Disinfection of Irrigation Water Using Titanium Electrodes

Abstract

This work reports on the electrochemical disinfection of natural irrigation water collected from the Waiahole Ditch Irrigation System in Hawaii using a batch cell assembled with titanium electrodes as both anode and cathode. Disinfection experiments were performed by applying a polarity-reversing direct current between the two titanium electrodes. The naturally occurring concentration of chloride in the water was 1.84 mg l−1 and no other chemicals were added. The applied current density was varied between 0 mA cm−2 and 2 mA cm−2, and the half-period (T/2) of the polarity-reversing direct current was varied between 5 s and 60 s. The best disinfection performance was achieved at 2 mA cm−2 and T/2 = 10 s, requiring only 5 min of treatment for the complete disinfection of E. coli (4-log reduction). E. coli was inactivated by free chlorine species electrogenerated at the titanium electrodes. Hydrogen peroxide, short-lived oxidants, and direct electron transfer most likely had minor contributions to the disinfection process. During the disinfection experiments, the concentrations of disinfection byproducts (ClO3 −, CHCl3, CHBrCl2, CHBr2Cl, and CHBr3) were significantly lower than recommendations for drinking water. The titanium electrodes consumed less electrical energy than platinum-coated titanium electrodes because they needed a lower current density to achieve similar disinfection efficiency.

Pyrite-based denitrification combined with electrochemical disinfection to remove nitrate and microbial contamination from groundwater

“…Patermarakis and Fountoukidis 44 in one of the first studies on electrochlorination with a low-cost Ti electrode achieved in average a 5-log removal of germs, without specifying the type, with 89.3 A h m −3 charge investment, resulting in 4 kW h m −3 SECw. A Pt/Ti anode was also used in the study of Qing et al 30 that reduced the microbial content of irrigation water by 5 log with 9 A h m −3 charge investment and achieved a three times higher free chlorine concentration, even though the initial Cl − concentration was as low as 1.85 mg/L. In their study to treat microbially contaminated groundwater, De Battisti et al 28 used a BDD electrode that eliminated the 200 MPN 100 mL −1 TC and E. coli load with a 28 A h m −3 charge density, however, no results were reported on the cell voltage obtained to allow for SECw calculations.…”

“…Regardless of the mechanism that led to the reduction of chlorination rates in the last hour of the experiment, what is most important in the case of disinfection is maintaining consistency and a stable voltage to ensure effective treatment. One way to achieve this may be through reverse polarity 30 , 44 . To ensure long-term operational stability of the electrodes for disinfection, further testing is required.…”

“…The ratio of the two is determined by the solution pH 26 , 27 . Electrochemical disinfection has been tested for directly treating groundwater or irrigation water contaminated with pathogens 28 – 30 , but also as a polishing step for bioreactor effluents 27 , 31 . The disinfection efficiency will depend upon the anode material, the Cl − concentration of the electrolyte, the pH and upon the organics and ammonia content of the water to be treated 22 .…”

Potentiometric Free Chlorine Detection without Using Conventional Reference Electrodes

“…Due to its strong oxidizing and sterilizing power, it can easily oxidize various organic pollutants and inactivate bacteria that may lead to infectious diseases. [2][3][4] However, it is consumed by complicated reactions while propagating through the water distribution system. 5 Recently, aging and deterioration of water supply infrastructures have become serious societal problems in many countries.…”