Alternative Technologies for Indirect Potable Reuse: A New Paradigm

Rising wastewater effluent discharge standards have led to more advanced wastewater treatment while growing demand has taxed existing drinking water supplies, making planned indirect potable reuse a feasible scenario for more utilities. A majority of planned indirect potable reuse schemes currently in operation or planned to be employed in the U.S. make use of advanced oxidation processes (AOPs) and reverse osmosis (RO), the full advanced treatment (FAT) technology, to ensure maximum removal of known and unknown contaminants.A 10 month indirect potable reuse pilot study in the Southeastern US is investigating the advanced treatment of wastewater for groundwater recharge to a brackish aquifer using ultrafiltration, ion exchange, ozone and ultraviolet light (UV) based AOPs, as well as biofiltration. Since this study is focusing on recharge options to a brackish receiving water body, these treatment processes are being examined as an alternative to the FAT approach of RO membranes. However, in addition to low nutrient limits (Orthophosphate < 0.01 mg/l), the regulatory community is still concerned about the potential for emerging contaminants entering the environment and water supply. Therefore, multiple pilot plants are being operated to evaluate and validate the formation and removal of nitrosamines and the removal of other emerging contaminants by these processes. The avoidance of RO membranes in the reclamation scheme could save the City upwards of $100 million (US) in capital expenses, in addition to the savings from operation and maintenance of a high pressure membrane system. This approach may also reduce the carbon footprint of the overall system.