Comparing Multiple MF/UF and RO Systems for Indirect Potable Reuse in Side-by-Side Comparison

摘要

The City of San Diego (City) is conducting a 1.0 million gallon per day (mgd) Water PurificationDemonstration Project to evaluate the feasibility of augmenting their current drinking water supply withpurified, recycled water from the North City Water Reclamation Plant (NCWRP). As part of this project,the City is evaluating two membrane filtration and two reverse osmosis (RO) units in side-by-sidecomparisons to evaluate performance, compare full-scale reliability, and determine the most economical,energy-efficient treatment approach for a potential full-scale facility.This paper will focus on the design criteria and first six months of operating performance for the membranefiltration and RO systems. The membrane filtration equipment includes two parallel 0.63-mgd units. Oneunit is a Pall microfiltration (MF) system and the second is an engineered ultrafiltration (UF) system,currently employing Toray membranes but capable of operating with membranes from multiple vendors.Two parallel 0.5-mgd RO trains are designed with one operating in a 2-stage configuration and the secondoperating in 3-stage. Both trains include energy recovery devices for an interstage pressure boost, a designrecovery of 80 percent, and an average operating flux of 12 gallons per day per square foot (gfd). The 2-stage train includes Hydranautics ESPA2-LD elements, similar to the ESPA2 elements used in severalexisting advanced treatment facilities in California. The 3-stage train includes Toray TML20 membranes,projected to improve total nitrogen rejection, which will be a critical criterion for a potential full-scalefacility used for reservoir augmentation.The project provides a rare opportunity to compare multiple vendors and membrane configurations in sideby-side operation at essentially full-scale capacity, giving valuable performance information for any utilityconsidering or currently operating an advanced water purification facility.