Define clarified water according to class 7 .
Answers
after cleaning water from the sewage we can get clarified water
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Question:
Define clarified water.
Answer:
The water obtained after scraping and skimming in the sewage treatment is called clarified water.
More Information:
The sewage treatment involves physical, chemical and biological processes which remove physical, chemical and biological matter present in wastewater. The sewage treatment consists of three stages, i.e., the first stage or the primary treatment, the second stage or the secondary treatment and the third stage or the tertiary treatment. During the primary treatment, the sewage is passed through coarse screens or sieves and large objects like cans, plastic packets, rags, etc., are removed. The liquid is then passed through a tank which removes grit and sand. After that the water is passed through settling or sedimentation tanks(the tank is sloped towards its centre) where solids like faeces settle at the bottom and this is called the sludge. Sludge is then removed with a scraper and the floating materials like oil and grease are removed by a skimmer. Then the water so obtained is called the clarified water. Now, the secondary treatment consists of treating the sludge with anaerobic bacteria to break it down into harmless substances. After this stage, the foul gas is no more present and the biogas produced in the process can be used as fuel or can be used to produce electricity. Air is pumped into the clarified water, obtained in the first stage, so that aerobic bacteria can grow. This bacteria eats up human excreta, food waste and other unwanted matter. After a number of hours, the bacteria settles at the bottom of the tank as activated sludge. Water from the top is removed. The activated sludge contains 97% water. It is dried out and the dried sludge is used as manure. And now the final stage comes, the tertiary treatment where chlorination(treatment with chlorine) is done to kill disease-causing organisms. Disinfection can also be done by the use of ozone. The water moe can be released into the distribution system.
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