TRANSIENT POLLUTION EVENTS - ACUTE RISKS TO THE AQUATIC ENVIRONMENT

For the most part investments in restricting the propagation of pollut ants have focused on managing a steady, invariant, average condition o f the aquatic environment. In this there has been success. But the act ivities of society, in all its forms of land use (urban, agricultural, and silvicultural), have presumably still the capacity to generate as much potential contamination of the environment as previously. It is simply that we have now placed effective barriers-our wastewater contr ol infrastructures - between these activities of society and the surro unding environment And just as there would be a concern for the long-t erm reliability of a dam structure for a water reservoir, so there mus t now be an increasing concern for the reliability of our wastewater c ontrol infrastructures. Such concern is generic: transient perturbatio ns about an equilibrium are as relevant to agricultural and silvicultu ral control infrastructures as they are to our systems of urban sewera ge and wastewater treatment. The paper assembles the diverse features of transient pollution events, their monitoring,modelling and criteria for management in order to make a start on providing a more coherent framework for their analysis. The notion of the frequency spectrum of system perturbations is used for this purpose. In this, succinctness i s achieved, so that a better appreciation of the relationships between long-term trends and high-frequency disturbances can be obtained. In particular, the problems of managing transient pollution events can be seen loosely against the backdrop of a project's life cycle, in a man ner that illuminates a tension in our attitudes towards the passive an d active paradigms of operating the control structures that protect th e environment from pollution. Copyright (C) 1996 IAWQ. Published by El sevier Science Ltd