Study On The Degradation Of Quinoline In Coal Coking Wastewater With Nontronite And Microorganism

Coal coking wastewater has complex compositions as an organic wastewater. It has high concentration of organic matters, high colority, toxicity and it is difficult to degrade. As the main contamination in coking wastewater, quinoline contributes a lot to the effluent COD. Quinoline is a kind of nitrogen heterocyclic compound and has carcinogenicity and mutagenicity. Long-term accumulation of quinoline in the environment can pollute the environment and damage human health. Microbial degradation is the most important way to remove quinoline contamination, but it can be affected by many other environmental factors and the effect is unsatisfactory. So it is important to find the efficient degradation method.Clay minerals are ubiquitous in sediments and soils. They are cheap, environmental friendly and safe. They have strong adsorption ability and are suitable for microbes to attach to grow. The huge surface areas of clay minerals can adsorb a lot of pollutants, and structural irons in lattices can be redoxed by microorganisms with the degradation of many pollutants. The reduced irons can generate free radicals under oxidative condition and decompose organic matter. It is an ideal material to strengthen the microbial degradation of quinoline.In this dissertation, we combined microorganisms and clay minerals, and applied aerobic- anaerobic cycle in the water treatment process to treat quinoline pollution. We studied on microbes and clay minerals through aerobic-anaerobic or anaerobic-aerobic process, and researched the microbial activities and clay mineral behaviors in the process of quinoline degradation. The results showed that clays could adsorb quinoline, the isotherm model fitted Langmuir adsorption and the adsorbtion was irreversible. XRD result showed that most of the quinoline entered the clay interlayers and changed the structure of clay.We found various quinoline degrading microorganisms in anoxic tanks and aeration tanks. They could reduce structural irons and use quinoline as sole carbon source. The microbes had abundant diversity, mainly related to phylums of Proteobacteria, Bacteroides and Firmicutes. These microorganisms had functions of iron reduction, denitrification and organic matter degradation. Quinoline degradation and iron reduction may be the result of synergistic effect of those organisms.During anaerobic-aerobic degradation process, the structure of clay mineral was changed, and generated secondary minerals. Quinoline desorbed from the clay, then was further degraded. The whole time of quinoline degradation was 198 hours, and reduced 20% iron. Not a single degradation pathway was involved. It included benzene cracking and heterocyclic cracking metabolic pathways. COD reduced by 33%.During aerobic-anaerobic degradation process, different chemical reduced clays generated a large number of hydroxyl radicals after oxidation. 100% reduced clay generated the most radicals, and had the highest rate of initial degradation. In aerobic degradation process, the relation of radical concentration, quinoline concentration and divalent iron concentration were linear. The whole time required to degrade quinoline was 150 hours. Only benzene cracking pathway was found. COD decreased by 45%, higher than that in anaerobic-aerobic treatment.