Industrial wastes

Since industrial wastes have a broader range of characteristics than domestic wastes, they are treated by a wider variety of processing schemes. Industrial wastes are more likely to contain toxic components that require physico-chemical instead of biological treatment. In some cases, industrial wastes are discharged to a municipal plant directly or after limited pretreatment. In other cases, they are treated in a separate plant designed for the specific wastes.

Mass transfer is an important consideration in many wastewater treatment systems. In order to carry out chemical and biological reactions, it is necessary to transfer substances into or out of the wastewater, as well as to move them adequately within the water to control concentration differences.

Sedimentation is the removal of solid particles from suspension by gravitational settling. Sedimentation basins are often referred to as either clarifiers or thickeners. The terms clarifiers and thickeners are often used interchangeably in describing tanks for effluent streams from activated sludge reactors.

In water treatment plants, sedimentation is used to remove readily settleable particles, flocculated or coagulated impurities, and precipitated impurities. In wastewater treatment plants, sedimentation is applied to a variety of organic and inorganic solids from raw or treated wastes. The purpose of biological waste treatment is to convert complex molecules into simple products and biomass by using a mixture of microorganisms.

Selection of treatment processes for sludge depends upon the nature of the sludge, environmental factors, and ultimate disposal options. The various alternatives examined to select the major processes are concentration, stabilization, conditioning, and dewatering.

3. Divide the text into some logical parts and entitle them.

4. Translate the following sentences into English using lexical material of the text:

1. Промышленные отходы требуют физико-химической обработки.

2. Для проведения химико-биологических реакций необходимо переместить вещества из сточных вод.

3. Осаждение – это удаление твердых частиц из суспензии путем свободного осаждения.

4. Термины «отстойники» и «сгустители» часто взаимозаменяемы при описании резервуаров для очищенных сточных вод.

5. Цель биологической обработки сточных вод заключается в преобразовании сложных молекул в простые продукты и биомассы с помощью микроорганизмов.

6. Выбор способов очистки шлама зависит от многих факторов.

Text C

1. Pay attention to the following words and word combinations:

greenhouse effect – парниковый эффект

in turn – в свою очередь

to radiate – излучать

insulating blanket – изолирующее одеяло

to be similar to smth. – схожий с чем-либо

to escape – улетучиваться

vapour – пар

to depend on smth.– зависеть от чего-либо

to determine – определять

2. Read the text and be ready to say if the following statements are true or false. Use the following phrases:

It seems to be wrong (right) …

As far as I know …

Far from it. …

If I am not mistaken…

To my mind…

It’s not true to the fact.

1. The atmospheric gases are strong absorbers of infra-red energy.

2. Absorption of infra-red energy by atmospheric gases is similar to effect of glass in a greenhouse.

3. Gases which act as an insulating blanket keep the earth very hot.

4. There wouldn’t be any life on the Earth without natural greenhouse effect.

5. Carbon dioxide is the most important natural greenhouse gas.

6. The concentration of water vapour is determined by the balance between the processes, which produce it, and those, which absorb it.

7. Greenhouse gases occur naturally in the atmosphere.