WATER AND WASTEWATER TREATMEN.
Modern society is centered around the industrial city. The flow of wastewater from these centers is generally large, and the area or volume into which the wastewaters are discharged is generally small in a relative sense. In addition, industrial processes often produce wastewaters that are toxic to many forms of living organisms. Examples are abundant and include acids and bases that normally change the environment rather than directly attacking organisms, toxic substances such as phenol from the petrochemical industry, and high-temperature cooling waters that can both alter the environment or cause thermal shock. Thus the increasing sophistication of society has resulted in the production of larger quantities of wastewater that generally are far more concentrated and potentially harmful to the receiving environment.
Even if toxic materials were not a problem in modern wastewaters the increasing volume would place great pressure on the engineering community to develop improved methods of wastewater treatment. Most cities have been using the same receiving waters for many years even though they have grown considerably in population and, hence, discharge quantity. Arguments can be made that any discharge is damaging, but in any case, the effects are closer to being an exponential rather that a linear function. As a result, many cities have found that the level of wastewater treatment necessary to protect receiving-water quality has increased much faster than the population, and, of course, the cost of treatment is exponentially related to the extent of treatment.
Water treatment for domestic and industrial use is directly related to the quality of the source. In many cases the source is also a receiver of industrial and domestic wastewaters, and therefore water treatment and wastewater treatment are closely tied together. In recent years there has been an increasing concern with asbestos, pesticides and chlorinated hydrocarbons found in small quantities in water supplies. Many of these compounds are known or suspected to be cancirogens. As far as threshold concentrations and mechanisms of infection are not known or understood, regulatory agencies are conservative in setting requirements.
Both treatment level and cost are engineering problems. The general problem statement is to provide maximum treatment at minimum cost.
Ex.1. Find the equivalents.
wastewater степень очистки
discharge качество
acids and bases нефтехимическая промышленность
toxic substances сброс, слив
petrochemical industry сточные воды
cooling waters предельно допустимая концентрация
receiving water кислоты и основания
quality водоём, принимающий сточные воды
extent of treatment охлаждающая вода
threshold concentration токсичные вещества
Ex.2. Correct the wrong statements and prove your idea.
1. The flow of wastewater from the industrial city is small compared with the area or volume in which it is discharged.
2. The increasing sophistication of society has resulted in production of smaller amounts of perfectly clean wastewaters.
3. Industrial wastewaters never contain toxic substances.
4. Water treatment for domestic use doesn’t depend on the quality of the source.
Ex.3. Translate the following.
Wastewater, wastewater treatment, wastewater treatment requirements; discharge, discharge quantities, discharge quantities growth; water, water supplies, water supplies pollution; treatment, treatment level, treatment level problems; infection, infection mechanisms, infection mechanisms understanding.
Ex.4. Choose and translate sentences which should be translated into Russian with «бы».
1. If all people of the world counted the atoms in a drop of water. . .
2. If energy can be changed from one form to another. . .
3. If a molecule could be seen. . .
4. If our sun was far enough from us. . .
5. If we consider chemical compounds. . .
6. If the conversion of water to ice was a physical transformation. . .
Ex.5. Translate the following paying attention to “if-clauses”
1. If we didn’t pollute lakes and rivers, we would have clean drinking water.
2. If we recycle all of our waste rubbish, we won’t pollute the environment.
3. If we all used bicycles, there wouldn’t be so much air pollution.
4. If people stopped using aerosols, it would help the environment.
5. If people shared their cars, there would be fewer cars on the roads.
6. There would have been no life on our planet if there hadn’t been water.
7. If factories stopped pouring toxic substances into lakes and rivers, there would be more clean water.
Ex.6. Translate the text into Russian in written form.
Many communities and industries must provide treatment system that would remove the toxic materials, growth stimulants and residual organics which are not easily removed by conventional wastewater treatment processes. The need for these advanced wastewater treatment processes may often be limited to short periods of the year, and therefore the problem of cost control becomes increasingly difficult.
Engineering responsibility for water and wastewater treatment begins with the determination of the treatment level necessary or desirable and extends to system design and operation. In most cases the level of treatment required is set by a regulatory agency that, in the USA at least, is largely influenced by engineers. While this fact is advantageous with respect to making communication between the agency and the designer simple, it places a responsibility on the engineering community to find methods of incorporating non-quantitative information into regulatory and design decisions.
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