PRETREATMENT TECHNOLOGY FOR REVERSE OSMOSIS MEMBRANE USED IN WASTEWATER RECLAMATION APPLICATION – PAST, PRESENT AND FUTURE – A LITERATURE REVIEW

The use of semi-permeable membranes for wastewater reclamation continues to increase as the demands created by increasing populations for potable water exceeds the available water supplies. Reclamation of secondary effluent for applications requiring very high quality water typically necessitates the use of reverse osmosis membranes (RO). It has been known since the initial pilot testing of RO on secondary effluent in the 1970s that successful application of RO requires that the RO feedwater receive a high level of pretreatment to control the rate and extent of fouling on the RO membranes Initially secondary effluent was successfully pretreated by lime clarification and granular media filtration. Microfiltration (MF) was successfully used as a pretreatment membrane for RO for wastewater reclamation beginning in 1995, since then MF has generally replaced lime clarification and media filtration as the preferred RO pretreatment technology. Subsequently ultrafiltration (UF) and recently membrane bioreactors (i.e. submerged micro- or ultrafiltration) have emerged as alternative RO pretreatment membranes. A literature review was conducted to gather information on past and current trends in pretreatment technologies for reverse osmosis membranes for wastewater reclamation. This literature review has identified new areas for research that could help to further develop pretreatment processes, and thereby make wastewater reclamation more technically and economically feasible.