Nitrate removal from drinking water using direct current or solar powered electrocoagulation

Abstract

Nitrate levels are frequently high in ground and surface waters mainly because of anthropogenic activities. Electrocoagulation (EC) is a viable alternative to conventional coagulation in drinking water treatment and has been successfully applied to remove nitrate from drinking water. The objective of this study was to determine optimum operating conditions for maximizing nitrate removal from drinking water using electrocoagulation followed by settling and filtration. Batch experiments were carried out using iron electrodes (mild steel) and four types of water were tested (groundwater, tap water, untreated water from IIT Water Works and double distilled water). Experiments were conducted with direct current (DC) power or solar power. Operating parameters such as initial nitrate concentration, voltage, electrocoagulation time and settling time were varied to determine optimum conditions for achieving maximum removal efficiency. Nitrate removals after electrocoagulation and after settling were determined for all experiments. In 22 DC power experiments with all waters tested, maximum removal efficiencies were 37% (after EC) and 38.21% (after EC and settling). The highest removal efficiency was obtained in double distilled (DD) water at 10 V, initial nitrate concentration of 452 ppm, EC time of 4 h, settling time of 4 h and an initial pH of 9.89. Multiple linear regression analysis of DD water experiments was done. Model 1 based on removal efficiency after EC only was found to be a good fit and was statistically significant. Five solar experiments were carried out and the maximum removal efficiency obtained was 53% with 3 h of electrolysis time. The initial nitrate concentration was 95.53 mg/L, voltage was 14 V and initial pH was 10.8. Electrocoagulation coupled with solar energy can be used in rural areas in decentralized mode.