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This study explored the effect stage number and plant type have on ammonia-nitrogen (NH 3 –N) removal kinetics in a two-stage pilot-scale vertical flow constructed wetland (VFCW) system treating landfill leachate. Half of the VFCW columns were planted with Typha latifolia and the other half Scirpus californicus , and half of the columns were loaded with municipal solid waste landfill leachate (diluted to 1 part leachate to 2 parts total) with the effluent from these columns was collected in two separate barrels. The remaining columns were loaded with the effluent collected from the first columns, creating a two-stage VFCW system with four unique pairs to be tested. The leachate used here experienced no prior pre-treatment, and average influent concentrations of NH 3 –N for the first- and second-stage VFCWs were 508 and 321 mg L−1, respectively— much higher than many other VFCW treatment systems. Some reduction in chemical oxygen demand was observed, as well as generation of nitrate and nitrite, evidence of nitrification. No apparent correlation between aboveground biomass and removal of NH 3 –N was observed. Overall removal efficiency of NH 3 –N through two stages of VFCWs was 53.7% for columns planted with T. latifolia and 58.3% for those planted with S. Californicus. Average NH 3 –N removal efficiencies for the first stage VFCWs were 32.7% and 34.3%, while those in the second stage were 31.3% and 36.5%; no significant difference was observed between the first and second stage, suggesting that stage number does not have a significant effect on the removal efficiency of NH 3 –N in the primary treatment of landfill leachate via VFCWs. However, average mass removal rates of NH 3 –N in the first stage were 166 and 175 mg L−1 d−1; the second stage was significantly lower at 99.4 and 112 mg L−1 d−1, indicating that the first stage removed more pollutants overall. [Display omitted] • Nitrification and denitrification observed throughout entire experiment. • Stage number not found to have a significant impact on NH 3 –N removal. • Higher accumulation of nitrite observed on second day of each loading period. • Results reported as k-values and mass removal rates to better contextualize results. [ABSTRACT FROM AUTHOR]

Bottom and combined ash samples from municipal solid waste incinerator (MSWI) facilities in Florida were compared with industry aggregate standards to determine suitability for use as a road base. Although MSWI ashes tested in this work generally conformed to these standards for bearing strength (i.e., limerock bearing ratios above 100%), blending with commercially available aggregates is proposed as a strategy for improving overall material homogeneity and quantity. This work presents that MSWI ash can exhibit acceptable parameters defined in existing specifications for road-base materials on their own or by blending with commercially available aggregates, bolstering existing supplies of base materials while contributing to landfill diversion. The overall trend for bearing strength decreases with increasing MSWI bottom ash replacement (except for recycled asphalt pavement), but there appears to be a positive correlation between blend coefficients of uniformity (Cu) and bearing strength (R2=0.5290). This suggests that gradation and material types may be parameters for identifying potential blends for advanced testing and developing quality control and assurance standards for material production and construction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Waste-derived soil amendments used to mitigate COPCs from MSWI ash leachate. • Experimental K d values for soil/amendment blends used in fate/transport model. • Data on sorption of COPCs from ash leachate using biochars presented. • Amendments may increase ash reuse potential from environmental risk viewpoint. This study explores modifying a sandy soil with a low solid to liquid partitioning coefficient (K d) by adding amendments including iron-rich industrial slag byproducts and biochars, which contain sorption sites for trace metals present in MSWI ash leachate (notably Sb, cited as a concern for reuse applications). K d values for Sb were determined for the sandy soil to be as low as 1.6 ± 0.1 L/kg. With amendments, K d values varied from 1.4 ± 0.2 L/kg for combined ash leachate exposed to a blend of sandy soil and 20% iron slag, to 990 L/kg for combined ash leachate exposed to a blend of sandy soil and 20% magnetic solids. A blend of 20% magnetic solids showed orders of magnitude increase beyond 100% sandy soil. The biochars showed limited capacity to reduce leached Sb in the ash-derived leachate, which is likely due to negative surface charges of the biochars and Sb at basic pH. A risk assessment (US EPA IWEM) performed using experimental K d for each blend suggests that using soil amendments could reduce leached concentrations at points of concern, which could open additional avenues for ash reuse. [ABSTRACT FROM AUTHOR]

Trace metals concentrations of 25 elements were determined for 22 subcomponents of biodegradable and non-biodegradable waste samples representing the United States municipal solid waste (MSW) stream collected during three separate waste sorts. The subcomponent trace metal concentrations and estimated composition results were used to predict trace metal concentrations present in the overall MSW stream along with MSW compost and waste to energy (WTE) ash, which were compared to health-based standards (i.e., US EPA regional screening levels) and to values previously reported in the literature. These estimates for potentially problematic elements like As and Sb could be attributed to abundant base materials in MSW, while other elements, such as Pb, were calculated at much lower concentrations than other published studies. This suggests that trace metals measured in actual MSW compost and WTE ash could originate not only from MSW base components but also from other sources, such as highly concentrated low-mass wastes (e.g., e-waste). While the removal of small quantity components with high metal concentrations may reduce concentrations of some potentially problematic metals (e.g., Pb), others (e.g., As and Sb) are likely to persist in quantities that impede reuse and recycling since they are present in the more abundant base MSW components (e.g., papers, plastics, organics). Promoting meaningful reductions in potentially problematic trace metals in MSW-derived materials may require reevaluating their presence in higher-volume, lower-concentrated MSW components such as paper, plastics, and organics. • Trace metal concentrations determined for 22 subcomponents of MSW stream. • Metal concentrations in MSW and derived products estimated using subcomponent data. • As and Sb concentrations in compost/ash linked to abundant base materials in MSW. • Some metals (e.g., Pb) were underestimated in MSW compost and ash. • Reducing trace metals in base materials may lead to impactful decreases in MSW. [ABSTRACT FROM AUTHOR]