Evaluation of on-Site Sanitation Systems: Efficiency of Baffled Septic Tanks

Abstract

Domestic wastewater from homes without sewerage is discharged directly into the ground, rivers or streams, which generates health and pollution problems. Septic tanks are used as an on-site treatment by a significant fraction of the world's population. This study aimed to evaluate the efficiency of domestic wastewater treatment using septic tanks with baffles implemented in rural households. The septic tanks were built and evaluated as part of a research project, focused on decentralized domestic wastewater treatment systems at the rural level. The septic tanks operated with detention times of 4.44; 2.67 and 1.90 days. The data was obtained through five monitoring campaigns with a fortnightly frequency, taking water samples at the entrance and exit of each septic tank. After sample collection, concentration levels of BOD5, COD, total suspended solids (TSS), nitrates, and phosphates were determined according to Standard Methods for the Examination of Water and Wastewater. A BOD5 removal of 31.28±8.69%, COD removal of 30.52±7.89%, TSS removal of 39.39±11.90% was obtained, while there was an increase in nitrates of 41.41±3.85% and an increase in phosphates of 46.89± 36.77%. The removal values were affected by the retention time and the initial concentration of the parameters. The data could be useful in designing and operating on-site septic tanks, characterizing strictly domestic contamination, as well as incorporating them into future research or innovations related to single-family homes. Likewise, these data could be entered into the databases used for the evaluation of septic tanks with baffles.