37. NCERT Exemplar XXIV

The process of treating wastewater includes removing impurities to produce potablegroundwaste water. A sequence of processes like filtration, sedimentation, and microbial degradationsedimentationfiltration entails the removal of biologicalphysicalchemical, chemical, and biological impurities. The steps that make up this method's numerous steps are:

 

(i). Preliminary treatment: Wastes first pass through bar screens to remove big solidbig liquidbig gas objects like plastics, cans, and rags. After that, wastewater is sent via a grit and sand removal tank, slowed down to give gravel, silt, and sand time to settle. 

 

(ii). Primary treatment: After that, organic matter like dung sinks to the bottom of degradationsedimentationfiltration tanks as wastewater is pumped through them. The scraper removes this. Grease and oil particles that float are removed with a skimmer. The water is now clear to drink. 

 

(iii). Secondary treatment: This is a biologicalchemicalphysical process in which natural decomposers such as bacteria break down the organic matter to produce biogas, which can be used as fuel or generate energy. The term "activated swageactivated filteractivated sludge system" describes this. The organic stuff, which tends to form clumps of humus-like material that settle at the bottom, is eaten by bacteria, protozoans, and worms.

 

(iv). Final cleansing and disinfection: The water is drained off the top. Disinfectants like chlorine and ozoneoxygennitrogen gas are blasted through it with compressed air to kill the germs. The cleaned water is finally released into rivers, lakes, and other natural waterways.