Effect of organic loading rate on organic matter and foulant characteristics in membrane bio-reactor

In this study, the influence of organic loading rate (OLR) on the performance of a membrane bio-reactor (MBR) was investigated. The MBR was operated with 6 different OLRs between 0.5 and 3.0 kg COD/m3 d. The hydrodynamic parameters of the MBR were kept constant. The hydraulic retention time and sludge retention time were kept at 8 h and 40 d respectively. From the experimental investigation, it was found that the removal efficiency of DOC, COD and NH4-N decreased when OLRs were increased from 0.5 to 3.0 kg COD/m3 d. Higher OLRs of 2.75–3.0 kg COD/m3 d resulted in a higher transmembrane pressure development. The fractionation of organic matters showed more hydrophilic substances with higher OLRs. A detailed organic matter characterization of membrane foulant, soluble microbial product and extracellular polymeric substances showed that bio-polymers type substances together with humic acid and lower molecular neutral and acids were responsible for membrane fouling.