Sewage sludge disposal constraints and opportunities

Abstract

The problems of disposing of sewage sludge, possibly by re-use on agricultural land are considered in the context of the interaction of traditional pollution control philosophies, policies and strategies of EEC member states. After briefly reviewing the evolution of the 'pragmatic' policies controlling the discharge of trade effluents to rivers or sewers, in England and Wales, investigations focus on problems caused by heavy metal contamination of sludge. Literature reviews are used to examine:- How sludges become contaminated; The extent of that contamination; How sludges have been disposed in the past; Some indication of the future contraints on disposal by those means. A contribution of the study is in an analysis of the evolution of the DOE/NWC 1981 Guidelines on the disposal of sludge to land. Guideline constraints are compared to those specified in proposals for an EC Directive. A further contribution is in carrying out a case study in which the implications for trade effluent controls in an inner city catchment treatement works area are considered, if sewage sludge at present disposed to sea is disposed by use on agricultural land. A simple model makes use of 1980/81 computer file data. Important features of the use of this model are in simulating the effects of reducing metal inputs from a few known key sources, and of the elimination of high sludge metal concentration cases on the achievement of simple and 95% probability of compliance with proposed EC constraints. Results are discussed in relation to the findings of literature reviews. The effectiveness of the current politico-economic frame-work is assessed. The use of traders' perceptions of the 'rules of the game' in evaluating current controls is explored. Techological and policy implications are deduced, conclusions reached and a basic premise questioned.