Study On Hydraulic Characteristics And Organic Wastewater Treatment Of Anaerobic-Aerobic Fluidized Bed With Waste Coke Particles As Biocarrier

The hydraulic characteristics and organic waste water treatment of anaerobic-aerobic fluidized bed bioreactor(AAFBBR) with waste coke particles(WCPs) as biocarrier were studied.In order to avoid fluidized bed being layered, the diameter range of WCPs was narrowed to 0.6~1.18 mm. The physical characteristics of WCPs are as follows: true density of 1598 kg/m3, bulk density of 675kg/m3, average particle size of 0.78 mm, a total porosity of 57.7%, water absorption(w/w) of 41.2% and specific surface area of 55.9 m2/g.The bed type changed from a fixed bed to a fluidized bed with the gradual increase of the superficial liquid velocity. The biocarrier was nearly still and the bed pressure increased in function of power with the increase of the superficial liquid velocity during stage of fixed bed. The bed gradually expanded and the bed pressure was almost steady during the period of fluidized bed. The expansion rate of the bed and pressure of the bed increased with the increase of the biocarrier quantity in the bioreactor at the same superficial liquid velocity. Based on the original definition of the critical fluidization velocity, the criticalfluidization velocity of the WCPs whose diameter were between 0.6 mm and 1.18 mm was about 0.39 cm/s.The startup of the AAFBBR was conducted by steps. First, anaerobic zone was started up. Then, the startup of aerobic zone began until some microorganisms existed on the surface of most of the biocarrier in the anaerobic zone. Finally, the startup of the system succeeded when there was mature biofilm attached on the biocarrier in the two zones. 62 days were consumed to start up this system. At the end of the startup, the biofilm thickness of the anaerobic and aerobic zones were 35~50 μm(15.3~17.6 mg VSS/g WCPs) and 50~130 μm(5.3~11.8 mg VSS/g WCPs)respectively. In addition, rich biological communities with nematodes and clock worm were observed in the AAFBBR. The effluent was nearly steady, and the COD removal rate of anaerobic, aerobic zones and the system were about 33%, 81% and 85% respectively.In the experiment of treatment of synthetic organic waste water, the COD removal of anaerobic, aerobic zones and total system were 30.7%,78% and 85.4% respectively under the condition of : influent flow of0.036 m3/h(HRT5.08 h), aeration intensity of 0.9 m3/h, initial COD concentration about 900 mg/L, circulating fluid velocity of 0.39 cm/s and0.54 cm/s in anaerobic and aerobic zones, and a initial p H of 7.0.