DISPOSAL OF REVERSE-OSMOSIS MEMBRANE CONCENTRATE

Anglian Water have built a reverse osmosis softening/iron and manganes e removal plant at Bunwell water treatment works, Norfolk, UK. Bunwell is a 3,500 m(3)/d borehole source. The on-site treatment is aeration followed by chlorination and rapid gravity sand filtration for iron an d manganese removal. The membrane plant produces 430 m(3)/d of permeat e at 82% recovery, thus also producing 50 m(3)/d of concentrate. The c oncentrate is blended with settled backwash water from the sand filter s and the blend is discharged to a surface water. The disposal of the concentrate was one of the main factors influencing the feasibility of this membrane application and will remain a factor for further applic ations. An increase in environmental awareness and more stringent regu lations may restrict disposal options in the future. Anglian Water are investigating membranes for a variety of applications which will prod uce different concentrates and associated disposal problems.