Fate of nitrogen in bioreactor landfills: lab-scale in situ aeration in well decomposed MSW

Dissertação para obtenção do Grau de Mestre em Engenharia do ambiente, perfil de engenharia sanitária

In Europe nowadays waste management is following new trends as recycling and compost processes. However, landfilling continues to have an important role in waste management, in fact, according to SOER 2012, by the year of 2010 37% of MSW was landfilled on EU-27 countries. The future perspective shows that landfilling will continue to be a valid option in the years to come. Landfills have an elevated post-closure time, since at least 30 years of monitoring are legally required. One of the main parameters to achieve landfill stabilization is: the leachate should not contain high concentrations of organics, ammonia, or heavy metals. With this regard operating a landfill as an aerated bioreactor as became an acceptable technique to diminish the aftercare period in the landfill, reducing also the costs of the leachate treatment. In this study six reactors filled with well decomposed MSW are aerated and several ammonium nitrogen and nitrate nitrogen injections (1000 mg N/l) were performed in order to understand the fate of nitrogen under these conditions. Specifically, nitrification and denitrification processes, and a possible volatilization of free ammonia was also monitored. The results shows that ammonium nitrogen was successfully removed in a range of 99,0 to 99,7%. Nitrate, when in the presence of readily available carbon, was removed in a range of 89,9 to 99%, however under well decomposed MSW conditions only 40,8 to 56,6% of nitrate nitrogen removal was achieved. Both autotrophic and heterotrophic denitrification were also assessed in order to understand whether the first occur and which is the obtained efficiency of nitrate removal in both cases.