The Role of Decentralisation in Sustainable Urban Water Systems - Essay Example

The Role of Decentralisation in Sustainable Urban Water Systems The world's escalating population growth and the rapid urbanization of the planet has placed a considerable demand on the existing infrastructure to provide fresh water and manage the wastewater and storm water resources. Ideally, an urban water system would provide ample freshwater to meet the increasing demand, and have a minimal ecological impact from the transport and management of water resources. Urban areas will vary in regards to their access to fresh water supplies, land management options, and economic practicalities. The myriad variables of "supply catchments, reservoirs, water consumption, stormwater systems, wastewater systems and receiving waters (rivers and bays)" all need to be carefully considered when designing a sustainable urban water system (Maheepala 2009, p. 1). In addition, the urban planner may need to consider the existing infrastructure, as well as the possibility of future expansion. The purpose of this paper is to examine the role that decentralisation will play in the future of urban water supplies, and the ecologically orientated technologies that are available and may be utilised within the urban water system. The urban water system is comprised of the clean water system for drinking and distribution, the wastewater from sewerage and treatment plants, and the storm water system that manages and directs drainage and overflow. In addition, it includes solid waste management, household sanitation, and wastewater disposal (Campos2 2009, p. 20). Clean fresh water needs to be free of toxins and harmful bacteria. In an effort to accomplish this, water is routed to a large centralised treatment plant to process and clean the water to make it acceptable for drinking and home use. A system of coagulation, flocculation, sedimentation, and filtration is used to treat water and remove the harmful components (Campos2 2009, p. 7). Chlorine is the most widely used disinfectant currently used to combat bacteria due to its low cost, ease of use, and relatively low toxicity (Hua, West, Barker & Forster 1999, p. 2735). However, chlorine is unpleasant and odorous and is ineffective at controlling the numerous pathogens in the water supply, whose discoveries have outstripped our ability to eliminate them (Hua et al. 1999 p. 2375; Campos2 2009, pp. 19-21). The large scale system of centralised collection, storage, and treatment is expensive and places the entire water supply at risk of contamination. Water stored at these facilities has come into contact with myriad toxins and poisons as it progresses through the water cycle. As more chemicals are introduced into the environment, it becomes ever more expensive and impractical to produce safe potable water. Centralised systems are large, expensive, and must often treat the water as if it is the worst case contamination scenario. Wastewater will require treatment, and the major concerns for waste water management are the levels of dissolved elements, nutrients, and toxins. A water quality model that considers the complexity of the wastewater discharge is instrumental in predicting the short and long-term environmental impact of wastewater discharges, but is expensive and difficult to sustain (World Bank Group 1998, p. 1). However, decentralising the system allows the water to be treated on a local basis, and only requires the treatment that is necessary for a small amount of water, such as local runoff or rainwater collection. In many cases this results in only minimal treatment requirements. A new technology that utilises solar cells produces sodium hypochlorite from a salt-water solution, which makes the small scale production of a disinfectant on a local level economically practical (Moya). Sanitizing the water, distribution, contamination, and storage are some of the difficulties that are inherent in a large centralised water supply that can be overcome by decentralisation. Research has indicated that "decentralised systems for water, wastewater and stormwater are not only more environmentally friendly than centralised options, they are also cheaper" (Maher & Lustig 2003, p. 30). The benefits that are gained from centralisation such as drought mediation, fire fighting, and health concerns are "in fact based on minimal scientific evidence" (Maher & Lustig 2003, p. 26). In addition, composting toilets and water re-use strategies can significantly reduce water use and further minimize the need for water transport and treatment (Maher & Lustig 2003, p. 27). Storm water systems manage runoff and overflow as rains and natural precipitation are created during wet weather flows. Ideally, a sustainable storm water system will replicate a natural drainage system, and have a collection and storage system located near the source for the purposes of controlling flooding, recharging groundwater, irrigation, and environmental enhancement (Campos2 2009, p. 13). Detention basins and retention ponds retain water after entering the system through a system of porous materials, gravel, vegetation, or other permeable surfaces (Campos2 2009, pp. 15-17). These retention mechanisms can be constructed locally on a small scale to reinforce the decentralised system's needs for a continual supply of water. Managing a sustainable urban water system necessitates that the water remain as clean as possible throughout its entire cycle. Minimizing exposure to toxins, heavy metals, pesticides, herbicides, and pathogens greatly reduces the wastewater treatment complexity and eliminates much of the process that is currently used in large scale treatment facilities. The points of contact with pathogens are most often in impoverished areas where poor sewerage, cross connections, back-siphonage, and problems in the distribution system are the major causes of water borne pathogen illness (Corvalan, Kjellstrm & Smith 1999, p. 659; Moe & Rheingans 2006, p. 42). In addition, biological pathogens can gain entrance into the water supply through "transmission through vectors proliferating in water reservoirs or other stagnant water or certain agricultural practices" (Pruss, Kay, Fewtrell & Bartram 2002, p. 537). Reducing the points of contact reduces the possibility of contamination. Pruss et al. (2002, p.542) concludes that there is a "high potential for disease reduction by simple interventions such as safe drinking water storage and disinfection in the home". Once again, locally stored and treated water is advantageous to sustainability. In conclusion, sustainable urban water systems will need to be localized and decentralised. This will simplify the treatment process and can utilize newer treatment technologies. Water can be stored near the source by creating a system of runoffs that mimic a natural watercourse. Decentralisation can also help control the supply and eliminate the contact that the water has to the myriad chemicals that pollute the environment. Water saving strategies such as waterless toilets and reusing of the grey water can further reduce the need for treatment and storage. Distribution is simplified and treatment becomes economically practical. The future of sustainable urban water supplies will rely on the local collection, treatment, and use of water through a decentralised system that produces clean water in an on-demand basis. References Campos1, L. (Dr.) (2009) Water systems - natural systems, in: Environmental Systems Civl4010/G016 (London, UK, University College London). Campos2, L. (Dr.) (2009) Engineered systems: water supply, urban drainage, and waste, in: Environmental Systems: CIVL4010/G016 (London, UK, University College London). Corvalan, C., Kjellstrm, T. & Smith, K. (1999) Health, environment and sustainable development: identifying links and indicators to promote action, Epidemiology, 10(5), 656-660. Hua, F., West, J., Barker, R. & Forster, C. (1999) Modeling of chlorine decay in municipal water supplies, Water Research, 33(12), 2735-2746. Maheepala, S. (2009, March 2009) Integrated water systems, http://www.csiro.au/resources/Integrated-Water-Systems.html (Commonwealth Scientific and Industrial Research Organisation). 26 May, 2009. Maher, M. & Lustig, T. (2003) Sustainable water cycle design for urban areas, Water Science and Technology, 47(7), 25-31. Moe, C. & Rheingans, R. (2006) Global challenges in water, sanitation and health, Journal of Water and Health, 04 Suppl, 41-57. Moya, C. http://www.urc-chs.com/news/newseritreanu.htm (Bethesda, MD, Center for Human Services). 26 May, 2009. Pruss, A., Kay, D., Fewtrell, L. & Bartram, J. (2002) Estimating the burden of disease from water, sanitation, and hygiene at a global level, Environmental Health Perspectives, 110(5), 537-542. World Bank Group (1998) Water Quality Models. Pollution Prevention and Abatement Handbook, pp. 1-7 (Washington, DC, World Bank). Read More