Study On Three-phase Internal Loop Biological Fluidized Bed Technology Of Oily Wastewater

In recent years, treatment of oily wastewater has been received people’s attentionintensively in oil field. At present, the oily wastewater treatment methods mainlyconsist of physical method, chemical method, biological method and somecombination technology and so on. Biological method is the most widely used to thetreatment oily wastewater in oil field due to its lost costs, good degradation effect,good stability and no-secondary pollution. In all the biological methods, three-phaseinternal loop biological fluidized bed is a new technology of wastewater treatment,which effectively combines chemical fluid equipment with biofilm process. It is givenmore and more attention because of its many advantages, such as high volume load,high mass speed, strong shocks, good stability, low occupied space and so on. Atpresent, active carbon as the carrier has been studied in the bio-fluidized bed reactorat home and abroad. But as cost of active carbon is high, its scale application islimited. Therefore, in this paper, semi coke as the carrier is studied in the three-phaseinternal loop biological fluidized bed first. At the same time, its properties areinvestigated, and treatment effects are compared between active carbon and semicoke.In this paper, main contents and conclusions are as follows:1. The conditions of the carrier film were studied. The results show that: Carrierbiofilm can be accomplished with fast sludge, But the film formation conditionsshould be suitable, and short residence time is useful for the formation of biofilm.2. With semi coke as the carrier, Effect of different operating conditions on treatmentof waste water were studied in three-phase internal loop biological fluidized bedreactor, such as organic concentration of the waste water, HRT, aeration volumeand temperature. Meanwhile, treatment effects are compared between activecarbon and semi coke. The results show that: （1） The organic concentration of the waste water all have a certain effect onbiological fluidized bed reactor of activated carbon and activated semi coke.The greater the organic concentration of the waste water, the more obvious theeffect.When the organic concentration of the waste water is moderate, atreatment effect of the two reactors is identical. With active carbon andactivated semi coke as the carriers respectively, oil removal rates are all87%,Oil contents of effluent are all under5mg/L, COD_Crremoval rates are allabove70%.（2） HRT has a larger effect on the biofilm progress of the carriers, when theorganic and inorganic nutrients of the water are basically the same, a relativelyshort HRT is in favour of biofilm formation. HRT has a larger effect ontreatment of waste water. With active carbon and activated semi coke as thecarriers respectively, the optimum HRT is3h. Under the condition, COD_Crremoval rates of two reactors are all77%, and oil removal rates arerespectively94%and92%. When HRT is higher than3h, COD_Crand oilremoval rates of two reactors all are lower.（3） The aeration volume has a larger effect on treatment of waste water. Whenusing the same aeration, biological fluidized bed reactor of activated carbonand activated semi coke have a similar treatment efficiency of the wastewater.With active carbon and activated semi coke as the carriers respectively, theoptimum aeration volume is0.20m3/h. Under the condition, COD_Crremovalrates of two reactors are respectively81%and83%, and oil removal rates arerespectively90%and92%. When the aeration is less than or greater than0.20m³h, COD_Crremoval rate is lower invariably.（4） T has a larger effect on treatment of waste water. When using the sametemperature, biological fluidized bed reactor of activated carbon and activatedsemi coke have a similar treatment efficiency of the wastewater. With activecarbon and activated semi coke as the carriers respectively, the optimum T is30℃, Under the condition, COD_Crremoval rates of two reactors are respectively81%and83%, and oil removal rates are respectively90%and87%.（5） When the optimum operating conditions（HRT、aeration volume、T） are3h、0.20m3/h and30℃respectively, With active carbon and activated semi cokeas the carriers respectively, oil removal rates and COD_Crremoval rates areessentially equal. Under the condition, COD_Crremoval rates of two reactorsare respectively81%and83%, and oil removal rates are respectively90%and92%, The average COD_Crof produced water are66mg/L and61mg/L,respectively.（6） As comprehensive range of operating conditions known, activated semi cokemay be applied to the inner loop three-phase biological fluidized bed to treatthe wastewater instead of activated carbon.