Membrane filtration and reverse osmosis purification of sewage: Secondary effluent for re-use at Eraring Power Station

Abstract

This paper describes the membrane filtration and reverse osmosis (RO) process currently being adopted for purification and re-use of secondary treated effluent at Pacific Power's Eraring Power Station. Reasons for selection of this purification scheme and plant design considerations are described. Secondary treated effluent is being made available by the Hunter Water Corporation from a new sewage plant being installed on the western side of Lake Macquarie. Effluent volume will rise from an initial 2 megalitres d to about 5 ML d by 2010 with an increase in population. The purification plant size will be increased in stages to match the increase in effluent quantity. Ultimately 95% of the power station's fresh water requirements of 4 ML d will be met by use of recycled water. Membrane filtration will be used for suspended solids removal and disinfection, chlorination for residual disinfection and RO for dissolved solids reduction. The treated effluent will be used at the station as feed to the water demineralizing plant for boiler make-up, direct make-up to the auxiliary cooling water system and for general station uses such as washdown and fire service systems. A separate recycled water storage and distribution system is being installed to service these requirements. The reduction of domestic water requirements at the station will reduce Pacific Power's operating cost by around $800,000 per annum, and domestic water supplies for the Hunter Region will be conserved. Hunter Water has been able to defer for 15 y the construction of a $2.7 million ocean discharge pipeline.