Dissolved air flotation separation for pretreatment of membrane bioreactor in domestic wastewater treatment

Due to requiring higher water quality standards over time, new technologies are being employed for wastewater treatment. Dissolved air flotation (DAF) and membrane bioreactor (MBR) technologies are widely employed as new technologies in wastewater treatment. DAF is used due to its excellent separation capability of suspended solids as well as oily material. MBR is used because it may provide a high level of mixed liquor suspended solids in a biological system and excellent separation capability too. In the investigation, separation by DAF, without addition of coagulant, could remove chemical oxygen demand by potassium dicromate (COD_cr) up to over 70%, biochemical oxygen demand (BOD₅) 73%, suspended solids (SS) 83%, total nitrogen (T-N) 55%, and total phosphorus (T-P) 65% in influent of municipal wastewater. Average overall removal rates of water quality parameters by the DAF-MBR system were very high such as COD_cr 95.9%, BOD₅ 99.7%, chemical oxygen demand by potassium permanganate) 93.6%, T-N 69.8%, NH₄-N 98.5%, T-P 78.2%, and SS 99.5%, which satisfy effluent water quality standards. Membrane separation in the MBR system produced a very low SS concentration of 1.27 mg/ℓ in the final effluent. It was proven that DAF separation is an excellent technology for pretreatment of wastewater treatment, especially for an MBR system.