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

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.

[1]  A. Johnston,et al.  Effectiveness of Different Precipitated Phosphates as Phosphorus Sources for Plants , 2004 .

[2]  S. Snyder,et al.  Toxicological relevance of pharmaceuticals in drinking water. , 2010, Environmental science & technology.

[3]  Tove A. Larsen,et al.  Source separation and decentralization for wastewater management. , 2013 .

[4]  K. Udert,et al.  Complete nutrient recovery from source-separated urine by nitrification and distillation. , 2012, Water research.

[5]  Bastian Etter,et al.  Total Nutrient Recovery from Urine – Operation of a Pilot-Scale Nitrification Reactor , 2013 .

[6]  E. Tilley,et al.  Low-cost struvite production using source-separated urine in Nepal. , 2011, Water research.

[7]  Nicholas J. Ashbolt,et al.  Viral persistence in source-separated human urine , 2002 .

[8]  C. Starkenmann,et al.  The influence of thermal reaction and microbial transformation on the odour of human urine , 2013 .

[9]  Tamar Kohn,et al.  Fate of the pathogen indicators phage ΦX174 and Ascaris suum eggs during the production of struvite fertilizer from source-separated urine. , 2011, Water research.

[10]  T A Larsen,et al.  Fate of major compounds in source-separated urine. , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[11]  S. H. Ferrer,et al.  SUSTAINABLE DEVELOPMENT OF WATER RESOURCES, WATER SUPPLY AND ENVIRONMENTAL SANITATION , 2006 .

[12]  Urs von Gunten.  Chemical oxidation processes , 2013 .

[13]  Kai M Udert,et al.  Struvite precipitation from urine with electrochemical magnesium dosage. , 2013, Water research.

[14]  Willi Gujer,et al.  Urea hydrolysis and precipitation dynamics in a urine-collecting system. , 2003, Water research.

[15]  M Maurer,et al.  Treatment processes for source-separated urine. , 2006, Water research.

[16]  S Uhlenbrook,et al.  Eutrophication and nutrient release in urban areas of sub-Saharan Africa--a review. , 2010, The Science of the total environment.

[17]  Elisa Roma,et al.  User perceptions of urine diversion dehydration toilets: Experiences from a cross-sectional study in eThekwini Municipality , 2013 .

[18]  Thor Axel Stenström,et al.  Evaluation of faecal contamination and microbial die-off in urine separating sewage systems , 1998 .

[19]  Joachim Clemens,et al.  Solar thermal evaporation of human urine for nitrogen and phosphorus recovery in Vietnam. , 2012, The Science of the total environment.

[20]  Ariane Schertenleib,et al.  Inactivation of pathogens in urine nitrification reactors , 2014 .

[21]  Zhi-Long Ye,et al.  Recovering phosphorus as struvite from the digested swine wastewater with bittern as a magnesium source. , 2011, Water science and technology : a journal of the International Association on Water Pollution Research.

[22]  Samuel J. Huber.  Temperature dependent removal of sodium chloride (NaCl) from synthetic nitrified urine , 2011 .

[23]  B. Escher,et al.  Pilot experiments with electrodialysis and ozonation for the production of a fertiliser from urine. , 2007, Water science and technology : a journal of the International Association on Water Pollution Research.

[24]  Kai M. Udert,et al.  VUNA - Nutrient Harvesting from Urine: Lessons from Field Studies , 2014 .

[25]  Eberhard Morgenroth,et al.  Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine. , 2015, Water research.

[26]  Elizabeth Tilley,et al.  Wood ash as a magnesium source for phosphorus recovery from source-separated urine. , 2012, The Science of the total environment.

[27]  Inmaculada Ortiz,et al.  Contributions of electrochemical oxidation to waste-water treatment: fundamentals and review of applications , 2009 .

[28]  M C M van Loosdrecht,et al.  Phosphate and potassium recovery from source separated urine through struvite precipitation. , 2007, Water research.

[29]  Hallvard Ødegaard,et al.  Nitrification of municipal wastewater in moving-bed biofilm reactors , 1995 .

[30]  D Hellström,et al.  Concentration of nutrients from urine and reject water from anaerobically digested sludge. , 2006, Water science and technology : a journal of the International Association on Water Pollution Research.

[31]  Max Maurer,et al.  The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine. , 2007, Water research.

[32]  Chris J. Brouckaert,et al.  Development of a Fully Automated Struvite Reactor to Recover Phosphorus from Source Separated Urine Collected at Urine Diversion Toilets in eThekwini , 2013 .

[33]  H Siegrist,et al.  Nitrification and autotrophic denitrification of source-separated urine. , 2003, Water science and technology : a journal of the International Association on Water Pollution Research.

[34]  D S Mavinic,et al.  Thermal decomposition of struvite and its phase transition. , 2008, Chemosphere.

[35]  Heather N. Bischel,et al.  Inactivation kinetics and mechanisms of viral and bacterial pathogen surrogates during urine nitrification , 2015 .

[36]  Avelino Núñez-Delgado,et al.  Chloride, sodium, potassium and faecal bacteria levels in surface runoff and subsurface percolates from grassland plots amended with cattle slurry. , 2002, Bioresource technology.

[37]  Tove A. Larsen,et al.  Separate management of anthropogenic nutrient solutions (human urine) , 1996 .

[38]  Mats Johansson,et al.  URINE SEPARATION – CLOSING THE NUTRIENT CYCLE , 2001 .

[39]  Lisa Joss,et al.  Direct and mediated electrochemical oxidation of ammonia on boron-doped diamond electrode , 2010 .

[40]  Teddy Gounden,et al.  Provision of free sustainable basic sanitation: the Durban experience , 2006 .

[41]  N. F. Rooij,et al.  Electrochemical oxidation of ammonia (NH4+/NH3) on thermally and electrochemically prepared IrO2 electrodes , 2011 .

[42]  Joachim Clemens,et al.  Nitrogen and Phosphorus Recovery from Human Urine by Struvite Precipitation and Air Stripping in Vietnam , 2011 .