Enhanced biological phosphorus and nitrogen removal using a sequencing anoxic/anaerobic membrane bioreactor (SAM) process

The innovative process SAM (sequencing anoxic/anaerobic membrane bioreactor) was developed to enhance biological phosphorus removal (EBPR), and its performance was investigated. A laboratory-scale experiment was performed to treat the household wastewater including toilet-flushing water. The aerobic zone with the submerged membrane was continuously aerated for nitrification and phosphorous uptake as well as fouling control. The mixed liquor was recycled from the aerobic zone to the anoxic/anaerobic sequencing zone intermittently to alternate the anoxic conditions for denitrification and anaerobic conditions for phosphorus release. During the operation, the flux was maintained almost constant at 10 L/m(2)/h (30 L/d). The modified Luzack-Ettinger (MLE) type MBR process, in which the mixed liquor was recycled continuously from aerobic zone to anoxic zone, was also introduced to compare with the SAM process. The phosphorous removal was much better in the SAM process, yielding 93% removal efficiency. By supplying strict anaerobic conditions without an internal recycle, the phosphorus release was induced in a significant amount, resulting in excellent uptake of phosphorus in the aerobic zone. The nitrogen removal efficiency of the SAM was about 60%, which was slightly lower than that of the MLE-type MBR process. However, it should be noted that the hydraulic retention time of the SAM process in the anoxic condition was 2.3 times shorter than that of MLE-type MBR process.