SELECT * FROM question_mgmt as q WHERE id=6145 AND status=1 SELECT id,question_no,question,chapter FROM question_mgmt as q WHERE courseId=11 AND subId=16 AND chapterId=478 and ex_no='1' AND status=1 ORDER BY CAST(question_no AS UNSIGNED) CBSE Free NCERT Solution of 7th science Wastewater Story describe the steps involved in getting clarified w

Question:

Describe the steps involved in getting clarified water from wastewater.

Answer:

We need water for all our as usual activities. Each and every process is in connection to the water that we use. Now a days, we waste water too much. Water conservation is not being done properly. So water is clarified from the wastewater (also known as sewage) generated by various activities like washing, laundries and etc. 

Clarified water from wastewater:
 Wastewater is collected and passed through bar screens where plastic bags, sticks, cans, napkins etc. are removed. This water then enters a grit and a sand removal tank.
 The speed of the water is decreased so that the sand particles get settled at the bottom of the tank. After this, the water is allowed to settle in a large tank which is tilted towards the centre.
 Solid wastes are settled and removal by the scraper and which is known as clarified water. Air is pumped in this water to help aerobic bacteria to grow.
 The bacteria consume the wastes by microbial action. These microbes settle down after several hours and the water at the top is removed.
 This water is discharged into rivers and oceans or is put to other uses. Nature cleans it up further. Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing it into the distribution system.


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