Energy Efficient Advanced Treatment Process for Microconstituents Removal

The objective of this study was to demonstrate the effectiveness of an advanced treatment process not utilizing reverse osmosis (RO) for removal of hormones, pharmaceuticals, and flame retardants (collectively termed microconstituents or chemicals of emerging concern [CECs]) from municipal effluent. The advanced treatment process consisted of (in the order of use): membrane filtration (MF), ozonation (O3), and biological activated carbon (BAC). The 15- month, continuous flow, 10.7 gpm, MF-O3-BAC demonstration study was conducted in two phases at the Reno-Stead Water Reclamation Facility (RSWRF): Phase 1 focused on ozone process optimization and bromate mitigation; Phase 2 was a 10-month steady-state demonstration of process performance. For RSWRF effluent, an ozone dosage of at least 5 mg/L was needed for desired CEC removals. Peroxide (year-round) and ammonia (seasonal) were added to mitigate bromate formation during ozonation. BAC removed flame retardants, and ozonation byproducts including NDMA (N-Nitrosodimethylamine), aldehydes, and biodegradable organic carbon. Findings of this study imply that MF-O3-BAC treatment is equally effective as RO-based treatment for CEC removals, but with substantially less energy utilization.