Study on a sequencing batch membrane bioreactor for wastewater treatment

This study investigated the effect of MLSS concentration in a sequencing ba tch membrane bioreactor on COD and nitrogen removal as well as flux. Two va lues of MLSS (5 g/l and 10 g/l) were investigated in this study. The streng th of the feed was varied to achieve a target F/M ratio of 0.5 based on COD . Accordingly, the concentration of COD was determined as 3.5 and 7.0 g/l f or the 5 and 10 g/l MLSS targets, respectively. The test results showed tha t an average COD removal of 98.5% was achievable. However, it was noted tha t nitrification inhibition occurred. Nitrification inhibition occurred beca use of two factors, namely high NH4+-N concentration and high DO demand. Hi gh NH4+-N in the feed led to the inhibition of nitratation and thus high ni trites are found in the effluent. High DO demand due to high feed COD conce ntration led to an extended period with low DO levels inside the reactor th us retarding the conversion of NH4+-N. The increase in the MLSS concentrati on from 5 to 10 g/l led to a decrease in the average flux from 11.1 l/m(2) h to 9.6 l/m(2) h. An increase in aeration, from 2.0 to 8.0 l/min, did not lead to any significant improvement in terms of fouling.