Vattenkemin i Fyrisån under snösmältningen
Chemical substances are spread diffusely and uncontrollably as a result of the increased consumption of goods. REVAQ is a certification system that works to reduce the flow of hazardous substances to Swedish treatment plants and to create a sustainable nutrient recycling. According to REVAQ, the yearly accumulating rate of metals should not exceed 0.2% in soil per year. Silver and bismuth are two metals that do not fulfill this requirement. The silver concentration in sludge decreased during the last decade, however the last few years, it has leveled off. The bismuth concentration has increased significantly since 2005.The aim of this study was to explore the types of plastics and paints that could be found to contain silver respectively bismuth, and to investigate whether these can be important sources of measured concentrations of silver and bismuth in sludge.The results of the substance flow analysis which was used in this study show that bismuth is probably found in ABS plastics, polyethylene plastics and polyamide plastics. These plastics are mainly found in household items.The inflows of metals in plastic to Stockholm are estimated to be 5 kg silver and 1.2 to 5.7 tons bismuth. In paints, the numbers are 19 kg of silver and 2.5 to 3.3 tons of bismuth.The stocks of metals in plastic in Stockholm are estimated to be 25 - 50 kg silver and 5.7 to 57 ton bismuth and in paints between 98 and 195 kg silver and 12 to 33 tons bismuth.The outflow of metals in plastic to Henriksdals treatment plants are estimated to be 300 g silver and 5-25 kg bismuth and in paints 0.5 kg silver and between 62 to 82 kg bismuth.According to this study, bismuth in plastic and paint are a contributing source to the measured concentrations in sludge (4.4 - 21 % respective 54 - 73 %). Silver in plastic and paints are not a relevant source for the amount of silver in sludge in treatment plants.