Work

Electrochemically assisted water softening with disinfectant production for wastewater reuse

Year: 2024

Type: article

Abstract: Highly purified wastewater has great potential for potable reuse but its treatment by commonly used technologies like reverse osmosis (RO) is facing challenges of membrane scaling/fouling. Herein, a chemical-free electrochemically assisted treatment process was developed and investigated for water softening with simultaneous disinfectant production; such a process could serve as a pretreatment step to control scaling/fouling in the subsequent RO treatment. The secondary effluent sampled from a local wastewater treatment plant was firstly treated by OH − -containing catholyte to raise the solution pH to ∼11 for hardness removal, and subsequently treated by H + - and chlor( am )ine-containing anolyte to adjust pH and achieve disinfection. The electrochemical treatment has decreased Ca 2+ and Mg 2+ from 1.8 and 0.9 mM to 0.3 and 0.4 mM with removal efficiencies of >80 % and > 50 %, respectively. Meanwhile, total coliform and E. coli were reduced by >5-log and > 4-log, and the final effluent had a pH of ∼7 and a residual chloramine concentration of ∼0.04 mM that would be suitable for further control of microbial contaminants. After 50-cycle operation, cathodic scaling was observed to reduce the cathodic OH − generation from 9.10 to 6.03 mM, resulting in an increase in energy consumption from 3.1 to 4.5 kWh m −3 . A mild acidic washing method was employed to remove scale deposits and recover cathodic OH − generation performance, enabling additional 30 cycles of consistent performance. Those results would encourage further exploration of electrochemical processes as a chemical-free pretreatment method for RO membrane fouling control in potable reuse. • Electrochemical cells can achieve water softening with chloramine formation • Cathodically generated OH − help remove hardness ions • Anolyte is used to adjust pH and introduce chloramine in the final effluent • Removal of microorganisms is simultaneously accomplished

Source: Desalination

DOI: 10.1016/j.desal.2024.118466

Authors: Kaichao Yang, Zhen He

Institution: Washington University in St. Louis

Language: English

Topic: Advanced oxidation water treatment

Subfield: Water Science and Technology

Field: Environmental Science

Domain: Physical Sciences

SDGs: Clean water and sanitation, Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $4,580