Impacts Of Membrane Process Residuals On Wastewater Treatment: Utility Surveys and Results

The WateReuse Foundation (WRF) initiated the study, “Impacts Of Membrane Process Residuals On Wastewater Treatment to provide practical guidance to utilities on evaluating and managing these residuals. One component of this study was to survey water and wastewater utilities. Two surveys were developed: one for wastewater utilities receiving membrane residuals, and one for water (potable) utilities routing residuals to wastewater systems. The objectives of the surveys were to learn from utilities: their experience with membrane residuals disposal; problems (with residuals disposal, planning, or otherwise) they have experienced with these discharges, and approaches taken to handle them; control procedures in place, or that they suggest, for addressing membrane residuals disposal; and suggestions on future research needs.Survey response rates were relatively low, as has been the case, unfortunately, for other, similar utility surveys. Nevertheless, a great deal of useful information was garnered from the surveys. A number of utility personnel reviewing and/or taking the surveys found much of the information in the surveys to be very informative and useful, such that the surveys point to information needs for developing planning and regulatory approaches that will be important as membrane usage grows.In discussing the surveys and results, potential problems with membrane residuals are reviewed, including effects on physical-chemical and biological unit operations. In addition, evaluation and permitting approaches are discussed for considering accepting membrane residuals discharges to a wastewater system. Evaluation procedures followed at different utilities include monitoring studies before and/or after membrane discharge is initiated. Discharge permits can include testing requirements, and imposition of quantitative limits, on specific discharge parameters, as necessary.