Nitrogen removal from landfill leachate via the nitrite route

Speciation and conversion of carbon and nitrogen in young landfill leachate during anaerobic biological pretreatment

There is an increasing need for landfill leachate pretreatment prior to discharge to wastewater treatment plants due to increasingly stringent sewer discharge limits. Lab-scale tests have shown that the anaerobic biological processes can effectively remove chemical oxygen demand and dissolved organic carbon from landfill leachate. Our work expands the knowledge in anaerobic leachate pretreatment by systematically studying the conversion of carbon and nitrogen species, particularly their recalcitrant fractions in a submerged anaerobic biofilm reactor using real-world leachate from a typical young municipal solid waste landfill. After reaching steady state, the reactor removed 41.7% of the fulvic acids (i.e., 1290 mg C/L). While compounds with a low degree of oxidation (O:C < 0.2) and compounds with a low degree of saturation (H:C < 1) were removed, compounds that were more oxidized (O:C > 0.2) and more saturated (H:C > 1) were produced. At steady state, 98% of recalcitrant dissolved organic nitrogen (i.e., rDON = 222 mg N/L) was removed. Compared to the DON in the raw leachate, the produced DON in the pre-treated leachate were more oxidized (O:C > 0.35) and more bioavailable (N:C > 0.07). The submerged anaerobic biofilm reactor may be an efficient leachate pretreatment method if rDON removal is needed.

Biomass growth and its mobility in an AnSBBR treating landfill leachate

This work used a pilot scale (with a total volume of 1300 L) Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR) to treat landfill leachate from São Carlos-SP (Brazil) as well as to evaluate the biomass growth and its behavior. Biomass from the bottom of a landfill leachate stabilization pond was immobilized in polyurethane foam cubes as inoculum. The leachate characteristics varied during the experiment. Ethanol or volatile fatty acids were added as additional substrate when the leachate was temporarily recalcitrant. After acclimation, the AnSBBR presented efficiency over 70% (COD removal). A mass balance model, biomass sampling and temporal concentration profiles were performed to obtain a biomass yield coefficient of Y_X/S = 0.0251 ± 0.0006 g_TVS g_{COD removed} (r² = 0.999). Additionally, it was observed that a variable fraction of the attached biomass may detach itself or present mobility during the batch time, however returning to fixed bed depending on the substrate type and concentration. This behavior has never been reported by the literature for attached biomass.

Ammonium removal in landfill leachate using SBR technology: dispersed versus attached biomass

Large concentrations and oscillations of ammonium nitrogen (NH₄⁺-N) in municipal landfill leachate pose considerable constraints to its further treatment in central wastewater treatment plants. The aim of this study was to evaluate and optimize two technologies for the pre-treatment of 600 L/day of landfill leachate: in particular, to optimize their operational conditions for NH₄⁺-N removal up to a level appropriate for discharge to sewers, i.e. <200 mg/L. Both technologies were based on a sequencing batch reactor (SBR), with two different biomass processes: (A) SBR with dispersed/flocculated biomass and (B) SBR with biomass attached to carriers. The results revealed that both technologies successfully reduced the NH₄⁺-N from 666 mg/L (on average) at the inflow to below 10 mg/L at the outflow with alkalinity adjustment in a 12-hour cycle. Both technologies achieved 96% removal efficiencies for NH₄⁺-N. However, SBR with dispersed biomass showed higher flexibility under varying conditions due to the shorter adaptation time of the biomass.