Biodegradation Of Quinoline-containing Wastewater By Dominant Bacterium In Moving-bed Biofilm Reactor

Moving-bed biofilm reactor (MBBR) has been widely used in coking wastewater treatment. While the degradation rate of nitrogenous heterocyclic compounds, like quinoline, is fairly low, which may easily result in COD concentration in effluent couldn’t be well satisfied with sewage discharge standard (GB 13456-2012). It is the weak competitiveness and low activity of microorganism degrading quinoline in MBBR, among the abundant and complex microorganism, that results in a low degradation rate of quinoline. So it is an urgent task to suit for a way to increase the biodegradation rate of nitrogenous heterocyclic compounds among which quinoline as a stand.There are many problems in the MBBR adding dominant bacterium technology in the process of industry application, including the reactor design and enlarge, the influence of various factors in the actual wastewater, and the oxygen mass transfer in system and so on, which all will make a significant affect on quinoline degradation performance.According to the above analysis, the paper presents a technology that loading the predominant quinoline bacterium on the carriers in MBBR, instead of traditional complex microorganism, strengthening the competitiveness and activity, and then the quinoline biodegradation performance is observed and studied in manual medium. Additionally, as to problems existing in industry application, three aspects will be investigated, involving quinoline degradation kinetic, actual wastewater influence, as well as oxygen mass transfer.The result shows that the biodegradation rate of quinoline arrived 96.3% in 23 h by predominant bacterium loaded on carriers in MBBR, while it is 97.11% in 45 h in degrading simply modeled wastewater, which has a 51.21-78.11% rise in quinoline degradation compared with traditional MBBR with complex microorganism. In real coking wastewater, there is 74.49% quinoline removed within 46 h, increased by 28.59-55.49% comparing to traditional technology. Adding phenol degrading bacterium into the new dominant bacterium system in MBBR could weaken the inhibition on quinoline degrading bacterium in coking wastewater treatment, leading to a rise of 19.07% compared to without adding phenol degrading bacterium system, and 47.66-74.56% to traditional MBBR technology. When in a lower quinoline concentration (lower than 100 mg/L), there is a good fit of zero degradation kinetic, while higher concentration (higher than 200 mg/L), first degradation kinetic.The oxygen mass transfer experiment presents that aeration intensity is the main factor in influencing oxygen mass transfer. KLa increases from 0.0025 to 0.066 s-1 with the increase of aeration intensity. Oxygen mass transfer performs the best in 10% carrier stuffing rate. Reactor height affects the gas-liquid transfer area through the change of pressure, leading to KLa gradually decreasing from 0.01069 to 0.00955 s-1 when gas bubble rises to liquid surface. Adding surface surfactant into distilled water, KLa decreases during its concentration range,0-0.015 g/L. NaCl added plays a significance role in variation of gas bubble’s ξ potential and surface tension, as a result of KLa increasing in NaCl concentration range of 0-20 g/L.