Optimizing Preliminary Disinfection for Indirect Potable Reuse

The Los Angeles Department of Water and Power (LADWP) will be implementing indirect potable reuse for its Donald C. Tillman Water Reclamation Plant. The facility will utilize microfiltration, reverse osmosis, and advanced oxidation to produce water for groundwater recharge. LADWP is conducting a 15-month pilot test, evaluating alternative processes, including the best method of disinfection for biogrowth control, as well as the best supply source when both secondary effluent and tertiary filtrate are available. While tertiary filtrate is traditionally considered a higher quality water to feed advanced treatment facilities, the use of polymer ahead of the tertiary filters is of concern, given its anticipated impact on n-Nitroso-dimethylamine formation and on potential fouling of the membranes. This paper presents the findings of bench-top and pilot-scale studies looking at the impact of different source waters and preliminary disinfection approaches on disinfection byproduct formation and membrane performance.