Removal of micropollutants by an electrochemically driven UV/chlorine process for decentralized water treatment

Yinqiao Zhang; Huijiao Wang; Yang Li; Bin Wang; Jun Huang; Shubo Deng; Gang Yu; Yujue Wang

doi:10.1016/j.watres.2020.116115

Removal of micropollutants by an electrochemically driven UV/chlorine process for decentralized water treatment

Water Res. 2020 Sep 15:183:116115. doi: 10.1016/j.watres.2020.116115. Epub 2020 Jul 1.

Authors

Yinqiao Zhang¹, Huijiao Wang¹, Yang Li¹, Bin Wang¹, Jun Huang¹, Shubo Deng¹, Gang Yu¹, Yujue Wang²

Affiliations

¹ School of Environment, Beijing Key Laboratory for Emerging Organic Contaminants Control, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China.
² School of Environment, Beijing Key Laboratory for Emerging Organic Contaminants Control, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China. Electronic address: wangyujue@tsinghua.edu.cn.

PMID: 32652347
DOI: 10.1016/j.watres.2020.116115

Abstract

The ultraviolet/chlorine (UV/Cl₂) process is an emerging advanced oxidation technology for micropollutant abatement in water and wastewater treatment. However, the application of the conventional UV/Cl₂ process in decentralized systems is limited by the transport and management of liquid chlorine. To overcome this limitation, this study evaluated an electrochemically driven UV/Cl₂ (E-UV/Cl₂) process for micropollutant abatement under conditions simulating decentralized water treatment. The E-UV/Cl₂ process combines UV irradiation with in situ electrochemical Cl₂ production from anodic oxidation of chloride (Cl^-) in source waters. The results show that with typical Cl^- concentrations present in water sources for decentralized systems (30-300 mg/L Cl^-), sufficient amounts of chlorine could be quickly electrochemically produced at the anode to enable E-UV/Cl₂ process for water treatment. Due to its multiple mechanisms for micropollutant abatement (direct photolysis, direct electrolysis, Cl₂-mediated oxidation, as well as hydroxyl radical and reactive chlorine species oxidation), the E-UV/Cl₂ process effectively eliminated all micropollutants (trimethoprim, ciprofloxacin, metoprolol, and carbamazepine) spiked in a surface water in 5 min. In contrast, at least one micropollutant with ∼20-80% residual concentrations could still be detected in the water treated by 10 min of UV irradiation, chlorination, electrolysis, and the conventional UV/Cl₂ process under similar experimental conditions. The electrical energy per order (E_EO) for micropollutant abatement ranged from 0.15 to 1.8 kWh/m³ for the E-UV/Cl₂ process, which is generally comparable to that for the conventional UV/Cl₂ process (0.14-2.7 kWh/m³). These results suggest that by in-situ generating Cl₂ from anodic oxidation of Cl^-, the E-UV/Cl₂ process can overcome the barrier of the conventional UV/Cl₂ process and thus provide a promising technology for micropollutant abatement in decentralized water treatment systems.

Keywords: Advanced oxidation process; Decentralized water treatment; Pharmaceutical; UV/Chlorine.

MeSH terms

Chlorine
Oxidation-Reduction
Ultraviolet Rays
Wastewater / analysis
Water Pollutants, Chemical*
Water Purification*

Substances

Waste Water
Water Pollutants, Chemical
Chlorine