JWSS - Journal of Water and Soil Science

Detergents are the main organic pollutants in the industrial and domestic wastewater. Electro-chemistry methods are advanced purification methods developed with high efficiency features. The goal of this study was to investigate the possibility of using electrocoagulation and the complementary flocculation process to achieve the highest removal efficiency of the detergent COD. So, with iron electrode, synthetic samples at the concentrations of 500, 750 and 1000 mg/l (with COD of 217, 268 and 370 mg/l, respectively) and with the initial pH levels of 5, 7.3 and 9 were tested. Variable parameters during the electrocoagulation process included the current duration at 3, 5 and 10 minutes, and the current density was at 4, 10, 16 and 22 mA/cm². The primary results showed that in the optimum conditions, the coagulation process and complementary flocculation could reduce the sample’s COD with an initial concentration of detergent (500 mg/l) from 217 mgO₂/l to 81.30 mgO₂/l. The electrocoagulation method could reduce the chemical oxygen demand to below the standard limit of environmental discharge (200 mgO₂/l) and compensate for the possibility of the irrigation of green spaces due to water shortages.

Shortage of water resources and renewable per capita in last 30 years is put Iran on crisis threshold. Wastewater reuse is one of the battle solutions for water shortage and prevents wastewater depletion and environmental pollution. Thus, a pilot scale experiment was carried out to evaluate an integrated anaerobic/aerobic treatment for removal of BOD₅ and COD, also to reduction of hydraulic retention time by considering optimum removal efficiency. The pilot was an anaerobic/aerobic bioreactor type under continuous-feeding regime based on a central composite design. The pilot was studied in different retention time and aeration was carried out between 5-15 hours. According to different retention times for COD removal efficiency, 24 hours was selected as optimum hydraulic retention time, that it is comparable to those obtained for 48 hours and over in plant roughly and could remove COD and BOD in acceptable ranges, results showed that average removal efficiency for BOD₅ were 63.86 and 83.99 percent in aerobic and anaerobic phases, respectively. The average removal efficiency for COD was 76.5 and 74.35 percent for anaerobic and aerobic sections, respectively. The average removal efficiency for BOD₅ and COD in this integrated aerobic-anaerobic pilot 95.24 and 94.8 percent, respectively.