Landfill leachate typically contains high concentrations of organic pollutants and, moreover, can be contaminated with water soluble nitrogen and sulfur compounds, chlorides, and heavy metals. When rainwater seeps through the landfill the water absorbs soluble organic and inorganic (harmful) substances. Due to exothermic decomposition processes inside the landfill, the leachate’s temperature is usually higher than that of the surrounding groundwater.   Untreated landfill leachate that reaches the natural water cycle poses a threat to the environment and therefore, it is collected and treated when necessary. Landfill leachate is usually brown in color, turbid, and has a distinctive odor. The treatment of landfill leachate is complicated, since its composition changes over the lifetime of the landfill and the concentration of contaminants can fluctuate sharply depending on the amount of precipitation.

The hazardous waste landfill managed by AMAND in Saxony’s Grumbach accrues organically-loaded leachate that, in addition, is highly contaminated with hydrogen sulfide and ammonium. Previously, contamination from hydrogen sulfide and ammonium caused an overload to communal treatment plants and created an overwhelming odor that emanated from the sewer system. DAS Environmental Expert was contracted to develop and install a suitable method for the treatment of the Grumbach landfill leachate. With the client’s best interests in mind, the waste water experts concentrated on developing a cost-effective treatment method, and they concluded a biological treatment method would be most suitable.

“We began by performing degradation tests in our laboratory using microorganisms; and the results were positive,” René Reichardt, Director of the Business Unit Water Treatment at DAS Environmental Expert says. “We were able to degrade the contaminants to the required degree.”

The Dresden environmental experts then set up an on-site pilot plant.

“This is how we discovered how to create accommodating conditions for the microorganisms so they would optimally perform the degradation,” Reichardt says. “Soon it became evident that the system would have to adapt to constantly changing conditions. During heavy rains, the system has to handle large volumes of lessened pollutant concentration. During dryness, however, the leachate becomes highly concentrated, and adapting the treatment method to both conditions became necessary.”

After having successfully tested the treatment method in the pilot plant, the system — in a third step ‑was scaled-up to its final size. At its core, the treatment method consists of three Trickle-Flow-Reactors (TFR) designed by DAS Environmental Expert that contain a carrier material populated by microorganisms that perform the degradation of contaminants. Two aerobic TFR-Reactors make it possible to reduce the organic load and to convert ammonium to nitrate. Subsequently, in an anoxic TFR-Reactor and by adding external carbon, the nitrate is transformed into inert gaseous nitrogen. Periodically, biomass sludge is removed from the reactor. Measurement equipment is checked regularly and preventative maintenance is performed yearly.

The system at the Grumbach landfill has been running since August 2013.   “We designed the treatment in such a way that biology handles the contaminants,” Reichardt says. “The system reduces ammonium nitrogen and sulfide concentrations of the inflow to values in compliance with strict effluent standards.”

During trouble-free operation, the treated water is free of odor and can safely be discharged into the communal waste water system for further treatment.   “The cost for treatment of landfill leachate usually ranges between 2 to 25 Euros per cubic meter, and at times is even higher,” Reichardt says. “For the Grumbach plant we have achieved consumption cost of about 6 Euro per cubic meter for chemicals and energy combined.”

“Looking back, contracting DAS Environmental Expert was the right decision”, Mirko Müller, project manager at Amand Umwelttechnik Grumbach, says. “The team is characterized by high expertise and a strong commitment. From initial installment, to technical supervision during the commissioning and optimization phase, and all the way to service and maintenance, the team lends support to us as the operators of daily procedures. The system’s concept is innovative, coherent and well-thought out. The guaranteed inflow and outflow limit values are safely reached and remain within the guidelines”.