Abstract
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
Highlights
Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d
It was reported that pre-coated DM could reduce the resistance of irreversible fouling and simplify the cleaning operation in wastewater treatment (Megat and Fakhrul, 2002; Muhammad and Anderson, 1997; Marc, et al, 1999).The satisfactory performance of pre-coated DM in activated sludge filtration was verified in a bench-scale experiment (Li et al, 2005)
The performance of the CDMBR was monitored by analysing influent, effluent and supernatant in aerobic reactor samples for selected parameter according to standard procedures, including CODCr, BOD5, TN, NH4+-N, NO3--N, NO2--N and pH (Chinese SEPA, 1997)
Summary
Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d. 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. Some problems on bio-fouling and cake formation limit the acceptance of MBR in wastewater treatment, especially for crossflow membrane bioreactors (CMBR). Soluble microbial product which would accumulate in the reactor by membrane rejection could inhibit the micro-organisms, especially the nitrifying bacteria, reported by Chudoba (1985), Rappaport et al (1979), Ross et al (1998). Cake formation is unavoidable in crossflow filtration This phenomenon can be exploited innovatively by forming a purpose-built dynamic membrane (DM) to substitute the involuntary layer. The quality of permeate and supernatant, as well as sOUR, was monitored in order to evaluated the performance of DM on SMP rejection and the influence of SMP on micro-organisms
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