Introduction

The world is experiencing rapid growth in urbanisation and industrialisation. The pace, depth, and magnitude of these changes, while bringing about benefits to local people, have exerted severe ecological stresses on both local human living conditions and regional life support ecosystem. Urban sustainability can only be assured with a human ecological understanding of the complex interactions among environmental, economic, political, and social-cultural factors and with careful design, planning and management grounded on ecological principles (WCED, 1987; Mansson, 1992 ; Van der Ryn & Cowan, 1996 ). The city, with its water, wastewater and other infrastructures, sits within an industrial-urbanised ecology of individual entities arranged one to another and bound together in a web of energy and material flows. In an ideal world the “waste” residue from the metabolism of one of these entities should become the feedstock of another 1 (Ausubel, 1992; Ekins & Cooper, 1993 ; Hallsmith, 2003 ).