§ Mr. Kilfedderasked the Secretary of State for Northern Ireland what proportion of the phosphorus entering Lough Neagh is estimated to come from sewage; and how much from other sources such as agricultural processes.
§ Mr. David MitchellIt is not possible to produce precise figures, but it is estimated that approximately half the phosphorus available for algal growth comes from sewage treatment works and the remainder from a variety of agricultural, industrial and domestic sources.
§ Mr. Kilfedderasked the Secretary of State for Northern Ireland what is the present position with regard to the ecological changes and water quality problems of Lough Neagh; whether there has been any improvement since the extensive pollution by algæ bloom in the late 1960s; and, in particular, whether the de-oxygenation of the lough has proceeded to such an extent that there is now hope of reversing the process.
§ Mr. David MitchellThere has not been a major surface algal bloom on Lough Neagh since 1967, but there have been fluctuations from time to time in the density of sub-surface algæ.
While there have been no measurable increases in the average level of algæ in the lough, the general level remains relatively high and peak levels have been increasing.
Detailed research over recent years by the Freshwater Biological Investigation Unit set up by the Departments of Agriculture and Environment for Northern Ireland indicated that phosphorus is the controlling nutrient in relation to algal bloom. The Department of the 103W Environment for Northern Ireland is carrying out a programme to install phosphorous reducing plant at 10 major sewage treatment works in the Lough Neagh area. The programme should be completed by March 1982. The Freshwater Biological Investigation Unit will continue to monitor the level of phosphorus loading in the lough. Pending the outcome of the Department's measures, it would be premature to form a view on the likely long-term level of de-oxygenation of the lough.