Real-life efficiency of urine source separation

Urine source separation (NoMix technology) is a promising innovation in wastewater management. To improve and further develop NoMix technology, it has been implemented in four Swiss households and at our research institute (Eawag). We conducted measurements during one year on frequency of toilet usage (in households 5.2/person/day for weekdays, and 6.3/person/day for weekends), flushing behavior (30–85% small flushes), and recovered urine. We calculate the amount of urine effectively recovered per voiding in NoMix toilets (138 ml/flush in households; 309 ml/flush in women's toilets at Eawag), and waterfree urinals (225 ml/usage). We estimate urine recovery in the households to be maximally 70–75% of the expected quantity, leaving room for technical and behavioral improvements. Based on sampling of N and P concentrations, we suspect nitrogen losses in the extended urine piping system. For households and workplaces, the daily and weekly flushing pattern is recorded. Our results are in accordance with literature data from a shorter period but with more people. These results represent a good dimensioning basis for future urine source separation applications. An example of extrapolation to an entire watershed is presented. The flushing pattern corresponds well with the typical nitrogen loading of a treatment plant.