Alternating pure oxygen and air cycles for the biostabilization of unsorted fraction of municipal solid waste.

Biostabilisation is a process of treating the unsorted fraction of municipal solid waste (UFMSW) mechanically pre-treated. Although concepts such as circular economy would seem to limit biostabilization, several authors have recently described the advantages of biostabilization in regions where recycling systems are inadequate. In this perspective, the development of new MBT technologies is of considerable importance. The objective of the study was to evaluate the effects of the use of alternating air and oxygen cycles on the treated waste stability as well as on the quality of leachate and process gaseous emissions. Two Herhof biocells were prepared for this purpose. One implemented the conventional process and the other the "Air + O2" process. The biostabilization of the inlet UFMSW (3965 ±â€¯1965 mgO2/kgVS/h) resulted in a final product with a dynamic respirometric index almost equal in both processes. The mass balance indicated that of the 400 tons representing the input waste, 37.57% were biostabilized waste, 0.29% leachate and 62.14% CO2 and odours. However, the biostabilized waste was lower than that of the conventional process (equal to 40.18%). The Air + O2 system resulted in a shorter duration, increased production of leachate (although characterized by higher quality) and process gaseous emissions quality. The energy balance (20.3 kJ/kg per input waste) and cost analysis (80.0 €/ton per input waste) showed values equal or better to those of the conventional system. By contrast, weakness was in the O2 diffusion system. Although a life cycle analysis is necessary, the results highlighted the feasibility of the proposal especially for emergency situations.

How can the role of leachate on nitrate concentration and groundwater quality be clarified? An approach for landfills in operation (Southern Italy).

Where the unique natural water resource is groundwater, the attention and the susceptibility of local communities and authorities to groundwater quality degradation risks can be so high to determine relevant problems to waste management, especially for landfills in operation or to be realised. A multi-methodological approach was suggested with the purpose to clarify the role of landfill leakage on groundwater quality degradation. The selected study area (SSA) hosts some landfills in a narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high hydrogeological complexity and vulnerability. News concerning nitrate and secondly iron groundwater concentration anomalously high caused concern in the population and strong local opposition to landfills. The multi-methodological approach includes: the hydrogeological site characterization; the chemical study and the multi-isotope characterization of groundwater and leachate; the land use analysis and the estimation of nitrogen contributions deriving from fertilizers; the mineralogical study of groundwater suspended particles to define the role of natural soil substances. The hydrogeological site characterisation highlighted the local peculiarities of the aquifer. The chemical study was used to define geochemical features, groundwater and leachate characteristics and their macroscopic mixing. The environmental isotopes of hydrogen, carbon, nitrogen, and oxygen were used to investigate the groundwater origin, the most relevant geochemical reactions, the existence of groundwater-leachate mixing, and the sources of anthropogenic NO3-. The land use analysis highlighted quantity and type of used fertilizers permitting to compare these with groundwater in terms of isotopic signature. The mineralogical study demonstrated the role of suspend natural particles due the presence of terre rosse (red or residual soils) in groundwater. The approach confirmed that there are not the groundwater quality degradation effects of landfills, contributing to reassure population and institutions, simplifying the waste management.