II. Подберите заголовок к каждой части текста:

a.Bio-solids handling

b.Screening

c.Wastewater Collection

d.Odor Control

e.Disinfection

f.Tertiary treatment

g.Secondary Treatment

h.Sludge Treatment

i.Primary Treatment

WASTEWATER TREATMENT

I. Прочитайте текст:

(1)Clean water is the key to the survival of humanity. Unfortunately, many fresh water sources are contaminated today. That is why concern for the environment becomes extremely necessary. In industry water is used very actively, but it returns into natural water bodies without proper cleaning. Wastewater treatment must become number one environmental challenge for enterprises. Thanks to the development of modern technology, we can achieve really high degree of wastewater treatment today.

(2)Waste water treatment is a process used to convert wastewater into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused. The latter is called water reclamation because treated wastewater can then be

used for other purposes. The treatment process takes place in a wastewater treatment plant (WWTP), often referred to as a Water Resource Recovery Facility (WRRF) or a sewage treatment plant. Pollutants in municipal wastewater (households and small industries) are removed or broken down.

The treatment of wastewater is a part of the universal field called sanitation. Sanitation also includes the management of human waste and solid waste, as well as stormwater (drainage) management.

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(3) Disposal or reuse

Although the problem of disposal or reuse occurs after treatment, it must be considered first. Since disposal or reuse are the objectives of wastewater treatment, disposal or reuse options are the basis for treatment decisions. Acceptable impurity concentrations may vary with the type of use or location of disposal. Transportation costs often make acceptable impurity concentrations dependent upon location of disposal, but expensive treatment requirements may encourage selection of a disposal location on the basis of impurity concentrations. Ocean disposal is subject to international treaty requirements. International treaties may also regulate disposal into rivers crossing international borders. Water bodies entirely within the jurisdiction of a single nation may be subject to regulations of multiple local governments. Acceptable impurity concentrations may vary widely among different jurisdictions for disposal of wastewater to evaporation ponds, infiltration basins, or injection wells.

Processes used

(4) Phase separation

Phase separation transfers impurities into a non-aqueous phase. Phase separation may occur at intermediate points in a treatment sequence to remove solids generated during oxidation or polishing. Grease and oil may be recovered for fuel or saponification. Solids often require dewatering of sludge in a wastewater treatment plant. Disposal options for dried solids vary with the type and concentration of impurities removed from water.

Production of waste brine, however, may discourage wastewater treatment removing dissolved inorganic solids from water by methods like ion exchange, reverse osmosis, and distillation.

Sedimentation

Solids like stones, excretes and other Impurities may be removed from wastewater by gravity when density differences are sufficient to overcome dispersion by turbulence. Gravity separation of solids is the primary treatment of sewage, where the unit process takes place in primary settling tanks (primary sedimentation tanks). It is also widely used for the treatment of other wastewaters. Solids that are heavier than water will be accumulated at the bottom of

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quiescent settling basins. More complex clarifiers also have skimmers to simultaneously remove floating grease like soap scum and solids like feathers or wood chips. Containers, such as API oil-water separators, are specifically designed to separate non-polar liquids.

Filtration

Colloidal suspensions of fine solids may be removed by filtration through fine physical barriers distinguished from coarser screens or sieves by the ability to remove particles smaller than the openings through which the water passes. Other types of water filters remove impurities by chemical or biological processes described below.

(5) Oxidation

Oxidation reduces the biochemical oxygen demand of wastewater, and may reduce the toxicity of some impurities. Secondary treatment converts organic compounds into carbon dioxide, water, and biosolids. Chemical oxidation is widely used for disinfection.

Biochemical oxidation

Secondary treatment by biochemical oxidation of dissolved and colloidal organic compounds is widely used in sewage treatment and is applicable to some agricultural and industrial wastewaters. Biological oxidation will preferentially remove organic compounds useful as a food supply for the treatment ecosystem. Concentration of some less digestible compounds may be reduced by co-metabolism.

Chemical oxidation

Chemical oxidation is used to remove some persistent organic pollutants and concentrations remaining after biochemical oxidation. Disinfection by chemical oxidation kills bacteria and microbial pathogens by adding ozone, chlorine or hypochlorite to wastewater.

(6) Polishing

Polishing refers to treatments following the above-mentioned methods. These treatments may also be used independently for some industrial wastewater. Chemical reduction or pH adjustment minimizes chemical reactivity of wastewater following chemical oxidation. Carbon filtering removes remaining contaminants and impurities by chemical absorption onto activated carbon. Filtration through sand (calcium carbonate) or fabric filters is the most common method used in municipal wastewater treatment.

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II. Укажите часть текста, содержащую следующую информацию:

a.Where the process of wastewater treatment takes place.

b.Removing particles with the help of screens or sieves.

c.Laws regulating disposal of wastewater into water bodies.

d.Final removal of remaining contaminants.

e.Primary treatment of sewage in sedimentation tanks.

f.Treatment of dissolved organic compounds.

CLEANING WATER

I. Прочитайте текст:

Let us find out how water is cleaned before it’s piped into homes and offices. In Europe and North America, water comes from different sources, mainly lakes, aquifers, or rives. Rivers are usually dammed to form reservoirs. But before they reach our homes, most of our water supplies have to be purified. This takes place in a water treatment works where impurities are removed to make the water clear, odour-free, and taste-free. So it should be perfectly transparent, smell of nothing, and taste of nothing.

First of all, water taken from a river or reservoir is screened to remove large bits of rubbish such as twigs, plastic bags, etc. This is done by passing it through a microstrainer. Then, it’s pumped to a water treatment works. At this stage, grit and organic matter, for example pieces of plants, algae, and bacteria, are still present in the water. The water is fed into an aerator, which sprays the water in order to obtain a good oxygen balance. At the same time, this spraying releases any trapped gases that might otherwise give a bad taste or odour. Following this, chemicals called coagulants are added. The function of these is to cause particles to stick together to form larger particles. The chemical normally used is alum, aluminium sulphate. This takes place in large tanks called flash mixers.

From here, the water passes into a sedimentation tank, sometimes called a settling basin. Here, the large particles are allowed to settle to the bottom. A sludge builds up at the bottom of the tank and

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