Start-up Of EGSB Reactor Treating Coking Wastewater

In recent years,with the rapid development of economy,the pollution of coking wastewater to environment is gradual severity.Components are complex in coking wastewater as a typical industrial wastewater,in which contains lots of toxic and difficult biodegradation materials.Besides, this kind of wastewater is difficult treatment and its flow is a large number.Precently the main treatment methods used in the coking wastewater control is still biological treatment method,such as A/O,A2/O,SBR and so on.However,there is no good ability to resist toxic so that it is hard to meet the requirements of discharge standard.The main characteristics of expanded granular sludge bed(EGSB) are high sludge concentration,high reflux ratio,high liquid upflow velocity which provide possibillity for the degradation of coking wastewater.But it is very important to domesticate granular sludge in coking wastewater treatment using EGSB reactor. Start-up of EGSB reactor treating coking wastewater was researched in the experiment in order to offer a theoretical basis for cultivating granular sludge that has adaptability for poisonous and hardly-degradable coking wastewater.The experiment is divided into two stages.The first stage is cultivating granular sludge in EGSB reactor inoculated with municipal digestion sludge using brewery wastewater.The second stage is acclimating granular sludge using coking wastewater under microaerobic conditions. The results shows that it takes 70 days for the culture of granular sludge in the EGSB reactor under municipal digestion sludge as seed sludge. With influent rewery wastewater pH of 6.29-7.16,influent COD concentration of 653-1897mg/L and influent loading rate of 2.7-13.1 kgCOD/(m3·d),COD removal efficiency is above 90%.At the time,there are plenty of biogas and granular sludge in the reactor.The mature granular sludge has large granular size and good settling performance with settling rates of 13-97m/h.The first phase is finished now.And then,the second stage,that is, is carried out.The granular sludge in the EGSB need domesticated when treating the coking wastewater.174 days are taken for the treating coking wastewater under micro-aerobic conditions by gradually increasing amount of oygenation(low 1.Om/h) in the refluxcolumn and liquid upflow velocity(2.1-3.0m/h) in the EGSB reactor.The influent pH,COD and ammonia-nitrogen concentration are 6.5-9.10,630-2300 mg/L and 55-330 mg/L, respectively. With influent flow of 1.OL/h and influent loading rate of 1.2-4.7 kgCOD/(m3·d), the micro-aerobic EGSB could attain 89% COD removal efficiency, and the average effluent COD concentration was only 90mg/L at the temperature of reactor of 30-33℃.The start-up of EGSB reactor treating coking wastewate is successful.The whole experiment lasts about 8 months.It is very obvious in the respect of sludge variation. At first,the sludge in EGSB reactor is flocculent and dispersed sludge. There are a lot of black granular sludge in the reactor after cultivating 70 days using brewery wastewater.The granules have smooth surfaces and regular shape.The granular size main are concentrate on 0.43mm-0.63mm and the maximal diameter of granular sludge exceed 2mm.The wheat granules appear at the end of the process of acclimating. Supplement of limited oxygen breaks up granular sludge so that particle size of the sludge is decreased. Meanwhile sludge concentration reduce to 13.20g/L. However, the activity of bacteria wasn't inhibited. The ability of supporting shock of small particles is better than that of large particles.Now, the granules have an enrichment microcommunity.There exist various different bacterias which are hyphomycete,coccus and bacillus from surface to interior of granular sludge in proper order. Besides,the granulars have very large specific surface areas and holes in the surface of it;the contact and mass transfer effect between wastewater and sludge are well.The results of paper research are very significant on quick start-up and application of EGSB in coking wastewater treatment to guide practice and theory.The process,treating coking wastewater using EGSB reactor under under micro-aerobic conditions, are valuable to reform current treatment methods used in the coking wastewater control.