Epsilon Archive for Student Projects

Abstract

In this study a comparative life cycle assessment was conducted, where a wastewater treatment method with a newly integrated struvite precipitation process was analyzed and compared with the conventional enhanced biological nutrient removal (EBNR) - based wastewater and sludge treatment. A case study was carried out based on data from a wastewater treatment plant in south Sweden, which was operating with EBNR, and started to use integrated struvite precipitation on pilot-scale in 2013. The aim of the study was to analyze and compare the environmental impacts of the two scenarios (Reference and Struvite scenario), and to identify which one was more favorable with regard to phosphorus recovery potential. The model included the avoided fertilizer production by the products (sewage sludge and struvite) but it did not include the environmental impacts from fertilizer application. Data regarding the two scenarios was acquired from the treatment plant and the operator of the struvite removal while the impact values were gathered from life cycle assessment databases.
The assessment showed that both scenarios had net negative impacts for all of the impact categories investigated due to conventional chemical fertilizers being replaced. The differences among the avoided impacts of the two scenarios were not considerable, indicating that the struvite precipitation in the plant, during the time period investigated, did not have much effect on the treatment. The Struvite scenario proved to be less favorable in the assessment, due to its increased energy consumption and the fact that the favorable effects of the struvite production did not suffice to balance the extra use of resources of the scenario. The avoided fertilizer production was found to be the most important for the result of the assessment. The chemicals used for the struvite precipitation exclusively showed little effect on the impacts, as the model was not sensitive to these factors.