Simultaneous high-strength organic and nitrogen removal with combined anaerobic upflow bed filter and aerobic membrane bioreactor

Biological treatment of high-strength nitrogen wastewater by a combined anaerobic (upflow sludge bed filter, UBF)/aerobic (membrane bioreactor, MBR) system has been studied. This system exhibited high performance on the removal of organic matter and nitrogen simultaneously. Organic and nitrogen concentrations increased from 6,000 to 14,500 mg/L and 300 to 1,000 mg/L, respectively. At the internal recycle ratio of Q (Q is the influent flow rate), average removal efficiencies of organic and total nitrogen were found to be 99 and 46%, respectively with the relatively short HRT of 24 h. When operated with the insufficient alkalinity supply, the organic removal efficiency in anaerobic reactor reduced from 98 to 82%. At high influent ammonia concentration, ammonification which is the + dissimilatory nitrate reduction to NH4 was observed. In case of membrane fouling, transmembrane pressure (TMP) of the combined process was about 9 times higher than that of a unit MBR under same operation conditions. The reason of severe fouling in the combined system might be caused by increased extracellular polymeric substance (EPS) and

In this study using a combined anaerobic/ aerobic (UBF/MBR) system for the treatment of strong nitrogen wastewater, following conclusions were obtained: • Higher organic and total nitrogen removal (99 and 46%) were possible at various organic and nitrogen loading rates. • Decreased alkalinity from 4,000 to 3,000 mg/L as (CaCO3) affected organic removal efficiency and denitrification in anaerobic UBF reactor. • Rapid TMP increase was observed at the combined process. And the TMP value of the combined system was nine times higher than that of unit process to obtain the same permeate flux. • In case of combined process, the total contents of EPS were higher than that of unit process. And the supernatant of combined process MBR showed more hydrophilic characteristic. These characteristics of sludge would affect the severe membrane fouling in the combined process. • EPS composition and SUVA was more sensitive parameter than surface charge and total EPS content, with respect to the change of recycle rate 100–300%.