Sewage treatment Primary treatment : Physical treatment to remove solids (from the liquid) Secondary treatment : Bilogical treatment brought about by aerobic and anaerobic bacteria Teiary treatment : Improving fuher the quality of effluent (advanced waste treatment process), sludge (stabilisation and dewatering), assist sedimentation and sludge treatment (chemical treatment by the addition of coagulants) Ref: Park 25th edition Pgno : 800