Removal of sulfides and sulfur recovery from anaerobically treated secondary wastewater using anion exchange

Abstract

Mainstream anaerobic biological secondary treatment of wastewater can reduce energy demand and biosolids production, but forms sulfides that interfere with disinfection for non-potable or potable wastewater reuse. In this study, pilot-scale anion exchange columns were evaluated for sulfide removal from a staged anaerobic fluidized membrane bioreactor (SAF-MBR). PWA5, a type 1 strong base anion exchange resin, performed best among four resins for removing sulfides from a synthetic solution with 160 bed volumes (BVs) treated before 20% breakthrough. Increasing the pH of SAF-MBR effluent to 8.6 doubled the number of BVs treated before 20% sulfide breakthrough from 22 BVs to 46 BVs, while removing 30% of DOC, 80% of UV₂₅₄, and 90–95% of anionic surfactants. The NaCl brine used to regenerate the columns was treated with H₂O₂ to oxidize sulfides to elemental sulfur for recovery. Reuse of the NaCl brine over 5 anion exchange treatment cycles indicated no decline in sulfide removal performance. Operating cost estimates based on results from experiments with a two columns in series configuration and 5 cycles of brine reuse ($0.42 per m³) were competitive with previous estimates for direct sulfide oxidation by H₂O₂ in SAF-MBR effluent, with costs decreasing to $0.33 per m³ for 10 cycles of brine reuse.