| 英文摘要 |
In a conventional food processing wastewater treatment process, the oil and grease was separated with dissolved air flotation. Then the oil scum and sludge shall be dewatered and concentrated with bulky volume. The post treatment of oily sludge was difficulty to handled with high process cost due to chemical addition and a large portion of impurity. A cost effective biological process shall be developed to treat the oil and grease associated with wastewater in a bio energy process. Three stages of aerobic, acidogenic and anaerobic methanogenic bioprocesses have been operated for one year to evaluate the feasibility of bioprocess combination for wasted food oil treatment. One ton of aerobic fluidized bed associated with a scum and biocarrier recirculation facilities was designed with innovative concept of extended retention time for oil-degrading bacteria. With returned attached biofilm and adsorbed oil on diatomaceous particles, elimination of floated scum and foaming was improved significantly in the first stage of aeration tank. More than 5,000mg/L of MLVSS was maintained to attain effective partial oxidation of oil and grease by aerobic activated sludge with the attached biofilm. Then with the partially oxidized oil and the additional ice cream wastewater, the second stage of anaerobically acidogenic fluidized bed received high volumetric loading at 17 kg COD/m3-day with HRT of 24 hours. The long-chain fatty acid was converted to volatile fatty acid at pH 5. 4,000mg/L of oil inflow could be stabilized while hydrogen biogas was produced at the composition range of 10 to 40%. However, high SS concentration of 4,000 to 8,000mg/L was carried over the anaerobic fluidized bed due to high growth rate of acidogene.
The third stage of anaerobically methanogenic fluidized bed was also operated with high volumetric loading of 20kg COD/m3-day and 37 hours of HRT. The pH range should be adjusted to 7.0. Fluctuated influent concentration with entrapped sludge impacted the stability of methanogenic performance. Interception and separation of the carried over sludge in both anaerobic fluidized bed were remedied with effluent setting tanks and sludge recirculation facilities. Modification of the hydraulic system is still required to improve the overflow scum in three stage due to oil interception and in complete biodegradation. Scale-up of three-stage bioenevgy process shall be enforced with larger volume of bioreactor up to one to three cubic meters and larger recirculating pipe diameter and pump to upgrade the agitation of oil-attached carriers and activated biomass. Three phases of oil degrading bacteria, hydrogen producing bacteria and anaerobic methanogenes were identified with molecular biomonitoring methods of DGGE and T-RFLP. High potential of these three groups of syntrophic microsystem was evaluated with S.OUR, BHP and BMP tests in series.The pilot plant study provides diverse operation parameters for the process design criteria in scale-up extent.
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