Takuya KAZAWA
Development of food waste treatment system that combines thermophilic and no addition of water anaerobic digestion with ammonia removal
Takashi YAMAGUCHI
The majority of food waste of useful biomass resources is incinerated now. The methane fermentation is paid to attention as the next generation energy production system of the resource circulation type that produces biogas with food waste. The no addition of water methane fermentation doesn't especially need the dilution water, and enable a great volume reduction of the digested sludge and the reduction in the disposal cost.On the other hand, the inhibitor of the methane fermentation exists in a high density as compensation in the non-dilution condition, too. Especially, the ammonia generated resolving the protein accumulates in a high density in the sludge, and the methane fermentation is obstructed. Making the pH adjustment and the fermentation tank multiphase is indispensable, and the cost reduction and the efficiency improvement of the ammonia removal are requested though there is an ammonia removal technology in the past as a workaround. To develop new garbage processing system that combined the high teperature no addition of water methane fermentation with the ammonia removal, continuous processing on the lab scale was done in this thesis.
As a result, NH4+-N concentration of the fermentation sludge was 1,800 mg/kg-w.w according to the effect of the ammonia removal of the biogas circulation. This reactor was able to achieve the recovery and the stabilization of the processing performance by adding the compound nutritive salt of Fe, Ni, and Co. And this reactor achieved Organic loading rate 9.6 kgCOD/m3/day and hydraulic retention time 30 days.The propionic acid degradation progresses remarkably by supplying Ni and Co, and moreover, the processing performance was able to be improved and to stabilize. The amount of generation of biogas on HRT 75 days was 201Nm3/ton-sub. As for this system, it was shown that it met efficient methane fermentation requirement (>150 Nm3) in a real machine enough, and the operation with a high cost performance was possible by securing HRT. It was shown that the limit of allowed OLR led to further allowance OLR rise by maintaining SRT from HRT long in relation to SRT and closeness.
Installing the precipitation tank in the methane fermentation tank latter part, and controlling the ammonia removal, the sulphide removal, the nutritive salt supply, and the sludge retention time suggested the realizability of highly effective methane fermentation processing.
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