Translate the words and word combinations in brackets.
Domestic (сточные воды) goes to a sewage treatment plant, where it is purified and recycled; much industrial wastewater, however, is fun- neled* into a (река), (ручей), or (океан) for subsequent recycling** by nature. Though nature can handle small quantities of certain wastes, (временный) or (долговременный / постоянный) damage has resulted from widespread disposal of this type. In some cases, legislation has prohibited the (сброс) of harmful (отходы), while in others (предварительная очистка) has been required.
*to funnel - просачиваться, выходить наружу
**recycling - переработка отходов
Match the terms and their definitions.
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a. liable to decay; subject to putrefaction or decomposition
b. material or substance that is not wanted; the unusable remains or byproducts of something
c. of or relating to the conditions that affect hygiene and health, esp. the supply of clean drinking water; hygienic and clean
d. semiliquid waste obtained from the processing of municipal sewage, often used as a fertilizer
e. the action or process of throwing away or getting rid of something
f. thick, soft, wet mud or a similar viscous mixture of liquid and solid components, esp. the product of an industrial or refining process
g. to allow a liquid, gas, or other substance to flow out from where it has been confined; the action of allowing a liquid, gas, or other sub- stance to flow out from where it is confined
h. waste from household sinks, showers, and baths, but not toilets
i. waste water and excrement conveyed in sewers
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Make a summary of the text according to the following plan.
1. The title of the text is “…” .
2. The text is devoted to … .
3. Such problems as… are touched upon in the text.
4. The text consists of … parts.
5. The first part deals with … .
6. The second (third, forth, etc.) part describes … .
7. The main idea of the text is to show … (to underline … / to prove
… / to inform the reader about ...).
8. In my opinion, the text is useful / informative / interesting. It is worth reading.
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Skim over the text. Answer the following questions.
Text B. Sewage Treatment Process
Sewage (wastewater) treatment is the process of removing contami- nants from wastewater, both industrial and domestic. It includes physi- cal, chemical, and biological processes to remove physical, chemical, and biological contaminants. Its objective is to produce environmentally safe sewage water (treated effluent) and a solid waste (sludge or biosol- ids) suitable for discharge or reuse back into the environment. Reuse is often for agricultural purposes, but more recently, sludge is being used as a fuel source.
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It used to be said that "the solution to pollution is dilution". Nature has an amazing ability to cope with small amounts of water wastes and pollution discharged into a body of water. A natural process of stream self-purification occurs. Densely populated communities generate such large quantities of sewage, however, that dilution alone does not prevent
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pollution. This makes it necessary to treat wastewater to some degree before disposal. Sewage treatment plants (STPs) reduce pollutants in sewage to a level which nature can handle. The sewage treatment plant plays vital role in the process of removing the contaminants from sewage to produce liquid and solid (sludge) suitable for discharge to the envi- ronment or for reuse.
Sewage can be treated close to where it is created (in septic tanks, biofilters, aerobic wastewater treatment systems), or collected and trans- ported via a network of pipes and pump stations to a municipal wastewater treatment plant. Industrial wastewater often requires special- ized treatment processes.
Stages of conventional sewage treatment at the wastewater treatment plant involve:
1. pretreatment (preliminary treatment);
2. primary treatment;
3. secondary treatment;
Tertiary treatment.
Here is step-by-step guide describing what happens at each stage of the treatment process.
Preliminary treatment removes materials that can be easily collected from the raw wastewater before they damage or clog the pumps and skimmers of primary treatment clarifiers. Pretreatment includes: screen- ing, grinding, sand and grit removal, dissolved air flotation, wastewater flocculation, prechlorination or preaeration, equalization.
Screening (straining) is the removal of all large objects (wood, stones, dead animals) in the influent sewage water using a screen (a trash rake, a mechanically cleaned bar screen, a manually cleaned screen in smaller or less modern plants); the materials are then sent to a landfill. Sand and grit settlement is accomplished in a sand trap or a grit cham- ber where the velocity of the incoming wastewater is carefully controlled to allow the materials to settle. Screens, grinders, and sand and grit traps are provided for the protection of other equipment in the STP. Dissolved air flotation and wastewater flocculation aid in the removal of suspend- ed solids and oil in the primary clarifier and reduce the biological load- ing on secondary treatment processes. Prechlorination or preaeration may be required to prevent odour problems and to eliminate septic con- ditions where wastewater has abnormally long runs to the plant. Equali-
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zation structures are used to regulate diurnal flow variations and to equalize flows to treatment facilities.
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Pict. 14. Process flow* diagram for a typical large-scale wastewater
Treatment plant
*process flow – технологический маршрут; последовательность технологических операций
1. What is sewage (wastewater) treatment?
2. What is the purpose of sewage treatment?
3. What amazing ability does nature have?
4. Why doesn’t dilution alone prevent pollution in densely populated communities?
5. Industrial wastewater requires specialized treatment processes, doesn’t it?
6. What do stages of conventional sewage treatment involve?
7. What kinds of materials does pretreatment remove?
8. What methods does preliminary treatment include?
9. How are all large objects removed during screening (straining)?
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10. Where is sand and grit settling accomplished?
11. Is prechlorination used to eliminate septic conditions, to remove suspended solids and oil, or to equalize diurnal flow variations?
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