Basic study on anaerobic biological filtration using a floating filter media.

An experiment of anaerobic filtration using a floating media was carried out in this study. In the present system, a bench-scale column of 50 mm in diameter and of 1500 mm in height and a floating media consisting of S-shaped polystyrene pieces were employed. The purpose of this study was to collect the basic data of anaerobic biological filtration using a floating media. Under the laboratory conditions, it was found that the start-up of an anaerobic biological filter took about half month at 20 degrees C and a lower BOD loading was favorable for this start-up. The BOD removal efficiency over 60% could be achieved at a BOD volumetric loading of the filter bed under 6 kg/m3/d. An effluent BOD concentration became high when the flow rate was high, especially with circulation of treated water, which afforded a large effect on an effluent BOD concentration. As for the mechanism of BOD removal by anaerobic filtration, it was evident that long retention time worked in favor for organic acid generation, and the circulation of treated water promoted decomposition of organic acids.

Effects of anaerobic/aerobic incubation and storage temperature on preservation and deodorization of kitchen garbage.

To develop a garbage recycling system for the purpose of the production of lactic acid (LA) to use as raw material for producing biodegradable plastics, the preservation and deodorization of garbage during storage are very important. Anaerobic incubation (i.e., storage) was prove to be more suitable than aerobic incubation during the garbage storage in terms of concentration of LA and soluble sugar, pH value, viable bacteria counts and offensive odour substances. This difference is due to a fact that the growth of putrefactive bacteria such as coliforms and Clostridium spp. appeared to be inhibited by anaerobic fermentation during the storage, because the fermentation caused a drop of garbage pH and generated inhibitory substances, i.e., bacteriocins. Under anaerobic condition, LA concentration in the stored garbage was found to be higher in the order: 37 > 25 > 50 > 5 degrees C, and the concentration of sugar accumulated during the 50 degrees C-storage was the highest. Among the conditions employed, the optimum condition for the storage of kitchen garbage was anaerobic at 5 degrees C.