Comparison of advanced water purification operations and performance for San Diego’s demonstration facility

Abstract

The City of San Diego (City) evaluated the option of indirect potable reuse with reservoir augmentation (IPR/RA), as a way to reduce dependence on imported water. The City’s concurrent Recycled Water Study evaluated ways to increase recycling, while reducing flows to the Point Loma Wastewater Treatment Plant (Point Loma). A 68 megaliters per day (MLD) capacity full scale advanced water purification facility (full scale facility) has been proposed to supply this water from the North City Water Reclamation Plant (North City). If reservoir augmentation is pursued, purified water would be blended with existing raw water supplies within San Vicente Reservoir and pass through an existing potable water treatment plant before use in the City’s drinking water supply (). As part of the City’s reservoir augmentation program, they commissioned a 3·8 MLD demonstration scale advanced water purification facility (demonstration facility) to verify consistent achievement of water quality criteria, facilitate public support, and aid in optimization of the proposed treatment processes. In June 2011, CDM Smith and team member MWH began a 12-month testing period followed by a 9-month operation period to determine the effectiveness of a three-step treatment process, including membrane filtration, through microfiltration (MF) and ultrafiltration (UF), reverse osmosis (RO), and ultraviolet light (UV) with advanced oxidation. The major objectives of the testing program included: demonstrate to the California Department of Public Health (now the State Water Resource Control Board Division of Drinking Water) and the Regional Water Quality Control Board (RWQCB) that the proposed advanced water purification (AWP) technology will produce a final product water quality that meets public health and surface water augmentation criteria; evaluate nutrient removal performance of the baseline AWP process train; implement a monitoring plan for Constituents of Emerging Concern (CECs) tailored to North City tertiary water characteristics and current recommendations of the State Water Resources Control Board; demonstrate integrity monitoring techniques and performance reliability measures for the AWP process train, which can be implemented at the full scale facility; and monitor and collect operational performance and maintenance requirements of the AWP equipment. This paper focuses on the membrane filtration and RO systems, evaluating the design criteria and operating performance, while comparing the performance of parallel treatment trains operating with different equipment and operating conditions.

Keywords:

• Potable reuse
• Reverse osmosis
• Membrane filtration