Inactivation of Escherichia coli in domestic wastewater by modified septic tank treatment

Abstract

The Sustainable Development Goals (SDGs) targets for the improvement of drinking water, sanitation, and hygiene (WASH) makes the development of wastewater infrastructure in many countries is increasing. In Indonesia, the development of sewer connections remained limited nationally, most households still rely on on-site sanitation systems that mainly use septic tanks technology. Septic tank as watertight containment itself cannot provide the treatment to comply with the effluent standard of domestic wastewater, while a lot of application of septic tank do not follow by suggested technology for further treatment. That makes the need of septic tank improvement as modified septic tank (MST) system. One of parameters removed by MST better is microbial content. This research aims to identify Escherichia coli inactivation in MST, how the process along the treatment impact E. coli concentration and identification the effectiveness of trichloroisocyanuric acid (TCCA) tablet application as disinfectant in E. coli inactivation, and concurrently safe to environment. This research was conducted in laboratory using MST reactor set-up consists of pre-sedimentation chamber, fixed bed anoxic chamber, and MBBR chamber to treat synthetic wastewater. The synthetic wastewater, composed by C6H12O6, NH4Cl, KH2PO4 and E. coli culture is used. With influent E. coli concentration was 108-109, it was reduced to 108 in pre sedimentation chamber, 106-107 in fixed bed anoxic chamber, 105-106 in MBBR chamber and final effluent, all in MPN/100 ml unit. E. coli was inactivated 99.84% along MST process but with relative high concentration to be discharged. Application of TCCA tablet 90% active chlorine with contact time 15 minutes is adequate to inactivate E. coli completely but generates high concentration of chlorine residual.