Chemical Technology January 2016

WATER TREATMENT

Rocinha Favela, Brazil. (Photo Ahln)

get on access to safe drinking water – as measured by the proportion of population using an improved drinking water source (Pro-poor policies in Kampala: www-wds.worldbank. org/external/default/WDSContentServer/WDSP/IB/2014 /02/24/000442464_20140224140639/) – was met in 2010, the progress in urban areas has not been able to keep up with the rapid pace of urbanisation. Between 1990 and 2012, the number of urban residents who did not have access to an improved drinking water source decreased by 1 percentage point. However, in absolute terms, the number of people in urban areas without access to an im- proved drinking water source increased from 111 million to 149 million [2], indicating that access to drinking water is actually deteriorating where the most rapid urbanisa- tion is outpacing public services. The situation is worse in sub-Saharan Africa, where urbanisation is happening most rapidly. In this region, the percentage of people who enjoyed piped water on their premises, which is the preferred option for urban areas, actually decreased from 42 % to 34 % [2]. This clearly indicates that access to ‘safe’ drinking water sources continues to be a major problem in cities in the developing world. Similar to trends in drinking water, the number of urban residents without access to improved sanitation increased by 40 %, from 541 to 754 million, between 1990 and 2012 [2]. Therefore, although sanitation coverage is generally higher in urban areas, because of rapid urbanisation, increasing numbers of urban residents, particularly the poor, are unable

opportunities for more sustainable use of water, including treating used water to standards that enable it to be used again. They are well positioned to rapidly adopt conserva- tion measures, and the concentration of people in compact settlements can reduce the cost of providing services such as water supply and sanitation. Furthermore, cities can connect with their hinterlands and support the protection of water resources in their surrounding areas by actively engaging in watershedmanagement or providing Payment for Ecosystem/ environmental Services (PES). Challenges Access to water supply and sanitation Rapid urbanisation, increased industrialisation, and improv- ing living standards generally combine to increase the over- all demand for water in cities. By 2050, global water demand is projected to increase by 55 %, mainly due to growing demand frommanufacturing, thermal electricity generation and domestic use, all of which mainly results from growing urbanisation in developing countries (Organisation for Eco- nomic Co-operation and Development – OECD) [1]. As easily available surfacewater and groundwater sources have been depleted inmany urbanised areas, cities will have to go further or dig deeper to access water, or will have to depend on innovative solutions or more advanced technolo- gies such as reverse osmosis for desalination, or reclaimed water to meet their water demands. Although the Millennium Development Goals (MDG) tar-

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Chemical Technology • January 2016