Abstract

Background and Objective: Considering 829000 annual diarrhoeal deaths due to water pollution worldwide, the World Health Organization has emphasized that countries should reduce this rate by upgrading their was tewater treatment sys tems. The purpose of this s tudy was to evaluate the performance of a modified up flow septic tanks reactor for treatment of synthetic was tewater. Materials and Methods: In this experimental s tudy, a modified septic tank sys tem based on the ups tream hydraulic regime, and also a conventional septic tank sys tem was designed, manufactured, and operated. The municipal was tewater was used to operate, and synthetic was tewater was used to maintain. The major performance indicators of septic tanks include: volatile solids (VS), volatile suspended solids (VSS), total suspended solids (TSS) and chemical oxygen demand (COD) were sampled and measured in triplicates. The experiments were done in three hydraulic retention times of 24, 48, and 72 hr. Finally, the results of the s tudy were analyzed by s tatis tical tes ts in the SPSS software. Results: The average removal of TSS, VS, VSS, and COD in HRT 24 h for the conventional reactor were 55.07, 27.36, 30.82, and 55.52, respectively, and for the ups tream-modified reactor at HRT 24 h were 66.57, 34.05, 38.47, and 65.57, respectively. Conclusion: Changing septic tanks to up flow regimes and creating a cylindrical shape in conventional septic tanks, the removal efficiency of conventional septic tanks was improved, and the effluent contamination load was reduced. © 2020, Tehran University of Medical Sciences. All rights reserved.