| In order to improve treatment efficiency of oil refinery wasterwater,the role of extracellular polymerics and process of nitrogen removal were studied.Using laboratory-scale sequencing batch reactors(SBRs),activated sluges taken from an oil refinery wasterwater treatment,were cultivated by 3 different kinds of synthetic wastewater containing glucose,glucose mixed diesel oil,diesel oil as carbon source respectively.After long period of cultivation,activated sluge fed with diesel oil(NO.3)turned dark and had a weaker settleability,of which the partical size was the largest and the dominant microorganisms were bacilus strains.Activated sluge fed with the mixture of glucose and diesel oil(NO.2)developed a brow color and had good settling ability as the one fed with glucose(NO.1)had.The particle size of No.2 was between the No.1 and No.3.The bacilus strains and pelleting strains were both abundant. Activated sluge fed with glucose had a yellow appearance and pelleting strains were dominant.Relative Hydrophobicity value of NO.2 and NO.3 was 85%,97% respectively,which suggest that lipophilic microorganisms were getting predominant since appetence between bacteria and diesel oil enhanced gradually.Zeta potentials of the two activated sluge were both in normal range and zoogloea flocculated well, which were helpful to adsorption and degradation of diesel oil by flocs and microorganisms.There were some metabolic intermediates of hydrocarbons generated during the aeration,such as alcohols,fatty acids and esters.When a mixture of diesel oil and glucose added as co-substrate,more kinds of fatty acids were metabolized,and diesel oil removal efficiency was higher(NO.2 and NO.3,61%and 52%respectively), which indicated that glucose did not restrain biodegradation of diesel oil when the mass ratio of the two was 1:1.5.With a few of glucose,biodegradation of diesel oil would be enhanced since the micro-ecosystem was improved and the growth of microorganisms was accelarated.There were a great deal of unsoluble yellow particles with sugar-alcohol matrix emerged in bioreactors added with diesel oil at the earlier stage of operation.Besides bacteria,there were chemicals composed of C,O,H found in the particles,and the mass ratio of C and O was 2.38～4.16.At the initial stage of operation,particles came into being because direct contact mechanism took the lead in hydrocarbon digestion. With quantities of hydrocarbon degrading bacteria increasing and the adaptability to diesel oil developing,particles disappeared gradually at the late stage of operation since emulsified hydrocarbon ingestion mechanism brought into play.Proteins and polysaccharides were the basis of Extracellular Polymeric Substances(EPS),whose total percentage was 96%,91%,80%and the mass ratio was 5.88,4.74,3.36 in SBR NO.1,NO.2 and NO.3.Under the induction of hydrocarbons,the percent contents of protein and polysaccharide were decreased, while the adsorption ability and surfaceactivity would get better because of the improved structure.Hydrocarbons also induced microorganisms to secrete more metabolites into medium.Surface-active substances such as proteins,polysaccharide, fatty acids and biosurfactants such as esters could disperse and emulsify disel oil at some level.During the ingestion of hydrocarbons,microorganisms could secrete some surface-active substances into extracellular and medium,which were finally favor of hydrocarbon biodegradation via hydrocarbon emulsification and appetence augment between bacteria and hydrocarbons.Mainly due to assimilation of hydrocarbon degrading bacteria,the concentration of TN and TP decreased steeply,respectively from 18mg/L and 3.6mg/L to 5mg/L and 1mg/L in 2 hours in bioreactors added with diesel oil.Simultaneous nitrification and denitrification(SND)might contribute to nitrogen removal slightly.However,glucose as single carbon source couldnot induce microorganism to remove nitrogen greatly,so the attenuation of nitrogen was not as distinct as in the other two bioreactors.
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