Low voltage iron electrocoagulation as a tertiary treatment of municipal wastewater: removal of enteric pathogen indicators and antibiotic-resistant bacteria

In this paper we analyse the feasibility of low voltage iron electrocoagulation as a means of municipal secondary effluent treatment with a focus on removal of microbial indicators, Antibiotic Resistant Bacteria (ARB) and nutrients. A laboratory scale batch unit equipped with iron electrodes was used on synthetic and real secondary effluent from a municipal wastewater treatment plant. Synthetic secondary effluent was separately assayed with spiked Escherichia coli WR1 and with bacteriophage (Phi X174, while real effluent samples were screened before and after treatment for E. coli , Extended Spectrum Betalactamaseproducing E. coli , Enterococci, Vancomycin Resistant Enterococci, Clostridium perfringens spores and somatic coliphages. Charge dosage (CD) and charge dosage rate (CDR) were used as the main process control parameters. Experiments with synthetic secondary effluent showed > 4log(10) and > 5log(10) removal for phage (Phi X174 and for E. coli WR1, respectively. In real effluents, bacterial indicator removal exceeded 3.5log(10), ARB were removed below detection limit ( >= 2.5log(10)), virus removal reached 2.3log(10) and C. perfringens spore removal exceeded 2.5log(10). Experiments in both real and synthetic wastewater showed that bacterial removal increased with increasing CD and decreasing CDR. Virus removal increased with increasing CD but was irresponsive to CDR. C. perfringens spore removal increased with increasing CD yet reached a removal plateau, being also irresponsive to CDR. Phosphate removal exceeded 99%, while total nitrogen and chemical oxygen demand removal were below 15% and 58%, respectively. Operational cost estimates were made for power and iron plate consumption, and were found to be in the range of 0.01 to 0.24(sic)/m(3) for the different assayed configurations. In conclusion, low voltage Fe-EC is a promising technology for pathogen reduction of secondary municipal effluents, with log(10) removals comparable to those achieved by conventional disinfection methods such as chlorination, UV or ozonation. (C) 2020 The Author(s). Published by Elsevier Ltd.

Automated summary

This study demonstrates the feasibility of low voltage iron electrocoagulation for municipal secondary effluent treatment, showing effective removal of microbial indicators, Antibiotic Resistant Bacteria (ARB), and viruses. Increasing the charge dosage of iron electrodes can enhance bacterial removal efficiency.