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प्रश्न
How is sewage water treated?
उत्तर
Sewage water is treated in three steps:
(i) Primary treatment - In this, the coarse and fine suspended , solids are removed by sedimentation, coagulation and precipitation.
(ii) Secondary treatment - It is essentially a biological treatment process which involves the removal of colloidal and dissolved organic substances and some toxic chemicals.
(iii) Tertiary treatment - Here, excess nutrients are removed to allow the reuse of that water.
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