AWWA JAW57270

For the Los Angeles Department of Water and Power (LADWP), membrane filtration offered the best option for treating water from the city's open reservoirs because the technology produced superior water quality, used minimal chemicals, required only a small footprint, and could be easily automated. Because of the lack of information about the comparative performance of major membrane filtration systems on high-quality open reservoir water, LADWP decided to pilot-test four membrane systems, two microfiltration and two ultrafiltration. In undertaking this research, the utility hoped to obtain practical, objective data that would help develop design criteria for full-scale installations with capacities of 6-10 mgd (23-38 ML/d). The membrane comparison considered a range of factors including flux, rate of fouling, and frequency and efficiency of chemical cleaning. Although all four systems tested produced similar quality water when the manufacturers' operating criteria were followed, the pilot testing did uncover important differences in flux, water recovery, and system maintenance. The key operating factors used in the city's final selection were the winning system's higher flux of 80 gfd (136 L/m2/h), its ability to withstand feedwater pressure of up to 60 psi (414 kPa), its relatively higher water recovery, and its resistance to a wide range of free chlorine concentrations. By evaluating the performance of the membrane systems at pilot-scale using reservoir water, LADWP was able to pinpoint the different membranes' potential strengths and shortcomings for the project's specific requirements. In addition, the pilot testing proved valuable because it provided essential operational information that could be used in the design of the full-scale installations. Includes 10 references, tables, figures.