solution finder

05 June 2019

Struvite

Author/Compiled by
Bastian Etter (Swiss Federal Institute of Aquatic Science and Technology – Eawag)
Elizabeth Tilley (Swiss Federal Institute of Aquatic Science and Technology – Eawag)
Dorothee Spuhler (seecon international gmbh)
Executive Summary

Urine, which contains valuable nutrients like nitrogen and phosphorus, can be applied to soil and used as fertiliser for crops. Though valuable, urine is sometimes difficult to transport and store and it does not have a pleasant odour. To overcome these issues, struvite can be produced. Struvite (MgNH4PO4•6H2O) has many of the fertilising properties of urine with several advantages: the volume and weight are reduced, it can be stored in a compact form and it is easy to handle, transport and apply- especially in a granulated form.

Advantages
Reduced weight and volume of nutrients (compared to urine)
Easy transport, storage and handling
No bad smell
Simple technology; can be built an operated almost anywhere
Construction with local materials
Easy operation (no electricity)
User-friendly fertiliser product
Disadvantages
High volumes of urine required
Low yields (approximately 1 kg struvite from 500 L urine)
Partial recovery of nitrogen and no recovery of potassium
Requires soluble magnesium source
Transport costs of urine (to the struvite production site) reduce economic viability
Effluent requires treatment or controlled reuse (i.e. fertigation)
Possible corrosion of metal appliances
In Out

Urine, Yellowwater

Fertiliser

Factsheet Block Title
What is Struvite?
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Through a basic precipitation reaction, the majority of phosphorus in urine can be crystallised into a white, odourless powder: struvite (MgNH4PO4•6H2O), sometimes also called Magnesium Ammonium Phosphate Hexahydrate (M-A-P). Struvite is a bioavailable, slow-release fertiliser; it is compact and can be stored, transported and applied easily, and does not smell (see the picture below). Through struvite recovery, over 90% of phosphate can easily be removed from urine.

Filtered and dried struvite powder. Source: ETTER (2009)
Filtered and dried struvite powder. Source: ETTER (2009)

 

Factsheet Block Title
How is Struvite formed?
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Urine contains phosphate (PO4) and ammonium (NH4). When magnesium (Mg) is added to urine, phosphate, ammonium and magnesium bind and form struvite (MgNH4PO4•6H2O), which can then be filtered out, collected, and dried into a powder (see the figure below).

Struvite formation in urine after magnesium addition. Source: ETTER (2009)
Struvite formation in urine after magnesium addition. Source: ETTER (2009)

 

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Where can Magnesium for the Precipitation be found?
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Various magnesium-containing substances can induce the precipitation of struvite- each with different qualities and costs. Bittern, the liquid, which remains after salt (NaCl) extraction from seawater, is highly concentrated with magnesium (and other minerals). Therefore, in coastal areas where salt is produced, this is an ideal source of magnesium. Furthermore, because it is a liquid, the bittern is easily dosed and readily mixed with urine.

Magnesite rock (MgCO3) can also be used as precipitant if it is treated properly. The rock powder is heated in a calcination kiln (analogous to lime calcination) to produce magnesium oxide (MgO), which dissolves in urine (untreated MgCO3 will not dissolve). If no local magnesium source is available, other magnesium compounds (e.g. magnesium chloride, MgCl2.6H2O or magnesium sulphate, MgSO4•7H2O), may be purchased, though they are likely to be more expensive.

Factsheet Block Title
How is the Struvite Reactor Built?
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A struvite reactor can be easily built, using locally available materials and skills (see the figure below). The main tank can be constructed with conventional plastic containers (e.g. polyethylene, polypropylene, polyvinylchloride) or galvanised steel sheets. The stirring mechanism, as well as the supporting structure should be assembled from steel, which is coated or galvanised for rust proofing. Pipes and fittings should be made of plastic to prevent corrosion.

Assembly of the struvite reactor. Source: ETTER (2009)
Assembly of the struvite reactor. Source: ETTER (2009)

 

Factsheet Block Title
How does the Struvite Reactor work?
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The reactor consists of a stirring mechanism, which is fitted inside the tank; a nylon cloth filter bag hangs below a valve to allow the main reactor to be drained (see the figure below). To start the process, the collected urine and magnesium are mixed for 10 minutes in the reaction tank. The valve is opened and the suspension is then drained into the filter bag. The filter bag retains the struvite while the effluent passes through. The filter bag is air dried for one to two days, after which point the struvite is ready to use. In field experiments, this type of reactor was able to recover over 90 % of the phosphate contained in the urine. Because struvite also precipitates naturally from urine, any precipitate in the collection system should be incorporated into the final product, in order to maximise nutrient recovery.

The basic steps of struvite production in the precipitation reactor. Source: ETTER (2009)
The basic steps of struvite production in the precipitation reactor. Source: ETTER (2009)

 

Factsheet Block Title
How can Struvite be Applied?
Factsheet Block Body

Struvite can be applied to fields just like any other fertiliser. In a simple granulation drum (see the figure below), the powder can be transformed into granules. In granular form, a fertiliser is easier to apply and does not cake in moist environments. Struvite performs comparably to diammonium phosphate (DAP) fertiliser and has the following advantages:

  • Bio-available: The nutrients in struvite can be readily absorbed by the plant.
  • Slow-release: Due to its low solubility, struvite guarantees a slow but steady nutrient supply.
  • Highly pure: contaminants (e.g. pharmaceuticals or heavy metals), which may be present in the urine, do not precipitate with the struvite.

 

Formation of granules in a rotating drum. Source: ETTER (2009)
Formation of granules in a rotating drum. Source: ETTER (2009)

 

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How can the Effluent be used?
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After the struvite is filtered out of solution, the same quantity of urine remains; this effluent still contains high concentrations of nutrients, particularly nitrogen and potassium. The effluent may be used in drip-irrigation for fertigation (fertigation is the combination of fertilisation and irrigation). Further nutrient recovery technologies are being developed to extract the remaining nutrients and complement struvite precipitation.
 

Applicability

Struvite precipitation may be appropriate for any situation where significant quantities of urine can be collected. Struvite can be produced from a variety of wastewaters (including domestic wastewater or liquid animal manure) but the process is more difficult and requires additional chemicals for pH control. Urine collection (labour) and transport (fuel) accounts for a large proportion of the costs, and therefore struvite production is more appropriate for areas where large volumes of urine are available within a small area; public toilets, schools and stadia are promising sources of urine.

Magnesium should be available in a suitably soluble form, in sufficient quantities and at an affordable price to allow for an economic operation of the struvite production plant. Whereas direct application of urine may face low social acceptance, struvite, as a urine-derived but odourless product is generally well accepted.

Library References
Further Readings

Low-cost Struvite Reactor - Construction Manual

The aim of this publication is to present and discuss the design drawings, from which a struvite precipitation reactor can be built. In addition, a breakdown of the building costs and some suggestions for improvements are presented.

ZANDEE, M. ETTER, B. (2011): Low-cost Struvite Reactor - Construction Manual. Duebendorf: Swiss Federal Institute of Aquatic Science and Technology (EAWAG) URL [Accessed: 05.06.2019]

The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology

Development of on-site sanitation facilities that treat excreta require knowledge of the waste stream entering the system. This paper contains data regarding the generation rate and the chemical and physical composition of fresh feces and urine. In addition, the impact on biological and thermal processes, physical separators, and chemical reactions is also assessed.

ROSE, C. ; PARKER, A. ; JEFFERSON, B. ; CARTMELL, E. (2015): The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology. In: Critical Reviews in Environmental Science and Technology: Volume 45 , 1827-1879. URL [Accessed: 25.11.2015]
Case Studies
Awareness Raising Material

This module introduces the importance of market-based RRR solutions. At the end of this module you have identified key challenges in your local sanitation and waste management system and a RRR-related business idea.

Cover image Module  1

This module sheds light on the importance of studying the business environment and its components like waste supply, market demand, competition and the institutional framework. At the end of this module you have gained insights to evaluating the potential of your business idea.

Cover image Module  2

This module shows how a business idea can be turned into a business model while putting a specific focus on understanding the customer and designing products that meet their needs. At the end of this module you will have developed a business model and positioned your offer in the market.

Cover image Module  3

This module focusses on planning the operations of a RRR related business. During this part RRR technologies will be introduced for different waste streams and tools for planning the production process. At the end of this module you will have blueprinted your production process and the required technology and production inputs.

Cover image Module  4

This module covers key aspects of financial planning and analysis. At the end of this module you will have forecasted your profits, cash flows, required investment and evaluated the financial viability of your business model.

Cover image Module  5

This module enables you to set objectives and plan activities for the launch of your RRR business and identify potential financing sources. At the end of this module you will have developed an action plan for launch and identified appropriate financing sources.

Cover image Module  6

Week 1: Identify challenges in your local sanitation & waste management

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Further Readings

SDG 6 along the water and nutrient cycles

This AGUASAN publication illustrates how the water and nutrient cycles can be used as a tool for creating a common understanding of a water and sanitation system and aligning it with SDG 6.

BROGAN, J., ERLMANN, T., MUELLER, K. and SOROKOVSKYI, V. (2017): SDG 6 along the water and nutrient cycles. Using the water and nutrient cycles as a tool for creating a common understanding of a water and sanitation system - including workshop material. Bern (Switzerland): AGUASAN and Swiss Agency for Development and Cooperation (SDC) URL [Accessed: 26.03.2019] PDF

Why shit matters [Video File]

TEDX TALKS (2019): https://www.youtube.com/watch?v=d4yD0kz34jg [Accessed: 28.03.2019]

"3 billion people worldwide live in cities without sewers or wastewater treatment plant infrastructure. This forces them to dump their waste into open waters, contaminating the drinking water for others downstream. Imagine if we could harness nutrients in wastewater instead of harming human and environmental health. Christoph Lüthi sees a renewable, locally produced and growing resource where others see only human waste. Watch his talk to learn why shit matters! "

Week 2: Identify RRR products and business opportunities

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Further Readings

A public-private partnership linking wastewater treatment and aquaculture (Ghana) - Case Study

AMOAH, P., MUSPRATT, A., DRECHSEL, P. and OTOO, M. (2018): A public-private partnership linking wastewater treatment and aquaculture (Ghana) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section IV, Chapter 15, pp.617-630. URL [Accessed: 26.03.2019]

Briquettes from agro-waste (Kampala Jellitone Suppliers, Uganda) - Case Study

GEBREZGABHER, S. and MUSISI, A. (2018): Briquettes from agro-waste (Kampala Jellitone Suppliers, Uganda) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section II, Chapter 3, pp.41-51. URL [Accessed: 26.03.2019]

Cooperative model for financially sustainable municipal solid waste composting (NAWACOM, Kenya) - Case Study

OTOO, M., KARANJA, N., ODERO, J. and HOPE, L. (2018): Cooperative model for financially sustainable municipal solid waste composting (NAWACOM, Kenya) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section III, Chapter 3, pp.362-370. URL [Accessed: 26.03.2019]

Week 1: Analyse waste supply

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Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 2: Analyse market demand

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Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 3: Analyse your competition

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Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 4: Analyse the institutional environment

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Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 1: Meet the Business Model Canvas

Download Materials
Further Readings

A public-private partnership linking wastewater treatment and aquaculture (Ghana) - Case Study

AMOAH, P., MUSPRATT, A., DRECHSEL, P. and OTOO, M. (2018): A public-private partnership linking wastewater treatment and aquaculture (Ghana) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section IV, Chapter 15, pp.617-630. URL [Accessed: 26.03.2019]

Briquettes from agro-waste (Kampala Jellitone Suppliers, Uganda) - Case Study

GEBREZGABHER, S. and MUSISI, A. (2018): Briquettes from agro-waste (Kampala Jellitone Suppliers, Uganda) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section II, Chapter 3, pp.41-51. URL [Accessed: 26.03.2019]

Cooperative model for financially sustainable municipal solid waste composting (NAWACOM, Kenya) - Case Study

OTOO, M., KARANJA, N., ODERO, J. and HOPE, L. (2018): Cooperative model for financially sustainable municipal solid waste composting (NAWACOM, Kenya) - Case Study. In: Otoo, M. and Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon (UK): Routledge - Earthscan. Section III, Chapter 3, pp.362-370. URL [Accessed: 26.03.2019]

Week 1: Plan your production process

Download Materials
Further Readings

Compendium of Sanitation Systems and Technologies. 2nd Revised Edition

This compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) URL [Accessed: 28.07.2014] PDF

Week 2: Understand the treatment process

Further Readings

Treatment technologies for urban solid biowaste to create value products: a review with focus on low- and middle-income settings

LOHRI, C. R., DIENER, S., ZABALETA, I. MERTENAT, A. and ZURBRÜGG, C. (2017): Treatment technologies for urban solid biowaste to create value products: a review with focus on low- and middle-income settings. In: Reviews in Environmental Science and Bio/Technology, Volume 16, Issue 1, pp 81–130. URL [Accessed: 26.03.2019] PDF

Week 3A: Design technology systems for nutrient recovery

Further Readings

Co-composting of Solid Waste and Fecal Sludge for Nutrient and Organic Matter Recovery

COFIE, O., NIKIEMA, J., IMPRAIM, R., ADAMTEY, N., PAUL, J. and KONÉ, D. (2016): Co-composting of Solid Waste and Fecal Sludge for Nutrient and Organic Matter Recovery. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 3. URL [Accessed: 27.03.2019]

Decentralized composting in India

DRESCHER, S. and ZURBRÜGG, C. (2004): Decentralized composting in India. In: Harper et al. Sustainable Composting: Case Studies in Guidelines for Developing Countries. Loughborough (UK): Water Engineering and Development Centre (WEDC), Loughborough University, Part2: Case Studies, Chapter 3, pp.15-27. URL [Accessed: 27.03.2019] PDF

Low Cost Composting Training Manual: techniques based on the UN-Habitat/Urban Harvest-CIP community based waste management initiatives

KARANJA, N., KWACH, H. and NJENGA, M. (2005): Low Cost Composting Training Manual: techniques based on the UN-Habitat/Urban Harvest-CIP community based waste management initiatives. Nairobi (Kenya): UN-Habitat. URL [Accessed: 27.03.2019]

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 3B: Design technology systems for energy recovery

Further Readings

Briquette Businesses in Uganda. The potential for briquette enterprises to address the sustainability of the Ugandan biomass fuel market

FERGUSON, H. (2012): Briquette Businesses in Uganda. The potential for briquette enterprises to address the sustainability of the Ugandan biomass fuel market. London (UK): Global Village Energy Partnership (GVEP) International. URL [Accessed: 27.03.2019] PDF

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 3C: Design technology systems for water recovery

Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Chapter 3 - Technology Selection

VEENSTRA, S., ALAERTS, G. and BIJLSMA, M. (1997): Chapter 3 - Technology Selection. In: Helmer, R. and Hespanhol, I. (Eds). Water Pollution Control - A Guide to the Use of Water Quality Management Principles. London (UK): World Health Organization (WHO)/United Nations Environment Programme (UNEP). URL [Accessed: 27.03.2019]

Guidelines for the safe use of wastewater excreta and greywater. Volume I. Policy and Regulatory Aspects

Volume I of the Guidelines for the Safe Use of Wastewater, Excreta and Greywater focuses on policy, regulation and institutional arrangements. Accordingly, its intended readership is made up of policy-makers and those with regulatory responsibilities. It provides guidance on policy formulation, harmonisation and mainstreaming, on regulatory mechanisms and on establishing institutional links between the various interested sectors and parties. It also presents a synthesis of the key issues from Volumes II, III, and IV and the index for all four volumes as well as a glossary of terms used in all four volumes is presented in Annex 1.

WHO (2006): Guidelines for the safe use of wastewater excreta and greywater. Volume I. Policy and Regulatory Aspects. Geneva: World Health Organisation URL [Accessed: 10.04.2019]

Guidelines for the safe use of wastewater excreta and greywater. Volume II. Wastewater Use in Agriculture

Volume II of the Guidelines for the safe use of wastewater, excreta and greywater provides information on the assessment and management of risks associated with microbial hazards and toxic chemicals. It explains requirements to promote the safe use of wastewater in agriculture, including minimum procedures and specific health-based targets, and how those requirements are intended to be used. It also describes the approaches used in deriving the guidelines, including health-based targets, and includes a substantive revision of approaches to ensuring microbial safety.

WHO (2006): Guidelines for the safe use of wastewater excreta and greywater. Volume II. Wastewater Use in Agriculture. Geneva: World Health Organisation URL [Accessed: 05.06.2019] PDF

Guidelines for the safe use of wastewater excreta and greywater. Volume III. Wastewater and Excreta Use in Aquaculture

Volume III of the Guidelines for the Safe Use of Wastewater, Excreta and Greywater deals with wastewater and excreta use in aquaculture and describes the present state of knowledge regarding the impact of wastewater-fed aquaculture on the health of producers, product consumers and local communities. It assesses the associated health risks and provides an integrated preventive management framework.

WHO (2006): Guidelines for the safe use of wastewater excreta and greywater. Volume III. Wastewater and Excreta Use in Aquaculture. Geneva: World Health Organisation URL [Accessed: 08.05.2019]

Guidelines for the safe use of wastewater excreta and greywater. Volume IV. Excreta and Greywater Use in Agriculture

Volume IV of the Guidelines for the Safe Use of Wastewater, Excreta and Greywater recognizes the reuse potential of wastewater and excreta (including urine) in agriculture and describes the present state of knowledge as regards potential health risks associated with the reuse as well as measures to manage these health risks following a multi-barrier approach.

WHO (2006): Guidelines for the safe use of wastewater excreta and greywater. Volume IV. Excreta and Greywater Use in Agriculture. Geneva: World Health Organisation (WHO) URL [Accessed: 09.05.2019] PDF

Week 3: Analyse financial viability

Further Readings

Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans

OTOO, M., DRECHSEL, P., DANSO, G., GEBREZGABHER, S., RAO, K. and MADURANGI G. (2016): Testing the implementation potential of resource recovery and reuse business models: from baseline surveys to feasibility studies and business plans. Colombo (Sri Lanka): International Water Management Institute (IWMI), CGIAR Research Program on Water, Land and Ecosystems (WLE). Resource Recovery and Reuse Series 10. URL [Accessed: 27.03.2019]

Week 1: Set objectives and plan activities for launch

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Further Readings

Week 2: Finance the launch

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Further Readings

Alternative Versions to