Study On Treating Coking Wastewater By EGSB Reactor Under Micro-Aerobic And The Performance Of Granular Sludge

To study the operating characteristics of EGSB reactor for coking wastewater treatment under micro-aerobic conditions,the influences of temperature,pH,oxygenation,liquid up-flow velocity(Vup)and influent organic loading on COD and volatile phenol removal efficiencies are investigated;In addition,the SEM photograph of the granular sludge,size distribution,settling velocity and sludge concentration such as MLSS and MLVSS are introduced to study the performance of granular sludge.The results show that:when the temperature is controlled between 26 and 31?,the reactor could ensure its efficient and stable operation,with COD removal reaching 75%and volatile phenol removal more than 96%;and the decline of the bioactivities of enzymes,due to the temperature suddenly droping to 12?,makes the COD and volatile phenol removal efficiencies reduce to 25%and 10%,respectively.When the temperature is controlled about 26 ? again,the COD and volatile phenol removal efficiencies reach to 66%and 96%in 12 days and 8 days later,respectively,indicating that the reactor has very strong ability of resisting temperature shock.pH is maintained between 8.02 and 9.23,which can guarantee the stability of the COD and volatile phenol removal.With the increasing of the oxygenation from 2000mL·min-1 to 100000mL·min-1,the COD and volatile phenol removal efficiencies are gradually improving,especially the volatile phenol removal.When the oxygenation is controlled in 10000mL·min-1,the COD and volatile phenol removal efficiencies rose to 76%and 97%,respectively.If the Vup of EGSB reactor is 2.0m·h-1,2.4m·h-1,2.9m·h-1 and 3.2m·h-1,the COD and volatile phenol removal efficiencies are 58.3%,63%,80%,85%and 95%,95%,98%,100%,respectively;which shows that the changes of volatile phenol removal is small with increasing the Vup,and the COD removal is the best when the Vup is 3.2m·h-1.When the reactor is in a stable state,the COD and volatile phenol removal efficiencies are fluculating in the range of 74 to 85%and 97 to 100%,respectively,which are less influenced by the organic loading.SEM photograph shows that there has no the phenomenon of flora layered growth in the internal and surface of the granular sludge,but the colony is blending to form a mixed habitat flora,which is beneficial to such different bacteria on the absorption of nutrients and metabolic.Furthermore,we can see from the experiment of sludge performance:the larger particle size of granular sludge is,the higher removal efficiency about the organism is in wastewater.The larger granular sludge is mainly concentrated in the bottom of the reactor,while in the upper of the reactor,there is the distribution of smaller particle size of sludge,in the three-phase separation only having flocculent sludge.The sludge settled properly in the settling velocity from 40 to 90 m·h-1,meanwhile,the sludge can long stay in the reactor.After four months of the operation,the MLVSS/MLSS value is improving from 42%to 56%,which means the microorganism quantity of granular sludge continues to increase.The subject is mainly studying on the effects of EGSB reactor under micro-aerobic conditions on COD and volatile phenol removal,and providing reference for future theoretical research and improvement of treatment process for coking wastewater.