Electrochemical disinfection of irrigation water with a graphite electrode flow cell

Abstract

In this work, we report experimental studies on the disinfection of irrigation water using a flow cell assembled with low-cost graphite plates as both anode and cathode. Natural irrigation waters collected from two irrigation locations (Reservoir 225 and Bott Well Pond) in Hawaii were used, and synthetic irrigation waters were prepared based on the chemical analysis of natural irrigation waters. The concentration of chloride was 10.2 mg/L in the synthetic Reservoir 225 water and 6.9 mg/L in the synthetic Bott Well pond water. Escherichia coli K12 ER2738 was selected as a model bacterium to evaluate the disinfection capability of the flow cell. Experiments performed in the synthetic irrigation waters showed that E. coli was inactivated by free chlorine species electro-generated from oxidation of chloride ions at the graphite anode. Complete removal of E. coli was achieved within 10 min in the synthetic irrigation waters. The disinfection of the natural irrigation waters took about four times longer than the disinfection of the synthetic irrigation waters. This result is most likely due to the presence of organic matter (and possibly other oxidizable species) in the natural irrigation waters. © 2020 Water Environment Federation • Practitioner points • Electrochemical flow cell disinfects to 99.9% with commercial graphite electrodes. • E. coli is removed in 10 min from synthetic irrigation water by a flow cell. • E. coli removal takes 4× longer in natural irrigation water. • A minimum current density of ≥1 mA/cm 2 is required for disinfection. • The primary disinfection mechanism is through chlorine generated from chloride ions.

Disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water using electrochemical flow cells: A case study in Hawaii

“…In contrast, in this field study, we used a smaller flow cell incorporating 2.5″ × 2″ graphite plates as both electrodes (Figure b). We also note that the volume of the irrigation water treated in each experiment was 2000 ml in our previous laboratory studies (Qing, Anari, Foster, et al, 2021), while it was 400 ml in this field study. Therefore, the ratio between the irrigation water volume and the electrode area was similar in the laboratory studies and field studies.…”

“…A detailed description of the flow cell design has been given in our previous publications (Qing, Anari, Abolhassani, et al, 2021; Qing, Anari, Foster, et al, 2021). Briefly, the flow cell consists of anode and cathode half‐cells, and in each of them, the electrode was fixed in an HDPE frame using 100% silicone sealant (Polyseamseal, Loctite) (Figure ).…”

“…Therefore, the storing and transportation of highly reactive chemical disinfectants such as chlorine gas and sodium hypochlorite are not necessary. In our previous works, we developed electrochemical flow cells for disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water (Qing, Anari, Abolhassani, et al, 2021; Qing, Anari, Foster, et al, 2021). Using a flow cell assembled with PtRu/graphite anode and graphite cathode, ammonia was efficiently removed from aquaculture wastewater via indirect oxidation (Qing, Anari, Abolhassani, et al, 2021).…”

“…Microorganisms, in particular, are quickly inactivated during frozen storage (Gao et al, 2006; Semanchek & Golden, 1998). Therefore, we carried out field tests on disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water using the electrochemical flow cells designed and tested in our previous laboratory studies (Qing, Anari, Abolhassani, et al, 2021; Qing, Anari, Foster, et al, 2021). We are reporting on two topics because both of them depend on the anodic oxidation of chloride ions to chlorine, which in turn oxidizes ammonia to nitrogen gas and inactivates pathogens.…”

Editorial: April 2021

“…April's issue of Water Environment Research presents new research on topics important to water quality engineers and scientists: biodegradation of hazardous organic compounds (Lee & Ulrich, 2020) and microconstituents (Rao et al, 2020), removal of fluoride (Bilici Baskan & Biyikli, 2020), membrane fouling (Liu et al, 2020), and electrochemical disinfection (Qing et al, 2020), among others. The issue also includes original research on nutrient removal from around the world: the microbial communities involved in anammox from Las Barrillas estuary, Mexico (Ronzón Bravo et al, 2020), impact of COD/TN on anammox for influents simulating those from Vietnam (Nguyen & Tran, 2020), and electrocoagulation for ammonia removal from landfill leachate in Malaysia (Hamid et al, 2020).…”