Nitrogen pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes

Abstract

Nitrogen emissions from municipal solid waste (MSW) landfills occur primarily via leachate, where they pose a long-term pollution problem in the form of ammonium. In-situ aeration was proposed as a remediation measure to mitigate nitrogenous landfill emissions, turning the anaerobic environment to anoxic and subsequently aerobic. As in-depth studies of the nitrogen cycle during landfill aeration had been largely missing, it was the aim of this work to establish a detailed nitrogen balance for aerobic and anaerobic degradation of landfilled MSW based on lab-scale experiments, and also investigating the effect of different water regimes on nitrogen transformation during aeration. Six landfill simulation reactors were operated in duplicate under different conditions: aerated wet (with water addition and recirculation), aerated dry (without water addition) and anaerobic (wet). The results showed that more than 78 % of the initial total nitrogen (TNinit) remained in the solids in all set ups, with the highest nitrogen losses achieved with water addition during aeration. In this case, gaseous nitrogen losses (as N2 due to denitrification) amounted up to 16.6 % of TNinit and around 4 % of TNinit was discharged via leachate. The aerated dry set-up showed lower denitrification rates (2.6-8.8 % of TNinit was released as N2), but was associated with the highest N2O emissions (3.8-3.9 % of TNinit). For the anaerobic treatment the main pathway of nitrogen discharge was the leachate, where NH4 accounted for around 8 % of TNinit. These findings provide the basis for improved management strategies to enhance nitrogen removal during in-situ aeration of old landfills.

Ten-years monitoring of MSWI bottom ashes with focus on TOC development and leaching behaviour

“…This is because complex microbial degradation and conversion processes in landfills break down proteins, the main nitrogen source contained in the waste, to NH3 as well as NH4 + (Mayerhofer, 2017). Ammonium is mainly discharged via landfill leachate, while ammonia escapes via gas phase (Brandstätter et al, 2015). Thus, NH4 + and DOC concentrations in leachates are good indicators of the landfill stage and play a major role concerning the duration of the aftercare necessary for bottom ash landfills.…”

The microbial metabolic activity on carbohydrates and polymers impact the biodegradability of landfilled solid waste

“…The total carbon content of the material is 5- to 10-fold higher than the total nitrogen concentration (Brandstätter et al. 2015a , b ). Thus, more abundant carbon fractions show lower error values than less abundant nitrogen-fractions.…”

“…In a similar experiment, denitrification was considered to mainly occur in externalized leachate tanks (Brandstätter et al. 2015b ), as these leachate reservoirs got charged with carbohydrates from leachate recirculation and provided anaerobic conditions.…”

Theoretical analysis of municipal solid waste treatment by leachate recirculation under anaerobic and aerobic conditions

“…(2015) (Brandstätter et al, 2015b). They propose that denitrification mainly occurred at the bottom of the reactor where leachate remained anaerobic.…”