Water reclamation using membranes: Permeate water quality comparison of MBR and tertiary membrane filtration Original Research Article

The purpose of this work is to compare two low pressure membrane filtration technologies commonly used to provide polished wastewater effluent. A pilot-scale membrane bioreactor (MBR) was operated in parallel with a full-scale conventional activated sludge (CAS) process. A portion of the secondary effluent from the full-scale plant was further treated by a pilot-scale tertiary membrane filtration (TMF) system. The MBR was operated at solids retention time (SRT) and mixed liquor suspended solids concentration (MLSS) values that were double and triple that of the CAS process, respectively. The permeate quality from these two pilot plants was monitored to detect differences in their performance. Analytes included COD, TOC, polysaccharides, proteins, color and specific UV254 absorbance (SUVA). The MBR permeate COD and TOC concentrations were consistently significantly lower than those for the CAS–TMF permeate. The average polysaccharide concentration was also found to be significantly lower in the MBR permeate; however the average color and SUVA were significantly higher in the MBR permeate. It is suggested that the differences in permeate quality are attributed to the higher SRT in the MBR and increased retention of colloidal organics in the bioreactor.