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

Abstract

Commissioned in 2010, the Arcadia Water Treatment Plant treats local groundwater to provide approximately 10 mgd of treated water as part of the City of Santa Monica's (Calif.) drinking water supply. The plant removes iron and manganese and then treats a portion of the water with reverse osmosis (RO) as a softening process to achieve desired levels of hardness. Shortly following the plant's commissioning, biological fouling occurred, first at the pretreatment cartridge filters and then spreading to the RO units. Chloramine dosing, long established as an effective strategy for RO biological fouling control in wastewater reuse, is not as widespread in groundwater treatment. Previous studies of chloramine use in surface water and groundwater RO systems reported an undesirable increase in salt transport, which can adversely affect treated water quality and decrease usable membrane life. Despite this, successful implementation of chloramine dosing was achieved at the Santa Monica facility, which has overcome fouling.