M.F. Espinosa1*, M. von Sperling2 and M.E. Verbyla3
1 Civil Engineer from the University of Cuenca, Ecuador. Master’s student in the Graduate Program in Sanitation, Environment and Water Resources of the Federal University of Minas Gerais (UFMG), Brazil. Students Scholarship Program – Agreement Graduate – PEC-PG, CAPES / CNPq – Brazil. 2 PhD in Environmental Engineering from Imperial College London. Professor at the Department of Sanitary and Environmental Engineering at UFMG, Brazil. 3 PhD in Environmental Engineering, University of South Florida – 4202 E. Fowler Ave. ENB 118, Tampa, FL 33620 – USA(free)
Waste stabilization ponds (WSPs) and their variants are one the most widely-used wastewater treatment system in the world and are particularly common in small cities and towns. The objective of this research was to assess the performance of a large number of WSP systems located in Brazil, Ecuador, Bolivia and the United States using statistical analysis from available monitoring data. A total of 388 full-scale pond systems with seven different configurations were studied, comprising combinations of aerobic, anaerobic, facultative, and maturation WSPs, as well as anaerobic reactors followed by WSPs. Descriptive statistics were obtained for each WSP system of the influent and effluent concentrations and the removal efficiencies for BOD5, TSS, N-ammonia and thermotolerant (fecal) coliforms (TTC) or E. coli, leading to a broad characterization of actual treatment performance based on more than 57,700 data. The median influent concentrations of BOD5, TSS, and N-ammonia were 431 mg/L, 355 mg/L and 41 mg/L, respectively; effluent concentrations were 56 mg/L, 71 mg/L, and 12 mg/L, respectively. The median removal efficiencies from all WSP systems were 80% for BOD5, 75% for TSS and 57% for N-ammonia. The influent concentrations of TTC and E. coli were consistent with ranges reported previously in the literature, with overall geometric mean removals of 3.0 log10 units for TTC and 2.2 log10 units for E. coli in all WSP systems. In general, the systems with Aerated Pond + Facultative/Maturation Pond, Anaerobic Reactor + Facultative Pond and Anaerobic Reactor + Other treatment + Maturation Pond had higher removal efficiencies than the systems with Facultative Pond and Facultative Pond + Maturation Pond. However, future research is needed to better understand the influence of design, operational, or environmental factors, particularly hydraulic retention time, temperature, and solar insolation.