To investigate the feasibility of implementing decentralized sewage treatment systems aiming to meet environmental standards, the performance of three decentralized wastewater treatment plants (WWTPs) comprising septic tanks and anaerobic filters (ST+AF) was evaluated. The ability of the WWTPs to comply with the provisions of the legislation and the technical literature was investigated by monitoring physical and chemical parameters at the entrance and exit of the WWTPs, from May 2017 to August 2018. Considering that factors such as operational routine, design of treatment systems, and the existence of pluvial contributions to the sewage network can influence the performance of WWTPs, an investigation of these factors was conducted. The results show that the ST+AF systems can meet the requirements of the legislation. The hypothesis raised in this study is that factors such as cleaning routine and dimensioning of the treatment units can influence the performance of the systems. The best performance was found in the WWTP submitted to frequent cleaning and whose ST dimensions were closest to those recommended by technical standards. The average annual efficiencies of removal of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in this WWTP assumed values of 93 and 89%, while its solid effluents presented concentrations 82% below the limit established in legislation. Finally, no rainwater contributions were found in the WWTPs, which may be associated with the use of short collection networks in decentralized systems.
Keywords: Anaerobic treatment; Domestic sewage; Performance indicators; Sanitation; Small systems; Wastewater treatment.
© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.