Direct electrolysis of underground water in production

Summary

The results of production tests of flow-through electrolyzers operating in the mode of direct electrolysis of natural surface water are presented. In the process of electrolysis, sodium hypochlorite for disinfecting water is synthesized from the chlorides present in the source water. Electrolyzers are a part of the water treatment plant. Krinitsa-45 block-modular water treatment plant with a capacity of 45 m³/day has been in operation since 2020. Flow-through electrolyzers are used for the disinfection of raw water (primary disinfection) and drinking water (secondary disinfection) by direct electrolysis; they operate with current reversal in automatic mode. The oxide coating of the electrodes is OIRTA (oxide-iridium-ruthenium-titanium anode) with the addition of tantalum. In the course of studies, the process parameters of the operation of the electrolyzers were determined. The current density was changed from 25 to 75 A/m², the concentration of active chlorine was determined, and the change in the voltage on the electrolyzer terminals was recorded. The measurements were taken every fortnight during past three years. Current density 40–50 A/m² was considered as optimal in terms of efficiency since it provided for 10–12% current efficiency by chlorine and 2–2.8 mg/dm³ active chlorine concentration. Using current reversal (polarity reversal time +1 hour and –1 hour) provided for operating a flow-through electrolyzer with natural water with a total hardness of about 9–11 meq/dm³ eliminating the use of hydrochloric acid for regular washing of the electrodes.

Key words

water disinfection , membraneless electrolysis , low-concentrated sodium hypochlorite , direct electrolysis of surface water