| The oily sludge is classified in the"National Hazardous Waste List（2016Edition）".Pollution control and reduction treatment at its source are pivotal parts in the treatment of the petroleum refining industry.This paper focused on the aeration tank sludge in the refinery,adopted the microbubble ozone（O3）process,electrolysis and microbubble O3（E+-microbubble O3）combined and calcium peroxide（Ca O2）and microbubble O3（microbubbles O3/Ca O2）combined processes were proposed in order to improve the utilization rate of O3.This paper discussed and optimized the treatment efficiency of three different processes,studied the carbon source release of oily sludge,the dissolution of nutrients,the degradation of total petroleum hydrocarbons（TPH）,the conversion process of organic matter and the characteristics of oily sludge,and the oxidation reaction mechanism,which provided technical support for the industrialization of the treatment and disposal of oily sludge materials.The main conclusions are as follows:（1）The microbubble ozonation process had a better treatment effect on sludge breaking and lysis,deoiling and detoxification.Under the conductions of p H 9,the O3 concentration 90 mg/L and the O3 reaction for 120 min in column equipped with a microbubble aeration.The soluble chemical oxygen demand（SCOD）and sludge solubility(DDSCOD)in the supernatant reached to 6275 mg/L and 25.8%respectively,which was twice the release of ordinary bubbles.The volatile fatty acids（VFAs）in the supernatant were mainly short-chain hydrocarbons acetic acid and propionic acid,accounting for around 1/5 of the total SCOD.After the oxidation treatment of microbubbles O3,the surface of the sludge was uneven,and the whole became loose.The molecular weight<5 k Da increased from 1%to 30%.The particle size of the largest sludge reduced from98.1μm to 45.6μm,which greatly improved the biodegradability.The removal rate of sludge TPH was 60.4%,and the remaining TPH was 2970 mg/kg,which met the emission standards.Compared with ordinary bubbles,ozonation of microbubbles increased the contribution rate by 9.30%.（2）The E+-microbubble O3 process was built to treat oily sludge.The process of electrolysis and microbubble O3 combined can increase the in-situ reuse of the gas released by O3 due to the low O3concentration mixed with a large amount of oxygen（O2）and the poor solubility of O3 in the system,and improve the O3 utilization rate.Under the conditions of p H 9,current density 30m A/cm2,electrode plate spacing 3 cm,and O3 concentration 90 mg/L,the reaction for 120 min,SCOD and DDSCOD reached to 7700 mg/L and 32.3%,respectively.VFAs accounted for around 1/4 of the total SCOD.The removal rate of TPH was 84.3%,and the remaining TPH was 1178 mg/kg.After the oxidation treatment of E+-microbubbles O3,the sludge floc structure was loose and small,showing a dispersed block structure.The molecular weight<5 k Da increased from 1%to 33%,and the largest particle size decreased from 98.1μm to 40.1μm.The main active substances in the E+-microbubble O3 system were O3 and·OH.The electrolysis driven reaction effectively increased the mass transfer of O3 from the gas phase to the liquid phase,promoted the self-decomposition rate of O3,and increased the output of hydroxyl radicals（·OH）in the E+-microbubble O3 system.（3）Based on the fact that Ca O2 can slowly release O2 and hydrogen peroxide（H2O2）at a"controllable"rate,the combined Ca O2with microbubble O3 process was developed to treat oily sludge.Under the conditions of p H 7 and Ca O2 dosage of 0.25g/g TS for 120 min,SCOD and DDSCOD reached to 7620mg/L and 31.8%,respectively,and VFAs accounted for around 1/6 of the total SCOD.The TPH removal rate of oily sludge was 70.3%,and the remaining TPH was 2227 mg/kg.After microbubble O3/Ca O2 treatment,sludge particles were scattered all over the place,and the crushing effect was better.The molecular weight<5 k Da increased from 1%to 30%,and the largest particle size decreased from 98.1μm to 51.8μm.The effect of hydrolyzed components on the lysis effect of oily sludge was arranged in the order of Ca O2>Ca（OH）2>H2O2>O3>Ca Cl2.Superoxide radicals（·O2-）and·OH were both the free radicals that played major roles in oxidation process,and the order of influencing the release of carbon sources from oily sludge was:·OH>·O2-.（4）The influence mechanism of the combined process of E+-microbubble O3 and microbubble O3/Ca O2 on the treatment effect of oily sludge was compared and discussed.E+-microbubble O3 process was better,and the release amount can reach to 7700 mg/L.TPH removal rate of oily sludge reached to84.3%,and the remaining TPH was 1178 mg/kg,which met the emission standard of Class B pollutants（<3000 mg/L）in the emission requirement"Control Standard for Pollutants in Agricultural Sludge"（GB4284-2018）.Oxides can not only effectively destroy sludge flocs,but also react with dissolved organic matter to oxidize them into small molecular substances,which greatly improved the biodegradability. |
