- Screening - Remove debris and moderate size particles by using fine screens .
- Grit removal - Remove sand and gravel to protect equipments from wear .
- Gravity sedimentation - Remove the suspended solids by flowing throught a large holding tank with baffles to slow down the wastewater flow .
- Chemical precipitation - To remove clloidal solids by using coagulants added to the wastewater.
- Secondary treatment (Biological )
- Aerobic process was used where bacteria metabolized the biodegrable organics using the dissolbed oxygen .
- The aerobic process can be achieve by :
- In a fixed film growth system , the organic sewerage is passed through a popilation of active microorganisms in a mobile or immobile solid (rock or plastic ) covered in a biomass ( slime ).
- This treatment configuration has been popular because of its stability , robustness and design simplicity .
- Common treatment system include :
Rotating Biological Contactor (RBC) System
B) Suspended growth system
- In a suspended growth system , microorganisms remain in suspension in the sewage.
- This system was developed as a result of studies that showed that if sewage is aerated over a long period of time , microorganisms grow and the organinsc in the sewage are removed .
- Common treatment system included:
- Aerated Lagoon System
- Conventional Activated sludge ( CAS ) system
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