Research On Biodegradability And Inhibitory Properties Of Heterocyclic Compounds And Polycyclic Aromatic Hydrocarbons

With the rapid development of industry, agriculture, medical and other industries, a large number of heterocyclic and polycyclic aromatic hydrocarbons pollutants were released into the environment, seriously endangering human and environmental health. Simultaneously, the poor removal efficiencies of this kinds of polluants greatly limited the efficiency of biological treatment. Biodegradation and control of heterocyclic and polycyclic aromatic hydrocarbons pollutants has became the focus of polluants control work. A comprehensive research on the biodegradability of the heterocyclic and polycyclic aromatic hydrocarbons pollutants and their inhibitory properties on other substances and the effects of cometabolism on their biodegradation can not only guide to improve biological treatment efficiency, but also has an important theoretical value for the prediction of migration, transformation of similar compounds in the environment and risk assessment.Methods of BOD5/CODcr ratio, CO2 production and dehydrogenase activity were employed to evaluate the biodegradabilities of pyridine, quinoline, diphenyl and naphthalene in the coal gasification wastewater. The BOD5/CODcr was less than 0.3 with concentrations greater than 100 mg/L, and the evaluation are non-biodegradable. The IB value of pyridine was 124.8, which was evaluated as biodegradable, and the IB values of quinoline, biphenyl and naphthalene were 54.2, 77.8 and 96.7 respectively, which were evaluated as non-biodegradable. Besides, dehydrogenase activities would be highly inhibited with a concentration more than 80 mg/L.The biodegradabilities and kinetics of pyridine, quinoline, diphenyl and naphthalene were investigated in different degradation conditions. Biodegradation kinetics of four heterocyclic and polycyclic aromatic hydrocarbons could be described by zero-order, zero-order, and first-order kinetics at aerobic, anoxic and anaerobic conditions. The relationship between aerobic degradation rate constants and substrate concentrations could be described by Edward kinetics equation, with kmax of 0.614 mg/(L·h), 1.058 mg/(L·h), 0.908 mg/(L·h) and 1.302 mg/(L·h) respectively, for pyridine, quinoline, diphenyl and naphthalene. The relationship between anoxic degradation rate constants and substrate concentrations could be described by Andrews kinetics equation, with kmax of 8.103 mg/(L·h), 8.926 mg/(L·h), 4.927 mg/(L·h) and 6.898 mg/(L·h) respectively; and The relationship between anaerobic degradation rate constants and substrate concentrations could be described by Aiba kinetics equation, with kmax of 1.103 1/h, 0.9338 1/h, 2.311 1/h and 4.977 1/h respectively, for the four polluants.Heterocyclic and polycyclic aromatic hydrocarbons could inhibit the biodegradation of other pollutants. In the aerobic condition, the inhibitive properties of pyridine and quinoline on the biodegradation other compounds were highly depression, diphenyl was moderate depression, naphthalene was slightly depression. In the anoxic condition, inhibitive properties were moderate depression for similar compounds and slightly depression for unsimilar compounds; and in anaerobic condition, inhibitive properties were slightly depression for similar compounds and moderate depression for unsimilar compounds.The biodegradabilities of the heterocyclic and polycyclic aromatic hydrocarbons were with phenol and glucose as co-metabolic substrates, respectively. The maximum aerobic degradation rates were 55.8%, 56.7%, 55.5% and 60.7%, maximum anoxic degradation rates were 83.0%, 89.8%, 72.7% and 74.7%, and maximum anaerobic degradation rates were 87.7%, 85.5%, 89.0% and 96.1%, respectively, for pyridine, quinoline, diphenyl and naphthalene. Both phenol and glucose could be used as co-metabolic substrates in anoxic degradation. However, the maximum anoxic degradation rates in phenol co-metabolism were bigger than that in glucose co-metabolism.Compared with A/O process, the effect of A1/A2/O was better in treating coal gasification wastewater, with the lower concentrations of CODcr, BOD5, TOC and ammonia. Removal rates of four pollutants were enhanced from 64.2%, 58.1%, 61.7% and 67.4% to 68.3%, 63.2%, 65.3% and 72.4%, with 200 mg/L glucose. The most suitable influent flow rate was 2:1 for anaerobic and anoxic, when the removal rates of pyridine, quinoline, diphenyl and naphthalene were 68.3%, 64.5%, 64.4% and 73.3%, respectively.By using linear regression analysis, the structural parameters affecting the biodegradabilities of the heterocyclic and polycyclic aromatic hydrocarbons were determined, and the QSBR models were established between the biodegradability and the structure parameters. Aerobic biodegradability is mainly determined by EHOMO, 1X and Log Kow; Anoxic biodegradability is mainly determined by ELUMO、Vm and 1X; Anaerobic biodegradability is mainly determined by EE、Vm and Log Kow.The results of this study have great application value and theoretical significance for the further understanding of the biological degradation and inhibition properties of pyridine, quinoline, diphenyl and naphthalene, and to guide the biological treatment of these pollutants and predict the retention of the similarly pollutants in the environment.