多環(huán)芳烴是一類廣泛分布于環(huán)境中的有機(jī)污染物,具有致毒、致突變、致癌等作用。美國 EPA 將 13 種多環(huán)芳烴的化合物列為優(yōu)先控制污染物。本論文以水溶性最強(qiáng)的多環(huán)芳烴——萘為研究對(duì)象,得出了萘的揮發(fā)模型和好氧微生物對(duì)萘的吸附模型。并對(duì)取自北京某污水處理廠的污泥進(jìn)行好氧培養(yǎng)和馴化,研究馴化后的好氧微生物對(duì)萘的降解動(dòng)力學(xué)。進(jìn)一步對(duì)馴化后的好氧微生物進(jìn)行分離,得到能夠高效降解萘的菌株,并對(duì)得到的純菌體進(jìn)行細(xì)胞固定化的研究。 在本研究中,首先研究了萘在水中的揮發(fā)模型(無 VSS 存在),結(jié)合試驗(yàn)數(shù)據(jù)和理論公式(Fick 第一定律)得出水溶液中萘的傳質(zhì)系數(shù) k 值為 2.49×10-7m/s,而完全由經(jīng)驗(yàn)公式計(jì)算出的 k 值為 2.538×10-6m/s,通過比較得出所使用模型的有效性;進(jìn)一步研究得出,當(dāng)萘溶液中 VSS 濃度為 500mg/L 時(shí),水溶液中萘的傳質(zhì)系數(shù) k 值為 2.18×10-7m/s。

Polycyclic aromatic hydrocarbons are a type of organic pollutants widely distributed in the environment, which have toxic, mutagenic, carcinogenic and other effects. The US EPA prioritizes the control of 13 polycyclic aromatic hydrocarbon compounds as pollutants. This paper takes naphthalene, the most water-soluble polycyclic aromatic hydrocarbon, as the research object, and obtains the volatilization model of naphthalene and the adsorption model of aerobic microorganisms on naphthalene. And aerobic cultivation and domestication of sludge from a sewage treatment plant in Beijing were carried out to study the degradation kinetics of naphthalene by domesticated aerobic microorganisms. Further isolate the domesticated aerobic microorganisms to obtain strains that can efficiently degrade naphthalene, and study the cell immobilization of the obtained pure bacterial cells. In this study, the volatilization model of naphthalene in water (without the presence of VSS) was first studied. Based on experimental data and theoretical formula (Fick's first law), the mass transfer coefficient k value of naphthalene in aqueous solution was determined to be 2.49 × 10-7m/s, while the k value calculated entirely from empirical formula was 2.538 × 10-6m/s. The effectiveness of the model used was compared and concluded; Further research has shown that when the concentration of VSS in naphthalene solution is 500mg/L, the mass transfer coefficient k value of naphthalene in aqueous solution is 2.18 × 10-7m/s.

通過吸附試驗(yàn)可知,馴化后的好氧活性污泥對(duì)水溶性萘的吸附在10分鐘即達(dá)到最大吸附量,在60分鐘時(shí)達(dá)到吸附-解吸平衡。馴化后的微生物對(duì)萘的吸附等溫曲線符合langmuir吸附等溫式,同時(shí)也符合Frendlich吸附等溫式。進(jìn)一步研究可知,在酸性條件下,活性污泥對(duì)萘的吸附量較大,且pH值的變化對(duì)吸附量的影響不大;當(dāng)pH大于7時(shí),活性污泥對(duì)萘的平衡吸附量隨著pH值的升高迅速降低。 馴化后的好氧微生物對(duì)萘的降解符合一級(jí)反應(yīng)動(dòng)力學(xué)。在VSS=100mg/L和VSS=200mg/L兩種情況下,反應(yīng)速率常數(shù)分別為:0.0824h-1和0.1302 h-1。 對(duì)馴化后的活性污泥中的微生物進(jìn)行分離,得到兩株細(xì)菌,革蘭氏染色均呈陽性。 最后分別使用 PVA-硼酸凝膠小球和 PVA-硼酸-紗布復(fù)合載體兩種方法對(duì)微生物細(xì)胞進(jìn)行固定化的研究,按照它們對(duì)萘的降解速率由大到小的順序排列:自由菌紗布固定化細(xì)胞凝膠小球固定化細(xì)胞。

According to the adsorption test, the domesticated aerobic activated sludge reaches its maximum adsorption capacity for water-soluble naphthalene in 10 minutes and reaches adsorption desorption equilibrium at 60 minutes. The adsorption isotherm curve of domesticated microorganisms for naphthalene follows both the Langmuir adsorption isotherm and the Frendlich adsorption isotherm. Further research shows that under acidic conditions, activated sludge has a greater adsorption capacity for naphthalene, and the change in pH value has little effect on the adsorption capacity; When the pH is greater than 7, the equilibrium adsorption capacity of naphthalene by activated sludge rapidly decreases with the increase of pH value. The degradation of naphthalene by domesticated aerobic microorganisms follows a first-order reaction kinetics. The reaction rate constants for VSS=100mg/L and VSS=200mg/L are 0.0824h-1 and 0.1302 h-1, respectively. Two bacterial strains were isolated from the domesticated activated sludge, and Gram staining was positive for both strains. Finally, two methods, PVA boric acid gel beads and PVA boric acid gauze composite carrier, were used to immobilize microbial cells. According to their degradation rate of naphthalene, they were arranged in order from high to low: free bacteria gauze immobilized cells gel beads immobilized cells.

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