Unbalanced nutrient cycles: costly removal and disposal of nitrogen, rather than its reuse as a fertilizer, is inefficient in terms of both energy and resource utilization. To overcome the above-mentioned problems, Nhapi and Gijzen (2005) developed the three–step strategic approach (see Figure 4.1), which specifically aims to change the urban water cycle and reduce the overall negative environmental impact of water use and thereby increase the sustainability of the system by the following means: