In addition to the established and proven technologies presented in unit 2 of the course, numerous innovative sanitation technologies are being researched, developed and tested in the field. Emerging technologies are those that have moved beyond the laboratory and small-pilot phase, and are currently (as of April 2014) being implemented in relevant contexts (i.e., in a developing country) and at a scale that indicates that expansion is possible (i.e., not a single unit).
The International Year of Sanitation (IYS) 2008 galvanized the sanitation sector by increasing visibility, engaging new actors and opening new funding streams. The entry of new funding sources, such as the Bill & Melinda Gates Foundation (www.gatesfoundation.org) and the International Finance Corporation/Water and Sanitation Program (www.ifc.org/sellingsanitation), and increased visibility and political will, such as that generated by having HRH King Willem-Alexander of the Netherlands as Chairman of the Secretary-General of the United Nations’ Advisory Board on Water and Sanitation (UNSGAB), has enabled substantial sector fund- ing and innovation in the past few years.
On a positive note, there are many innovative, exciting technologies under research and development; they are too numerous to include in this section. Most of these innovations, however, are currently still too costly, too technically complex and/or resource intensive for widespread application, or have not yet been proven at a significant scale in developing countries. Yet, several recently developed technologies have moved beyond the laboratory phase, are being applied in a developing country context, and at a scale indicating that sustainable dissemination is feasible. Some of the most promising emerging technologies that have already been proven in the field under variable operational and waste composition conditions are listed below.
Many of the innovations in the sanitation field relate to business models and logistics. A variety of social enterprises are seeking to develop sustainable business models that provide technology and/or collection and/ or treatment services at a low cost to unserved communities, which were previously considered too poor to pay for sanitation. Indeed, «Base of the Pyramid» customers are gaining increased attention because of their collec- tive demand and purchasing power.
We are looking forward to updating the course with additional technologies and business models in the future when more have proven to be financially and technically sustainable. Here, we briefly summarize some of the most promising, widespread innovations which we expect to become commonplace in the years to come:
Peepoo
The Peepoo bag is a biodegradable bag designed for excreta collection when a permanent User Interface technology is not available. It is a single-use bag that is meant to be held in one hand or put over a small holder (e.g., a small bucket or a cut PET bottle) and has 2 layers.
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The inner layer is folded over the hand to protect it or over a small container. After defecating or urinating into the inner layer, the outer bag is tied shut. The difference between the Peepoo bag and a regular plastic bag is the fact that (a) the inside bag is coated with urea which disinfects the faeces, and (b) the bag is biodegradable.
Bags when full should be transported to a composting facility before they start to break down (about 4 weeks). They are made of a bio-plastic that breaks down into water, carbon dioxide and biomass. Therefore, they do not need to be removed from, and actually contribute to, the composting process.
The bags are safe to handle and remain odour free for at least 24 h, giving the user time to safely transport them to an appropriate collection point. The bags are light (about 12 grams) and can hold up to 800 mL of excreta. They are not meant to replace a permanent technology (e.g., VIP, S.3), but are recommended for use as a sanitation solution for people who do not have access to any (e.g., internally displaced persons, emergency situations, etc.).
They can also be used by people who, for safety reasons, cannot access their closest sanitation facility (e.g., if shared toilets are too far or closed at night). The challenge, as with other mobile/container based sanitation technologies, is the effective management of collecting and composting the bags.
The Peepoo bag has been extensively used in Kenya, the Philippines, South Africa, and Bangladesh, among other places.
References
Peepoople. www.peepoople.com (last accessed April 2014)
Vinnerås, B., Hedenkvist, M., Nordin, A. and Wilhelmson, A. (2009). Peepoo Bag: Self-Sanitising Single Use Biodegradable Toilet. Water Science & Technology 59 (9): 1743-1749.
How to use Peepoo from Peepoople on Vimeo.
Compost Filter
Several variations of the compost filter exist. Its concept is based on combined filtration and aerobic digestion of solids.
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[The biofil digester
Source: biofilcom.org]Unlike a Septic Tank (S.9), where solids settle to the bottom and degrade under anaerobic conditions, the solids are separated from liquids by a porous medium (filter bed or bag) in a compost filter.
They remain on/in the filter and are then broken down by the aerobic organisms that survive in the organic matrix. Maintaining a low volume of water in the collected solids is essential to the success of the compost filter. Thereby, the filter is able to maintain aerobic conditions without being saturated.
This can be ensured by regularly adding layers of straw or wood chips to it. Different design variations exist. There are permanent filters made, for example, from concrete, or removable filter bags that can be used to support the organic filter material. In addition, the design determines how frequently the accumulating solids need to be removed and further treated, as well as how long the process can continue without replacing the filter.
A double-chamber design works on the principle of alternation (as with Dehydration Vaults for faeces, S.7, or Twin Pits for Pour Flush, S.6); each side can be used for a year, and the content is then allowed to rest and decompose while the other side is in use. There are also designs that work continuously with a single chamber (e.g., the Biofil Digester, see references).
Essential to the compost filter design is secondary treatment of the effluent, e.g., in a Constructed Wetland (T.7-T.9) and/or Waste Stabilization Ponds (T.5). Depending on the intended end-use, the composted solids may also require further treatment.
References
Biofil (n.d.). The Biofil Toilet System. The Toilet Facility that Makes Good Sanitation Sense.
Biofilcom. www.biofilcom.org (last accessed April 2014)
Gajurel, D. R., Li, Z. and Otterpohl, R. (2003). Investigation of the Effectiveness of Source Control Sanitation Concepts Including Pre-Treatment with Rottebehaelter. Water Science & Technology 48 (1): 111-118.
Hoffmann, H., Rüd, S. and Schöpe, A. (2009). Blackwater and Greywater Reuse System Chorrillos, Lima, Peru – Case Study of Sustainable Sanitation Projects. Sustainable Sanita- tion Alliance (SuSanA), Eschborn, DE. Available at: www.susana.org/library
LaDePa Sludge Pelletizer
The Latrine Dehydration and Pasteurisation (LaDePa) pelletizer is a sludge drying and pasteurization technology capable of producing a dry, pelletized soil amender from pit latrine sludge.
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[Latrine Dehydration & Pasteurisation Pelletizer]It can be fed at a rate of about 1,000 kg/h sludge (30-35% solids content) and the output rate is about 300 kg/h dried pellets (60-65 % solids content). Garbage that ends up in pits (plastic bags, shoes, etc.) is separated from the sludge by a screw compactor: the screw pushes the sludge through 6 mm holes onto a porous, continuous steel belt, while the waste material is ejected through a separate outlet so that it can be collected and disposed of.
The extruded sludge falls in an open matrix of spaghetti-like strands, in a layer varying in thickness from 25-40 mm, onto the porous belt and passes first through a pre-drying section that utilizes the waste heat from the internal combustion engine of the power plant.
The partially dried sludge pellets then travel through a patented «Parseps Dryer» that makes use of medium-wave infrared radiation. The pellets are, thereby, pasteurized and dried by using an extractor fan that draws the hot air through the porous belt and the open matrix of sludge. This increases the drying capability without increasing the energy output. The pellets that emerge are free of pathogens and suitable for all edible crops. The whole process takes 16 minutes.
An important disadvantage of the LaDePa process is that it is relatively energy intensive and relies on a constant source of energy (electricity/diesel).
The eThekwini Municipality in Durban, South Africa, has been running LaDePa trials for about 2 years. Evidence from the trials, in conjunction with their VIP pit emptying program, indicates that they should be able to treat approximately 2,000 t of VIP sludge a year with one plant.
The product has a registered trademark (GrowEthek) and, once the product has been licensed as a low nutrient fertilizer, it will be bagged and sold. Based on the sale price of GrowEthek, the LaDePa generates about $27/h, which can offset the operating costs. The LaDePa was designed by Particle Separation Systems (PSS), which offers the equipment on a rental basis or for sale. If the rental option is preferred, there is an establishment fee and a maintenance contract. If the equipment is purchased outright, there would still be a maintenance contract, but no establishment fee.
References
Harrison, J. and Wilson, D. (2012). Towards Sustainable Pit Latrine Management through LaDePa. Sustainable Sanitation Practice 13: 25-32. Available at: www.ecosan.at/ssp
Particle Separation Systems. www.parsep.co.za (last accessed April 2014)
Wilson, D. and Harrison, J. Personal communication (February 2014)
Struvite Production from Urine
Urine contains most of the excess nutrients excreted from the body. Nitrogen and phosphorus are two elements essential for plant growth and are present in urine in significant amounts.
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[Schematic of a struvite reactor with stirring mechanism and filter bag]Concentrations vary dramatically, but values around 250 mg/L PO4-P and 2,500 mg/L NH4-N are not atypical). In order to take advantage of the nutrients, including potassium, sulphur, etc., stored urine can be directly applied to crops and fields (see D.2), or processed into a solid fertilizer called struvite (NH4MgPO4-6H2O).
Struvite is produced by adding some kind of soluble magnesium source (magnesium chloride, bittern or wood ash) to the urine. Magnesium binds with the phosphorus and nitrogen, and precipitates out into a white, crystalline form. Struvite crystals must be filtered out of the solution, dried and then processed into a useable form.
It is currently produced in Durban, South Africa, from 1,000 litres of urine per day that is collected from household urine-diverting dry toilets. When there is no use or desire for urine-derived nutrients (e.g., in dense urban areas), struvite is a convenient way of producing a compact nutrient product that can be easily stored, transported and used when and where it is needed.
A disadvantage, however, is that struvite production produces an equivalent volume of effluent with a high pH and ammonium concentration that requires further treatment. Other important elements, such as potassium, also remain in the solution.
Yet, struvite production is simple, requiring little more than a mixing chamber and filter, and has been proven to work in many countries and contexts. As a first step in a nutrient recovery strategy, it is effective, but should not be implemented without a subsequent effluent treatment strategy.
Examples of effective effluent management are drip irrigation systems that distribute the liquid directly onto crop roots, although the distribution is limited by head and available area, or nitrification of the urine (which is still in the development phase).
References
Etter, B., Tilley, E., Khadka, R. and Udert, K. M. (2011). Low-Cost Struvite Production Using Source-Separated Urine in Nepal. Water Research 45 (2): 852-862.
Grau, M. G. P., Rhoton, S. L., Brouckaert, C. J. and Buckley, C. A. (2013). Development of a Fully Automated Struvite Reactor to Recover Phosphorus from Source Separated Urine Collected at Urine Diversion Toilets in eThekwini. WEF/IWA International Conference on Nutrient Removal and Recovery 2013, 28-31 July, Vancouver, CA. Available at: www.eawag.ch/vuna
Ostara Nutrient Recovery Technologies Inc. www.ostara.com (last accessed April 2014)
www.eawag.ch/stun (last accessed April 2014): Nutrient Valorization from Urine in Nepal (STUN)
The Struvite Poster (Eawag). Download PDF ›››