Traditionally, water and sewerage as well as waste and energy services are provided through centralized networks that rely on large scale infrastructure. This approach to delivery of urban services is responsible for the major improvements in public health and quality of live in the developed world. However, in the developed world the infrastructure has now grown to a size that poses major challenges for maintaining and upgrading existing assets. In the developing world on the other hand, the centralized large scale approach to utility services has often failed to deliver desired outcomes, due to the large initial investment necessary and because the urban poor are not capable of paying for these services.
To address these problems new combinations of public and private sector involvement are proposed to improve the existing infrastructure. In parallel to this trend, it is advocated to re-think the traditional approach to service delivery, taking into consideration small scale, decentralized solutions that combine the water/wastewater, energy and waste services.