Mallaig Water Treatment Works – Nanofiltration Process Plant

ACWA designed, built and commissioned a nanofiltration plant at Scottish Water’s Mallaig water treatment work. The process is capable of treating up to 1,764m3/day of raw Highland Loch Water – containing variable but generally high levels of suspended solids and colouration – and recover high quality permeate at a rate of 85%.

The process design of the nanofiltration plant for Scottish Water’s Mallaig Treatment Works comprises prefiltration, chemical dosing, a single pass membrane system and post treatment including remineralisation, chlorination and phosphate dosing for prevention of plumbo solvency.

The plant uses well-proven nanofiltration elements, specially developed to treat water with high levels of suspended solids and colouration. The membrane system, designed to accept pre-filtered water at a rate of up to 88.2m3/hour, comprises four arrays of eight pressure tubes, each containing long spiral wound elements. Pressure and flow transmitters are used to monitor the feed, concentrate and permeate sides of the system, whilst chlorine, flow, turbidity and pH meters, monitor the water quality and output.