Simplified wastewater treatment allowing compliance to several criteria for reuse

Abstract UASB reactors followed by polishing ponds comprise simple and economic wastewater treatment systems, capable of reaching a very high removal efficiency of pathogenic organisms, leading to the potential use of the effluent for unrestricted irrigation. However, for other types of reuse (urban and industrial), ponds are limited in the sense of producing effluents with high suspended solids (algae) concentrations. The work investigates a system with coarse rock filters for polishing the pond effluent. The overall performance of the system is analysed, together with the potential for different types of reuse. The excellent results obtained (mean efluente concentrations: BOD: 27 mg L-1, COD: 97 mg L-1, SS: 26 mg L-1, E. coli: 450 MPN per 100mL) indicate the possibility of unrestricted use of the effluent for agriculture and restricted urban and industrial uses, according to WHO and EPA.