Primary treatment involves screening, grit removal  and clarification/sedimentation.  Secondary treatment involves digestion of the waste water through aerobic. Or anaerobic processes ir both to dissolve the complex organic waste material into compound and simple compounds and oxidising them to reduce it's oxygen demand (BOD and COD) and Suspended solids etc. Nutrients like nitrogen and phosphorous may not be removed in this stage. The effluent also may contain BOD more than 30 mg/l which is not permissible as per Indian CPCB latest norms. To reduce the BOD etc.further and to remove nutrients like Nitrogen and Phosphorous, Tertiary treatment through constructed wetlands /polishing ponds etc. may be adlpted. Alternatively, SBR/MBR process may be adopted to achieve latest CPCB norms for effluent discharge. Ultimately the effluent should be discharged in an environment friend ly way so as to maintain the desired Dissolved Oxygen of about 4 so as to enable aquatic life to sustain when the effluent is discharged to water bodies.

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Primary treatment involves screening, grit removal  and clarification/sedimentation. 

Secondary treatment involves digestion of the waste water through aerobic. Or anaerobic processes ir both to dissolve the complex organic waste material into compound and simple compounds and oxidising them to reduce it's oxygen demand (BOD and COD) and Suspended solids etc. Nutrients like nitrogen and phosphorous may not be removed in this stage. The effluent also may contain BOD more than 30 mg/l which is not permissible as per Indian CPCB latest norms.

To reduce the BOD etc.further and to remove nutrients like Nitrogen and Phosphorous, Tertiary treatment through constructed wetlands /polishing ponds etc. may be adlpted. Alternatively, SBR/MBR process may be adopted to achieve latest CPCB norms for effluent discharge. Ultimately the effluent should be discharged in an environment friend ly way so as to maintain the desired Dissolved Oxygen of about 4 so as to enable aquatic life to sustain when the effluent is discharged to water bodies.