Even after the closure of landfill sites leachate continues to migrate over a long period of time. Their pollutant concentrations are high and it may take centuries until environmental standards are met. As Nitrogen is one of the parameters that decrease very slowly with time, adequate long term leachate treatment will be necessary in order to secure a sufficient elimination in the aftercare period.
This work focuses on the implementation of simple, reliable systems that provide efficient biological nitrogen elimination along with low energy consumption and minimal maintenance requirements. The main aim is to reduce the pollutant concentration in order to meet environmental standards and enable effluent discharge to receiving waters. The investigated systems are fixed bed reactors. For the nitrification process, two different vertical flow systems with different filter materials were used, while the denitrification system was a horizontal flow system using fixed carbon compound (TOC) to enable biological nitrate elimination.
The results of the investigations show that full nitrification occurs up to a maximal loading rate of 0,25 kg NH4-N/(m³d). Besides the effect of varying loading rates changes in pH-value and temperature, and their impact on the nitrification rate were examined.
Pre-treated straw was found to be suitable as carbon source for the denitrification process. At a loading rate of 0,8 - 1,6 l/(kgFBd) long term denitrification rates of 30 g NO3-N/(m³d) will be attained. Under these conditions the pre-treated straw can serve as carbon source for 5 – 6 months. Therefore straw replacement is required only 2 to 3 times per year.
Results from this study show that the different treatment systems provide an efficient nitrogen removal from landfill leachate. In a worst case situation a plant of 0,6 ha area would be required for a 30 ha landfill site. This seems, beside the minimum energy and maintenance requirements, a good pre-condition for the implementation of such a treatment system for the aftercare of landfill sites.