Study On Hydraulic Characteristics And Wastewater Treatment Of Biological Fluidized Bed With Waste Coke Particles As The Biocarrier

Fluidized bed bioreactor （FBBR） introduces chemical fluidizationtechnology into the field of wastewater treatment and integrates activatedsludge process with biofilm technology. This process boasts suchadvantages as small floor area, high efficiency of organic removal and goodcapability of resisting impactive loading. This paper mainly studiedhydraulic characteristics and organic wastewater treatment of a FBBR withwaste coke particles （WCPs） as the biocarrier. WCPs with a diameter rangeof0.6to2.3mm have some physical characteristics as follows: averageparticle size of1.07mm, bulk density of600kg/m³, true density of1600kg/m³, a total porosity of62.5%, water absorption rate of0.377g/g, and aBET specifc surface area of55.0m²/g.In the experiment of solid-liquid FBBR, the bed type changed from afixed bed, to a expanded bed, to a traditional fluidized bed and then to acirculating fluidized bed gradually with the increase of the superficialliquid velocity. Minimum fluidization velocity varied with the differentquantity of WCPs, and the value was measured at0.7-1.2cm/s. The gasholdup increased with the increase of WCPs and superficial gas velocityrespectively, and decreased with the increase of superficial liquid velocity.Gas holdup and superficial gas velocity have a logarithmic relationship,and the fitting equation wasε=2.60U^0.88. Volumetric oxygen mass transfercoefficient K_La increased with the increase of superficial gas velocity, andincreased at first and then decreased with the increase of WCPs quantity. The startup of the FBBR used the method of rapid draw off sludge, andsucceeded after15d. At the end of start-up, the effluent water was almoststeady, and the COD removal rate was around90%. The attached biomasswas4.0-4.5mg VSS/g WCPs, and bioflm thicknesses was35-110μm. Inaddition, rich biological communities with clock worm, nematodes andinclined pipe vermin was observed in the FBBR.In the experiment of treatment of synthetic domestic sewage using aFBBR with WCPs as the biocarrier, the effluent COD concentration wasless than100mg L-1, corresponding to a COD removal of over90%. Theseresults reached the second order of “National Wastewater DischargeStandard”, under the conditions of: HRT at2.5-3.0h, aeration intensity of45.9m³m-2h-1, initial COD concentration less than2000mg/L, arecirculating liquid velocity of2.477cm/s, and a pH of7.0-8.0.