Debugging the Plant – Managing Reverse Osmosis Biofouling at a Groundwater Treatment Plant

The Arcadia Water Treatment Plant treats local groundwater to provide up to 10 MGD of treated water as part of the City of Santa Monica?s drinking water supply. The plant removes iron and manganese, and then treats a portion of the water with reverse osmosis as a softening process to achieve desired levels of hardness. Shortly following commissioning, biological fouling occurred first at the pretreatment cartridge filters then spread to the RO units. This paper discusses the process and results of plant troubleshooting used to overcome the fouling, including the successful implementation of chloramine dosing.