Transformation of Waste Stabilization Ponds: Reengineering of an Obsolete Sewage Treatment System

Abstract

Waste Stabilization Ponds (WSPs) are commonly used for sewage treatment. These systems are composed of a series of ponds: (1) anaerobic ponds, (2) facultative ponds, and (3) maturation ponds. WSPs generally produce good-quality effluent in terms of organic matter and pathogen removal, but their application has disadvantages. The most serious disadvantages are a long retention time, the release of biogas, and the impossibility of removing nutrients. A promising alternative to the use of WSPs is replacing the anaerobic pond and facultative pond with an upflow anaerobic sludge blanket (UASB) reactor, with the advantages of greatly reducing the retention time and the biogas capture. The post-treatment ponds of the UASB reactor effluent involve oxygen production and the biological consumption of carbon dioxide, which raises the pH. An experimental investigation showed that it is possible to use polishing ponds in a sequential batch regime instead of continuous flow. This modification accelerates the decay of pathogens and accelerates the increase in pH, which, in turn, facilitates the removal of nitrogen and phosphorus. This produces a good-quality effluent with low concentrations of biodegradable organic material, nutrients, and pathogens. This good-quality effluent is obtained in a system without energy consumption or auxiliary materials and with a much smaller area than conventional stabilization ponds.