Direct Potable Reuse Piloting: Optimizing Chloramination, Operationalizing Ultrafiltration, and Understanding Zero Liquid Discharge Options

A pilot study was deployed at the John T. Hickerson Water Reclamation facility to analyze the viability of high recovery direct potable water reuse (DPR), aiming for zero liquid discharge (ZLD). This pilot consists of a chloramination system and ultrafiltration (UF) as pretreatment for reserve osmosis (RO) followed by UV-peroxide, granular activated carbon (GAC), and concentrate-enhanced recovery reverse osmosis (CERRO). Stabilizing the chloramination and UF system was the first step to ensure efficiency during the downstream processes. The formation of monochloramine is essential for the mitigation of biofouling of the UF membranes. The formation of monochloramine occurs by specific liquid ammonium sulfate (LAS) and sodium hypochlorite (bleach) dosing. However, the varying quality of the influent prevented the constant formation of an exact concentration of monochloramine. The specific flux measured the efficiency of the ultrafiltration system. Since specific flux is affected by flux, biofouling in the membranes negatively impacts its stabilization. Backwashes and chemically enhanced backwashes were performed as needed to mitigate biofouling.Water quality parameters were analyzed, including pH, conductivity, oxidation-reduction potential, turbidity, alkalinity, ion chronography, and total dissolved solids. Results demonstrate that chloramination and UF are effective pretreatment processes as concentrations of elements and turbidity decreased from influent samples to UF filtrate samples. Future research will include studying the efficacy of the RO, UV-peroxide, GAC, and CERRO systems, which will produce a high salinity concentrate. The power consumption of several systems to further decrease the liquid present (heated screw conveyor, land disposal, and evaporation) in the concentrate are discussed.