ANRIKNING AV FOSFOR I STADSREGIONEN EN FOSFORBUDGET FÖR STOCKHOLM 1990 / Accumulation of Phosphorus in Urban Regions - a Phosphorus Balance for Stockholm 1990
Dephosphatation in sewage has reduced the P-loading on the recipients, but has at the same time resulted in an accumulation of P in urban regions. Will this accumulation with time give rise to increased pollution from non-point sources of P? In order to quantify the P turnover in urban regions, a P-balance has been calculated for Stockholm, 1990. About 1 000 tons of P were imported mainly in food and chemical products. About 800 tons were transported to the sewage treatment plants. 70 tons passed through these plants and reached the Baltic Sea. Organic household-wastes contained 165 tons of P. 70 % of the P in sludge was deposited at a concentration of 13 320 kg/ha, and 30 % was distributed on farmland at a concentration of 166 kg/ha and 5 yrs. The P content in harvested crop in this regions is 13 kg/ha. The accumulation of P was calculated to be approximately 80 %. It was concluded that there is an urgent need of new methods/systems for P management, which permit increased recycling of this limited natural recource.