HYGIENE OF THE INHABITED PLACES.
SOIL AND HEALTH. PROBLEMS OF PROTECTING THE SOIL. BASES OF THE SANITARY CLEANING OF THE INHABITED PLACES. HYGIENE OF HABITATION. MICROCLIMATE, HEATING, VENTILATION.
HYGIENE OF NATURAL AND ARTIFICIAL ILLUMINATION IN APARTMENTS.
Planning of the city includes the most comfortable conditions of life and health care. It enables complex improvement and prophylaxis of pathogenic influences of environment. Some sanitary rules should be kept while planning cities, dwelling territories. District planning. Countryside planning, industrial construction, transport routes planning. The permission for construction and exploitation of resident houses should be certified by the State Hygienic Sanitary Service if the condition of the object meets the sanitary demands. Those demands were proven scientifically (evidence based) and adapted in hygiene of residential areas, air hygiene, water hygiene and sanitary engineering. Planning of city, town or village is the functional division of its territory, its technical equipment and social organization which enable the best conditions of life, health, social and professional activity of the population, education, rest and sport.
Planning of the site foresees the rational involvement of natural resources. There are climatic factor, landscape, soil, water reservoirs, subterranean waters and forests. Climate is the multiannual weather regimen, which is typical for the area. It influences human life, health and activity greatly. Sun radiation, air temperature and humidity, atmospheric pressure wind direction and velocity, sedimentation rate are the points of great sanitary concern. Climatic factors should be taken into consideration during general planning, area choice, building system, houses orientation, thickness of walls and deepness of the basement, aeration type, central heating planning, water supply and gardening planning. Microclimate is the complex characteristic of air temperature state in some areas. Microclimate can change every hundred meters due to the type of surface (water, meadow, forest) or landscape (highland, valley, northern or southern slope). Large cities have special microclimate different from the one in the neighboring areas. The reasons of this phenomenon are as follows:
v Concrete and asphalt pavements and large buildings consume heat in summer and then irradiate it (average annual air temperature in city is 1-3°C higher, humidity is lower by 5-10%)
v Uprising air flows from the city causing the migration of peripheral cold air to the center
v Multistoried houses decrease the wind velocity by two and more times
v Atmospheric smoke decreases sun UV radiation by 20-50%
Requirements to the city territory:
v No marshes or flooding danger, low ground water level, uncontaminated soil, available vegetations.
v Relief slope within 0.5-10% providing drainage of rainwater and ditch drainage
v Sufficient water supply
v No minerals under the construction zone
v Good transport connection
Functional organization of the city territory.
The basic principle is division of city into functional zones. There are five basic functional zones of the city:
1. Selitebe zone
2. Industrial zone
3. Communal storage zone
4. External transport zone
Streets. There are highways (60 m width and more), district streets (over 35 m in width) and intrablock passaged (15 m in low storied sites, 25 m in multistoried sites). The means of streets improvement are:
v Trash cans
v Street lights
v Small architecture constructions
v Street vegetations
Vegetation zone should occupy at least 40-50% of the dwelling territory. Hygienic importance of vegetations:
Protection from wind, dust and noise
Microclimate optimization, humidity normalization, aerodynamic shadow
Bactericide activity of phytoncides
Dust fixation by grass
Esthetic and psychohygienic importance
Potential source of allergens
Dust absorption on plants surface
The general principles of planning are the same but country has some peculiarities.
The area for a new village should be located in healthy zone with low ground water level, free from flooding, with a good water supply and natural rainwater drainage, protected from winds if possible. Absolute demand: no highways should cross the village dwelling zone; the same concerns agricultural routes and cattle routes. The elements of planning are dwelling zone, municipal center and production zone. The improvements are water supply, sewers (especially in farming villages), rational cleaning mode, vegetation rate and optimal ration of zones.
The structure of dwelling zone depends on its constriction planning: sectional dwelling, houses without gardens (gardens stay separately), blocked building with gardens (garden area 0.06 ha) and farmhouses with garden areas 0.12-0.15 ha. These construction zones differ in building types, gardening areas and the sanitary technical supply. Farmhouses can be located along the streets or stay in groups. Production zone contains farms and other technical buildings. It has some hazardous properties (odor, dust, noise, water waste) and should meet the following requirements:
It should be built at some distance from the dwelling zone
It should be located down the river and the domination wind direction
The space between the zones should be 50-1500 m (depending on the farm size and its type), the space should be vegetated.
Municipal center comprises school, kindergarten, medical center, club, bath, laundry, canteen, bakery, shops, post office. It should be placed close to the most improved part of the dwelling zone.
Urban areas: The formal definition of urban areas describes them as concentrations of nonagricultural workers and nonagricultural production sectors.
Urbanization: an increasing proportion of the total population of regions and nations to live in places defined as urban. In other words a process of relative concentration of population in urban areas.
Urban growth: absolute increase in the physical size and total population of urban areas.
SOIL AND HEALTH. PROBLEMS OF PROTECTING THE SOIL.
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.
How is Wastewater Treated to Remove Pollutants?
Physics, Chemistry, Microbiology and Engineering are all involved in purifying wastewater so that it can be safely returned to the environment.
Wastewater treatment plants can be divided into two major types:
Biological and Physical/Chemical.
Biological plants are more commonly used to treat domestic or combined domestic and industrial wastewater from a municipality. They use basically the same processes that would occur naturally in the receiving water, but give them a place to happen under controlled conditions, so that the cleansing reactions are completed before the water is discharged into the environment.
Physical/chemical plants are more often used to treat industrial wastewaters directly, because they often contain pollutants which cannot be removed efficiently by microorganisms-- although industries that deal with biodegradable materials, such as food processing, dairies, breweries, and even paper, plastics and petrochemicals, may use biological treatment. And biological plants generally use some physical and chemical processes, too.
A physical process usually treats suspended, rather than dissolved pollutants. It may be a passive process, such as simply allowing suspended pollutants to settle out or float to the top naturally-- depending on whether they are more or less dense than water. Or the process may be aided mechanically, such as by gently stirring the water to cause more small particles to bump into each other and stick together, forming larger particles which will settle or rise faster-- a process known as flocculation. Chemical flocculants may also be added to produce larger particles. To aid flotation processes, dissolved air under pressure may be added to cause the formation of tiny bubbles which will attach to particles.
Filtration through a medium such as sand as a final treatment stage can result in a very clear water. Ultrafiltration, nanofiltration, and reverse osmosis are processes which force water through membranes and can remove colloidal material (very fine, electrically charged particles, which will not settle) and even some dissolved matter. Absorption (adsorption, technically) on activated charcoal is a physical process which can remove dissolved chemicals. Air or steam stripping can be used to remove pollutants that are gasses or low-boiling liquids from water, and the vapors which are removed in this way are also often passed through beds of activated charcoal to prevent air pollution. These last processes are used mostly in industrial treatment plants, though activated charcoal is common in municipal plants, as well, for odor control.
Some examples of chemical treatment processes, in an industrial setting, would be
· converting a dissolved metal into a solid, settleable form by precipitation with an alkaline material like sodium or calcium hydroxide. Dissolved iron or aluminum salts or organic coagulant aids like polyelectrolytes can be added to help flocculate and settle (or float) the precipitated metal.
· converting highly toxic cyanides used in mining and metal finishing industries into harmless carbon dioxide and nitrogen by oxidizing them with chlorine
· destroying organic chemicals by oxidizing them using ozone or hydrogen peroxide, either alone or in combination with catalysts (chemicals which speed up reactions) and/or ultraviolet light
A common set of processes that might be found at a municipal treatment plant would be:
· Preliminary treatment to remove large or hard solids that might clog or damage other equipment. These might include grinders (comminuters), bar screens, and grit channels. The first chops up rags and trash; the second simply catches large objects, which can be raked off; the third allows heavier materials, like sand and stones, to settle out, so that they will not cause abrasive wear on downstream equipment. Grit channels also remove larger food particles (i.e., garbage).
· Primary settling basins, where the water flows slowly for up to a few hours, to allow organic suspended matter to settle out or float to the surface. Most of this material has a density not much different from that of water, so it needs to be given enough time to separate. Settling tanks can be rectangular or circular. In either type, the tank needs to be designed with some type of scrapers at the bottom to collect the settled sludge and direct it to a pit from which it can be pumped for further treatment-- and skimmers at the surface, to collect the material that floats to the top (which is given the rather inglorious name of "scum".) The diagram below shows the operation of a typical primary settling tank.
· Secondary treatment, usually biological, tries to remove the remaining dissolved or colloidal organic matter. Generally, the biodegradation of the pollutants is allowed to take place in a location where plenty of air can be supplied to the microorganisms. This promotes formation of the less offensive, oxidized products. Engineers try to design the capacity of the treatment units so that enough of the impurities will be removed to prevent significant oxygen demand in the receiving water after discharge.
There are two major types of biological treatment processes: attached growth and suspended growth.
MICROCLIMATE, HEATING, VENTILATION
Light-colored materials reflect sunlight; dark materials absorb the radiation. A house with dark walls and roof is less expensive to heat in winter, but more costly to cool in summer. Light-colored walls and roofs lower cooling costs but increase the need for winter heating.
Low-branching trees should be avoided on the southeastern and/or southwestern exposures or low branches should be removed (Plants used to shade windows from the sun should be far enough away not to restrict air movement. Shrubs near the windows can be positioned to further funnel moving air into the house . If shrubs are to provide low shade for exposures facing prevailing summer winds, use species that have small leaves and an open branching pattern.
Shrubs and trees should be positioned around the air-conditioned home to divert the prevailing southern breezes away from the house, the exact opposite of what would be desired for a passively cooled home. A multilayered summer windbreak should be designed along the southern exposures and away from the home. The tallest components of the windbreak should be the closest to the house. In this way, a "wind ramp" can be created that will channel the breezes over the home. Along and close to the walls that face the direction of summer winds, a foundation planting of shrubs should be used to create a dead-air space that reduces or eliminates warm air infiltration. During the mild transitional months of fall and early spring, natural ventilation is desirable, even in homes that are air conditioned during the peak of the hot season. The south-facing foundation shrubs can be pruned in September to permit air movement, and then allowed to fill out again the following spring, if such pruning does not disrupt the aesthetic integrity of the landscape. Shade trees positioned between windows and prevailing summer winds should be low branching to provide maximum protection against air movement. Additional tall shrubs can be placed nearby but on the windward side of east and west windows.
Plants release water through pores in their leaves. The evaporative loss of this water is called transpiration. As hot air passes over the surface of the leaves, the moisture absorbs some of the heat and evaporates. The air surrounding the leaf surface is thus cooled by the process.
Electric Lighting, illumination by means of any of a number of devices that convert electrical energy into light. The types of electric lighting devices most commonly used are the incandescent lamp, the fluorescent lamp, and the various types of arc and electric-discharge vapor lamps .
Radical changes in incandescent lamp design have resulted from substituting compact fused-quartz glass tubes for glass bulbs. These new, stronger-walled bulbs have made tungsten-halogen lamps, a variation of the incandescent lamp, possible. Tungsten-halogen lamps use the regenerative cycle of halogens to return evaporated tungsten particles to the filament, thus extending the life of the bulb. The high temperatures required to take advantage of halogen’s regenerative cycle made this idea impossible until the walls of the bulb could be made stronger by the introduction of quartz. These bulbs are filled with a mixture of argon and halogen (usually bromine) gases along with a small amount of nitrogen.
Components of a Fluorescent Lamp A fluorescent lamp consists of a phosphor-coated tube, starter, and ballast. The tube is filled with an inert gas (argon) plus a small amount of mercury vapor. The starter energizes the two filaments when the lamp is first turned on. The filaments supply electrons to ionize the argon, forming a plasma that conducts electricity. The ballast limits the amount of current that can flow through the tube. The plasma excites the mercury atoms, which then emit red, green, blue, and ultraviolet light. The light strikes the phosphor coating on the inside of the lamp, which converts the ultraviolet light into other colors. Different phosphors produce warmer or cooler colors. Electric-discharge lamps depend on the ionization and the resulting electric discharge in vapors or gases at low pressures if an electric current is passed through them (see Ion). Representative examples of these types of devices are the mercury-vapor arc lamp, which gives an intense blue-green light and is used for photographic and roadway illumination, and the neon lamp, which is employed for decorative sign and display lighting. In newer electric-discharge lamps, other metals are added to mercury and phosphor on the enclosing bulbs to improve color and efficacy. Glasslike, translucent ceramic tubes have led to high-pressure sodium vapor lamps of unprecedented lighting power.
The fluorescent lamp is another type of electric-discharge device used for general-purpose illumination. It is a low-pressure mercury vapor lamp contained in a glass tube, which is coated on the inside with a fluorescent material known as phosphor. The radiation in the arc of the vapor lamp causes the phosphor to become fluorescent. Much of the radiation from the arc is invisible ultraviolet light , but this radiation is changed to visible light if it excites the phosphor. Fluorescent lamps have several important advantages. By choosing the proper type of phosphor, the light from such lamps can be made to approximate the quality of daylight. In addition, the efficiency of the fluorescent lamp is high. A fluorescent tube taking 40 watts of energy produces as much light as a 150-watt incandescent bulb. Because of this illuminating power, fluorescent lamps produce less heat than incandescent bulbs for comparable light production.
Position of the house: It is better the house faces or is oriented to the north or the south. The light is not uniform through the day in the east or the west. Besides, the direct sunlight will heat up the room, especially during summer. The north-south oriented house has a better chance for uniform lighting.
Windows: A tall window facilitates greater penetration of light. A broad window enables better diffusion of light. The natural lighting is further influenced by the extent of sky that is visible. The ideal window size should be 10% of the floor space.