Nutrients and pollutants in sewage sludge from 1975 to 1999

The composition of sewage sludge is intensively monitored since 25 years in Switzerland. The nutrient contents have undergone only minor changes. Simultaneously to an increasing production of sewage sludge the nutrient loads have increased during the first 15 years and since remained stable. Except for copper, the load of most heavy metals continuously decreased after an increase during the first five years, as heavy metal contents sharply declined. In spite of this, sewage sludge will probably disappear as a fertilizer up to 2005. This is due to additional needs to protect the health of man and environment from risks as well as to the market risk.