BIOLOGISK RENINGSANLÄGGNING FÖR LAKVATTEN FRÅN DEPONI / Biological treatment plant for leachate from landfill
A treatment plant for landfill leachate was created in 1997 in connection to Gärstad waste treatment plant near the town of Linköping, Östergötland, Sweden. The treatment plant consists of one aerated outlevelling basin (former clay pit) and three constructed ponds. The ponds are 0.3 m in the first half (to keep oxygen in the water) and 0.5 m in the second half (to get oxygen free conditions). The ponds are 150 m in length and 25 m in width. The total area of the treatment plant is 7,5 ha. The retention time in the system is 7 months.
About 160 000 m3 of leachate are formed each year. The energy production at Tekniska Verken generates about 80000 tons of ashes and clinker. 60000 tons comes from incineration of 230000 tons of sorted house-hold waste and the remaining part comes from incineration of wood and coal. The clinker and ashes from the incineration gives the biggest contribution in the leachate of treatable substances such as ammonium, CODCr and BOD7. Most of the ammonium comes from reduction of NOx-gases in the flue gases. Urea and ammonia are used as reduction agents. In 1999 nitrogen, phosphorus and organic materials have been reduced with 78 %, 80 % and 60 % respectively. In the calculations no consideration has been taken of the dilution in the system. The dilution varies from 20 to 30 %.
Seed dispersal, rhizome plantation and lake sediment as seed bank have been used to establish plants in the ponds.