Impact of a Sand Filtration Pretreatment Step on High-Loaded Greywater Treatment by an Electrocoagulation Technique

Greywater (GW) treatment by the electrocoagulation (EC) technique alone might not meet the required standards in terms of pollutant removal, specifically when GW contains high loads of pollutants. In this preliminary study, a sand filtration (SF) unit was integrated with the EC technique as a pretreatment step to enhance the EC process for treating high-loaded GW. Three different voltage gradients were investigated (5 V/cm, 10 V/cm, and 15 V/cm) in the EC unit. The results demonstrated that the pretreatment SF step can contribute significantly to reducing pollutant concentrations in the greywater to be treated by EC. In terms of physical impurities, the results showed that the SF pretreatment step reduced the turbidity and the color of the treated GW by 28.4%, and 9.4%, respectively. The COD concentration was reduced by 25.5% by the SF step, which allowed a reduction of EC steady state time in the EC unit from 45 min to 30 min at an applied voltage of 15 V/cm. In addition, a high COD removal rate of 87.8% from high-load greywater was achieved with an energy consumption of only 4.11 kWh/m(3) in comparison with 6.21 kWh/m(3) without the SF step, which is equivalent to a 34% saving in energy consumption.

Automated summary

In this study, a sand filtration (SF) unit was integrated with the electrocoagulation (EC) technique as a pretreatment step to improve the treatment efficiency for high-loaded greywater. The results showed that the SF pretreatment step significantly reduced pollutant concentrations in the greywater. The SF step also reduced turbidity and color by 28.4% and 9.4% respectively, and decreased COD concentration, allowing for a shorter steady state time in the EC unit and a higher COD removal rate with lower energy consumption.