Browsing by Author "Trois, C."

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    Compositional and physicochemical changes in waste materials and biogas production across 7 landfill sites in UK
    (Elsevier, 2016-08-28) Frank, R. R.; Cipullo, Sabrina; Garcia, J.; Davies, S.; Wagland, Stuart Thomas; Villa, Raffaella; Trois, C.; Coulon, Frederic
    The aim of this study was to evaluate the spatial distribution of the paper and fines across seven landfill sites (LFS) and assess the relationship between waste physicochemical properties and biogas production. Physicochemical analysis of the waste samples demonstrated that there were no clear trends in the spatial distribution of total solids (TS), moisture content (MC) and waste organic strength (VS) across all LFS. There was however noticeable difference between samples from the same landfill site. The effect of landfill age on waste physicochemical properties showed no clear relationship, thus, providing evidence that waste remains dormant and non-degraded for long periods of time. Landfill age was however directly correlated with the biochemical methane potential (BMP) of waste; with the highest BMP obtained from the most recent LFS. BMP was also correlated with depth as the average methane production decreased linearly with increasing depth. There was also a high degree of correlation between the Enzymatic Hydrolysis Test (EHT) and BMP test results, which motivates its potential use as an alternative to the BMP test method. Further to this, there were also positive correlations between MC and VS, VS and biogas volume and biogas volume and CH4 content. Outcomes of this work can be used to inform waste degradation and methane enhancement strategies for improving recovery of methane from landfills.
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    Evaluating leachate recirculation with cellulase addition to enhance waste biostabilisation and landfill gas production
    (Elsevier, 2016-07-05) Frank, R. R.; Davies, S.; Wagland, Stuart Thomas; Villa, Raffaella; Trois, C.; Coulon, Frederic
    The effect of leachate recirculation with cellulase augmentation on municipal solid waste (MSW) biostabilisation and landfill gas production was investigated using batch bioreactors to determine the optimal conditions of moisture content, temperature and nutrients. Experimentation was thereafter scaled-up in 7 L bioreactors. Three conditions were tested including (1) leachate recirculation only, (2) leachate recirculation with enzyme augmentation and (3) no leachate recirculation (control). Cumulative biogas production of the batch tests indicated that there was little difference between the leachate and control test conditions, producing on average 0.043 m3 biogas kg−1 waste. However the addition of cellulase at 15 × 106 U tonne−1 waste doubled the biogas production (0.074 m3 biogas kg−1 waste). Similar trend was observed with the bioreactors. Cellulase addition also resulted in the highest COD reduction in both the waste and the leachate samples (47% and 42% COD reduction, respectively). In both cases, the quantity of biogas produced was closer to the lower value of theoretical and data-based biogas prediction indicators (0.05–0.4 m3 biogas kg−1 waste). This was likely due to a high concentration of heavy metals present in the leachate, in particular Cr and Mn, which are known to be toxic to methanogens. The cost-benefit analysis (CBA) based on the settings of the study (cellulase concentration of 15 × 106 U tonne−1 waste) showed that leachate bioaugmentation using cellulase is economically viable, with a net benefit of approximately €12.1 million on a 5 Mt mixed waste landfill.
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    Sustainable landfill leachate treatment using refuse and pine bark as a carbon source for biodenitrification
    (Taylor & Francis, 2014-12-17) Frank, R. R.; Trois, C.; Coulon, Frederic
    Raw and 10-week composted commercial garden refuse (CGR) materials and pine bark (PB) mulch were evaluated for their potential use as alternative and sustainable sources of carbon for landfill leachate bio-denitrification. Dynamic batch tests using synthetic nitrate solutions of 100, 500 and 2000 mg NO3 L−1 were used to investigate the substrate performance at increasing nitrate concentrations under optimal conditions. Further to this, sequential batch tests using genuine nitrified landfill leachate with a concentration of 2000 mg NO3 L−1 were carried out to evaluate substrates behaviour in the presence of a complex mixture of chemicals present in leachate. Results showed that complete denitrification occurred in all conditions, indicating that raw and composted CGR and PB can be used as sustainable and efficient media for landfill leachate bio-denitrification. Of the three substrates, raw garden refuse yields the fastest denitrification rate followed by 10-week composted CGR and PB. However, the efficiency of the raw CGR was lower when using genuine leachate, indicating the inhibitory effect of components of the leachate on the denitrification process. Ten-week composted CGR performed optimally at low nitrate concentrations, while poor nitrate removal ability was found at higher nitrate concentrations (2000 mg L−1). In contrast, the PB performance was 3.5 times faster than that of the composted garden refuse at higher nitrate concentrations. Further to this, multi-criteria analysis of the process variables provided an easily implementable framework for the use of waste materials as an alternative and sustainable source of carbon for denitrification.