The effect of fluidised bed softening on metal content in drinking water: 11 years of experience from vombverket, sydvatten ab

摘要

Sydvatten is a municipally owned drinking water producer and wholesale drinking water supply company with a yearly production of approximately 70 M m~3 supplying 800 000 inhabitants in 14 municipalities in the south of Sweden with drinking water. Drinking water is produced at two waterworks with different raw water resources.In 1997-1999, the waterworks Vombverket was supplemented by a softening plant through fluidized bed technology. Softening was regarded necessary in order to reduce copper corrosion in the houses, where the most common pipe material is copper, and to reduce the copper content in digestion sludge from the wastewater treatment plants of the municipalities. Softening has been in operation for several years with good results. The copper content in sewage sludge from wastewater treatment plants in Malmo has declined from 1300 mg/kg dry weight to less than 500 mg/kg dry weight. Low calcium content in tap water also decreases the use of shampoo, soap, detergent, dishwashing liquid, tea and coffee in the household with possible savings as a result. The introduction of central softening has decreased the content of magnesium, strontium, zinc and manganese in drinking water marginally. It has increased the sodium content with 25 mg/l due to addition of caustic soda for softening and pH-increase, and decreased the calcium content with 42 mg/l.