IMPACT OF SLUDGE DISPOSAL TO SEA - FINAL REPORT
Report No FR0086
S C Nixon, T ap Rheinallt, I D Codling, S G Wills
To assess the environmental impact of the disposal of sewage sludge to sea by undertaking case-study investigations at the Thames estuary and Liverpool Bay disposal sites.
The Water Utilities want to be assured that their sludge disposal to sea operations are environmentally acceptable and what decisions over the future of marine disposal are made on a scientific basis. In addition there are concerns among a number of EC member states and environmental pressure groups*over the effects of sludge disposal to sea. It should be noted that since the study commenced the UK government has announced, in March 1990, that it has decided to phase out the disposal of sludge to sea by 1998.
Thames estuary case study
Liverpool Bay studies
The Thames estuary case study has shown that it is difficult to detect any effects from sludge disposal to sea at dispersive sites. The application of toxicity tests and, to a lesser extent, sub-lethal stress measurements has shown these to be potentially more sensitive and to offer some promise for future monitoring programmes. However, development work is underway to enable these measurements to be related to pollution effects at the population or ecosystem level. It is, therefore, recommended that bioassays should be considered in any future monitoring programme.
Though the disposal of sludge to sea is to be phased out over the next eight years, the Water Utilities involved will have to continue to monitor the disposal grounds as a condition of their dumping licence. For the most part it is likely to be recommended by MAFF that the procedures outlined by the Marine Pollution Monitoring Management Group's Coordinating Group on Monitoring of Sewage Sludge Disposal Sites (CGMSD) should be followed.
However, if the prevalence of fish disease in the vicinity of sludge disposal grounds is to be monitored then it is recommended that the protocol adopted by the International Council for the Exploration of the Sea (ICES) is followed rather than that from the CGMSD. It is recommended that the sludge disposal sites are monitored after the end of sludge disposal to determine whether there are any detectable changes and/or improvements in the ecosystem.
V RESUME OF CONTENTS
This report describes the legislation and conventions that apply to the disposal of sewage sludge to sea, and the work undertaken by the Coordinating Group on Monitoring Sewage Sludge Disposal Sites in arriving at appropriate EQO/EQSs and protocols for monitoring programmes.
The main findings from a four year intensive study at the UK's largest sewage sludge disposal site in the Thames estuary are reported, and a detailed description of a study of fish disease undertaken in Liverpool Bay in 1989 is also given.
Copies of the Report are available from FWR, price £25.00 less 20% to FWR Members