| After pretreatment,high concentration refinery wastewater produced from a petroleum refining plant discharge into the sewage treatment plant.The refinery wastewater has high organic concentration,low biogradability and fluctuation of water quantity and quality,which greatly influence the stable operation of the following biochemical unit.The up-flow anaerobic sludge blanket(UASB)reactor has been widely used in the petrochemical wastewater treatment field because of its good ability to degrade the refractory organics.But in practical engineering,we often encounter some problems such as over low sludge concentration in UASB reactor and poor treatment effect.In this study,UASB reactors are operated to explore the method to shorten the start-up period of reactors and accelerate the anaerobic sludge granulation process.Three kinds of organic polymers are used in the study: chitosan,cationic polyacrylamide(CPAM)and polymeric aluminum chloride(PAC).A control flask is operated without polymer,while the sludge of the other twelve flasks is added with different polymer concentration.All flasks are operated in thermostatic shakers(37?,120r/min).Experimental results demonstrate that after two months of operation,the COD removal rates of all flasks have reached more than 90% and VSS concentrations have grown to different extent,among which the most proliferous one is polyacrylamide with concentration of 4mg/g VSS,accelerating the VSS growth rate by 54%(35% higher than control flask).The start-up process of UASB reactor is accompanied with the increase of organic loading.As organic loading reaches a certain degree(10 kg COD/(m3·d)),the UASB reactor is considered to be successfully started and enters the stable operation stage.The organic loading rate is increased in three ways.Finding which way is the fastest one to increase the loading rate is the purpose of this study.Organic loading rate is increased by 0.33 kg COD/(m3·d)as soon as the COD removal rate reaches above 50%.Experimental results show that fixing the influent COD concentration at 2000mg/L while reducing hydraulic retention time(HRT)(48h?5h)is the best way to accelerate the start-up of UASB reactor.Based on the conclusions drawn from the above two points,sewage from a refinery wastewater treatment plant is used as subject,and the water quality and biodegradability are tested and analyzed.Two UASB reactors are operated in different method.After the addition of flocculent to UASB reactors,anaerobic microbial cells are enclosed with flocculent,with good settling performance and less residual sludge in the effluent.Experimental results show that the reactor's anti-shock loading capability is obviously improved.PAM reactor has better anti-shock loading capability than PAC reactor,with the period gradually shortened from 8~9 days at the beginning to 3 days at the end of the experiment.After 102 days' operation,the OLR of PAM reactor reaches 10 kg COD/(m3·d),at a time when the OLR of PAC UASB reactor is still at 7 kg COD/(m3·d)around.It is also one month earlier than the blank control reactor.In addition,the anaerobic sludge granulation is also observed.The laboratory results indicate that after three months operation,60% of PAM anaerobic sludge can be cultivated to granules with diameter of 2.0~3.6 mm and maximum diameter reaches 4 mm.Finally,the organic components and oil content of the UASB reactor are tested and analyzed.The GC-MS analysis shows that after treatment,the phenolic content of refinery wastewater decreases significantly after treatment,only accounted for 15% of the relative contents of effluent organic matters,and organic acids of long carbon chains hydrolyze into shorter carbon chains.The biological toxicity is obviously decreased,and the biodegradability of wastewater is improved.The results of oil organic matters by using infrared oil measuring instrument show that the total oil and organic petroleum components are well degraded. |
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