Blue Diversion Autarky – Wastewater Treatment off the Grid

Autarky at a glance

The Blue Diversion Autarky toilet is a sanitation system which provides hygiene and comfort without relying on water and wastewater infrastructure. Water, urine and feces are collected separately and treated on site in specific modules. The Blue Diversion Autarky toilet recycles water for hand washing and flushing, recovers nutrients for fertilizer production and inactivates pathogens reliably. The treatment modules can be replaced, integrated in other sanitation systems or used as stand-alone units. One example is the hand washing station, which was also developed by the Blue Diversion Autarky team.

Blue Diversion Autarky was launched in the context of the “Reinvent the Toilet Challenge” funded by the Bill & Melinda Gates Foundation. The project is currently in its second project phase. Blue Diversion Autarky is the continuation of the Blue Diversion project.

 

Blue Diversion Autarky toilet
Blue Diversion Autarky toilet
Blue Diversion Autarky handwashing station

Guiding principles

Safety & comfort

The Blue Diversion Autarky toilet offers the safety and comfort of a modern flush toilet without requiring piped water or sewerage.

Safety & comfort

Source separation

Pathogen inactivation, nutrient recovery and water recycling for flushing and hand washing are achieved by the separate treatment of feces, urine and water.

Source separation

Modularization

A modular design allows for a wide range of applications. Single modules can be used alone or combined with other technologies. One example is the stand alone hand washing station.

Modularization

Research at a glance

The Blue Diversion Autarky system is based on the separate treatment of water, urine and feces. The core process for the water treatment is a gravity-driven membrane (GDM) filtration. After post-treatment in the form of an activated carbon filter and an electrolysis unit to remove microorganisms, the same water can be reused for flushing and hand washing. Urine is pretreated to eliminate malodor and pathogens, as well as to avoid the loss of nutrients. The volume of urine is then reduced by evaporating the water. The product is a concentrate of organic and inorganic nutrients, that can be used as fertilizer. The treatment of the feces is based on hydrothermal oxidation (HTO). Using high temperature and pressure, the feces are mineralized  to  carbon dioxide, water and precipitated inorganic solids.

We recently field-tested the Blue Diversion Autarky toilet in a 14-people household in a peri-urban zone of Durban, South Africa.The toilet system functioned well and the recycled water was readily used. As the adoption of new sanitation technology does not depend on the technical functionality alone, the testing was closely accompanied by a team of social scientists. The results of our socio-technical assessment and a detailed evaluation of the water treatment system are available throughopen access publications (see below).

 

Publications

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      authors => protected'Sutherland, C.; Reynaert, E.; Dhlamini, S.; Magwaza, F.;
          Lienert, J.; Riechmann, M. E.; Buthelezi, S.; Khumalo,&
         nbsp;D.; Morgenroth, E.; Udert, K. M.; Sindall, R. 
         C.' (230 chars)
      title => protected'Socio-technical analysis of a sanitation innovation in a peri-urban househol
         d in Durban, South Africa' (101 chars)
      journal => protected'Science of the Total Environment' (32 chars)
      year => protected2021 (integer)
      volume => protected755 (integer)
      issue => protected'' (0 chars)
      startpage => protected'143284 (12 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'field test; water reuse; source separation; service delivery; social accepta
         nce; transdisciplinary research' (107 chars)
      description => protected'The provision of water and sanitation for all that is safe, dignified, relia
         ble, affordable and sustainable is a major global challenge. While centraliz
         ed sewer-based sanitation systems remain the dominant approach to providing 
         sanitation, the benefits of non-sewered onsite sanitation systems are increa
         singly being recognised. This paper presents the outcomes of the testing of 
         the Blue Diversion Autarky Toilet (BDAT), a sanitation system providing hygi
         ene and dignity without relying on water and wastewater infrastructure, in a
          peri-urban household in Durban, South Africa. The BDAT was used by a single
          household as their only form of sanitation during three months of technical
          and social testing. An analysis based on technical data in combination with
          interpretive, qualitative research methods revealed that the BDAT functione
         d well and achieved high levels of social acceptance in the test household. 
         The flushing, cleanliness and odour-free nature of the sanitation technology
         , its functionality, the household's previous sanitation experience, and the
         ir experience with and understanding of water scarcity, were the main factor
         s underpinning their positive response to this innovation in sanitation. The
          testing process resulted in broader developmental benefits for the househol
         d, including improved basic services due to the upgrading of the electrical 
         and existing sanitation system, social learning, and improved relationships 
         between household members and the local state. A transdisciplinary research 
         process, which emerged through the assessment, enabled the integration of di
         fferent forms of knowledge from multiple actors to address the complexity of
          problems related to the development of socially just sanitation. The benefi
         t of engaging with societal actors in sanitation innovation and assessing it
         s outcomes using both the technical and social sciences is evident in this p
         aper.' (1905 chars)
      serialnumber => protected'0048-9697' (9 chars)
      doi => protected'10.1016/j.scitotenv.2020.143284' (31 chars)
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      originalId => protected23229 (integer)
      authors => protected'Sutherland, C.; Reynaert, E.; Sindall, R. C.; Riechmann,
          M. E.; Magwaza, F.; Lienert, J.; Buthelezi, S.; Kh
         umalo, D.; Dhlamini, S.; Morgenroth, E.; Udert, K. 
         M.' (230 chars)
      title => protected'Innovation for improved hand hygiene: field testing the Autarky handwashing 
         station in collaboration with informal settlement residents in Durban, South
          Africa' (159 chars)
      journal => protected'Science of the Total Environment' (32 chars)
      year => protected2021 (integer)
      volume => protected796 (integer)
      issue => protected'' (0 chars)
      startpage => protected'149024 (13 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'community participation; hand hygiene; WASH; technology field test; water re
         cycling; transdisciplinary research' (111 chars)
      description => protected'Safe and accessible water services for hand hygiene are critical to human he
         alth and well-being. However, access to handwashing facilities is limited in
          cities in the Global South, where rapid urbanisation, service backlogs, lac
         k of infrastructure and capacity, and water scarcity impact on the ability o
         f local governments to provide them. Community participation and the co-prod
         uction of knowledge in the development of innovative technologies, which are
          aligned with Water, Sanitation and Hygiene (WASH) principles, can lead to m
         ore sustainable and socially-acceptable hand hygiene systems. This paper pre
         sents the outcomes of the testing of the Autarky handwashing station, a tech
         nology that provides onsite treatment and recycling of handwashing water, in
          an informal settlement in Durban, South Africa. The transdisciplinary resea
         rch approach adopted enabled the participation of multiple stakeholders with
          different knowledge systems in the framing, testing and evaluation of the s
         ystem. The process of co-producing knowledge, as well as the outcomes of the
          testing, namely high levels of functionality and social acceptability of th
         e technology, supported the WASH principles. The evaluation revealed that th
         e Autarky handwashing station is a niche intervention that improved access t
         o safe and appealing handwashing facilities in an informal settlement. Its n
         ovel design, socially desirable features, reliability and ability to save wa
         ter increased its acceptance in the community. The testing of the system in 
         a real-world context revealed the value of including communities in knowledg
         e production processes for technology innovation. Further work is required t
         o ensure that real-time monitoring of system function is feasible before suc
         h systems can be implemented at larger scale.' (1793 chars)
      serialnumber => protected'0048-9697' (9 chars)
      doi => protected'10.1016/j.scitotenv.2021.149024' (31 chars)
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Socio-technical analysis of a sanitation innovation in a peri-urban household in Durban, South Africa

The provision of water and sanitation for all that is safe, dignified, reliable, affordable and sustainable is a major global challenge. While centralized sewer-based sanitation systems remain the dominant approach to providing sanitation, the benefits of non-sewered onsite sanitation systems are increasingly being recognised. This paper presents the outcomes of the testing of the Blue Diversion Autarky Toilet (BDAT), a sanitation system providing hygiene and dignity without relying on water and wastewater infrastructure, in a peri-urban household in Durban, South Africa. The BDAT was used by a single household as their only form of sanitation during three months of technical and social testing. An analysis based on technical data in combination with interpretive, qualitative research methods revealed that the BDAT functioned well and achieved high levels of social acceptance in the test household. The flushing, cleanliness and odour-free nature of the sanitation technology, its functionality, the household's previous sanitation experience, and their experience with and understanding of water scarcity, were the main factors underpinning their positive response to this innovation in sanitation. The testing process resulted in broader developmental benefits for the household, including improved basic services due to the upgrading of the electrical and existing sanitation system, social learning, and improved relationships between household members and the local state. A transdisciplinary research process, which emerged through the assessment, enabled the integration of different forms of knowledge from multiple actors to address the complexity of problems related to the development of socially just sanitation. The benefit of engaging with societal actors in sanitation innovation and assessing its outcomes using both the technical and social sciences is evident in this paper.
Sutherland, C.; Reynaert, E.; Dhlamini, S.; Magwaza, F.; Lienert, J.; Riechmann, M. E.; Buthelezi, S.; Khumalo, D.; Morgenroth, E.; Udert, K. M.; Sindall, R. C. (2021) Socio-technical analysis of a sanitation innovation in a peri-urban household in Durban, South Africa, Science of the Total Environment, 755, 143284 (12 pp.), doi:10.1016/j.scitotenv.2020.143284, Institutional Repository

Innovation for improved hand hygiene: field testing the Autarky handwashing station in collaboration with informal settlement residents in Durban, South Africa

Safe and accessible water services for hand hygiene are critical to human health and well-being. However, access to handwashing facilities is limited in cities in the Global South, where rapid urbanisation, service backlogs, lack of infrastructure and capacity, and water scarcity impact on the ability of local governments to provide them. Community participation and the co-production of knowledge in the development of innovative technologies, which are aligned with Water, Sanitation and Hygiene (WASH) principles, can lead to more sustainable and socially-acceptable hand hygiene systems. This paper presents the outcomes of the testing of the Autarky handwashing station, a technology that provides onsite treatment and recycling of handwashing water, in an informal settlement in Durban, South Africa. The transdisciplinary research approach adopted enabled the participation of multiple stakeholders with different knowledge systems in the framing, testing and evaluation of the system. The process of co-producing knowledge, as well as the outcomes of the testing, namely high levels of functionality and social acceptability of the technology, supported the WASH principles. The evaluation revealed that the Autarky handwashing station is a niche intervention that improved access to safe and appealing handwashing facilities in an informal settlement. Its novel design, socially desirable features, reliability and ability to save water increased its acceptance in the community. The testing of the system in a real-world context revealed the value of including communities in knowledge production processes for technology innovation. Further work is required to ensure that real-time monitoring of system function is feasible before such systems can be implemented at larger scale.
Sutherland, C.; Reynaert, E.; Sindall, R. C.; Riechmann, M. E.; Magwaza, F.; Lienert, J.; Buthelezi, S.; Khumalo, D.; Dhlamini, S.; Morgenroth, E.; Udert, K. M. (2021) Innovation for improved hand hygiene: field testing the Autarky handwashing station in collaboration with informal settlement residents in Durban, South Africa, Science of the Total Environment, 796, 149024 (13 pp.), doi:10.1016/j.scitotenv.2021.149024, Institutional Repository

More about water treatment

The water treatment system, referred to as Water Wall, recycles hand washing water, toilet flush water (separated from the major part of urine and feces), or both. A multi-barrier approach with four treatment stages ensures that the water is safe for reuse.

  • The first barrier and core of the treatment is an aerated bioreactor, in which microorganisms degrade contaminants such as soap, urine, and feces.
  • As the second barrier, the water is then filtered by gravity through an ultrafiltration membrane. The membrane pores are smaller than the size of bacteria and most viruses, providing water that is microbiologically safe after filtering through the membrane.

Contacts

Eva Reynaert Group leader Tel. +41 58 765 6681 Send Mail
Prof. Dr. Eberhard Morgenroth Tel. +41 58 765 5539 Send Mail

The combined biological treatment and membrane filtration without cleaning will produce a biofilm on the membrane. This effect is desirable in a gravity-driven membrane (GDM) approach, as the biofilm also contributes to the removal of organic carbon. The GDM system achieves approximately 95% removal of organic carbon.

The filtered water is stored in a clean water tank.  Additional treatment is required to limit regrowth of pathogens and potential contamination.

  • The third treatment barrier, an activated carbon filter, removes remaining organic contamination in the clean water tank by adsorption.
  • Finally, the fourth and last barrier, an electrolysis unit, further reduces organic carbon concentrations and produces a chlorine residual, both of which help to limit pathogen growth during storage.
Water treatment process

Current activities

With this setup, we were able to develop a small series of Water Wall prototypes for treating and recycling hand washing water or toilet flush water. These prototypes were extensively tested under laboratory conditions, under which they reliably removed pathogens, nutrients, malodor, and color from recycled water. However, when moving outside the laboratory, we expect a much higher variability of the number of users, composition of the water and external conditions. This is why we are currently exposing different configurations of the Water Wall to real-life conditions.

Update: our results from field tests in Switzerland and South Africa have now been published. The open access publication can be found here: https://doi.org/10.1016/j.wroa.2020.100051.

Water wall

 

 

A Water Wall as part of a complete toilet system. The biological treatment takes place in the lower tank, with the ultrafiltration membrane sitting on the bottom of the tank. The activated carbon filter and the electrolysis unit are located in the upper tank.

Publications

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   0 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=20895, pid=124)
      originalId => protected20895 (integer)
      authors => protected'Reynaert, E.; Greenwood, E. E.; Ndwandwe, B.; Riechmann,
          M. E.; Sindall, R. C.; Udert, K. M.; Morgenro
         th, E.' (163 chars)
      title => protected'Practical implementation of true on-site water recycling systems for hand wa
         shing and toilet flushing' (101 chars)
      journal => protected'Water Research X' (16 chars)
      year => protected2020 (integer)
      volume => protected7 (integer)
      issue => protected'' (0 chars)
      startpage => protected'100051 (13 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'field test; water recycling; hand washing; toilet flushing; wastewater reuse
         ; biologically activated membrane bioreactor (BAMBI)' (128 chars)
      description => protected'On-site wastewater reuse can improve global access to clean water, sanitatio
         n and hygiene. We developed a treatment system (aerated bioreactor, ultrafil
         tration membrane, granular activated carbon and electrolysis for chlorine di
         sinfection) that recycles hand washing and toilet flush water.<br />
Three p
         rototypes were field-tested in non-sewered areas, one in Switzerland (hand w
         ashing) and two in South Africa (hand washing, toilet flushing), over period
         s of 63, 74 and 94 days, respectively.<br />
We demonstrated that the system
          is able to recycle sufficient quantities of safe and appealing hand washing
          and toilet flush water for domestic or public use in real-life applications
         . Chemical contaminants were effectively removed from the used water in all 
         prototypes. Removal efficiencies were 99.7% for the chemical oxygen demand (
         COD), 98.5% for total nitrogen (TN) and 99.9% for phosphate in a prototype t
         reating hand washing water, and 99.8% for COD, 95.7% for TN and 89.6% for ph
         osphate in a prototype treating toilet flush water. While this system allowe
         d for true recycling for the same application, most on-site wastewater reuse
          systems downcycle the treated water, i.e., reuse it for an application requ
         iring lower water quality. An analysis of 18 selected wastewater reuse speci
         fications revealed that at best these guidelines are only partially applicab
         le to innovative recycling systems as they are focused on the downcycling of
          water to the environment (e.g., use for irrigation). We believe that a para
         digm shift is necessary and advocate for the implementation of risk-based (a
         nd thus end-use dependent) system performance targets to evaluate water trea
         tment systems, which recycle and not only downcycle water.' (1730 chars)
      serialnumber => protected'2589-9147' (9 chars)
      doi => protected'10.1016/j.wroa.2020.100051' (26 chars)
      uid => protected20895 (integer)
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   1 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=22034, pid=124)
      originalId => protected22034 (integer)
      authors => protected'Ziemba,&nbsp;C.; Sharma,&nbsp;P.; Ahrens,&nbsp;T.; Reynaert,&nbsp;E.; Morgen
         roth,&nbsp;E.' (89 chars)
      title => protected'Disruptions in loading and aeration impact effluent chlorine demand during b
         iological greywater recycling' (105 chars)
      journal => protected'Water Research X' (16 chars)
      year => protected2021 (integer)
      volume => protected11 (integer)
      issue => protected'' (0 chars)
      startpage => protected'100087 (10 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'permeate quality; hand washing water; decentralized; chlorination; biologica
         lly activated membrane bioreactor (BAMBi); gravity-driven membrane (GDM) tre
         atment' (158 chars)
      description => protected'Greywater recycling systems designed for high-quality applications, such as 
         hand washing, must deliver microbially safe and aesthetically acceptable wat
         er under the challenging operating conditions present where such systems are
          needed most urgently. As chlorination is the most popular strategy for redu
         cing bacterial concentrations in greywater, understanding chlorination in th
         e context of disruptive and challenging operation is essential to designing 
         robust treatment. In this study, we have examined how disruptions through ov
         erall increased loading, interrupted aeration and increased ammonia loading 
         have impacted the chlorine demand of the water produced by a greywater recyc
         ling system. We also presented concentrations of significant chemicals that 
         contributed to this chlorine demand. The results indicate that a 1 d period 
         with 8 times (8x) the normal design loading produced a peak chlorine demand 
         of 0.74 mg Cl<sub>2</sub>/L, which is approximately double the baseline valu
         e. While this chlorine demand can be overcome by adding more chlorine, tests
          involving disruptions in aeration or feeding additional ammonia into the bi
         oreactor produced much greater increases (&gt;30x). The risks of increased c
         hlorine demand on microbial safety can be overcome by limiting ammonia input
         s to the system, providing backup systems to ensure sufficient aeration, or 
         through additional anti-bacterial measures that do not depend on maintaining
          residual chlorine.' (1463 chars)
      serialnumber => protected'2589-9147' (9 chars)
      doi => protected'10.1016/j.wroa.2020.100087' (26 chars)
      uid => protected22034 (integer)
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   2 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=20446, pid=124)
      originalId => protected20446 (integer)
      authors => protected'Ziemba,&nbsp;C.; Larivé,&nbsp;O.; Reynaert,&nbsp;E.; Huisman,&nbsp;T.; Morg
         enroth,&nbsp;E.' (91 chars)
      title => protected'Linking transformations of organic carbon to post-treatment performance in a
          biological water recycling system' (110 chars)
      journal => protected'Science of the Total Environment' (32 chars)
      year => protected2020 (integer)
      volume => protected721 (integer)
      issue => protected'' (0 chars)
      startpage => protected'137489 (8 pp.)' (14 chars)
      otherpage => protected'' (0 chars)
      categories => protected'biologically activated membrane bioreactor (BAMBI); decentralized; greywater
         ; electrolysis; granular activated carbon (GAC)' (123 chars)
      description => protected'Ozone, electrolysis and granular activated carbon (GAC) were examined as pot
         ential post-treatments to follow a household-scale biologically activated me
         mbrane bioreactor (BAMBi), treating a wash water containing trace urine and 
         feces contamination. Each post-treatment was evaluated for abilities and rea
         ction preferences to remove or transform dissolved organic carbon (DOC), che
         mical structures that contribute color, and assimilable organic carbon (AOC)
         , which can support bacterial regrowth. Batch treatment with each technology
          demonstrated an ability to remove ≥95% DOC. Ozone demonstrated a reaction
          selectivity through increased reaction rates with larger compounds and colo
         r-contributing compounds. Electrolysis and GAC demonstrated generally less-s
         elective reactivity. Adding post-treatments to full-scale systems reduced DO
         C (55-91%), AOC (34-62%), and color (75-98%), without significant reaction s
         electivity. These reductions in DOC and AOC were not linked to reduction of 
         bacterial concentrations in treated water. Reductions in bacterial concentra
         tions were observed with ozone and electrolysis, but this is credited to oxi
         dation chemicals produced in these systems and not the removal or transforma
         tions of organic materials.' (1243 chars)
      serialnumber => protected'0048-9697' (9 chars)
      doi => protected'10.1016/j.scitotenv.2020.137489' (31 chars)
      uid => protected20446 (integer)
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      pid => protected124 (integer)
   3 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=18717, pid=124)
      originalId => protected18717 (integer)
      authors => protected'Ziemba,&nbsp;C.; Larivé,&nbsp;O.; Deck,&nbsp;S.; Huisman,&nbsp;T.; Morgenro
         th,&nbsp;E.' (87 chars)
      title => protected'Comparing the anti-bacterial performance of chlorination and electrolysis po
         st-treatments in a hand washing water recycling system' (130 chars)
      journal => protected'Water Research X' (16 chars)
      year => protected2019 (integer)
      volume => protected2 (integer)
      issue => protected'' (0 chars)
      startpage => protected'100020 (10 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'greywater; regrowth; decentralized; assimilable organic carbon (AOC); biolog
         ically activated membrane bioreactor (BAMBi); hydroxyl radical' (138 chars)
      description => protected'Innovative solutions are necessary to enable the decentralized recycling of 
         greywater for applications requiring high-quality water, such as hand washin
         g. While physical barriers such as ultrafiltration membranes effectively pre
         vent the passage of bacteria, and chemical and biological treatments can eff
         ectively reduce the carbon content of the treated water, there exists a know
         ledge gap regarding the application of anti-bacterial strategies to prevent 
         the growth of harmful bacteria following treatment. In this study, the efflu
         ent water from a household-scale greywater treatment system was fed to seven
          parallel experimental post-treatment tanks: three receiving direct chlorina
         tion with free chlorine residuals of 0.2, 1 or 5 mg Cl<sub>2</sub>/L, three 
         with chlorine produced through electrolysis at the same residual concentrati
         ons, and one control with no chlorine added. For increasing concentrations o
         f direct chlorination, the median total cell count (TCC) values were 9 × 10
         <sup>4</sup>, 2.9 × 10<sup>4</sup> and 1.8 × 10<sup>3</sup> cells/mL, resp
         ectively. Electrolysis treatment produced very similar TCC concentrations, 8
         .8 × 10<sup>4</sup>, 1.1 × 10<sup>4</sup> and 2.3 × 10<sup>3</sup> cells/
         mL. The TCC concentrations were lower than the concentration of the water en
         tering each tank (~3 × 10<sup>5</sup> cells/mL). Intact cell count (ICC) me
         asurements indicated that the viable cell concentrations, were less than 10%
          of the TCC values. Though electrolysis treatment can produce powerful oxida
         nts, such as hydroxyl radical, there was no evidence that electrolysis in th
         is system provided additional benefits beyond chlorine production for contro
         l of total or intact cell counts. Oxidation of bacteria by chlorine was the 
         dominant anti-bacterial mechanism in our system. Monitoring of dissolved org
         anic carbon (DOC) and assimilable organic carbon (AOC) did not suggest that 
         carbon-limitation significantly impacted cell counts when chlorination or el
         ectrolysis treatment was...' (2497 chars)
      serialnumber => protected'2589-9147' (9 chars)
      doi => protected'10.1016/j.wroa.2018.100020' (26 chars)
      uid => protected18717 (integer)
      _localizedUid => protected18717 (integer)modified
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      pid => protected124 (integer)
   4 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=17193, pid=124)
      originalId => protected17193 (integer)
      authors => protected'Ziemba,&nbsp;C.; Larivé,&nbsp;O.; Reynaert,&nbsp;E.; Morgenroth,&nbsp;E.' (73 chars)
      title => protected'Chemical composition, nutrient-balancing and biological treatment of hand wa
         shing greywater' (91 chars)
      journal => protected'Water Research' (14 chars)
      year => protected2018 (integer)
      volume => protected144 (integer)
      issue => protected'' (0 chars)
      startpage => protected'752' (3 chars)
      otherpage => protected'762' (3 chars)
      categories => protected'soap; nitrogen; micro-nutrients; biologically activated membrane bioreactor 
         (BAMBi); gravity-driven membrane (GDM); handwashing' (127 chars)
      description => protected'On-site biological hand washing water treatment can improve global access to
          safe hand washing water, but requires a thorough understanding of the chemi
         cal composition of the water to be treated, and an effective treatment strat
         egy. This study first presents a detailed characterization of the individual
          inputs to hand washing water. We demonstrate (1) that soap is likely the mo
         st significant input in hand washing water, representing ∼90% of mass load
         ing, and (2) that inputs to hand washing water have low concentrations of bi
         ologically-essential macro- and micro-nutrients (nitrogen, phosphorus, potas
         sium, copper, zinc, molybdenum and cobalt) with respect to carbon, which may
          impair biological carbon removal. This study next formulates a recipe that 
         recreates a representative composition of hand washing water and develops a 
         procedure to identify and supplement nutrients in which this recipe is estim
         ated to be deficient. Batch testing of the nutrient-supplemented hand washin
         g water with an inoculum of planktonic bacteria demonstrated improved assimi
         lable organic carbon removal (99% vs. 86% removal) and produced lower final 
         DOC concentrations (1.7 mg<sub>C</sub>/L vs. 3.5 mg<sub>C</sub>/L) compared 
         to realistic (nutrient-deficient) washing water. Supplementing nutrients did
          promote cell growth (50x higher final total cell count). Full-scale testing
         
         
         eration (100 days) can deliver effective carbon removal (95%) without detrim
         ental fouling or other disruptions caused by cell growth. This work demonstr
         ates that biological treatment in a BAMBi system, operated with appropriate 
         nutrient-balancing offers an effective solution for decentralized treatment 
         of light greywater.' (1843 chars)
      serialnumber => protected'0043-1354' (9 chars)
      doi => protected'10.1016/j.watres.2018.07.005' (28 chars)
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      authors => protected'Nguyen,&nbsp;M.&nbsp;T.; Allemann,&nbsp;L.; Ziemba,&nbsp;C.; Larivé,&nbsp;O
         .; Morgenroth,&nbsp;E.; Julian,&nbsp;T.&nbsp;R.' (123 chars)
      title => protected'Controlling bacterial pathogens in water for reuse: treatment technologies f
         or water recirculation in the Blue Diversion Autarky Toilet' (135 chars)
      journal => protected'Frontiers in Environmental Science' (34 chars)
      year => protected2017 (integer)
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      issue => protected'' (0 chars)
      startpage => protected'90 (13 pp.)' (11 chars)
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      categories => protected'water for reuse; pathogen; inactivation; regrowth; biologically active membr
         ane bioreactor; biostability' (104 chars)
      description => protected'The Blue Diversion AUTARKY Toilet is a urine-diverting toilet with on-site t
         reatment. The toilet is being developed to provide a safe and affordable san
         itation technology for people who lack access to sewer-based sanitation. Wat
         er used for personal hygiene, hand washing, and flushing to rinse urine- and
          feces-collection bowls is treated, stored, and recycled for reuse to reduce
          reliance on external water supplies. The system provides an opportunity to 
         investigate hygiene of water for reuse following treatment. Treatment in the
          toilet includes a Biologically Activated Membrane Bioreactor (BAMBi) follow
         ed by a secondary treatment technology. To identify effective secondary trea
         tment, three options, including granular activated carbon (GAC) only, GAC+ch
         lorine (sodium hypochlorite), and GAC+electrolysis are considered based on t
         he bacterial inactivation and growth inhibition efficiency. Four different h
         ygiene-relevant bacteria are tested: <i>Escherichia coli, Enterococcus faeca
         lis, Pseudomonas aeruginosa, and Salmonella typhimurium</i>. Our evaluation 
         demonstrates that—despite treatment of water with the BAMBi—<i>E. coli</
         i>, P. aeruginosa, and S. typhimurium have the potential to grow during stor
         age in the absence of microbial competition. Including the indigenous microb
         ial community influences bacterial growth in different ways: <i>E. coli</i> 
         growth decreases but P. aeruginosa growth increases relative to no competiti
         on. The addition of the secondary treatment options considerably improves wa
         ter quality. A column of GAC after the BAMBi reduces <i>E. coli</i> growth p
         otential by 2 log<sub>10</sub>, likely due to the reduction of carbon source
         s. Additional treatments including chlorination and electrolysis provide fur
         ther safety margins, with more than 5 log<sub>10</sub> inactivation of <i>E.
          coli</i>. However, reactivation and/or regrowth of <i>E. coli</i> and P. ae
         ruginosa occurs under in the absence of residual disinfectant. Treatment inc
         luding the BAMBi, GAC, a...' (2123 chars)
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      doi => protected'10.3389/fenvs.2017.00090' (24 chars)
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      authors => protected'Ravndal,&nbsp;K.&nbsp;T.; Künzle,&nbsp;R.; Derlon,&nbsp;N.; Morgenroth,&nbs
         p;E.' (80 chars)
      title => protected'On-site treatment of used wash-water using biologically activated membrane b
         ioreactors operated at different solids retention times' (131 chars)
      journal => protected'Journal of Water, Sanitation and Hygiene for Development' (56 chars)
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      issue => protected'4' (1 chars)
      startpage => protected'544' (3 chars)
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      categories => protected'biologically activated membrane bioreactor (BAMBi); full solids retention; p
         article colonization; permeate flux stabilization; suspended solids retentio
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      description => protected'Biologically activated membrane bioreactors (BAMBis) were operated at suspen
         ded solids retention times (SRT) of 7 and 102 days and at full solids retent
         ion. The effect of these different approaches of operation on substrate and 
         nutrient conversion, and on permeate flux was investigated. Variations in or
         ganic loads and aeration intensities were also studied. Permeate flux stabil
         ized during long-term operation independently of suspended SRT. Removal of o
         rganic substrate was independent of solids concentrations and remained stabl
         e over the long term. Microorganisms colonizing the surface of particles wer
         e found as the main mechanism responsible for degradation of organic substra
         te in the particulate form. BAMBi appeared to be a robust technology, adapte
         d to on-site treatment of used wash-water, as it can be operated without con
         trol of suspended SRT. Thus BAMBis can be operated for long periods without 
         any control of biofouling and sludge formation, leading to low maintenance n
         eeds. When BAMBis were operated at low aeration, the formation of anoxic zon
         es led to combined nitrification and denitrification and thus significant ni
         trogen removal.' (1155 chars)
      serialnumber => protected'2043-9083' (9 chars)
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      authors => protected'Künzle,&nbsp;R.; Pronk,&nbsp;W.; Morgenroth,&nbsp;E.; Larsen,&nbsp;T.&nbsp;
         A.' (78 chars)
      title => protected'An energy-efficient membrane bioreactor for on-site treatment and recovery o
         f wastewater' (88 chars)
      journal => protected'Journal of Water, Sanitation and Hygiene for Development' (56 chars)
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      issue => protected'3' (1 chars)
      startpage => protected'448' (3 chars)
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      categories => protected'Blue Diversion; maintenance; resilience; sustainable development; urban slum
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      description => protected'The present study describes the development of a new type of aerated membran
         e bioreactor referred to as a biologically activated membrane bioreactor (BA
         MBi) for on-site treatment of high-strength wastewater. The treated wastewat
         er is reused for flushing and personal hygiene. BAMBi is an adaptation of a 
         gravity-driven membrane reactor, originally developed for the purpose of tre
         ating river water to drinking water quality. Initially, a series of reactor 
         configurations were tested and it was found that the simplest possible confi
         guration could treat the wastewater to an acceptable standard, provided that
          a polishing step for color removal and disinfection was introduced. A comme
         rcial electrolysis unit was utilized for polishing. The energy consumption o
         f BAMBi is 0.8 kWh/m<sup>3</sup> of water treated, which can be considered l
         ow for an on-site membrane bio reactor application.' (887 chars)
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Practical implementation of true on-site water recycling systems for hand washing and toilet flushing

On-site wastewater reuse can improve global access to clean water, sanitation and hygiene. We developed a treatment system (aerated bioreactor, ultrafiltration membrane, granular activated carbon and electrolysis for chlorine disinfection) that recycles hand washing and toilet flush water.
Three prototypes were field-tested in non-sewered areas, one in Switzerland (hand washing) and two in South Africa (hand washing, toilet flushing), over periods of 63, 74 and 94 days, respectively.
We demonstrated that the system is able to recycle sufficient quantities of safe and appealing hand washing and toilet flush water for domestic or public use in real-life applications. Chemical contaminants were effectively removed from the used water in all prototypes. Removal efficiencies were 99.7% for the chemical oxygen demand (COD), 98.5% for total nitrogen (TN) and 99.9% for phosphate in a prototype treating hand washing water, and 99.8% for COD, 95.7% for TN and 89.6% for phosphate in a prototype treating toilet flush water. While this system allowed for true recycling for the same application, most on-site wastewater reuse systems downcycle the treated water, i.e., reuse it for an application requiring lower water quality. An analysis of 18 selected wastewater reuse specifications revealed that at best these guidelines are only partially applicable to innovative recycling systems as they are focused on the downcycling of water to the environment (e.g., use for irrigation). We believe that a paradigm shift is necessary and advocate for the implementation of risk-based (and thus end-use dependent) system performance targets to evaluate water treatment systems, which recycle and not only downcycle water.
Reynaert, E.; Greenwood, E. E.; Ndwandwe, B.; Riechmann, M. E.; Sindall, R. C.; Udert, K. M.; Morgenroth, E. (2020) Practical implementation of true on-site water recycling systems for hand washing and toilet flushing, Water Research X, 7, 100051 (13 pp.), doi:10.1016/j.wroa.2020.100051, Institutional Repository

Disruptions in loading and aeration impact effluent chlorine demand during biological greywater recycling

Greywater recycling systems designed for high-quality applications, such as hand washing, must deliver microbially safe and aesthetically acceptable water under the challenging operating conditions present where such systems are needed most urgently. As chlorination is the most popular strategy for reducing bacterial concentrations in greywater, understanding chlorination in the context of disruptive and challenging operation is essential to designing robust treatment. In this study, we have examined how disruptions through overall increased loading, interrupted aeration and increased ammonia loading have impacted the chlorine demand of the water produced by a greywater recycling system. We also presented concentrations of significant chemicals that contributed to this chlorine demand. The results indicate that a 1 d period with 8 times (8x) the normal design loading produced a peak chlorine demand of 0.74 mg Cl2/L, which is approximately double the baseline value. While this chlorine demand can be overcome by adding more chlorine, tests involving disruptions in aeration or feeding additional ammonia into the bioreactor produced much greater increases (>30x). The risks of increased chlorine demand on microbial safety can be overcome by limiting ammonia inputs to the system, providing backup systems to ensure sufficient aeration, or through additional anti-bacterial measures that do not depend on maintaining residual chlorine.
Ziemba, C.; Sharma, P.; Ahrens, T.; Reynaert, E.; Morgenroth, E. (2021) Disruptions in loading and aeration impact effluent chlorine demand during biological greywater recycling, Water Research X, 11, 100087 (10 pp.), doi:10.1016/j.wroa.2020.100087, Institutional Repository

Linking transformations of organic carbon to post-treatment performance in a biological water recycling system

Ozone, electrolysis and granular activated carbon (GAC) were examined as potential post-treatments to follow a household-scale biologically activated membrane bioreactor (BAMBi), treating a wash water containing trace urine and feces contamination. Each post-treatment was evaluated for abilities and reaction preferences to remove or transform dissolved organic carbon (DOC), chemical structures that contribute color, and assimilable organic carbon (AOC), which can support bacterial regrowth. Batch treatment with each technology demonstrated an ability to remove ≥95% DOC. Ozone demonstrated a reaction selectivity through increased reaction rates with larger compounds and color-contributing compounds. Electrolysis and GAC demonstrated generally less-selective reactivity. Adding post-treatments to full-scale systems reduced DOC (55-91%), AOC (34-62%), and color (75-98%), without significant reaction selectivity. These reductions in DOC and AOC were not linked to reduction of bacterial concentrations in treated water. Reductions in bacterial concentrations were observed with ozone and electrolysis, but this is credited to oxidation chemicals produced in these systems and not the removal or transformations of organic materials.
Ziemba, C.; Larivé, O.; Reynaert, E.; Huisman, T.; Morgenroth, E. (2020) Linking transformations of organic carbon to post-treatment performance in a biological water recycling system, Science of the Total Environment, 721, 137489 (8 pp.), doi:10.1016/j.scitotenv.2020.137489, Institutional Repository

Comparing the anti-bacterial performance of chlorination and electrolysis post-treatments in a hand washing water recycling system

Innovative solutions are necessary to enable the decentralized recycling of greywater for applications requiring high-quality water, such as hand washing. While physical barriers such as ultrafiltration membranes effectively prevent the passage of bacteria, and chemical and biological treatments can effectively reduce the carbon content of the treated water, there exists a knowledge gap regarding the application of anti-bacterial strategies to prevent the growth of harmful bacteria following treatment. In this study, the effluent water from a household-scale greywater treatment system was fed to seven parallel experimental post-treatment tanks: three receiving direct chlorination with free chlorine residuals of 0.2, 1 or 5 mg Cl2/L, three with chlorine produced through electrolysis at the same residual concentrations, and one control with no chlorine added. For increasing concentrations of direct chlorination, the median total cell count (TCC) values were 9 × 104, 2.9 × 104 and 1.8 × 103 cells/mL, respectively. Electrolysis treatment produced very similar TCC concentrations, 8.8 × 104, 1.1 × 104 and 2.3 × 103 cells/mL. The TCC concentrations were lower than the concentration of the water entering each tank (~3 × 105 cells/mL). Intact cell count (ICC) measurements indicated that the viable cell concentrations, were less than 10% of the TCC values. Though electrolysis treatment can produce powerful oxidants, such as hydroxyl radical, there was no evidence that electrolysis in this system provided additional benefits beyond chlorine production for control of total or intact cell counts. Oxidation of bacteria by chlorine was the dominant anti-bacterial mechanism in our system. Monitoring of dissolved organic carbon (DOC) and assimilable organic carbon (AOC) did not suggest that carbon-limitation significantly impacted cell counts when chlorination or electrolysis treatment was applied. This work demonstrates that either direct chlorination or electrolysis treatment are able to reduce bacteria concentrations over long-term operation of a hand washing water treatment system. We recommend selecting chlorine residual targets such that a chlorine residual is maintained during periods of challenging operating conditions. We observed that a target residual of 1 mg Cl2/L, in our system, maintained the TCC below the concentration found in Zürich drinking water.
Ziemba, C.; Larivé, O.; Deck, S.; Huisman, T.; Morgenroth, E. (2019) Comparing the anti-bacterial performance of chlorination and electrolysis post-treatments in a hand washing water recycling system, Water Research X, 2, 100020 (10 pp.), doi:10.1016/j.wroa.2018.100020, Institutional Repository

Chemical composition, nutrient-balancing and biological treatment of hand washing greywater

On-site biological hand washing water treatment can improve global access to safe hand washing water, but requires a thorough understanding of the chemical composition of the water to be treated, and an effective treatment strategy. This study first presents a detailed characterization of the individual inputs to hand washing water. We demonstrate (1) that soap is likely the most significant input in hand washing water, representing ∼90% of mass loading, and (2) that inputs to hand washing water have low concentrations of biologically-essential macro- and micro-nutrients (nitrogen, phosphorus, potassium, copper, zinc, molybdenum and cobalt) with respect to carbon, which may impair biological carbon removal. This study next formulates a recipe that recreates a representative composition of hand washing water and develops a procedure to identify and supplement nutrients in which this recipe is estimated to be deficient. Batch testing of the nutrient-supplemented hand washing water with an inoculum of planktonic bacteria demonstrated improved assimilable organic carbon removal (99% vs. 86% removal) and produced lower final DOC concentrations (1.7 mgC/L vs. 3.5 mgC/L) compared to realistic (nutrient-deficient) washing water. Supplementing nutrients did promote cell growth (50x higher final total cell count). Full-scale testing in a biologically activated membrane bioreactor (BAMBi) system treating 75 L/day of nutrient-supplemented hand washing water showed that long-term operation (100 days) can deliver effective carbon removal (95%) without detrimental fouling or other disruptions caused by cell growth. This work demonstrates that biological treatment in a BAMBi system, operated with appropriate nutrient-balancing offers an effective solution for decentralized treatment of light greywater.
Ziemba, C.; Larivé, O.; Reynaert, E.; Morgenroth, E. (2018) Chemical composition, nutrient-balancing and biological treatment of hand washing greywater, Water Research, 144, 752-762, doi:10.1016/j.watres.2018.07.005, Institutional Repository

Controlling bacterial pathogens in water for reuse: treatment technologies for water recirculation in the Blue Diversion Autarky Toilet

The Blue Diversion AUTARKY Toilet is a urine-diverting toilet with on-site treatment. The toilet is being developed to provide a safe and affordable sanitation technology for people who lack access to sewer-based sanitation. Water used for personal hygiene, hand washing, and flushing to rinse urine- and feces-collection bowls is treated, stored, and recycled for reuse to reduce reliance on external water supplies. The system provides an opportunity to investigate hygiene of water for reuse following treatment. Treatment in the toilet includes a Biologically Activated Membrane Bioreactor (BAMBi) followed by a secondary treatment technology. To identify effective secondary treatment, three options, including granular activated carbon (GAC) only, GAC+chlorine (sodium hypochlorite), and GAC+electrolysis are considered based on the bacterial inactivation and growth inhibition efficiency. Four different hygiene-relevant bacteria are tested: Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Salmonella typhimurium. Our evaluation demonstrates that—despite treatment of water with the BAMBi—E. coli, P. aeruginosa, and S. typhimurium have the potential to grow during storage in the absence of microbial competition. Including the indigenous microbial community influences bacterial growth in different ways: E. coli growth decreases but P. aeruginosa growth increases relative to no competition. The addition of the secondary treatment options considerably improves water quality. A column of GAC after the BAMBi reduces E. coli growth potential by 2 log10, likely due to the reduction of carbon sources. Additional treatments including chlorination and electrolysis provide further safety margins, with more than 5 log10 inactivation of E. coli. However, reactivation and/or regrowth of E. coli and P. aeruginosa occurs under in the absence of residual disinfectant. Treatment including the BAMBi, GAC, and electrolysis appear to be promising technologies to control bacterial growth during storage in water intended for reuse.
Nguyen, M. T.; Allemann, L.; Ziemba, C.; Larivé, O.; Morgenroth, E.; Julian, T. R. (2017) Controlling bacterial pathogens in water for reuse: treatment technologies for water recirculation in the Blue Diversion Autarky Toilet, Frontiers in Environmental Science, 5, 90 (13 pp.), doi:10.3389/fenvs.2017.00090, Institutional Repository

On-site treatment of used wash-water using biologically activated membrane bioreactors operated at different solids retention times

Biologically activated membrane bioreactors (BAMBis) were operated at suspended solids retention times (SRT) of 7 and 102 days and at full solids retention. The effect of these different approaches of operation on substrate and nutrient conversion, and on permeate flux was investigated. Variations in organic loads and aeration intensities were also studied. Permeate flux stabilized during long-term operation independently of suspended SRT. Removal of organic substrate was independent of solids concentrations and remained stable over the long term. Microorganisms colonizing the surface of particles were found as the main mechanism responsible for degradation of organic substrate in the particulate form. BAMBi appeared to be a robust technology, adapted to on-site treatment of used wash-water, as it can be operated without control of suspended SRT. Thus BAMBis can be operated for long periods without any control of biofouling and sludge formation, leading to low maintenance needs. When BAMBis were operated at low aeration, the formation of anoxic zones led to combined nitrification and denitrification and thus significant nitrogen removal.
Ravndal, K. T.; Künzle, R.; Derlon, N.; Morgenroth, E. (2015) On-site treatment of used wash-water using biologically activated membrane bioreactors operated at different solids retention times, Journal of Water, Sanitation and Hygiene for Development, 5(4), 544-552, doi:10.2166/washdev.2015.174, Institutional Repository

An energy-efficient membrane bioreactor for on-site treatment and recovery of wastewater

The present study describes the development of a new type of aerated membrane bioreactor referred to as a biologically activated membrane bioreactor (BAMBi) for on-site treatment of high-strength wastewater. The treated wastewater is reused for flushing and personal hygiene. BAMBi is an adaptation of a gravity-driven membrane reactor, originally developed for the purpose of treating river water to drinking water quality. Initially, a series of reactor configurations were tested and it was found that the simplest possible configuration could treat the wastewater to an acceptable standard, provided that a polishing step for color removal and disinfection was introduced. A commercial electrolysis unit was utilized for polishing. The energy consumption of BAMBi is 0.8 kWh/m3 of water treated, which can be considered low for an on-site membrane bio reactor application.
Künzle, R.; Pronk, W.; Morgenroth, E.; Larsen, T. A. (2015) An energy-efficient membrane bioreactor for on-site treatment and recovery of wastewater, Journal of Water, Sanitation and Hygiene for Development, 5(3), 448-455, doi:10.2166/washdev.2015.116, Institutional Repository

More about urine treatment

Two processes are necessary to treat the source-separated urine in the toilet: urine stabilization and water removal.

The main goal of the Autarky urine stabilization is the prevention of urea hydrolysis, a process converting urea to volatile ammonia and carbon dioxide. Through the addition of calcium hydroxide to fresh urine, the pH increases to values above 12 and thus prevents microbial urea hydrolysis. 

Contacts

Michel Riechmann Tel. +41 58 765 5748 Send Mail
Prof. Dr. Kai Udert Tel. +41 58 765 5360 Send Mail

Additionally, the high pH kills pathogens and prevents biological processes that produce malodor. When calcium hydroxide is added to the urine only about the amount dissolves that is needed to reach the necessary high pH value. This allows providing a depot of the reagent in the stabilization reactor; thus, no expensive and complicated dosage mechanisms are required. Moreover, calcium hydroxide, also known as hydrated lime, is a cheap reagent and readily available worldwide.

The direct application of human urine as fertilizer is a common practice in many rural areas around the globe. However, the high water content of urine – no matter if stabilized or not – requires significant storage capacity and can make the collection and transport to the agricultural fields very costly. Volume reduction does not only reduce costs for storage and transport, but could also facilitate field application of the concentrated fertilizer. Standard volume reduction techniques are most often energy intensive processes, because they require high temperature (distillation) or pressure (reverse osmosis).

Offering an alternative to these processes, our approach uses forced convection to reduce the volume of the urine. The evaporation reactor consists of a stacked tray system to create a large surface area. Fans generating a high air stream accelerate the evaporation of the the water from the incoming urine. The offgas is filtered through an activated carbon filter, preventing the emission of organic contamination or malodour.

Once a month, the system needs to be serviced. Tasks are to refill the calcium hydroxide depot and to harvest the trays. The remaining end-product is a concentrate of inorganic and organic nutrients that can be used as fertilizer in agriculture.

Current activities

The stabilization and evaporation reactors have been subject to extensive testing. These tests were supported by lab tests of specific parts of the reactors and a computer model simulating the system. Based on the collected information, the two reactors underwent a major redesign, allowing for an increased evaporation efficiency along with reduced overall size. Another focus of the redesign was the integration of service appliances, e.g. for harvesting of the produced nutrient concentrate.

To validate the technic in real-life settings several field tests of one to four months were conducted. The urine module was tested as part of the Autarky toilet system at Eawag campus in Dübendorf (Switzerland), as well as in a large family household in a Durban Township (South Afrika). As an individual entity, field tests of the urine module took place attached to a mobile Tinihouse (Au, Switzerland) and on a mountain hut (Leglerhütte, Switzerland).

Update: Technical details and everything about the field tests can now be found in our latest publication (open-access): https://doi.org/10.1016/j.wroa.2021.100124

 

 

Urine module
The urine module built-in the Blue Diversion Autarky toilet

Publications

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      originalId => protected24043 (integer)
      authors => protected'Riechmann,&nbsp;M.&nbsp;E.; Ndwandwe,&nbsp;B.; Greenwood,&nbsp;E.&nbsp;E.; R
         eynaert,&nbsp;E.; Morgenroth,&nbsp;E.; Udert,&nbsp;K.&nbsp;M.' (137 chars)
      title => protected'On-site urine treatment combining Ca(OH)<sub>2</sub> dissolution and dehydra
         tion with ambient air' (97 chars)
      journal => protected'Water Research X' (16 chars)
      year => protected2021 (integer)
      volume => protected13 (integer)
      issue => protected'' (0 chars)
      startpage => protected'100124 (12 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'field testing; resource recovery; urine stabilization; calcium hydroxide; so
         urce separation; Blue Diversion Autarky' (115 chars)
      description => protected'We present the results of three field tests and three laboratory tests of a 
         new physical-chemical urine treatment system, which can recover all nutrient
         s, while pathogens are inactivated. The system consists of two steps. In the
          first reactor, biological processes including urea hydrolysis are prevented
          by mixing fresh urine with calcium hydroxide (Ca(OH)<sub>2</sub>). Due to t
         he high pH value and the high availability of calcium, phosphate can be reco
         vered by precipitation. The high pH value also fosters the inactivation of m
         icroorganisms, including pathogens. In the second reactor, water is evaporat
         ed at low energy consumption by blowing unheated ambient air over the stabil
         ized urine. Stabilization in the first reactor was successful in all field a
         nd laboratory tests. The pH value remained between 12 and 13, except for sho
         rt dips due to shortages of Ca(OH)<sub>2</sub>. Nearly all phosphorus (92-96
         %) precipitated and could be recovered as calcium phosphate in the first rea
         ctor, while nitrogen and potassium overflowed with the urine into the evapor
         ation reactor. The efficiency of the second treatment step was very differen
         t for field and laboratory experiments and depended on the duration of the e
         xperiment. During a four-day laboratory test, nitrogen recovery was 98%. In 
         contrast, nitrogen recovery was only around 20% in the long-term field exper
         iments. The high nitrogen losses occurred, because biological urea hydrolysi
         s was not inhibited anymore, when the pH value in the second reactor decreas
         ed due to the dissolution of high amounts of carbon dioxide from the ambient
          air. Potassium was not subject to any significant loss, and the measured re
         covery in the solid evaporation product was 98%. Evaporation rates ranged be
         tween 50 g m<sup>-2</sup> h<sup>-1</sup> (RH = 82±13%, T = 12±6°C) and 13
         0 g m<sup>-2</sup> h<sup>-1</sup> (RH = 60±19%, T = 24±5°C) in the three 
         field tests. Apart from some disturbances due to low supply of Ca(OH)<sub>2<
         /sub>, the urine module ...' (2324 chars)
      serialnumber => protected'2589-9147' (9 chars)
      doi => protected'10.1016/j.wroa.2021.100124' (26 chars)
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   1 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=10403, pid=124)
      originalId => protected10403 (integer)
      authors => protected'Randall,&nbsp;D.&nbsp;G.; Krähenbühl,&nbsp;M.; Köpping,&nbsp;I.; Larsen,&
         nbsp;T.&nbsp;A.; Udert,&nbsp;K.&nbsp;M.' (115 chars)
      title => protected'A novel approach for stabilizing fresh urine by calcium hydroxide addition' (74 chars)
      journal => protected'Water Research' (14 chars)
      year => protected2016 (integer)
      volume => protected95 (integer)
      issue => protected'' (0 chars)
      startpage => protected'361' (3 chars)
      otherpage => protected'369' (3 chars)
      categories => protected'urine; source separation; stabilization of urea; inhibition of urease; phosp
         horus recovery' (90 chars)
      description => protected'In this study, we investigated the prevention of enzymatic urea hydrolysis i
         n fresh urine by increasing the pH with calcium hydroxide (Ca(OH)<SUB>2</SUB
         >) powder. The amount of Ca(OH)<SUB>2</SUB> dissolving in fresh urine depend
         s significantly on the composition of the urine. The different urine composi
         tions used in our simulations showed that between 4.3 and 5.8 g Ca(OH)<SUB>
         2</SUB> dissolved in 1 liter of urine at 25 °C. At this temperature, the p
         H at saturation is 12.5 and is far above the pH of 11, which we identified a
         s the upper limit for enzymatic urea hydrolysis. However, temperature has a 
         strong effect on the saturation pH, with higher values being achieved at low
         er temperatures. Based on our results, we recommend a dosage of 10 g Ca(OH)
         <SUB>2</SUB>·L<SUP>−1</SUP> of fresh urine to ensure solid Ca(OH)<SUB>2</
         SUB> always remains in the urine reactor which ensures sufficiently high pH 
         values. Besides providing sufficient Ca(OH)<SUB>2</SUB>, the temperature has
          to be kept in a certain range to prevent chemical urea hydrolysis. At tempe
         ratures below 14 °C, the saturation pH is higher than 13, which favors che
         mical urea hydrolysis. We chose a precautionary upper temperature of 40 °C
          because the rate of chemical urea hydrolysis increases at higher temperatur
         es but this should be confirmed with kinetic studies. By considering the bou
         ndaries for pH and temperature developed in this study, urine can be stabili
         zed effectively with Ca(OH)<SUB>2</SUB> thereby simplifying later treatment 
         processes or making direct use easier.' (1558 chars)
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      authors => protected'Udert,&nbsp;K.&nbsp;M.; Larsen,&nbsp;T.&nbsp;A.; Biebow,&nbsp;M.; Gujer,&nbs
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      title => protected'Urea hydrolysis and precipitation dynamics in a urine-collecting system' (71 chars)
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      categories => protected'urine separation; NoMix; ureolysis; precipitation; struvite; calcium phospha
         te' (78 chars)
      description => protected'Blockages caused by inorganic precipitates are a major problem of urine-coll
         ecting systems. The trigger of precipitation is the hydrolysis of urea by ba
         cterial urease. While the maximum amount of precipitates, i.e. the precipita
         tion potential, can be estimated with equilibrium calculations, little is kn
         own about the dynamics of ureolysis and precipitation. To gain insight in th
         ese processes, we performed batch experiments with precipitated solids and s
         tored urine from a urine-collecting system and later simulated the results w
         ith a computer model. We found that urease-active bacteria mainly grow in th
         e pipes and are flushed into the collection tank. Both, bacteria and free ur
         ease, hydrolyse urea. Only few days are necessary for complete urea depletio
         n in the collection tank. Two experiments with precipitated solids from the 
         pipes showed that precipitation sets in soon after ureolysis has started. At
          the end of the experiments, 11% and 24% of urea was hydrolysed while the ma
         ss concentration of newly formed precipitates already corresponded to 87% an
         d 97% of the precipitation potential, respectively. We could simulate ureoly
         sis and precipitation with a computer model based on the surface dislocation
          approach. The simulations showed that struvite and octacalcium phosphate (O
         CP) are the precipitating minerals. While struvite precipitates already at l
         ow supersaturation, OCP precipitation starts not until a high level of super
         saturation is reached. Since measurements and computer simulations show that
          hydroxyapatite (HAP) is the final calcium phosphate mineral in urine soluti
         ons, OCP is only a precursor phase which slowly transforms into HAP.' (1664 chars)
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On-site urine treatment combining Ca(OH)2 dissolution and dehydration with ambient air

We present the results of three field tests and three laboratory tests of a new physical-chemical urine treatment system, which can recover all nutrients, while pathogens are inactivated. The system consists of two steps. In the first reactor, biological processes including urea hydrolysis are prevented by mixing fresh urine with calcium hydroxide (Ca(OH)2). Due to the high pH value and the high availability of calcium, phosphate can be recovered by precipitation. The high pH value also fosters the inactivation of microorganisms, including pathogens. In the second reactor, water is evaporated at low energy consumption by blowing unheated ambient air over the stabilized urine. Stabilization in the first reactor was successful in all field and laboratory tests. The pH value remained between 12 and 13, except for short dips due to shortages of Ca(OH)2. Nearly all phosphorus (92-96%) precipitated and could be recovered as calcium phosphate in the first reactor, while nitrogen and potassium overflowed with the urine into the evaporation reactor. The efficiency of the second treatment step was very different for field and laboratory experiments and depended on the duration of the experiment. During a four-day laboratory test, nitrogen recovery was 98%. In contrast, nitrogen recovery was only around 20% in the long-term field experiments. The high nitrogen losses occurred, because biological urea hydrolysis was not inhibited anymore, when the pH value in the second reactor decreased due to the dissolution of high amounts of carbon dioxide from the ambient air. Potassium was not subject to any significant loss, and the measured recovery in the solid evaporation product was 98%. Evaporation rates ranged between 50 g m-2 h-1 (RH = 82±13%, T = 12±6°C) and 130 g m-2 h-1 (RH = 60±19%, T = 24±5°C) in the three field tests. Apart from some disturbances due to low supply of Ca(OH)2, the urine module functioned without any substantial failures and was simple to maintain. The minimum consumption of Ca(OH)2 at full capacity was 6 g·L-1 urine and the electricity demand was 150 Wh kg-1 water evaporated from urine, resulting in operational costs of 0.05 EUR pers-1 d-1.
Riechmann, M. E.; Ndwandwe, B.; Greenwood, E. E.; Reynaert, E.; Morgenroth, E.; Udert, K. M. (2021) On-site urine treatment combining Ca(OH)2 dissolution and dehydration with ambient air, Water Research X, 13, 100124 (12 pp.), doi:10.1016/j.wroa.2021.100124, Institutional Repository

A novel approach for stabilizing fresh urine by calcium hydroxide addition

In this study, we investigated the prevention of enzymatic urea hydrolysis in fresh urine by increasing the pH with calcium hydroxide (Ca(OH)2) powder. The amount of Ca(OH)2 dissolving in fresh urine depends significantly on the composition of the urine. The different urine compositions used in our simulations showed that between 4.3 and 5.8 g Ca(OH)2 dissolved in 1 liter of urine at 25 °C. At this temperature, the pH at saturation is 12.5 and is far above the pH of 11, which we identified as the upper limit for enzymatic urea hydrolysis. However, temperature has a strong effect on the saturation pH, with higher values being achieved at lower temperatures. Based on our results, we recommend a dosage of 10 g Ca(OH)2·L−1 of fresh urine to ensure solid Ca(OH)2 always remains in the urine reactor which ensures sufficiently high pH values. Besides providing sufficient Ca(OH)2, the temperature has to be kept in a certain range to prevent chemical urea hydrolysis. At temperatures below 14 °C, the saturation pH is higher than 13, which favors chemical urea hydrolysis. We chose a precautionary upper temperature of 40 °C because the rate of chemical urea hydrolysis increases at higher temperatures but this should be confirmed with kinetic studies. By considering the boundaries for pH and temperature developed in this study, urine can be stabilized effectively with Ca(OH)2 thereby simplifying later treatment processes or making direct use easier.
Randall, D. G.; Krähenbühl, M.; Köpping, I.; Larsen, T. A.; Udert, K. M. (2016) A novel approach for stabilizing fresh urine by calcium hydroxide addition, Water Research, 95, 361-369, doi:10.1016/j.watres.2016.03.007, Institutional Repository

Urea hydrolysis and precipitation dynamics in a urine-collecting system

Blockages caused by inorganic precipitates are a major problem of urine-collecting systems. The trigger of precipitation is the hydrolysis of urea by bacterial urease. While the maximum amount of precipitates, i.e. the precipitation potential, can be estimated with equilibrium calculations, little is known about the dynamics of ureolysis and precipitation. To gain insight in these processes, we performed batch experiments with precipitated solids and stored urine from a urine-collecting system and later simulated the results with a computer model. We found that urease-active bacteria mainly grow in the pipes and are flushed into the collection tank. Both, bacteria and free urease, hydrolyse urea. Only few days are necessary for complete urea depletion in the collection tank. Two experiments with precipitated solids from the pipes showed that precipitation sets in soon after ureolysis has started. At the end of the experiments, 11% and 24% of urea was hydrolysed while the mass concentration of newly formed precipitates already corresponded to 87% and 97% of the precipitation potential, respectively. We could simulate ureolysis and precipitation with a computer model based on the surface dislocation approach. The simulations showed that struvite and octacalcium phosphate (OCP) are the precipitating minerals. While struvite precipitates already at low supersaturation, OCP precipitation starts not until a high level of supersaturation is reached. Since measurements and computer simulations show that hydroxyapatite (HAP) is the final calcium phosphate mineral in urine solutions, OCP is only a precursor phase which slowly transforms into HAP.
Udert, K. M.; Larsen, T. A.; Biebow, M.; Gujer, W. (2003) Urea hydrolysis and precipitation dynamics in a urine-collecting system, Water Research, 37(11), 2571-2582, doi:10.1016/S0043-1354(03)00065-4, Institutional Repository

Decrey, L., and Kohn, T. (2017) Virus inactivation in stored human urine, sludge and animal manure under typical conditions of storage or mesophilic anaerobic digestion.  Environmental Science: Water Research & Technology.

Antonini, S., et al. (2012). "Solar thermal evaporation of human urine for nitrogen and phosphorus recovery in Vietnam." Sci Total Environ 414: 592-599.

Pahore, M. M., et al. (2010). "Rational design of an on-site volume reduction system for source-separated urine." Environ Technol 31(4): 399-408.

More about feces treatment

In the Blue Diversion Autarky toilet, the feces are separated from the flush water and collected in a container at the bottom of the toilet. They may contain pathogens and must be inactivated quickly to avoid anaerobic decomposition and the emission of malodorous gases. 

Contact

Frédéric Vogel (PSI/ FHNW) frederic.vogel@psi.ch

In our approach, the organic matter of the fecal sludge is completely mineralized to carbon dioxide, water and minerals such as phosphate salts. The remaining streams are off-gas and a mixture of water and minerals. The off-gas contains mainly nitrogen, carbon dioxide and oxygen. This mixture can be safely vented to the atmosphere. The aqueous stream may be utilized as a fertilizer.

The process used to treat the feces is called “hydrothermal oxidation” or HTO. When mixed with air and heated above around 400°C under high pressure, the fecal sludge decomposes and is oxidized completely to carbon dioxide and water. The water in the sludge does not evaporate but mixes with the air and provides a reaction environment for an efficient conversion of the organic matter within a few minutes.

Current activities

For a better understanding of the HTO process, we are developing a comprehensive computer model of the reactor. This computer model is fed with data from experiments carried out in small autoclaves with real fecal sludge. We determined that the oxidation reaction is rapid above around 300°C and runs to completion within only a few minutes at 400°C.

We are currently improving the third prototype generation of the so-called FOX reactor (short for feces oxidation). This reactor will be field tested with real users soon. We are also working on the design of a more compact version of the FOX reactor, so it can be tested as part of the complete Blue Diversion Autarky toilet in the future.

Publications

Hübner, T.; Roth, M.; Vogel, F. (2016).  Hydrothermal oxidation of fecal sludge: experimental investigations and kinetic modeling, Ind. Eng. Chem. Res. 55 (46), pp.11910-11922 

Mangold, F.; Pilz, St.; Bjelić, S.; Vogel, F. (2019). Equation of state and thermodynamic properties for mixtures of H2O, O2, N2, and CO2 from ambient up to 1000 K and 280 MPa. The Journal of Supercritical Fluids, Volume 153, 104476

Team

The Blue Diversion Autarky team consists of researchers and experts from the Swiss Federal Institute of Aquatic Science (Eawag), the Paul Scherrer Institue (PSI), the University of Applied Sciences and Arts Northwestern Switzerland (FHNW) and from EOOS. The project is supported by an advisory board of six international commercial partners. Funding is provided by the Bill and Melinda Gates Foundation (BMGF).

Partner projects

Blue Diversion Toilet - an attractive, safe and affordable sanitation solution

VUNA - nutrient recovery from human urine

Nest - exploring the future of buildings