which are created by soil microorganisms and which are called humus, and by strange for soil organic substances, which came into the soil from outside in the result of natural processes and technogenic (anthropogenic) pollution.

Soil moisture can be both in solid and liquid forms, and in the form of vapour. From hygienic point of view of the most interesting is liquid moisture, which can be in forms of: 1) hygroscopic water, which is condensed on the surface of the soil particles; 2) membranous water, which remains on the surface of soil particles; 3) capillary water, which is kept by capillary forces in thin pores of soil; 4) gravity free water, which is influenced by gravity or hydraulic head and fills in soil big pores.

Soil air is a mixture of gases and vapour, which fills in soil pores. According to its composition it differs from atmosphere air and constantly interacts with it by diffusion and concentration gradient. Soil air and water oppose to each other in respect of space in pores. Natural compound of soil air is controlled by oxygen utilization rate and carbon dioxide generation as the result of microbiological processes of mineralization of organic substances. With growth of depth content of carbon dioxide in soil air increases and oxygen content - decreases.

 

Soil Texture

You can glean much about your soil’s composition by how its texture feels in your hands when it is wet or dry. So grab some and have a feel!

Soil ty

 

ustainable Soil Structure Management

Hygienic significance of soil

 

Soil is:

- the medium, where processes of transformation and soil energy accumulation take place;

- leading member of turnover in nature, the medium, in which different complicated processes of destruction and synthesis of organic substances take place continuously;

- main element of biosphere, where processes of migration, transformation and metabolism of all chemical substances both of natural and anthropogenic (technogenic) origin take place. Migration takes place both in short (soil –– plant –– soil, soil –– water –– soil, soil –– air –– soil) and long (soil –– plant –– animal –– soil, soil –– water –– plant –– soil, soil –– water –– plant –– animal –– soil, soil –– air –– water –– plant –– animal –– soil etc.) migration chains;

- forms the chemical structure of foodstuffs of vegetable and animal origin;

- plays an important role in formation of water quality of surface and ground sources of domestic and drinking water-supply;

- affects qualitative structure of contemporary atmosphere;

- of endemic importance – anomalous natural chemical structure of soil in endemic provinces is a reason of rise and local spreading of endemic diseases (geochemical endemic diseases): endemic fluorosis and caries, endemic goiter, foot-and-mouth disease (FMD), molybdenum gout, endemic osteoarthritis or Kashin-Beck disease, endemic cardiomyopathy (Keshan's disease), selenosis, boric enteritis, endemic nephropathy etc.;

- of epidemic importanceit can be a transmission factor of pathogens of infection diseases and invasions to people: enteric infections of bacterial (typhoid, paratyphoids А and В, bacillary dysentery, cholera, coli-entheritis), viral (virus A hepatitis, enterovirus infections: poliomyelitis, Coxsackie virus infection, ЕСНО) and protozoa ethiology (amebiasis, lambliosis); zooanthroponosis (types of leptospirosis: infectious jaundice or VasylyevVail disease, anicteric leptospirosis, brucellosis, tularemia, anthrax); mycobacteria of tuberculosis; spore-forming clostridia – pathogens of tetanus, gas gangrene, botulism; geohelminthosis – ascaridiasis, trichocephalosis, ankylostomiasis.

- the place for liquid and soil domestic and industrial waste disposal due to natural purification processes (soil sanitary significance). Soil natural purification is characterized by presence of saprophytic decomposers, nitrifying and nitrofying bacteria, elemental organisms, larvae, worms, fungi, viruses, coliphages and by its physical-and-chemical properties. It consists in soil capability to transform organic compounds into mineral substances good for plantsassimilation:  carbohydrates – into water and carbon dioxide; fats– into glycerin and fatty acids and thenalso into water and carbon dioxide; proteins – into amino acids with ammonia and ammonia salts evolvement and their further oxidation to nitrites and nitrates; protein sulfur – into hydrogen sulfide etc.

Methods of land parcel sanitary inspection and soil sampling

Sanitary inspection of the land parcel includes:

- definition of ground assignment (territory of a hospital, preschool institutions, schools, industrial enterprises, objects of waste disposal of domestic, industrial, construction origin, etc);

- visual inspection of the parcel, determination of character and location of sources of soil pollution (distance), relief, drain direction of precipitation waters, flow direction of ground waters;

- determination of soil texture (sand , clay sand, loamy soil, chernozem);

- determination of points for soil sampling for analysis: places near the source of pollution and near test area of known clean soil (at a distance of this source).

Samples are taken byenvelope” technique on rectangular or square areas of 10×20 meters or more. In each of five sampling points of the envelope1 kg of soil is taken from the depth of 20 cm for samples. An average sample of 1 kg mass is prepared from taken samples.

 

Gather your soil sample from the root zone rather than from the surface. You'll need at least one cup of soil.

 

Criteria of soil sanitary state

Group of indices

Indices

Sanitary-and-physical

Texture of soil, filtration coefficient, air and water permeability, capillarity, moisture capacity, total hygroscopic moisture

Physical-and-chemical

Active reaction (рН), absorption capacity, total absorbed bases

Chemical safety criteria:

- chemical agents of natural origin

Background content of total and movable forms of macro- and microelements of non-contaminated soil

- chemical agents of anthropogenic origin (soil pollution indices, ЕCS)

Amount of pesticide residues, total content of heavy metals and arsenic, content of movable forms of heavy metals, oil and oil products’ content, content of sulphides, content of carcinogens (benzpyrene) etc.

Epidemic safety criteria:

- sanitary-chemical

Total organic nitrogen, Khlebnikoff’s sanitary number, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, organic carbon, chlorides, soil oxidation

- sanitary-microbiological

Total number of soil microorganisms, , microbial number, titer of bacteria of colibacillus group (coli-titer), titer of anaerobes (perfingens-titer), pathogenic bacteria and viruses

- sanitary-helminthological

Number of eggs of helminthes

- sanitary-enthomological

Number of larvae and chrysalides of flies

Radiation safety indices

Soil activity

Soil natural purification indices

Titer and index of thermophile bacteria

 

All indices are divided into direct (allow to assess the level of soil contamination and level of danger for population health directly from the results of laboratory analysis of taken samples and indirect (allow to draw a conclusion of the existence of soil contamination, its prescription and duration by comparison of the results of soil laboratory analysis with test clean soil of the same type, which was taken as a sample from non-contaminated areas).

Sanitary number of Khlebnikoffis a ratio of humus nitrogen (pure soil organic substance) to total organic nitrogen (consists of humus nitrogen and nitrogen of strange for soil organic substances that contaminate it). If soil is pure, sanitary number of Khlebnikoff equals to 0.98-1.

Soil coli-titeris a minimal amount of soil in grammas, in which one bacteria of colibacillus group is found.

Soil anaerobe titer (perfingens-titer) is a minimal amount of wastes in grammas, in which an anaerobic clostridia is found.

Soil microbial numberis a number of microorganisms in one gram of soil that grew up on 1.5% beef-extract agar at temperature 370С during 24 hours.

 

Soil classification according to texture (according to N.А. Kachinskiy)

Names of soils according to texture

Content of particles, %

Clay particles of a diameter smaller than 0.01 mm

Sand particles of a diameter larger than 0.01 mm

Heavy clay soils

larger than 80

smaller than 20

Clay soils

from 80 to 50

from 20 to 50

Heavy loamy soil

from 50 to 40

from 50 to 60

Medium loamy soil

from 40 to 30

from 60 to 70

Light loamy soil

from 30 to 20

from 70 to 80

Clay sands

from 20 to 10

from 80 to 90

Sandy

from 10 to 5

from 90 to 95

Light sandy

smaller than 5

larger than 95

 

Filtration capability of soils of different texture

 

Filtration capability

Time of absorption, s*

Type of soil

Large

<18

coarse-grained – and medium size - grained sand

Medium

18––30

fine-grained sand,

light clay sand

Small, but sufficient for active realization of processes of organic decontaminations

30––180

Light adobe

Small and insufficient for realization of processes of organic decontaminations

>180

Heavy and medium clay sands and loamy soil, clays

 

A hole of 0.3×0.3 m in diameter and 0.15 m in depth is dug and quickly filled up with water (12.5 dm3). With the help of chronometer the period of absorption is timed.

 

SOIL POLLUTION

Soil pollution is usually a consequence of insanitary habits, various agricultural practices, and incorrect methods of disposal of solid and liquid wastes, but can also result from fallout from atmospheric pollution. It is closely linked with the ultimate fate of those substances that are unlikely to undergo the natural recycling processes to which putrescible matter is subject. In industrialized countries, soil pollution is associated mainly with:

(1) The use of chemicals, such as fertilizers and growth-regulating agents, in agriculture;

(2) the dumping on land of large masses of waste materials from the mining of coal and minerals and the smelting of metals.   Toxic or harmful substances can be leached out of such materials and enter the soil;

(3)          The dumping on land of domestic refuse and solids resulting from the treatment of sewage and industrial wastes.

(4)          The soil is thus becoming increasingly polluted with chemicals, including heavy metals and products of the petroleum industry, which can reach the food chain, surface water, or ground water, and ultimately be ingested by man.

 

In many countries of the world, and particularly in the developing ones, soil pollution with pathogenic microorganisms is still of major importance. In such countries, intestinal parasites constitute the most important soil pollution problem, as a result both of the improper disposal of human excreta, waste water, and solid wastes, and of incorrect agricultural practices. Thus it is estimated that about one-third of the world's popula­tion is infected by hookworm, while one out of every four people in the world may be infected with Ascaris lumbricoides.

Soil Pollution by Biological Disease Agents

Biological agents that can pollute the soil and cause disease in man can be divided into three groups:

(1) pathogenic organisms excreted by man and transmitted to man by direct contact with contaminated soil or by the consumption of fruit or vegetables grown in contaminated soil (man-soil-man);

(2)   pathogenic organisms of animals, transmitted to man by direct contact with soil contaminated by the wastes of infected animals (animal-soil-man); and

(3)   pathogenic organisms found naturally in soil and transmitted to man by contact with contaminated soil (soil-man).

Man-soil-man

Enteric bacteria and protozoa

Enteric bacteria and protozoa can contaminate the soil as a result of: (a) insanitary excreta disposal practices; or (b) the use of night soil or sewage sludge as a fertilizer, or the direct irrigation of agricultural crops with sewage. Soil and crops can become contaminated with the bacterial agents of cholera, salmonellosis, bacillary dysentery (shigellosis) and typhoid and paratyphoid fever, or with the protozoan agent of amoebiasis. However, these diseases are most often water-borne, and transmitted by direct person-to-person contact, or by the contamination of food. Flies that breed in, or come into contact with, faecal-contaminated soil can serve as mechanical carriers of disease organisms.

Parasitic worms (helminthes)

Soil-transmitted parasitic worms or geo-helminthes are characterized by the fact that their eggs or larvae become infective after a period of incubation in the soil.

Animal-soil-man

In a number of zoonoses (diseases of animals transmissible to man), the soil may play a major part in transmitting the infective agent from animal to man.

Leptospirosis

This disease affects both animals and man in all parts of the world. The epidemiology of the disease follows a characteristic pattern similar to that of other zoonoses, namely animal to animal, and animal to man. In some areas, sheep, goats, and horses become infected. Rodent carriers include rats, mice, and voles. The dispersion of leptospires is associated with specific environmental condi­tions, particularly those that bring animal carriers, water, mud, and man together. Animal carriers often excrete a profusion of leptospires—up to 100 million per ml—in the urine. If this is excreted into water or mud that is neutral or slightly alkaline, the leptospires may survive for weeks. Susceptible animals and man entering this environment are exposed to the agent and may develop infection varying from an inapparent reaction to an acute fulminating fatal disease. Leptospires usually enter the body through the mucous membranes or broken or macerated skin. Agricultural workers in irrigated fields, and in rice and cane fields in particular, often become infected.

Anthrax

The number of reported cases of anthrax in man is relatively small compared with the figures for other zoonoses; nevertheless, anthrax is still of importance both as a human disease and because of its economic impact on animal husbandry. The spores of Bacillus anthracis are very resistant to chemical and environmental influences and can survive for years in certain soils as well as in animal products, such as hides, hair, and wool. When anthrax infections in livestock become established in a district, a relatively permanent enzootic focus of infection is created because of the long period for which the spores can remain viable in the soil.

Other diseases

Among other diseases that follow the sequence animal-soil-man, mention should be made of the following: visceral larva migrans, due mainly to Toxocara canis, listeriosis, Clostridium perfringens infections, lymphocytic choriomeningitis, South American types of haemorrhagic fever, tuberculosis, salmonellosis, and tularaemia. Although most of these diseases and infections are transmitted predominantly by direct animal-man contact, or through the contamination of food by animal droppings and wastes, soil pollution may also play an important part.

Soil-man

Mycoses

Fungi and actinomycetes that grow normally as saprophytes in soil or vegetation cause most of the serious subcutaneous, deep-seated and systemic mycoses. Under certain circumstances, however, they become pathogenic and invade specific tissues or entire systems.

Tetanus

Tetanus is an acute disease of man induced by the toxin of the tetanus bacillus growing anaerobically at the site of an injury. The organism has a world-wide distribution, though cases of the disease are comparatively infrequent today. The infectious agent, Clostridium tetani, is excreted by infected animals, especially horses. The imme­diate source of infection may be soil, dust, or animal and human faeces.

Botulism

This is a frequently fatal type of poisoning caused by bacterial toxins produced by Clostridium botulinum. The reservoir of the organism is soil and the intestinal tract of animals. The toxin is formed by the anaerobic growth of spores in food, which is the immediate source of poisoning. The disease is usually transmitted by the ingestion, without previous cooking, of food from jars or cans imperfectly sterilized during canning, the canned or preserved food having been infected with soil contaminated by Cl. Botulinum.

Soil Pollution and Solid Wastes Disposal Urban areas

The land serves as a major repository for the solid wastes of urban and industrial areas. Solid wastes disposal in metropolitan areas has a number of public health implications.

The problem of greatest concern stems from the fact that, with increasing urbanization and the consequent increase in the area occupied by buildings, the land available for depositing wastes is correspondingly reduced.

In highly industrialized countries, even the solid wastes from agriculture can become a problem, particularly when livestock and poultry wastes near urban centres become a breeding ground for flies and cause a serious odour nuisance on decomposition.

Production per head of solid wastes varies considerably from country to country, but with rising living standards the amount of refuse produced is everywhere on the increase. In the USA and some European countries this increase is estimated at about 3 % per year by volume, and 2 % per year by weight.

The problems of land pollution by wastes differ in a number of import­ant respects from those of water or air pollution, since the polluting material remains in place for relatively long periods of time unless removed, burned, washed away, or otherwise destroyed.

In many of the more developed countries, aesthetic considerations have become important in wastes disposal and there is less readiness to accept unsightly, open refuse dumps and junk heaps as an inevitable blot on the landscape. Insects and rodents, which breed in such dumps, and odours from decomposing organic matter or from slow smouldering fires, can cause severe nuisance and public health problems.

With the increasing utilization of land for urban development, pressure to dispose of solid wastes by methods other than land disposal has led to new pollution problems. Improper incineration can lead to severe air pollution, while discharge into water leads to overloading of treatment facilities and to increased pollution in already heavily burdened watercourses.

Agricultural land pollution

In the past, nutrient materials in the agricultural economy followed a clearly defined cycle: from the land to plants, from plants to animals, and then back to the land again. In some of the more highly industrialized countries, the use of chemical fertilizers has short-circuited this cycle, and many agricultural areas now have large surpluses of plant and animal wastes that, unless properly disposed of, can cause soil pollution. The problem becomes particularly severe where urban areas border on agri­cultural land. In these fringe areas, agricultural solid wastes may ulti­mately have to be handled in the same way as urban wastes.

As agriculture becomes more intensive, so that increasing quantities of synthetic materials, such as pesticides, nutrients, and control agents, are used, chemical soil pollution coupled with increasing amounts of excess organic waste materials leads ultimately to severe land pollution problems in agricultural areas.

Contamination of the Soil by Toxic Chemicals

Agricultural chemicals

Fertilizers are intended to fortify the soil for the raising of crops, but incidentally may contaminate the soil with their impurities. Irrigation of farmlands and orchards may do this if the source of water is polluted by industrial wastes that contain synthetic organic chemicals. During the last few decades, herbicides, insecticides, fungicides, soil conditioners, and fumigants have produced intentional alterations of agricultural, horticul­tural, and silvicultural soils. The chemicals used may pollute the soil water.

Solid wastes from industry

Leach ate from industrial solid wastes may contain poisonous chemicals in solution; these may be concentrated in nature by various organisms in the human food chain.

A recent study has shown that the disposal of industrial solid wastes constitutes a major source of land pollution by toxic chemicals. It has been estimated that some 50 % or more of the raw materials used by industry ultimately become waste products, and that about 15 % can be considered deleterious or toxic. In the United Kingdom, close to one million tons of materials classified as flammable, acid, caustic, or indisputably toxic are dumped annually by industry. This amounts to about 20 kg per person per year. A major portion of these wastes is dumped on the land either by private contractors or by arrangement with local authorities. Some wastes are dumped at sea or incinerated.

These wastes have, in certain instances, given rise to severe problems of soil pollution, either by poisoning the soil or crops, or by eventual entry into ground-water and surface-water sources.

Radioactive materials

Radioactive materials can reach the soil and accumulate there, either from atmospheric fallout from nuclear explosions, or from the release of liquid or solid radioactive wastes produced by industrial or research establishments. The two most important radionuclides with long half-lives produced by nuclear fission are '"Sr (half-life 28 years) and 137Cs (half-life 30 years). Fallout of relatively recent origin and discharges from nuclear reactors also contain a number of other radionuclides of importance from the ecological point of view, e.g., 131I, u°Ba + 140La, 106Ru + 106Rh, 144Ce + 144Pr, etc.

Levels of radiation from fission products deposited in the soil by fallout in the northern hemisphere are about 10-30 % of those due to natural radioactive substances in the soil. Many authorities feel that there is very little evidence to date to show that this increase in radiation levels could affect soil fauna or their predators, but increased radioactive fallout could in time result in levels of soil contamination high enough to cause concern.

Conclusion

Pollution of the land by the biological agents of disease remains one of the major causes of debilitating infections in the rural and semi-rural areas inhabited by the majority of the world's population. Land pollution by toxic chemicals from agriculture and industry, leading to the contamina­tion of soil, food, and water, may prove to be a significant hazard to health in the more industrialized areas of the world. The problems arising from the dumping on land of the ever-increasing amounts of domestic and indus­trial solid wastes will become more acute as world population and the degree of urbanization increase.

Mechanic content of soil and it’s hygienic meaning

Sanitary condition of soil depends greatly on its structure.

         Soil consists of dense, liquid, gas and alive components. Soil solution is water with solved gases, mineral and organic compounds. The types of soil liquid component are film, capillary and gravitation water. Dense component consists of mineral compounds and humus – biogenic heavy-molecular dark colored soil (humine acids, humane and ulmine). Gas components ratio depends on amount of pores and the sanitary condition of soil. Soil microflore, plants and animals inhabiting depends on climatic and geologic conditions.

         Mechanic analysis data make available the following divisions of soils: stony, gravel, cartilage, sandy (>80% sand and <10% of clay); sandy loam soil (50-80% of clay), lesser loamy soil (30-50% of clay), loamy soils (50-80% of clay), clay soils (>80% of clay), lime soils (>80% of clay), chalk soils, lessic soils (mixture of small sand particles with lime clay), black earth (>20% of humus), turf soils etc.

In pity soil the main component is organic substances of soil. The soil, which content the big-size of grain (sand, subs and), have a big pores. At the same time, the size of that pores is not very big: it is near 25-40 % from general volume of soil. The soil, which content the big size pores, have a good penetration for water and air, that is why it’s dry and content much air in it.The soil, which have the small size of grain ( it’s clay and peat) content the big number of small pores; the clay have 45-50% of pores and peat have – to 84% once. In consequence, the soil of small size of pores, which have the grain of small size – have bigger dampness and bad penetration for water and air.

According to cleanness the soil is divided on

 

Coli-tytre

Perfringens-tytre

Number of helminthes eggs in 1 kg

Sanitary index*

Flies chrysalis in 0.25 m2

Clean

>1.0

>0.1

0

0.98-1.0

0

Low pollution

1.0-0.01

0.1-0.001

10

0.85-0.98

1-9

Polluted

0.01-0.001

0.001-0.0001

10-100

0.7-0.85

10-25

Heavily polluted

<0.001

<0.0001

>100

<0.7

>25

Methods of sanitary analysis of soil:

        sanitary entomological

        sanitary-helmontologic analysis

        sanitary-biological

        sanitary-chemical

        sanitary-physical

        sanitary-radiological

 

There are the indices of soil disperse capacity.

         The disperse properties of soil determine its air content: filtration capacity, water content, capillarity, hygroscopic properties, evaporation capacity.

         The epidemiological importance of soil depends on its capacity of infections, invasions and infestations spreading.

         Ecologic and epidemiological analysis of soil should include the evaluation of their biogeocenoses, the following ways of toxic, radioactive and biological agents transmission are possible:

         Sanitary-entomological studies determine a number of winged flies, maggots, pre-chrysalis and chrysalis.

         Sanitary-helminthological analysis defines quantity of helminthes eggs and larvae.

Cleaning of the soil

Self-regeneration of soil results in destruction of organic compounds to the level of mineral salts: nitrites, sulfates, carbonates which can be consumed by plants. Pathogenic microflora perishes suppressed by the antagonistic soil microbes associations and the soil chemical aggression. Helminthes eggs are being destroyed by UV sun radiation, parching etc. Fitoncides produced by some plants are able to kill pathogenic microbes.

         Nitrification is the basic process of soil regeneration. It’s the conversion process of restored organic nitrogen compounds into oxydated inorganic ones. There are heterotrophic and autotrophic nitrification ways. Heterotrophic nitrification is performed by living organisms (fungi included), which affect both organic and inorganic niter compounds Nitrification is the basic natural way of nitrates conversion. The optimum temperature range for nitrificating bacteria is 25-37°C, the process fails under 3°C and over 50°C. Most nitrificators are aerobic, their growth and development claims good soil aeration. The most active nitrification processes run in porous soils with particles sized 2-10 mm (sandy soils, sandy loam, black earth). Soil cultivation and ploughing helps aeration. Soil humidity under 25-30% suppressed nitrification.

NITROGEN CYCLE

         The most interesting of all vital phenomenon taking place in soil is disposal and utilization of organic matter. This is illustrated by nitrogen cycle.

 STEPS:     

Organic proteins burried in soil are decomposed by putrefactive bacteria. Result is formation of amino compounds & then these compounds are broken down into NH3 & CO2.

 CO2 escapes from these compounds in atmosphere.

 Ammonia in soil is converted into ammonium chloride or ammonium carbonate.   In soil, ammonia is oxidized by action of nitrifying bacteria first into nitrates and then in nitrites.

 Nitrites are taken up by plants, which are in turn taken up by animals. If nitrites are found in soil water, it indicates pollution and signifies active bacterial action and presence of organic matter. Nitrates alone are index of past pollution only.

                   Significance of Nitrogen Cycle

.Purification of atmosphere

Organic decomposition

3.     Fertilization power of soil increases

Nitrate (NO3) containing water is preferred. It is further purified.

СLEANING  OF POPULATED PLACES

Disposal of Solid Wastes

Solid wastes include domestic refuse and other discarded solid materials, such as those from commercial, industrial, and agricultural operations; they contain increasing amounts of paper, cardboard, plastics, glass, and other packaging materials, but decreasing amounts of ash. The amounts produced are increasing throughout the world; urban wastes alone amount to about 600 kg per capita annually, and for industrialized countries pro­bably at least 700 kg per capita, with an annual increase of 1-2 %. As the density of domestic waste is decreasing, annual per capita volumes of up to 5 cubic metres are common. These figures do not include the additional solid wastes produced by agricultural and industrial operations, and as a by­product of sewage treatment.

The insanitary collection and disposal of solid wastes creates serious health hazards, e.g., by encouraging the breeding of flies, mosquitos, rodents, and other vectors of disease. It may also contribute to water pollution, air pollution, and soil pollution. It has adverse effects on land values, constitutes a public nuisance, and thus contributes to the deteriora­tion of the environment.

The appropriate intervention and control measures are the rapid removal of refuse from premises by an efficient collection system and the proper processing of refuse before final disposal or re-use.

A refuse disposal system includes essentially: (1) the transportation system, using automotive vehicles, railway transport, pneumatic transport in pipelines under vacuum, and liquid transport in trunk sewers. Transfer stations for changing from one method of transport to another (e.g., truck hauling to railway hauling) are also necessary; (2) facilities for the pro­cessing of solid wastes, possibly using one or more of the following tech­niques: segregation of refuse components, incineration, composting, pulverization, compaction, and grinding; and (3) facilities for the sanitary discharge of residues into the environment, e.g., sanitary landfill, controlled discharge into bodies of water, and discharge into the air of combustion gases and particulate matter.

There are numerous alternatives for the handling and disposal of solid wastes. In selecting the best, consideration must first be given to the protection of the health of the community and the prevention of public nuisances. The salvaging of constituents of refuse, such as paper, glass, steel, etc., for re-use by industry must also be considered.

Methods of collection and disposal

The rapid increase in the production of wastes is causing storage, collection, and transportation difficulties, as well as problems of treatment and final disposal.

Storage is largely a local problem; it becomes acute in housing develop­ments and apartment blocks where adequate provision for storage has not been made. Collection and transportation have recently been intensively studied in various parts of the world, using operations research techniques, with a view to improving efficiency and lowering costs. Unconventional systems, such as hydraulic or pneumatic transport in pipes, are being developed, especially for new towns and residential areas. These developments, which are very promising, will eventually reduce collection costs and minimize human contact with solid wastes.

Collection and transportation costs vary widely, depending on popula­tion density, route planning, the location of disposal sites, labour costs, etc. Careful planning of routes and of pick-up procedures should make significant savings possible.

Substantial savings in handling costs can be achieved by conservation (reducing the volume of waste), land disposal and on-site treatment, both anaerobically or through the use of oxidation ponds or aeration ditches.

The most difficult problem, however, remains that of disposal. Because of the potential nuisance involved, the choice of disposal sites is often a source of serious" controversy. Ideally, the site should be selected or the basis of regional studies. The disposal methods of choice are incineration, sanitary landfill, and composting. Unfortunately, indiscriminate dumping is still practised, both on land and on sea. Incinerator design is improving as combustion efficiency improves and greater control is obtained over gaseous emissions; even after incineration, however, a sizeable volume of ash remains.

Composting, although it has widespread popular appeal, has become increasingly uneconomical as a means of disposal, both because of the changing nature of refuse and the difficulty in disposing of the compost itself.

Sanitary landfill is everywhere the most popular method of disposal. While it requires the use of relatively large areas, it can be used effectively for land reclamation purposes; when properly managed it can be inoffensive, and avoid both air pollution and, to a large extent, leaching and resulting water pollution. A modification of the process is being developed in certain areas; refuse is hauled relatively long distances by rail, and disposal is combined with strip-mining operations.

Other processes, still at the experimental stage, include pulverization into a dense, homogeneous, and relatively inoffensive material. This process reduces transport costs and land area requirements for sanitary landfill. Investigations are also being carried out on the high-pressure compaction of refuse into blocks of high density. These blocks could be used as a filling material and for the reclamation of derelict land.

The importance of recycling in refuse disposal has been emphasized by the conservation-minded. It is almost always a marginal operation from an economic point of view, although aluminium, glass, iron, paper, and other materials can be reclaimed.

Sanitary purification of settlements

 

It is a set of measures that provide for the fulfillment of hygienic requirements during arrangement and exploitation of equipment and facilities that are meant for collecting, temporary keeping, transportation, destruction and utilization of solid and liquid domestic and industrial waste.

Waste these are remains of substances and articles that have been created as the result of domestic, economic and industrial human activity, and cannot be used at the scene of their creation so that their accumulation and keeping make the sanitary condition of the environment worse. They are divided into liquid: 1) sewage from cesspool toilets; 2) slops (from cooking and dish and floor washing etc.) and 3) waste waters: domestic, industrial, runoffs, municipal waste water and solid: 1) garbage (domestic refuse); 2) rubbish (kitchen waste products); 3) waste from patient care and prophylaxis institutions (including specific ones –– used dressing, used disposable autotransfusers and syringes, remains of medicines, remains of organs and tissues after surgical operations, dead bodies of laboratory animals etc.); 4) institutional waste (schools, preschool institutions, high schools and academies, offices, etc; 5) waste of public catering establishments; 6) waste of animal origin (dead bodies of animals, pus, forfeit foodstuff); 7) waste of commercial facilities; 8) industrial waste; 9) slags from boiler houses; 10) construction waste, urban soil; 11) street sweepings.

 

There are three different systems of waste disposal: flushing” removal, “pick-up” removal and combined removal.

Flushing system is used in the settlements, which are provided with sewerage (pipe) system through which liquid and partially fine solid waste float to waste disposal plants; the rest of solid waste is removed by special motor transport.

Pick-up system is used in the settlements without sewerage systems. At that both liquid and solid domestic waste (SDW) is removed to areas of disposal and utilization by special motor transport. Such method of disposal of solid waste is called purification, and of liquid wastes sanitation.

Combined system is used in the settlements that are partially provided with sewerage system. According to combined system liquid waste from the part of settlement, provided with sewerage system, is removed through this system, and from the part of the settlement where there is no sewerage system – with the help of cesspoolage transport. All solid waste is removed by sanitary purification transport.

Sanitary purification of settlement must be systematic (to be performed according to agreed plan and schedule), regular (waste removal in warm seasondaily, in cold seasononce per 1-3 days), utility (to be performed by utilities and community services, or trusts) and to be independent from wishes of some officials or institutions. It consists of three stages: I –– collection and temporary keeping of solid domestic waste; II –– removal; III –– disposal and treatment.

Collection, removal (transportation) of solid domestic wastes.

In case of neighbourhood-based system SDW is collected into special dustbins that are located at specially arranged plots on the territory near the houses and later on, according to the schedule, it is removed by special motor transport to the place of disposal. In case of door-to-door-based system waste is collected in apartments. At the certain time inhabitants take it out to a dust-cart. There are two different methods used in case of neighbourhood-based system - method of "fixed" container (waste from dustbins is emptied into dust-carts and dustbins are placed back) and method of "disposeable" container (dustbins together with solid waste are removed by dust-carts to waste disposal places, while empty and clean dustbins are left instead of the used ones).

For garbage and other solid waste removal special motor carsdust-cartsare used. For method of "fixed" container they use dust-carts 93/М, 53/М, КО-404, КО-413 etc., for method of " disposeable " container dust-carts М-30. They are mounted on the chassis of the trucks GAZ-93а, GAZ -53, MAZ -500А.

Solid domestic waste disposal. All methods of SDW disposal have to meet the following basic hygienic requirements:

- they must provide reliable disposal, transformation of waste into harmless from epidemic and sanitary point of view substrate. From epidemic point of view solid domestic waste is very dangerous: when titer is 10-6-10-7, titer of anaerobes is - 10-5-10-6, microbial number achieves tens and hundreds of billions, contains pathogenic and conditionally pathogenic bacteria, viruses, eggs of helminthes. Especially dangerous is waste from patient care and prophylaxis institutions, which is approximately 10-100 times more contaminated by microorganisms than domestic waste;

- quickness – ideal method is the one that makes possible effective waste disposal during the same period of time in which the waste is formed;

- they must prevent laying eggs and larvae and chrysalides development of flies (Musca domestica) both in waste during its disposal and in substrate, which was obtained in the result of the disposal;

- they must prevent access of rodents during waste disposal and to convert waste into unfavourable for their life and development substrate;

- they must prevent air pollution by volatile products of demolition of organic substances (SDW contain up to 80 % of organic substances, 20-30 % of which easily rot in summer and at the same time evolve stinking gases: hydrogen sulphide, indole, skatole and mercaptans);

- in the process of waste disposal neither surface nor ground waters may be polluted;

- they must provide the best and safe for peoples health use of SDW properties, because they contain up to 6% of utilizable waste; by its burn one can receive heat energy, by biothermal treatment –– organic fertilizers, and food waste may be used for cattle feeding.

According to the final result methods of SDW disposal are divided into: utilizing (waste processing into organic fertilizers, biological fuel, separation of secondary raw materials, e. g. scrap metal, for industry, use as a power-plant fuel) and liquidation (land disposal, sea disposal, incineration without help of heat). According to technological principle methods of disposal are divided into: 1) biothermal (plough-lands, improved dumps, waste store grounds, waste composting fields, bio-chambers, plants for biothermal treatment; in rural area in farms –– compost heaps, hotbeds); 2) thermal (combustion plants without or with utilization of heat energy, which is created in the result of this process; pyrolysis leading to formation of fuel gas and similar to mineral oil - lubricating oil); 3) chemical (hydrolysis); 4) mechanical (waste separation with further utilization,  pressing into construction blocks); 5) combined.

Most widely used are biothermal methods. They are based on the complicated processes of soil natural organic purification from pollutants that may be represented in diagram:

 

Organic

substances

(proteins, fats, carbohydrates)

+

Microorganisms

(bacteria, fungi, actinomycete, algae, protozoa)

+

Oxygen of the air

 

 

 

 

 

 

Humus

(newly synthesized by microorganisms  organic matter)

+

Carbonates, phosphates, nitrates, sulphtes

+

Energy

 

 

Biothermal disposal makes it possible to solve two tasks: 1) to decompose complex organic matters of waste and its metabolism products (urea, uric acid etc.) into simpler compounds in order to synthesize by special microorganisms in presence of ambient air a new, stable, safe from sanitary point of view substance, called humus; 2) to destroy vegetative forms of pathogen and conditionally pathogenic bacteria, viruses, protozoa, eggs of helminthes, eggs and larvae of flies, seeds of weeds.

Efficiency of biothermal method of waste disposal depends on:

- aeration of waste (it is necessary to fan 25 air volumes for 1 volume of SDW);

- waste moisture (if moisture < 30 %, SDW must be moistened artificially; if > 70 %, it is necessary to install  devices for its lessening);

- content of organic substances in waste that are capable to rot easily (mustn’t be  < 30 %, in the ration of carbon to nitrogen 30:1), and inorganic compounds (less than 25 %);

- waste particlessize (optimal size is 25-35 mm);

- waste active reaction (рН) (optimal рН is 6.5-7.6);

- degree of output contamination by mesophilic and thermophilic microorganisms (artificial inoculation is carried out for stimulation of purification);

- thermal conditions (more quickly temperature will rise in the thickness of waste, better and more reliable biochemical destruction of organic substances and pathogenic microflora will be).

Sanitary inspection of systems of waste collection, transportation and disposal requires objective assessment of their efficiency, which is impossible without territory sanitary survey, soil sampling and its laboratory analysis.

 REFERENCES:

Principal:

·         Hygiene and human ecology. Manual for the students of higher medical institutions/ Under the general editorship of V.G. Bardov. – K., 2009. – PP. 14-34, 71-106.

  • Datsenko I.I., Gabovich R.D .Preventive medicine. - K.: Health, 2004, pp. 14-74.

  • Lecture on hygiene.

additional:

  • Kozak D.V., Sopel O.N., Lototska O.V. General Hygiene and Ecology. – Ternopil: TSMU, 2008. – 248 p.

  • Dacenko I.I., Denisuk O.B., Doloshickiy S.L. General hygiene: Manual for practical studies. -Lviv: Svit, 2001. - P. 6-23.

  • A hand book of Preventive and Social Medicine. – Yash Pal Bedi / Sixteenth Edition, 2003 –  p. 26-36, 92-97.