The kinetics of crossflow dynamic membrane bioreactor
Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d. The removal efficiencies of organic substances and nitrogen averaged over 99% and 80%, respectively. The observed sludge yield was only 0.14 g SS·g-1 COD·d-1 at an SRT of 30 d and sludge organic loading about 0.3 g COD·g-1 SS·d-1. Based on total organic carbon TOC measurement, accumulation of soluble microbial products (SMP) in the supernatant caused by membrane separation was observed during the initial operational period. SMP in the supernatant was verified biodegradable subsequently through molecular weight distribution (MWD) analysis. Specific oxygen uptake rate (sOUR) decreased with MLSS increasing in the reactor, which could be expressed by a exponential function. sOUR maintained in the range of 4-5 mg O2·h-1·g -1 VSS while oxygen uptake rate (OUR) increased with MLSS concentration. Despite the low sOUR level of Nitrosomo and Nitrobacter, nitrifying capacity of CDMBR remained high enough to qualify nitrogen removal.
Water SA Vol.32 (2) 2006: pp.199-204