Study On The Influence Of Diatomite In EGSB On Coking Wastewater Treatment

In recent years, with the rapid development of coking industry, the damage caused by coking wastewater was growing. The coking wastewater has more complex component. Some of them are refractory organic matters and are difficult to biodegrade. So it is difficult to deal with. In this investigation, expanded granular sludge bed(EGSB) is used to treat coking wastewater under microaerobic condition. There are three contents for this experiment, the removal effieieney of EGSB reactor, the removal effieieney of EGSB with diatomite and the further treatment of coking wastewater.In the first stage of this experiment, COD removal effieieney of EGSB continuously improve with the change of operating parameter, such as influent flow, recycle flow and so on. The optimal operation condition of the EGSB is influent flow of1L/h, recycle flow of22L/h. At this condition, the effluent COD decreases from2940mg/L to1000mg/L. COD removal rate is66%. Influence of aeration rate on COD removal rate is obvious. The optimal aeration rate13000mL/min. ORP is the more effective control parameter for the EGSB reactor, which normally has the values of380to400mV. Influence of temperature on COD removal rate is not important. When it is necessary, the operation parameters could be adusted to ensure the stable operation of the reactor. More over, the addition of trace elements is indispensable.Through the experiment with serum bottle, we identified that optimal dosege of diatomite was500mg/L. After the addition of diatomite, the removal rate of COD was continuously improved with the increase of recycle flow rate. The optimal operation condition of the EGSB is influent flow of1L/h, recycle flow of24L/h. At this condition, the effluent COD decreases from1700mg/L to263mg/L. And the highest COD removal rate is85%. The reactor stops running for one month. Restart the reactor for only10days, COD removal rate could be more than80%, which was the normal removeal rate before the stopping. The characteristics of granular sludge in two stages showed that group with the diameter between0.43～0.63mm is prior to other in COD removing. The number of granular sludge in group0.43～0.63mm is increasing with the addition of diatomite in EGSB reactor. In the same time, the dropping velocity is increased too. The exixtence of these small size, high activity granular sludge is the advantage of EGSB reactor. At last, further treatment of coking wastewater is discussed. EGSB are compared with activated sludge process, two-stage EGSB under microaerobic condition is adopted to treat coking wastewater.