INTEGRATED WASTE-DISPOSAL STRATEGY FOR THE ORKNEY-ISLANDS - A CASE-STUDY

The Orkney Islands are situated several miles off the north east coast of Scotland and comprise about 40 separate islands, of which about 16 have a significant number of inhabitants. The total population is abo ut 20,000 with 7,500 living in Kirkwall, the main town. The EU Urban W aste Water Treatment Directive (UWWTD) has presented the Orkney Island s Council with an opportunity to develop an integrated waste disposal strategy for the entire group of islands, The problems which must be o vercome are common to many island communities with limited land availa bility and seasonal industries based on agriculture and fishing. The w aste disposal strategy developed by Orkney Islands Council provides an integrated solution to a complex problem and takes into account the s hortage of available land for sludge disposal and the effect of efflue nt treatment costs on the economics of interdependent island industrie s. The strategy involves the construction of a new sewerage system to intercept the Kirkwall outfalls and deliver the sewage to a new treatm ent site prior to long sea outfall discharge. The most significant ind ustrial discharges each contain a very high proportion of soluble BOD. As a result, primary treatment alone cannot achieve the reductions is SS and BOD required by the UWWTD. Some industrial. effluents will the refore be pre-treated before discharge to sewers. The sludge disposal strategy has been developed to provide sustainability and outlet secur ity. Accordingly two disposal routes have been proposed. These are lan d disposal or drying and co-incineration with domestic waste in a new incineration complex. Sludge from the outlying communities will be dew atered using a mobile centrifuge before being transported to Kirkwall for ultimate disposal.