Study the following statements about ozone.
I. It is essential for breathing of living organisms.
II. It is used to disinfect water.
III. It absorbs ultraviolet rays.
IV. Its proportion in air is about 3%.
Which of these statements are correct?

Chlorine is used in municipal water treatment plant to

Which of the following organisms produce biogas from sludge in the digester tank of a wastewater treatment plant?

One of the following type of trees are said to help in purifying wastewater quite rapidly when planted all along the sewage ponds. These are

Which of the following is a part of inorganic impurities of the sewage?

Which one of the following is a quality of wastewater?

Which of these methods should not be used for disposal of urine and faeces if no sewage system is available?

Chemical used to disinfect water is:

Pick from the following one chemical used to disinfect water:

The full form of WWTP is:

Cleaning of water is a process of removing ______________

Drains get blocked by ____________ and _____________

Vermi-composting toilets use ______________ to treat human waste.

Stagnant water blocked in drains is good breeding place for _______________

Bacteria play important _______________ in sewage treatment.

What is a chemical toilet?

What is the function of a skimmer in a water treatment plant?

What is waste water?

How can we make water clean?

Contaminated water is a potential health hazard. Name any two diseases that could be caused by consumption of contaminated water.

Name two chemicals used to disinfect wastewater.

Name two things that can be made from sludge extracted during treatment of sewage.

Bleaching powder is mixed in water, why? Think and give appropriate reason for it.

Sanitation can be improved. Explain, what step should be taken to improve it.

Why you are advised not to throw soft toys, used tea leaves, cotton and sanitary towels into drains?

Name two chemicals used to disinfect water.

Suggest two alternative arrangements for sewage disposal where there is no sewerage system.

Give reasons for each of the following.
We should not the drain throw cooking oil and fats down the drain. 

How can we control water pollution?

What are the different types of inorganic and organic impurities generally present in sewage?