The deep-ocean option for the disposal of sewage sludge

Summary Present methods of disposal of high-bulk low-toxicity wastes, such as sewage sludge, into shallow marine environments are beginning to be questioned by many environmentalists. The alternative options generally considered all have environmental costs. A novel approach of discharging such wastes as slurries into the deep ocean at depths of 4,000 m close to the abyssal sea bed is considered. Such disposal would fulfil all the criteria required by the Oslo Convention before dumping at sea can be permitted, in that it isolates the waste from Man's ambit and offers no threat to present or foreseeable uses of the ocean. It also seems to fulfil the criteria of the World Conservation Strategy, so long as the oxygen levels in the deep waters of the ocean are not reduced excessively. The improvements in the quality of coastal seas would offset the doubling in the economic cost of disposal.Dr Martin V. Angel is the Head of the Biological Oceanography Group at the Institute of Oceanographic Sciences Deacon Laboratory. He serves on the Council of the WWF, UK and is a member of its Conservation Review Group. He is also a member of the IUCN Commission of Ecology, with particular interests in conservation of oceans and Antarctica. His professional expertise is in the ecology of deep-living pelagic organisms in the oceans but he is also an editor of a research journal,Progress in Oceanography and an external examiner for the Open University.