Screening membranes for COD removal from dilute wastewater

Wastewaters containing organics dramatically contaminate the environment. As an example, wastewater from alcohol manufacturing plant has a chemical oxygen demand (COD) as high as 35,000–40,000 mg/1. The wastewater is normally polished to decrease the COD to 3000 mg/1 by aerobic and anaerobic biological treatment. Ideally COD should be declined to 200 mg/l to obtain the quality for discharge to the environment. Membranes may be used in combination with biological treatment to decrease the COD to a desirable level. However dissimilar membranes in the same range (e.g. reverse osmosis) perform diversely. In this work various reverse osmosis membranes were challenged with biologically treated wastewater from an alcohol manufacturing plant to remove COD. Totally eight polymeric membranes (FT30, PVD, DSII, DS, BW30, 37100, 3750 and NF45) were employed. The polyethylene terphetalate PVD membrane showed outstanding performance with higher flux and complete (100%) COD removal. The hydrophilic polysulfone 37100 membrane showed moderate performance (86% COD removal). This membrane declined the COD value to the ideal level (less than 200 ppm). Nanofiltration polyterphetalate NF45 membrane showed high ability for removal of organics (98%) due to loose structure. These results exhibit the ability of membranes in combination with other treatment processes (biological treatment) to clarify the wastewater for discharge to the environment.