| Liquid hydrocarbon and catalytic gasoline spent caustic generated in the oil refining process of refinery were researched in this article with biological treatment method, liquid hydrocarbon spent caustic was detoxificated with air oxidation method, and the catalytic gasoline spent caustic was also disposed harmlessly by the use of nitrification and denitrification technology.In this research, SBR reactor was adopted to study the biological treatment process of liquid hydrocarbon spent caustic.When the reaction condition was kept at the temperature of30℃, the pH value between7.0to8.5, and the aeration of0.3L/min in the simulated wastewater processing, the activated sludge was domesticated successfully, it achieved a good performance on salt-tolerance, and had a stable effect on the degradation of sulfide and organic matter. When the S2-load was0.1kg/(m3·d), and there was enough dissolved oxygen in the system, the sulfide were all converted to SO42-basically, and the removal rate of sulfide arrived at100%.In the liquid hydrocarbon spent caustic, the sulfide concentration was9180mg/L, COD concentration was63300mg/L, alkalinity exceed300000mg/L, TDS was over230000mg/L, the B/C was below0.1, and it had poor biodegradability. GC-MS results showed that the main organic component of the spent caustic was sulfidic organic compound, and its rate exceeded85%.In the experiment, the SBR reactor was controlled at temperature of30℃and kept with enough DO. When the influent TDS concentration was40g/L, and the influent pH value was10.5, liquid hydrocarbon spent caustic was researched as treatment objection. The activated sludge was domesticated successfully, and it had a good performance under halo-alkaline conditions. When the total sulfur load was0.9kgS/(m3·d), the sulfide removal efficiency arrived at about100%, and the COD removal rate was83.8%. S2-were mainly converted to SO42-, and the conversion rate was96%. Further studies showed that the SBR reactor had a relatively stable effect on the treatment of spent caustic diluted three times, and the sludge load should be kept between0.75-1.15kgCOD/kgMLVSS·d. When the influence was three times-diluted spent caustic, and the total sulfur load was1.5kgS/(m3·d). the removal efficiency of sulfur compounds were always above99%, there was not any sulfide detected in the effluent, the oxidation rate of S2-to SO42-declined, and there were a lot of elemental S mixed in the effluent.The kinetic equation of liquid hydrocarbon caustic sludge biodegradation was obtainned by fitting the biodegradation data of spent caustic with the Monod correction equation and Haldane equation, and it showed that the Sn was454mg/L. It could be seen from the combination of these two models that there were a certain amount of substances which were diffcult to be biodegradable in the spent caustic, and the excessive concentration of spent caustic would inhibit microbial activity significantly.In this study, the toxicity-reduction research of synthetic wastewater and liquid hydrocarbon spent caustic were carried out with air oxidation-biological treatment method. It was found that the air oxidation-biological treatment method could effectively increase the oxidation rate of S2-to SO42-, and thereby reduce the generation rate of elemental sulfur. In addition, the two-step method could also effectively shorten the reaction time, and improve the reaction load.The characteristics of catalytic gasoline spent caustic was studied in this study, and it was found that its COD concentration was370000mg/L, volatile phenol content arrived at118000mg/L, the alkalinity and TDS were very high, and the biodegradability was poor. GC-MS results showed that the main component of spent caustic was phenolic compounds, wich take76.9%of all the organic components, and the additional20.1%were sulfidic organic compounds.SBR process was taken to make treatment to catalytic gasoline spent caustic. After the pretreatment, COD removal efficiency of spent caustic was over97%, phenol content decreased by99.9%, and B/C rose to0.4which showed good biodegradability. After the biological treatment to pretreated spent caustic in SBR reactor, it was found that the effect of SBR-2system which take industrial sludge was abviously better than that of SBR-1system which use municipal sludge.In addition, the effect of A/O process to spent caustic and ammonia wastewater which made spent caustic as the only carbon source was investigated with A/O reactor. The results showed that the treatment effect of the process which make spent caustic as the only carbon source was quite stable, the main organic matter in the spent caustic were all degradated. and the effluent NH3-N concentration was below the detection limit. In order to ensure the quality of effluent, the proportion of spent caustic to the concentration of the influent ammonia should be5. |
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