UBC Theses and Dissertations
Anaerobic digestion of dairy manure using the microwave hydrogen peroxide advanced oxidation process Chan, Ian Ching Yuen
Anaerobic digestion (AD) of dairy manure is an alternative to traditional manure management using land application. There are many benefits of AD but it is currently not an economically viable option in many parts of North America. The focus of this investigation was to determine whether liquid dairy manure treated by microwave hydrogen peroxide advanced oxidation process (MW/H₂O₂-AOP) would increase the anaerobic biodegradability of the substrate, producing higher methane yields. Biochemical methane potential (BMP) tests were conducted to measure biogas generation and the Modified Gompertz equation was used to determine the kinetics of anaerobic biodegradability. The research found that MW/H₂O₂-AOP was effective in solubilizing nutrients and organics in liquid dairy manure, but it does not necessarily translate into enhanced anaerobic biodegradability. The BMP tests revealed that digestion of untreated dairy manure at 35ºC had the highest methane yields. Severe inhibition was observed for the digestion of acidified dairy manure. This was attributed to sulfide inhibition. In addition, ammonia concentrations were suspected as the main reason for severe inhibition of microwave treated dairy manure with no acid addition, but a number of other factors could also be responsible, including sulfide, light metals and lack of temperature acclimation for inoculum. Pretreatment of sewage sludge and BMP tests were also conducted to compare the effect of MW/H₂O₂-AOP with dairy manure. The results showed that the microwave treatment had a positive impact on anaerobic digestibility of sewage sludge, especially for mesophilic digestion. At 35ᵒC, MW alone generated the highest methane yields followed by MW/H₂O₂ and then the control. In terms of methane yield, microwave treatment improved the methane production rate for mesophilic digestion, but not thermophilic digestion. The positive results for BMP tests of microwave treated sewage sludge suggest that the influence of microwave treatment on anaerobic biodegradability is substrate and solid concentration specific. There was no clear and consistent increase or decrease in soluble metal (Ca, K, Mg, Na) concentrations after MW/H₂O₂-AOP. However, it was found that acidified treatment was effective in releasing calcium and magnesium into solution. After digestion, the soluble calcium, potassium, magnesium and sodium content of dairy manure was reduced.
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