WASTE-WATER INFRASTRUCTURE - CHALLENGES FOR THE SUSTAINABLE CITY IN THE NEW MILLENNIUM

Aspects of the technologies that might be employed in the wastewater i nfrastructures of cities in the longer-term future are discussed. For this purpose a wastewater infrastructure is defined as the string of u nit process technologies used to recycle and return the waterborne res iduals of a city to its surrounding environment. In the cities of Euro pe aad North America, for example, this infrastructure conventionally comprises the urban sewer network, wastewater treatment plant, and rec eiving water body. To provide context and direction for the discussion , the impact of the city and its wastewater infrastructure on the surr ounding environment is reviewed over a time-scale of centuries. Two an alogies are employed in order to illustrate this impact: the concept o f a city's 'metabolism' within the global cycling of materials; and th e notion of gauging the 'health' of the system through something akin to measuring the 'pulse-rate' of an organism. Three scenarios are draw n for the possible pattern of adaptation and more radical change in th e technological composition of the city's future wastewater infrastruc ture. These may culminate in a structure altogether different from tha t with which we are familiar today, i.e. a decentralised, highly segre gated system in which control and manipulation of the composition of a ny residual at its source is maximised. Further, it is argued that the issue of reliability of performance may be a critical (technological) factor in choosing a preferred form of wastewater infrastructure. We do not discuss the economic, social or cultural dimensions of our subj ect; we acknowledge that these are likely to be decisive consideration s, the seeming technological attraction of any option notwithstanding. Copyright (C) 1996 Elsevier Science Ltd.