Preparation Of Mineral Adsorbent And Its Application In Biological Treatment Of Emulsified Oil Wastewater

With the rapid development of our country's economy,a large amount of oily wastewater is produced in the petrochemical,mechanical processing,food processing and other industries every year.Oily wastewater can reduce dissolved oxygen in water,hinder photosynthesis of aquatic plants,cause aquatic organisms to die,and destroy the utilization value of water resources.Irrigation of farmland with oily wastewater can block soil pores and cause crop yield reduction or death in severe cases.Moreover,the migration of oil in the soil may cause serious groundwater pollution.Due to the presence of the surfactant in emulsified oil wastewater,it is difficult to separate the emulsified oil from the wastewater even after standing for a long time.At present,the common treatment methods for emulsified oil wastewater are physical method,chemical method and biological method.Among them,the biological method is widely used because of its advantages of low investment,energy saving and high efficiency,and no secondary pollution.However,this method also has problems such as poor adaptability to impact load and unstable effluent water quality in the water treatment process.In this paper,the combination of adsorption and biological methods is used to remove organic matter from emulsified oil wastewater.For the first time,sepiolite,magnesia and fly ash were selected as the main raw materials,and porogen,binder and other components were added to prepare the composite mineral adsorbent.The main mineral composition of the adsorbent is diopside,forsterite,calcium aluminum feldspar and silica.The response surface analysis method is used to optimize the preparation conditions of the adsorbent.The prepared adsorbent has higher mechanical strength,more voids,and the specific surface area is 1.446m2/g(BET).The DFT pore size distribution curve shows that the adsorbent is mainly composed of mesopores and macropores,and the structure contains a large number of active bonds of Si-O,Ca-O and Mg-O,which can effectively adsorb pollutants in the wastewater.The physical properties of the adsorbent was characterized,and the test results show that all the indicators meet the requirements of the?artificial ceramsite filter for water treatment?(CJ/T299-2008).And the adsorption performance of the adsorbent was characterized too.The simulated emulsified oil wastewater was prepared by using 0#diesel,alkylphenol ethoxylate(OP-10)and water under the action of high shear mixing emulsifier.The effects of adsorption time,adsorbent dosage,wastewater pH,wastewater temperature and other factors on the adsorption performance of the adsorbent were discussed.The results show that with the increase of adsorption time,the upward trend of the COD adsorption amount in the simulated emulsified oil wastewater by the adsorbent is slower,and the adsorption can be basically balanced after 12 hours of adsorption.When the wastewater is close to neutral,the adsorption performance is better.When the initial COD concentration was 382.25 mg/L,the wastewater temperature is 30?,the wastewater pH is 7,and the adsorbent dosage is 40g/L,the average COD concentration after adsorption for 12h is 39.24mg/L,the average COD removal rate is 89.73%,and the average COD adsorption capacity is 8.58 mg/g.The adsorption isotherm of composite mineral adsorbent on COD and petroleum hydrocarbon in simulated emulsified oil wastewater accords with Langmuir adsorption isotherm model.The adsorption kinetics follows the quasi-secondary kinetic model.And the adsorption process is jointly controlled by intraparticle diffusion and membrane diffusion.The SBBR reactor(R3)using a composite mineral adsorbent as a microbial carrier is compared with an SBR reactor(R1)using only activated sludge and an SBBR reactor(R2)using a commercially available bioceramic carrier as a carrier.When the operating conditions and the influent water quality are exactly the same,R3 reactor has a higher membrane forming speed and stable effluent quality during the start-up phase of the reactor,and the COD and TN removal rates are better than other in the reactor operation phase.The total petroleum hydrocarbon concentration in the inlet and outlet water of R1,R2 and R3 reactors were measured by gas chromatography.The results showed that the removal rates of C15-C28 and C29-C36 in the reactor(R3)with composite mineral adsorbent as carrier were higher than the R1,R2 reactor.The microbial population structure in each reactor was tested and analyzed after stable operation for a period of time.The Acinetobacter with petroleum hydrocarbon degradation and denitrification function had the highest abundance in the R3 reactor.In summary,the combination of adsorption and biological method to treat emulsified oil wastewater can not only reduce the impact of the influent loads on the microbial flora in the reactor due to the adsorption of pollutants in the wastewater by adsorbent,but also promote the enrichment and growth of the flora with petroleum hydrocarbons as nutrients on the surface of the adsorbent,and improve the structure of the flora.At the same time,it can also solves the problems of limited capacity and difficulty in regeneration of the adsorbent in the adsorption method.