Study On Removal Of High-strength Ammonium From Wastewater With Membrane Bioreactors

Ammonium nitrogen as a nutrient to aquatic plants contributes toeutrophication, which is a big threat to the aquatic ecosystem and human health.Among wastewater treatment technologies, membrane bioreactor (MBR) process isof great potential both technically and economically, especially in reuse ofdomestic/municipal wastewater and treatment of high-strength ammoniumwastewater. The objective of this study is to compare the effectiveness of variousMBR processes on nitrogen removal from high-strength ammonium wastewater inorder to determine the optimal one.In this study, a full-scale MBR, sequencing oxic MBR (SOMBR), a sequencinganoxic/oxic MBR (SAOMBR), a continuous anoxic/oxic MBR (CAOMBR), and acontinuous oxic/anoxic/oxic MBR (COAOMBR) were studied. The efficiencies ofammonium nitrogen (NH₄⁺-N) and total nitrogen (TN) removal of all the processeswere analyzed with emphasis on studying the factors influencing nitrification anddenitrification.For the full-scale MBR, distribution of dissolved oxygen (DO) and its effectson the effluent quality were studied. A mathematical equation correlating withtemperature and tatio of height to diameter was developed. The mathematical modelcan be used to explain the causes of low DO (0.1 to 0.5 mg/L) occurring in thereactor with an effective height of 1.2 to 1.45 m and an equivalent diameter of 1.54m. The results show that Nitrification in the SOMBR process is zero order reactionwith respect to NH₄⁺-N and nitrite nitrogen (NO₂^--N), having rate constants of 64.45mg/(L·h) and 20.06 mg/(L·h), respectively. The reaction rate constant for NH₄⁺-N is13.7 times larger than the conventional actived sludge, and the constant for NO₂^--Nis 2.0 times large than the suspended bio-film bed nitrification reactor.The proformance of the CAOMBR process and affenting factors in operationwere studied in detail. The operational conditions of short-cut nitrification anddenitrification were summarized. Feasibility of using single reactor for high activityammonium removal over nitrite (SHARON) combined with anaerobic ammoniumoxidation (ANAMMOX) for nitrogen removal was tested. The main factors causingmembrane fouling and the prevention measures were also introduced at the end ofpaper.The research results show that COAOMBR process is most efficient in term ofnitrogen removal, and when the ammonium nitrogen removal efficiency of 98.5%and sufficient carbon source for denitrification exists, the removal of TN is onlylimited by reflux ratio in CAOMBR process.