Domestic wastewater treated for agricultural reuse

Abstract

Four post-treatment systems of an upflow anaerobic sludge blanket (UASB) reactor were evaluated regarding chemical and sanitary qualities. At an experimental station for biological treatment of sewage (EXTRABES) located in Campina Grande - PB, Brazil, the physical, chemical and biological parameters of the effluents from a UASB reactor and its post-treatment systems were monitored for two years. A baffled anaerobic filter (AF), a horizontal gravel bed (GB); a constructed wetland (CW) and a series of five polishing ponds were the systems used to treat the UASB reactor effluent. The chemical oxygen demand (COD) data in the post-treatment effluents ranged from 60 to 80 mg.L^-1, which means a good efficiency in organic matter removal, exception made for polishing ponds (PP) (155 mg.L^-1) due to the algal growth. The greater nutrient removal was observed in the CW, which can be explained by the presence of the macrophytes. Concerning pathogens occurrence there is not a significant difference between the AF and the CW effluents, both with appropriate concentrations for restricted reuse. Only the PP had concentrations less than 103 CFU.100 ml^-1, the maximum value determined by the World Health Organization for unrestricted reuse. The helminthes eggs were efficiently removed into all analyzed treatments. The UASB was efficient in terms of organic matter and solids removal, favoring all post-treatment systems.

Key words: Domestic wastewater treatments, sanitary quality, reuse.