The performance and potential of faecal separation and urine diversion to recycle plant nutrients in household wastewater

In household wastewater and biodegradable solid waste, the main proportion of the plant nutrients are found in the toilet water (i.e. in urine and faeces). In order to recover most of these nutrients, with the purpose of decreasing the emission of eutrophicating agents and of increasing their recycling, present waste and wastewater systems have to be changed. If the urine and the faeces are collected, up to 91%, 83% and 59% for N, P and K, respectively, can be recovered and recycled from the household wastewater. The urine was collected separately in a double flushed urine-diverting toilet and the faeces were separated from the flushwater using two parallel Aquatrons. The Aquatron separates by a combination of a whirlpool effect, gravitation and surface tension. In this study, nitrogen and phosphorus from the faeces were separated to 73% and 58%, respectively, to the dryer fraction. The combination of faecal separation and urine diversion in the house Ekoporten made it possible to collect 60% of N, 46% of P and 43% of K from the wastewater, indicating that this method is an alternative when aiming to recover plant nutrients while still wanting to use water-flushed, urine-diverting toilets, though the potential to collect the nutrients is much higher.