Proceedings

Introduction
The treatment and disposal of sewage sludge has been for many years the Cinderella of the sewage treatment process. The emphasis was placed on achieving effluent quality standards with the aim of cleaning up the rivers and water courses into which the effluent was discharged. However, the simple fact was that meeting improvements in effluent quality standards meant an increase in sludge production and in many cases a growing problem for those responsible for the treatment process. For some the solution was to dump the “untreated” sludge into large lagoons in the hope that the problem would go away, thankfully others took the problem more seriously with investment in anaerobic digestion and disposal to agricultural land. In Europe the latter was brought into sharp focus with the publication and enforcement by national governments of the EC Directive 86/278/EEC (June 1986) on “the protection of the environment, and in particular of the soil, when sludge is used in agriculture”. Thus the emphasis began to move towards developing sustainable solutions for the treatment and disposal of sewage sludge.
The US was also aware of the growing problem of acceptability of sewage sludge as a valued resource. In order to overcome this issue they introduced a changed emphasis by introducing the term “BIOSOLIDS”. The US Environment Protection Agency (EPA) was required under the Clean Water Act Amendments of 1987, to “develop a new regulation to protect public health and the environment from any reasonably anticipated adverse effects of certain pollutants that might be present in sewage sludge.” This led to the publication of the EPA Guide to Part 503 Rule (September 1994) introducing a two tier quality class definition of biosolids: Class A and Class B.