Chemically enhanced primary treatment of municipal wastewater with ferrate(VI)

Chemically enhanced primary treatment (CEPT) with ferrate(VI), a multifunctional treatment agent, was investigated for the treatment of municipal wastewater in a laboratory-scale study. The treatment performance was evaluated at different ferrate(VI) doses (0.0-9.0 mg/L as Fe) and pH (6.0 and 7.5). The optimal removals of total suspended solids (TSS) (52%), total chemical oxygen demand (COD) (34%), and total phosphorus (47%) were achieved at the highest ferrate(VI) dose (9.0 mg/L as Fe) and the weakly alkaline condition (pH 7.5). The pollutant abatements principally ascribed to the formation of large-sized aggregate and ensuing sedimentation fell within the reported ranges of CEPT with traditional coagulants. However, different from conventional CEPT, ferrate(VI) appreciably removed recalcitrant dissolved organic phosphorus (49%) and simultaneously inactivated total coliform (3.30 log removal) and Escherichia coli (3.67 log removal) at 9.0 mg/L Fe(VI) and pH 7.5. The CEPT with ferrate(VI) offers an innovative alternative for improving municipal wastewater treatment. Practitioner points Ferrate(VI) represents a promising agent for chemically enhanced primary treatment (CEPT) of municipal wastewater. CEPT with ferrate(VI) can effectively alleviate TSS, total COD, and total P via the formation of large-sized aggregates and ensuing sedimentation. Ferrate(VI) can substantially remove recalcitrant dissolved organic phosphorus in municipal wastewater. Different from other CEPT coagulants, ferrate(VI) can appreciably inactivate bacterial indicators during CEPT. Higher ferrate(VI) dose and weakly alkaline pH favor the performance of ferrate(VI) CEPT.

Automated summary

Chemically enhanced primary treatment (CEPT) with ferrate(VI) was found to be effective in removing TSS, total COD, and total P from municipal wastewater by forming large-sized aggregates and facilitating sedimentation. Ferrate(VI) also demonstrated substantial removal of recalcitrant dissolved organic phosphorus and inactivation of bacterial indicators during the treatment process. Higher ferrate(VI) dose and weakly alkaline pH conditions were found to be favorable for the performance of ferrate(VI)-based CEPT.