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.