Techno-Economic Assessment of Struvite Phosphorus Recovery from Sewage Sludge Treatment in Sri Lanka

Abstract

Phosphorous is a nutrient that is considerably available in treated sludge coming out from municipal sewage treatment. In conventional sewage treatment plants, a larger portion of phosphorous remains unrecovered in the treated sludge. In this study, the techno-economic feasibility of phosphorous recovery in the form of struvite from treated sewage sludge is assessed for an already functioning sewage treatment plant in Sri Lanka. For comparative assessment between possible struvite phosphorous recovery technologies, two scenarios are considered, i.e., Scenario (A): wet chemical method with incineration and Scenario (B): wet chemical method without incineration. Composition data of treated sewage sludge is obtained from an existing sewage treatment plant, and design data for conceptualized struvite phosphorous recovery processes are retrieved from the published literature. According to the assessment results, scenario (A) provides a greater phosphorous recovery of 16.2 kg/day. However, the total energy consumption of 50,907.04 MJ/day in Scenario (A) is approximately six times higher than that of Scenario (B). The economic parameters, as well as the freshwater eutrophication impact reduction potentials for both scenarios are further analyzed. The most appropriate struvite phosphorous recovery technology for an existing or future sewage treatment plant in terms of technoeconomic aspects are discussed.