PROJECT DESCRIPTION
BACKGROUND
In accordance with the aims set out in the "Guidelines of the European Council regarding pollution caused by the discharge of certain dangerous substances in the waters of the Community (EG ABIL 129/23)", it is necessary for the Member States of the EU to implement comprehensive measures for the protection of water from certain long-lived, toxic and biologically accumulative substances. Organic halogen compounds rank highly among these dangerous substances. They are analytically detected as AOX (Adsorptive organic halogen compounds). The most important AOX-emitter is leakage water from waste dumps used for the deposition of waste from settlements (eg. landfill sites). For this reason, the Federal Republic of Germany insists on leakage water from waste dumps being treated in compliance with article 7a of the Water Resource Law. In the case of discharge into public sewers, pretreatment is necessary to remove dangerous substances.
OBJECTIVES
As the operator of the landfill Nattheim, the administrative waste management office of Heidenheim county wanted to install a new, innovative operative procedure, using SBR (Sequencing Batch Reactor) technology for a more cost-effective treatment of landfill water leachate. SBR facilitates filtration of waste water in a periodic time frame (sequencing) and in one, discontinously operating reservoir. The hydraulic flexible technology is energy efficient and helps to reduce operating costs. Through a combination of basic biological cleaning and extensive cleansing through adsorption on activated carbon in a reactor, an additional cost-saving was also expected. Pre-tests showed that during high capacity periods activated carbon is loaded with COD- and AOX-compounds; while during low capacity periods the microorganisms reduce the chemical substances in the service reservoir. In this way, the activated carbon is regenerated. Although, no great technical references exist for the SBR-technology, Heidenheim county decided to use the SBR-technology, for the first time in Europe, as a pre-treatment of landfill leachate water. This was done in the form of a pilot project. The expected results were a considerable reduction of landfill leachate water filtration costs. A comparison of all submitted offers showed that with a successful system in place, costs of around 4.5 €/m3 could be reduced to ca. 2.5 €/m3, a reduction of about 40%. This does not take account of the cost saving of biological regeneration of the activated carbon. The true potential cost saving still remains to be seen, since the long-term behavior of the activated carbon sludge mixture is unknown.
RESULTS
The results of the first year of operation showed that it was possible to purify leakage water from the Nattheim waste dump with the technology employed, and that this was achieved in accordance with legal requirments. Evaluation of the operational data for 1998 showed that a total of 24,000 cubic metres of leakage waste water was successfully treated in the new SVA pilot waste dump at Nattheim. About 35 tons of CSB, 20 tons of nitrogen and 130 Kgs of phosphorous were eliminated in the first year of operation. A significant reduction of about 80% of the input load was also registered for the dangerous AOX organic halogen compounds. This was equivalent to the elimination of 32 kg of AOX in one year. There was also a positive impact as regards the amount of energy consumed. Compared with existing processes, it was possible to reduce energy expenditure from approx. € 1.70 per cubic metre to about € 0.5 per cubic metre. The expected regeneration of powdered activated carbon was only possible to a limited extent. However, load capacities of 0.3 to 0.4 Kg per Kg of SCB/PAK were achieved with the powdered carbon dosage used directly in the biological phase. Therefore, approximately the same load capacities as with downstream granular activated carbon filtration were achieved. In conclusion, the outcome of the pilot project is that a new type of process for waste dump leakage water purification has come to maturation with the innocvative and cost effective SBR technology. The results of the first year of operation showed that it was possible to purify leakage water from the Nattheim waste dump with the technology employed, and that this was achieved in accordance with legal requirments. Evaluation of the operational data for 1998 showed that a total of 24,000 cubic metres of leakage waste water was successfully treated in the new SVA pilot waste dump at Nattheim. About 35 tons of CSB, 20 tons of nitrogen and 130 Kgs of phosphorous were eliminated in the first year of operation. A significant reduction of about 80% of the input load was also registered for the dangerous AOX organic halogen compounds. This was equivalent to the elimination of 32 kg of AOX in one year. There was also a positive impact as regards the amount of energy consumed. Compared with existing processes, it was possible to reduce energy expenditure from approx. € 1.70 per cubic metre to about € 0.5 per cubic metre. The expected regeneration of powdered activated carbon was only possible to a limited extent. However, load capacities of 0.3 to 0.4 Kg per Kg of SCB/PAK were achieved with the powdered carbon dosage used directly in the biological phase. Therefore, approximately the same load capacities as with downstream granular activated carbon filtration were achieved. In conclusion, the outcome of the pilot project is that a new type of process for waste dump leakage water purification has come to maturation with the innocvative and cost effective SBR technology.
