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Ecological sanitation, also known as ecosan or eco-san, are terms coined to describe a form of sanitation that usually involves urine diversion and the recycling of water and nutrients contained within human wastes back into the local environment. Introduction to ecological sanitation An ecological sanitation (ecosan) viewpoint sees human waste and wastewater as an opportunity. When properly designed and operated, ecosan systems provide a hygienically safe, economical, and closed-loop system to convert human wastes into nutrients to be returned to the soil, and water to be returned to the land. Alternatively, solid wastes are converted into a biofuel. The primary application for ecosan systems has been in rural areas where connection to a sanitary sewer system is not possible, or where water supplies are very limited.[1] The main objectives of ecological sanitation are:[2] To reduce the health risks related to sanitation, contaminated water and waste[3] To prevent the pollution of surface and ground water To reuse nutrients or energy contained within wastes. History of reuse-oriented sanitation approaches The recovery and use of urine and feces has been practiced by almost all cultures. This is why bad sanitation is a world-wide problem. The reuse was not limited to agricultural production. The Romans, for example, were aware of the bleaching attribute of the ammonia within urine and used it to whiten clothing.[4] The most widely known reuse in agriculture has occurred in China. Reportedly, the Chinese were aware of the benefits of using excreta in crop production before 500 B.C., enabling them to sustain more people at a higher density than any other system of agriculture. The value of “night soil” as a fertilizer was recognized with well-developed systems in place to enable the collection of excreta from cities and its transportation to fields. However, its use promoted disease to such an extent that in Chinese cuisine almost all vegetables are thoroughly cooked.[5] Elaborate systems were developed in urban centers of Yemen enabling the separation of urine and excreta even in multi-story buildings. Feces were collected from toilets via vertical drop shafts, while urine did not enter the shaft but passed instead along a channel leading through the wall to the outside where it evaporated. Here, feces were not used in agriculture but were dried and burnt as a biofuel. In Mexico and Peru, both the Aztec and Inca cultures collected human excreta for agricultural use. In Peru, the Incas had a high regard for excreta as a fertilizer, which was stored, dried and pulverized to be utilized when planting maize. In the Middle Ages, the use of excreta and greywater was the norm. European cities were rapidly urbanizing and sanitation was becoming an increasingly serious problem, whilst at the same time the cities themselves were becoming an increasingly important source of agricultural nutrients. The practice of using the nutrients in excreta and wastewater for agriculture therefore continued in Europe into the middle of the 19th Century. Farmers, recognizing the value of excreta, were eager to get these fertilizers to increase production and urban sanitation benefited.[6] The increasing number of research and demonstration projects for excreta reuse carried out in Sweden from the 1980s to the early 21st century aimed at developing hygienically safe closed loop sanitation systems. Similar lines of research began elsewhere, for example in India, in Zimbabwe, in the Netherlands, Norway and Germany. These closed-loop sanitation systems became popular under the name “ecosan”, “dewats”, “desar”, and other abbreviations. They placed their emphasis on the hygenisation of the contaminated flow streams, and shifted the concept from waste disposal to resource conservation and safe reuse.[7] Concepts of ecological sanitation Ecological sanitation (Ecosan) is based on an overall view of material flows as part of an ecologically and economically sustainable wastewater management system tailored to the needs of the users and to the respective local conditions. It does not favour a specific sanitation technology, but is rather a new philosophy in handling substances that have so far been seen simply as wastewater and water-carried waste for disposal.[8] According to Esrey et al. (2003)[9] ecological sanitation can be defined as a system that: Prevents disease and promotes health Protects the environment and conserves water Recovers and recycles nutrients and organic matter Ecosan offers a flexible framework, where centralised elements can be combined with decentralised ones, waterborne with dry sanitation, high-tech with low-tech, etc. By considering a much larger range of options, optimal and economic solutions can be developed for each particular situation.[10] Thus, the most important advantages of ecological sanitation systems are: Improvement of health by minimising the introduction of pathogens from human excreta into the water cycle Promotion of safe, hygienic recovery and use of nutrients, organics, trace elements, water and energy Preservation of soil fertility Contribution to the conservation of resources through lower water consumption, substitution of mineral fertiliser and minimisation of water pollution Improvement of agricultural productivity and food security Preference for modular, decentralised partial-flow systems for more appropriate cost-efficient solutions adapted to the local situation Promotion of a holistic, interdisciplinary approach Material flow cycle instead of disposal of valuable resources Technologies of ecosan systems Determining ecosan systems as ecological sanitation is not easy, for it is not just one specific technology, but a new approach based on an ecosystem-oriented view of material flows. The following diagram gives an overview of the different collection, treatment and reuse possibilities of the five flow streams considered in ecological sanitation systems: Gtz-technologies-for-ecosan.jpg Further information on ecosan technologies can be found in "Ecological Sanitation" by Winblad et al.,[11] in "Toilets that make compost" by Peter Morgan[12] or in the gtz-ecosan technical data sheets,[13] among other relevant literature. Project examples Examples of ecosan projects can be found among others in the collection of project data sheets of gtz ecosan[14] or on the Enhanced Global Map of ecosan activities by EcoSanRes.[15] In the following some examples are given that underline the diversity of ecosan projects: Guangxi province, China - large-scale project of urine diverting dehydration toilets The dissemination programme of ecological dry toilets for Hsinchu County, Guangxi province, one of the poorest provinces in China, started in 1997 with support of UNICEF, SIDA and the Red Cross and has been expanded to 17 provinces until the year 2003. By this year, the scale of the project had increased to approximately 685,000 toilet units – today more than one million double vault urine diversion dehydration toilets (UDDTs) are installed in rural areas of China. In UDDTs, urine and faeces are collected separately: The urine is collected in the front and led by a plastic pipe to a storage canister from where it can be used as a fertilizer in agriculture, the faeces fall at the back in one of two ventilated storage chambers and are covered with ash for better dehydration. After about one year of storage the dried material can be removed and used as a soil conditioner in agriculture.[16] KfW, Frankfurt, Germany - vacuum toilets + greywater treatment The sanitation concept of the modern office building “Ostarkarde” of the KfW Bankengruppe in Frankfurt is based on a separate excreta and greywater collection. While urine and faeces are collected via vacuum toilets and a vacuum sewerage using much less water for flushing, the greywater from hand washing and kitchen is collected and treated separately in a compact activated sludge reactor combined with membrane filtration. The treated greywater is then reused for toilet flushing and cleaning water. The amount of greywater can be reduced by 76% by this cost-efficient system which could be one of the prior choices for sanitation systems of newly constructed office buildings.[17] Tanum Municipality in Sweden has introduced urine separation toilets to recover phosphorus. Paul Calvert, a British engineer and boat builder, who has lived in southern India for long, has been working on the development of dry compost toilets in southern India[18] for over a decade. Today, his group provides technology and hand-holding for different ecologically sustainable solid waste management systems, of which the primary model is the ecosan toilet. This toilet separates the solid waste and converts it into compost-fertilizer, while using the urine and black-water (used for washing after defecation) for kitchen gardens. SOIL in Haiti built ecological dry toilets as part of the emergency relief effort following the 2010 Haiti earthquake. More than 20,000 Haitians are currently using SOIL ecological sanitation toilets and SOIL has produced over 400,000 liters of compost as a result. The compost is used for agricultural and reforestation projects.[19] Similar project by UNDP and Earth Aid Finland has built composting toilets provided by Biolan in Haiti to fight cholera in to improve the general sanitary conditions.[20] Wherever the Need[21] build ecosan facilities in various parts of the developing world. They predominantly work in Tamil Nadu (India), where the Tamil Nadu State Government provides subsidies for their work. Wherever the Need have also constructed ecosan in other parts of rural India, Kenya and Sierra Leone. Their ecosan projects have positively affected 50,000 people in the developing world. Arguments for the use of ecological sanitation Often, water used in flush toilets is of drinking quality. Only 1% of global water is drinkable, therefore, it is a precious resource.[22] Water fit to drink is being used for other purposes that can use lesser quality water, such as toilets. But if we used the water in toilets to help with the bad water, many lives would be saved. Mixing feces and urine makes treatment difficult. All waste water treatment plants use some natural/biological processes, but nature does not normally have this waste water, so there are no microbes that can deal with this mix. In order to treat waste, treatment plants have to do this in stages. Each stage treats a different component of the mix by creating the right environment for microbes to do their work (aerobic, anaerobic, anoxic and the right pH). This is costly and requires energy. A mix of domestic and industrial effluent in water cannot be treated properly, for heavy metals and other pollutants make this water unsuitable for reuse. This is normally discharged into the ground or water bodies. Because of the complexity of the treatment process, treatment plants tend to be large. This requires costly infrastructure to build and maintain it, often out of the reach of poorer communities. A major consideration in low-lying geographies is pollution of ground water by traditional pit-latrines. In many areas where the water table is high, pit latrines directly pollute the water table, potentially affecting the large numbers of people. Eco-san toilets, especially dry compost toilets, ensure that the excreta or urine does not reach the water table. John Jeavons states that responsible, safe and legal composting of human waste could be key to maintaining nutrient levels in the world soils. Urea is the major component of urine, yet we produce vast quantities of urea by using fossil fuels. By properly managing urine, treatment costs as well as fertilizer costs can be reduced. Feces also contains recognized nutrients, and could be used for modern agriculture, as micronutrient deficiency is a significant problem. In fact, a 2010 study in Finland showed that the use of urine and the use of urine and wood ash "could produce 27% and 10% more red beet root biomass."[23] |
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