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Chapter 10. Designing Cities for People: Reducing Urban Water Use
The one-time use of water to disperse human and industrial wastes is an outmoded practice, made obsolete by new technologies and water shortages. Water enters a city, becomes contaminated with human and industrial wastes, and leaves the city dangerously polluted. Toxic industrial wastes discharged into rivers and lakes or into wells also permeate aquifers, making water—both surface and underground—unsafe for drinking.
The current engineering concept for dealing with human waste is to use vast quantities of water to wash it away, preferably into a sewer system, where it may or may not be treated before being discharged into the local river. The “flush and forget” system takes nutrients originating in the soil and typically dumps them into the nearest body of water. Not only are the nutrients lost from agriculture, but the nutrient overload has contributed to the death of many rivers and to the formation of some 200 dead zones in ocean coastal regions. This outdated system is expensive and water-intensive, it disrupts the nutrient cycle, and it can be a major source of disease and death. 39
Sunita Narain of the Centre for Science and Environment in India argues convincingly that a water-based disposal system with sewage treatment facilities is neither environmentally nor economically viable for India. She notes that an Indian family of five, producing 250 liters of excrement in a year and using a water flush toilet, contaminates 150,000 liters of water when washing away its wastes. 40
As currently designed, India’s sewer system is actually a pathogen-dispersal system. It takes a small quantity of contaminated material and uses it to make vast quantities of water unfit for human use. With this system, Narain says both “our rivers and our children are dying.” India’s government, like that of many other developing countries, is hopelessly chasing the goal of universal water-based sewage systems and sewage treatment facilities—unable to close the huge gap between services needed and provided, but unwilling to admit that it is not an economically viable option. 41
This dispersal of pathogens is a huge public health challenge. Worldwide, poor sanitation and personal hygiene claim the lives of some 2 million children per year, a toll that is one third the 6 million lives claimed by hunger and malnutrition. 42
Fortunately, there is a low-cost alternative: the composting toilet. This is a simple, waterless, odorless toilet linked to a small compost facility. The dry composting converts human fecal material into a soil-like humus, which is essentially odorless and is scarcely 10 percent of the original volume. Table waste can also be incorporated into the composter. These compost facilities need to be emptied every year or so, depending on design and size. Vendors periodically collect the humus and market it as a soil supplement, thus ensuring that the nutrients and organic matter return to the soil, reducing the need for energy-intensive fertilizer. 43
This technology sharply reduces residential water use compared with flush toilets, thus cutting water bills and lowering the energy needed to pump and purify water. As a bonus, it also reduces garbage flow if table waste is incorporated, eliminates the sewage water disposal problem, and restores the nutrient cycle. The U.S. Environmental Protection Agency now lists several brands of dry compost toilets approved for use. Pioneered in Sweden, these toilets work well under the widely varying conditions in which they are now used, including Swedish apartment buildings, U.S. private residences, and Chinese villages. 44
Interest in ecological sanitation, or ecosan, as it is commonly referred to, is spiraling upward as water shortages intensify. Since 2005, international ecosan conferences have been held in several countries, including India, South Africa, Syria, Mexico, and China. The movement, led by the Swedish International Development Agency, can now point to projects in at least a dozen countries. Although ecosan is not yet mainstream, it is fast becoming so. 45
The first large community to be built with dry compost toilets in every residence is on the outskirts of Dongsheng in Nei Monggol (Inner Mongolia). Designed to house 7,000 people, the town is scheduled for completion by the end of 2007. In this system, urine, which contains 80 percent of the nutrients leaving the human body, is diverted into a designated container. It is then collected and recycled directly onto the land as a fertilizer supplement. Both human solid waste and kitchen waste are composted into a rich humus, sanitized, and used as an organic fertilizer. For many of the 2.6 billion people who lack sanitation facilities, composting toilets may be the answer. 46
China has emerged as the world leader in this field, with some 100,000 urine-diverting, dry compost toilets now in use. Among the other countries with these toilets in the demonstration stage or beyond are India, Uganda, South Africa, Mexico, Bolivia, and seven countries in West Africa. Once a toilet is separated from the water use system, recycling household water becomes a much simpler process. 47
For cities, the most effective single step to raise water productivity is to adopt a comprehensive water treatment/recycling system, reusing the same water continuously. With this system, only a small percentage of water is lost to evaporation each time it cycles through. Given the technologies that are available today, it is quite possible to recycle urban water supplies comprehensively, largely removing cities as a claimant on scarce water resources.
Some cities faced with shrinking water supplies and rising water costs are beginning to recycle their water. Singapore, for example, which buys water from Malaysia at a high price, is beginning to recycle water, reducing the amount it imports. For some cities, water recycling may become a condition of their survival. 48
Individual industries facing water shortages are moving away from the use of water to disperse industrial waste. Some companies segregate effluent streams, treating each individually with the appropriate chemicals and membrane filtration, preparing the water for reuse. Peter Gleick, lead author of the biannual report The World’s Water, writes: “Indeed, some industries, such as paper and pulp, industrial laundries, and metal finishing, are beginning to develop ‘closed-loop’ systems where all the wastewater is reused internally, with only small amounts of fresh water needed to make up for water incorporated into the product or lost in evaporation.” Industries are moving faster than cities, but the technologies they are developing can also be used in urban water recycling. 49
At the household level, water can also be saved by using more water-efficient showerheads, flush toilets, dishwashers, and clothes washers. Some countries are adopting water efficiency standards and labeling for appliances, much as has been done for energy efficiency. When water costs rise, as they inevitably will, investments in composting toilets and more water-efficient household appliances will become increasingly attractive to individual homeowners.
Two household appliances—toilets and showers—together account for over half of indoor water use. Whereas traditional flush toilets used 6 gallons (or 22.7 liters) per flush, the legal U.S. maximum for new toilets is 1.6 gallons (6 liters). New toilets with a dual-flush two-button technology use only 1 gallon for a liquid waste flush and 1.6 gallons for a solid waste flush. Shifting from a showerhead flowing at 5 gallons per minute to a 2.5 gallons-per-minute model cuts water use in half. With washing machines, a horizontal axis design developed in Europe uses 40 percent less water than the traditional top-loading U.S. models. 50
The existing water-based waste disposal economy is not viable. There are too many households, factories, and feedlots to simply try and wash waste away on our crowded planet. To do so is ecologically mindless and outdated—an approach that belongs to a time when there were far fewer people and far less economic activity.
39. Sunita Narain, “The Flush Toilet is Ecologically Mindless,” Down to Earth, 28 February 2002, pp. 28–32; dead zones from U.N. Environment Programme, “Further Rise in Number of Marine ‘Dead Zones’,” press release (Nairobi: 19 October 2006).
40. Narain, op. cit. note 39.
42. World Health Organization, World Health Report 2007 (Geneva: 2007), p. 4; U.N. Food and Agriculture Organization (FAO), The State of Food Insecurity in the World 2005 (Rome: 2005).
43. U.S. Environmental Protection Agency (EPA), “Water Efficiency Technology Factshee—Composting Toilets,” fact sheet (Washington, DC: September 1999); Jack Kieffer, Appalachia—Science in the Public Interest, Humanure: Preparation of Compost from the Toilet for Use in the Garden (Mount Vernon, KY: ASPI Publications, 1998).
44. EPA, op. cit. note 43; EPA, “Wastewater Virtual Tradeshow Technologies,” at www.epa.gov/region1/assistance/ceitts/wastewater/techs.html, updated 10 September 2007.
45. EcoSanRes (ESR) and Stockholm Environment Institute (SEI), EcoSanRes Phase 2 Project Document: 2006–2010 (Stockholm: 22 February 2006), p. 14; ESR, “Conferences,” at www.ecosanres.org/news-publications.htm, updated 21 September 2007; ESR, “Ecological Sanitation Research,” at www.ecosanres.org, updated 21 September 2007.
46. ESR, “China-Sweden Erdos Eco-Town Project, Dong Sheng, Inner Mongolia, China,” at www.ecosanres.org/asia.htm, updated 21 September 2007; ESR, “Sweden-China Erdos Eco-Town Project, Dongsheng, Inner Mongolia,” Fact Sheet 11 (Stockholm: May 2007); nutrients in urine from Innovative Practices to Enhance Implementation of WSSD Targets-Swedish Initiative for Ecological Sanitation, Water and Sanitation, Background Paper No. 20, presented at 8th Special Session of the Governing Council/ Global Ministerial Environment Forum, Jeju, South Korea, 29–31 March 2004; people lacking sanitation from U.N. Development Programme, Human Development Report 2006 (New York: 2006), p. 33.
47. Number of compost toilets from Innovative Practices, op. cit. note 46; ESR and SEI, op. cit. note 45.
48. Tony Sitathan, “Bridge Over Troubled Waters,” Asia Times, 23 August 2002; “ Singapore Opens Fourth Recycling Plant to Turn Sewage into Water,” Associated Press, 12 July 2005.
49. Peter H. Gleick, The World’s Water 2004–2005: The Biennial Report on Freshwater Resources (Washington, DC: Island Press, 2004), p. 149.
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