JWSS - Journal of Water and Soil Science

Shortage of water resources and renewable per capita in last 30 years is put Iran on crisis threshold. Wastewater reuse is one of the battle solutions for water shortage and prevents wastewater depletion and environmental pollution. Thus, a pilot scale experiment was carried out to evaluate an integrated anaerobic/aerobic treatment for removal of BOD₅ and COD, also to reduction of hydraulic retention time by considering optimum removal efficiency. The pilot was an anaerobic/aerobic bioreactor type under continuous-feeding regime based on a central composite design. The pilot was studied in different retention time and aeration was carried out between 5-15 hours. According to different retention times for COD removal efficiency, 24 hours was selected as optimum hydraulic retention time, that it is comparable to those obtained for 48 hours and over in plant roughly and could remove COD and BOD in acceptable ranges, results showed that average removal efficiency for BOD₅ were 63.86 and 83.99 percent in aerobic and anaerobic phases, respectively. The average removal efficiency for COD was 76.5 and 74.35 percent for anaerobic and aerobic sections, respectively. The average removal efficiency for BOD₅ and COD in this integrated aerobic-anaerobic pilot 95.24 and 94.8 percent, respectively.

The reuse of treated wastewater in countries such as Iran that suffers from drought is considered an important challenge in water management programs. The application of modern wastewater treatment systems particularly attached growth systems, owing to the short time required for start-up, low land requirements, and the absence of problems associated with sludge handling may be a resolution. The objective of this study is to investigate the performance of the Moving Bed Biofilm Reactor (MBBR) in treating synthetic municipal wastewater and selecting an appropriate model. In this way, a bench-scale reactor possessing an effective volume of 15 liters, and synthetic wastewater with influent COD of 500 mg/l (similar to typical municipal wastewater) has been used and the experiments with media filling percentages of 30%, 50%, and 70% and hydraulic retention times (HRT) of 4, 8, and 12 hours have been carried out. The observed data show that the optimum bulk density and hydraulic retention time are 50% and 4 hours, respectively. Also, the kinetic study of reactor performance indicates that Grau second-order model has better conformation with Moving Bed Biofilm Reactor results. In addition, a regression model for predicting effluent COD based on the filling percentage and retention time is presented.