56 The Future of Water in African Cities
Box 2.9 (continued) Figure B2.9.1 Existing Urban Water Supply and Future Groundwater Source for Dar es Salaam, Tanzania
Source: Foster et al., 2010b.
Innovative Technologies Can Play a Role Technological innovations can help respond to the challenge of servicing more people with water and wastewater services under conditions of diminishing supply. Innovative treatment technologies might enhance recycling of wastewater and ensure that water can be used multiple times. Energy-efficient treatment options have been developed around natural systems (such as constructed wetlands and soil aquifer treatment), providing reliable treatment of multiple contaminants in a single system. Flexible technologies, such as small-scale, decentralized stormwater measures, can be optimized over time. Established technologies, such as membrane technologies, have recently undergone developments that drastically reduce their production costs, allowing small-scale applications to become cost-effective (Peter-Varbanets et al., 2009). Treatment technologies have traditionally been viewed as linear systems, where water enters and leaves the system as a single stream of specific quality. A perspective to treatment based on innovative technologies is emerging where waters of different qualities are received and produced within a single system (Bieker et al., 2010; Cornell et al., 2011; Otterpohl et al., 2003). In addition, recent advances have generated effi-