Environmental Engineering Notes for SSC JE Civil Engineering

Environmental engineering deals with the supply of safe drinking water, the disposal of waste water and the control of pollution. It is a regular part of the Civil Engineering paper in SSC JE, with direct questions on water treatment, sewage and BOD. These environmental engineering notes for SSC JE explain the steps of water treatment, the distribution systems, the sewage treatment and the pollution terms in simple tables with practice questions.

Sources and Demand of Water

Quality of Water

Steps of Water Treatment

1. Screening: removes floating objects.
2. Plain sedimentation: heavy particles settle.
3. Coagulation: chemicals like alum (aluminium sulphate) make fine particles stick together.
4. Flocculation and sedimentation: flocs settle in the tank.
5. Filtration: removes the remaining fine particles and bacteria.
6. Disinfection: kills the germs, mainly by chlorination.
7. Storage and distribution.

Filters

Disinfection and Softening

• Chlorination is the most common method of disinfection; bleaching powder and chlorine gas are used.
• The chlorine needed to kill the germs and to react with the impurities is called the chlorine demand, and the remaining part is the residual chlorine.
• At the break point, all the ammonia and the organic matter are oxidised, and further chlorine becomes free residual chlorine.
• Other methods of disinfection are ozone, ultraviolet (UV) rays and boiling.
• Softening of hard water is done by the lime-soda process or by the zeolite (ion exchange) process.

Distribution Systems of Water

Sewage and Sewerage Systems

Sewage Treatment

• The sludge is digested in an anaerobic digester, which gives methane gas (biogas).
• A septic tank is used for the sewage of a single house or a small group.
• Self-purification of a river has four zones: degradation, active decomposition, recovery and clean water zone.

Pollution Terms

Quick Tips

• Learn the order of the steps of water treatment.
• Remember that the grid iron system is the best distribution system.
• Remember that BOD is measured at 20 degrees Celsius for 5 days.
• Remember that rapid sand filters need coagulation and are backwashed.

Quick Revision Points

• pH of drinking water should be 6.5 to 8.5.
• BOD is measured for 5 days at 20 degrees Celsius.
• Alum is used as the coagulant.
• Chlorination is the common method of disinfection.
• A septic tank serves a small group of houses.

Practice Questions With Answers

1. Which chemical is commonly used as a coagulant?
   Answer: Alum
2. What is the acceptable pH range of drinking water?
   Answer: 6.5 to 8.5
3. At what temperature and for how many days is BOD measured?
   Answer: 20 degrees Celsius for 5 days
4. Which method is mostly used for disinfection of water?
   Answer: Chlorination
5. Which distribution system is the best?
   Answer: Grid iron system
6. Which filter needs backwashing?
   Answer: Rapid sand filter
7. Which gas is obtained from the digestion of sludge?
   Answer: Methane
8. What is the unit of turbidity?
   Answer: NTU
9. Which sewerage system carries sewage and storm water separately?
   Answer: Separate system
10. Which salts cause temporary hardness?
    Answer: Bicarbonates of calcium and magnesium

How to Practise This Chapter

Learn the steps of water and sewage treatment in a flow chart and revise the tables daily. Then solve questions from our practice papers, the free SSC quizzes and the previous year papers page. Read the related chapters, Building Materials, Concrete Technology and Surveying. See all topics on the SSC JE Civil Engineering notes page. For the environment basics, read the General Science notes.

Frequently Asked Questions

What is environmental engineering?

Environmental engineering is the branch of civil engineering that deals with water supply, waste water disposal, solid waste and pollution control.

What are the steps of water treatment?

The steps are screening, sedimentation, coagulation, flocculation, filtration, disinfection and storage.

What is coagulation?

Coagulation is the addition of a chemical like alum to water, so that the fine particles join together and settle easily.

What is chlorination?

Chlorination is the addition of chlorine to water to kill the germs. It is the most common method of disinfection.

What is hardness of water?

Hardness is caused by calcium and magnesium salts. Temporary hardness is removed by boiling, and permanent hardness needs chemical softening.

What is BOD?

BOD is the Biochemical Oxygen Demand, the amount of oxygen bacteria need to break down the organic matter in water in 5 days at 20 degrees Celsius.

What is the difference between BOD and COD?

BOD measures the oxygen needed by bacteria for organic matter, while COD measures the oxygen needed for the chemical oxidation of all matter, so COD is greater than BOD.

What is a septic tank?

A septic tank is an underground tank that treats the sewage of a single house or a small group of houses.

What is the activated sludge process?

It is a biological method of sewage treatment in which the sewage is mixed with air and active bacteria to break down the organic matter.

Which distribution layout is the best?

The grid iron system is the best because the water circulates well and there are no dead ends.

Is environmental engineering important for SSC JE Civil?

Yes. It gives direct questions on water treatment, sewage and pollution in every year.

How many questions come from environmental engineering in SSC JE?

Usually three to five questions come from environmental engineering, but the number changes from year to year.