On the Relation Between Urban Wastewater Management Needs and Receiving Water Objectives

INTRODUCTION In the past, the growth of urban agglomerations in Europe caused major disruptions in basic needs such as public health, hygiene, and safety against flooding. Starting in the last century, large scale urban drainage systems were implemented to tackle the worst water related problems in urban areas. Subsequently, flood protection and public health improved dramatically. At the same time, the quality of receiving waters deteriorated as a result of the increased and more polluted discharges. Wastewater treatment schemes were implemented to alleviate this problem. Today, among urban drainage engineers the concept still prevails that "receiving water protection is equal to pollution discharge reduction". While the engineer traditionally focuses on water quality and its improvement, biologists claim that the ecological quality of a receiving water is determined by numerous factors of which many are only poorly understood. A reasonable water quality is merely a