Conventional wastewater treatment plants include a primary sedimentation tank (PST) to remove suspended solids and organics. A possible alternative to PST is the adsorption/bio-oxidation (AB) process, which comprises a high-rate activated sludge (HRAS) process (A-stage), which removes chemical oxygen demand primarily by bio-flocculation, adsorption, bioaccumulation and settling, followed by biological nutrient removal (BNR) (B-stage). Biosorption has been reported to be suitable for wastewaters containing high suspended solids and colloids concentration. The main parameters to consider are the solid residence time, hydraulic residence time, aeration control, velocity gradient inside the contact tank, settling time, concentration of mixed liquor suspended solids, sludge recycle ratio and temperature. Sewage and industrial wastewaters were collected from various local industries including petrochemical, chemical, electroplating, food processing and pharmaceuticals industries. The wastewater parameters were determined from a composite sample collected by auto samplers over a period of 24 h.