The role of source separation in nutrient recovery – Comparison of alternative wastewater treatment systems

Abstract

The availability of mineral fertilizers is becoming more challenging in the future. In source separated human urine, nutrient ratio is suitable for fertilizer use and nutrients are readily available for plants. In this study the aim was to acquire scientific data of the environmental impacts and nutrient potentials of wastewater separating systems, i.e. urine and blackwater source separation. At the same time, general acceptance on the use of human urine in agriculture wanted to be improved. In addition, the value of urine as a fertilizer was calculated. The focus of the study was on rural areas but comparison between different systems included also the nutrient potential of urban areas as well. Based on the results, human urine was found to be an environment friendly fertilizer. Applying source-separation systems in rural areas, four times more phosphorus and over thirty times more nitrogen could be recovered compared to the current wastewater treatment system. Furthermore, eutrophication impact is reduced to one fifth. However there is a risk of increased soil acidification but it can be minimized with advanced spreading techniques, like deep injection. The results of this study support the use of source-separation technologies for nutrient recovery.