Technologies for the treatment of source-separated urine in the eThekwini Municipality

Abstract

In recent years, a large number of urine-diverting dehydration toilets (UDDTs) have been installed in eThekwini to ensure access to adequate sanitation. The initial purpose of these toilets was to facilitate faeces drying, while the urine was diverted into a soak pit. This practice can lead to environmental pollution, since urine contains high amounts of nutrients. Instead of polluting the environment, these nutrients should be recovered and used as fertiliser. In 2010 the international and transdisciplinary research project VUNA was initiated in order to explore technologies and management methods for better urine management in eThekwini. Three treatment technologies have been chosen for the VUNA project. The first is struvite precipitation, a technology which has already been tested in multiple projects on urine treatment. Struvite precipitation is a simple and fast process for phosphorus recovery. Other nutrients, such as nitrogen and potassium, remain in the effluent and pathogens are not completely inactivated. Therefore, struvite precipitation has to be combined with other treatment processes to prevent environmental pollution and hygiene risks. The second process is a combination of nitrification and distillation. This process combination is more complex than struvite precipitation, but it recovers all nutrients in one concentrated solution, ensures safe sanitisation and produces only distilled water and a small amount of sludge as by-products. The third process is electrolysis. This process could be used for very small on-site reactors, because conversion rates are high and the operation is simple, as long as appropriate electrodes and voltages are used. However, nitrogen is removed and not recovered and chlorinated by-products are formed, which can be hazardous for human health. While urine electrolysis requires further research in the laboratory, struvite precipitation and nitrification/distillation have already been operated at pilot scale.

Health Risks for Sanitation Service Workers along a Container-Based Urine Collection System and Resource Recovery Value Chain

“…Primary data was collected in August 2014 within the scope of VUNA (Valorisation of Urine Nutrients in Africa), a research project to optimize urine collection and treatment for fertilizer production. 33 UDDTs at households that participated in the study were equipped with 20-L plastic jerry cans to capture the urine outside of the dry toilet superstructure. The containers were collected by EWS staff approximately weekly.…”

Modeling the low pH limit of Nitrosomonas eutropha in high-strength nitrogen wastewaters

“…The SHARON (Single reactor High activity Ammonia Removal Over Nitrite) process for instance is deliberately operated at pH values above 7 and temperatures of 30 C (Hellinga et al, 1999), because under these conditions AOB grow faster than NOB causing the wash out of the latter. In contrast, NOB should be retained in nitrification reactors with urine, when nitrified urine is further processed to a fertilizer product (Udert et al, 2015). To ensure that NOB are retained in the system, this process is operated at pH values as low as 6 or even below (Etter et al, 2013), where the growth rate of AOB is reduced strongly.…”

Self-Powered Bioelectrochemical Nutrient Recovery for Fertilizer Generation from Human Urine

“…Several technologies have been proposed for nutrient recovery from urine, including struvite precipitation [10][11][12][13], ammonia stripping [14][15][16][17], stabilization + distillation [18][19][20], electrochemical concentration such as electrodialysis [21,22], and membrane distillation [23,24]. All these technologies require one or more of the following: high energy consumption, high chemical requirements, and/or control systems to ensure operability.…”