Biodegradation of Phenol from Wastewater by Microorganism Immobilized in Bentonite and Carboxymethyl Cellulose Gel

This study presents a microbial process for phenol degradation in coking wastewater. The optimum immobilized condition of the strain for degrading phenol was determined through orthogonal experiment. The free and immobilized microorganisms were examined for their capabilities on degrading phenol. Results indicated that the optimum immobilized conditions were 20% microorganism suspension, 5% bentonite, 3% sodium carboxymethyl cellulose content, and 1 h of crosslinking time. The biodegradation rate was optimized at 35°C and 0.23 gmL⁻¹ of immobilized microorganism bead. The degrading rate for the immobilized microorganism bead was up to 95.96% at an initial phenol concentration of 100 mgL⁻¹; however, the immobilized microorganism considerably took more time (288 h) to reach 94.6% removal efficiency at a much higher concentration of 1000 mgL⁻¹. The batch experiment demonstrated that 94.50% of phenol was removed using the beads with the immobilized microorganism at an initial concentration of 500 mgL⁻¹. By contrast, only 24.60% and 33.88% of phenol were degraded using the gel beads without and with free microorganisms, respectively. The immobilized microorganism beads can used reused for up to nine cycles at the same initial phenol concentration (50 mgL⁻¹) and can be stored up to 40 d without loss of its degradation capacity.

本研究提出了一种针对焦化废水中苯酚降解的微生物处理工艺。本研究通过正交试验确定了该降解苯酚菌株的最佳固定化条件，并对比考察了游离微生物（free microorganism）与固定化微生物（immobilized microorganism）的苯酚降解性能。结果表明，最佳固定化条件为：微生物悬浮液占比20%、膨润土（bentonite）添加量5%、羧甲基纤维素钠（sodium carboxymethyl cellulose）含量3%，交联时间1小时。当反应温度为35℃、固定化微生物微球投加量为0.23 g·mL⁻¹时，生物降解速率达到最优。当初始苯酚浓度为100 mg·L⁻¹时，固定化微生物微球的降解率可达95.96%；而当初始苯酚浓度提升至1000 mg·L⁻¹时，固定化微生物需要更长时间（288小时）才能达到94.6%的去除效率。批量试验结果显示，在初始苯酚浓度为500 mg·L⁻¹的条件下，搭载固定化微生物的微球可实现94.50%的苯酚去除率；与之相比，未负载微生物的凝胶微球（gel bead）与仅搭载游离微生物的凝胶微球对苯酚的降解率仅分别为24.60%和33.88%。该固定化微生物微球在初始苯酚浓度为50 mg·L⁻¹的条件下可重复使用至多9个周期，且可储存长达40天而不损失其降解性能。