【作者】 李大鹏；

【导师】 马放；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 博士

【摘要】 生物絮凝剂作为一种高效、无毒、安全、可生物降解的绿色净水剂,代表了絮凝剂的重要研发方向之一。然而制备成本偏高和作用范围相对较窄等劣势是制约其规模化应用的主要瓶颈问题。针对上述问题,本文立足于廉价生物质废料的资源化利用,开展了以秸秆和谷氨酸废液制取生物絮凝剂及其净水效能的研究。在优化了产絮菌F2-F6发酵条件的基础上,考察分批补料发酵方式对产絮菌F2-F6的影响。确定初始葡萄糖浓度为10g/L时,碳源补料的最佳参数为：碳源最佳补料种类为葡萄糖,最佳补料时间为发酵15h时,补料浓度为0.1%,补料方式为一次性投加；氮源补料不会增加生物絮凝剂产量,无需补加氮源。产絮菌F2-F6经分批补料发酵24h后,其生物量增加了37.04%,絮凝剂产量增加了40.9%,糖利用率提高了5.51%,絮凝剂得率提高了28.15%,结果显示分批补料发酵效果明显好于分批发酵。根据产絮菌F2-F6发酵过程的特点,在Logistic方程和Luedeking-Piret方程的基础上,建立了其发酵过程中菌体生长、基质消耗和产物形成的动力学方程。采用Origin7.5软件对试验数据进行处理,得到了产絮菌F2-F6的分批发酵动力学模型参数；模型预测值和试验值吻合较好,说明所建立的方程能较好地预测其实际发酵过程,具有很好的适用性。采用正交试验等方法对秸秆预处理工艺进行了优化,优化后的预处理条件为：粒度40目的秸秆,在温度80℃、质量分数1%的NaOH溶液中反应90min。预处理后的秸秆经过微生物降解,转化率可以达到70.3%,还原糖产率为10.6%。产絮菌F2-F6利用秸秆糖化液产絮,絮凝率可达94%；秸秆经过纤维素复合酶水解,在秸秆浓度50g/L,酶用量0.2g酶/g秸秆条件下,酶解得率为49.65%,以酶解液培养产絮菌F2-F6产絮,絮凝率达到96.5%。说明秸秆经过预处理后,可以作为碳源替代葡萄糖制取生物絮凝剂,每吨秸秆制取生物絮凝剂产量最大值为87kg。基于谷氨酸废液的浓度梯度策略构建谷氨酸废液培养基：浓度为20%的谷氨酸废液中补加8g/L的葡萄糖,无需添加额外的氮源即可作为替代培养基培养产絮菌F2-F6,絮凝率可达95.4%。废水培养基培养产絮菌F2-F6的最佳发酵条件为：温度30℃、初始pH7.0、摇床转速140rpm、种子液接种量8%、发酵时间20h。每升谷氨酸废液可以制备生物絮凝剂8.5g。发酵过程中,产絮菌细胞生长和絮凝产物合成对发酵体系中溶解氧的要求存在差异,结合分阶段供氧控制策略,在谷氨酸废液和絮凝剂培养基制备生物絮凝剂的发酵过程中,需要集中大量供氧的时间分别为8h和21h。结合谷氨酸生产工艺特点,提出了以秸秆和谷氨酸废液为底物生产生物絮凝剂的工艺流程,确定了生产过程主要操作条件及控制策略；并制定了生物絮凝剂生产的产品质量标准；对经济效益、环境效益和社会效益进行了简要分析。针对饮用水原水进行了生物絮凝剂与助剂的复配絮凝试验,并探讨最佳投剂方式及投剂量。结果显示,将生物絮凝剂与助剂复配使用可以得到最佳处理效果,在满足出水水质需求的同时,总投剂量显著降低。更多还原

【Abstract】 The bioflocculant (BF) is one of most potential research and development direction of flocculants because of its many advantages such as high efficiency, nontoxicity, easy biodegradability and healthy security. However, the high cost and narrow application fields of BF fermentation are the bottleneck problems limiting the industrial production and application of bioflocculant. Consequently, concentrating on on the resource utilization of multivariate biomass wastes, research on the preparation of compound bioflocculant (CBF) using glutamate wastewater and its production process were conducted.Based on the optimization of fermentation conditions, effects of fed-batch fermentation on the bacterium F2-F6 were investigated. The optimal parameters of the carbon source fed were as follows:lOg/L of the initial glucose concentration, glucose fed-types,15h of the best fed-batch fermentation time,0.1% of the concentration of fed-batch, one time fed-batch mode. There were no need for nitrogen addition as the nitrogen addition did not ehance the production of (CBF). The two types of fermentation methods, the batch fermentation and fed-batch fermentation, had been compared. After feeding, the biomass, BF production, sugar utilization and the output rata of BF had increased 37.04%,40.90%,5.51%,28.15%, respectively compared that of the fermentation without feeding. The production of (CBF) by feeding mode was greater than that of batch mode fermentation.The fermentation process of bioflocculant producing bacteria was studied in batch system. Based on the equations of "Logistic equation" and "Luedeking-Piret equation", the kinetic models reflecting its fermentation features of strain growth, substrate consumption and product generation were constructed respectively. The experimental data were processed with the Origin 7.5 software and the batch fermentation kinetics model parameter was obtained. The good agreement of predicted values with the experimental results showed that the kinetic models were applicable for predicting the actual fermentation process.Rice straw pretreatment process was optimized by orthogonal experiment. The optimal condition of NaOH- pretreated rice straw was temperature 80℃concentration of NaOH solution 1.0%, reaction time 90min, suitable smashed rice straw 40 mesh. Pretreated rice straws were degraded by cellulose degradation bacterium. The degradation rate and reduced sugar yield are 70.3% and 10.6%. Flocculation producing bacteria could utilize the saccharifyed liquid of rice straw and produce bioflocculant. The flocculation rate of bioflocculant can reach 94%. Pretreated rice straws were hydrolyzed by cellulase. The hydrolysis yield rate was 49.65% when the rice straw concentration was 50g/L, the cellulase dosage was 0.2g/g substrate. Flocculation rate of enzymatic hydrolysate was 96.5%. It illuminated that the pretreated rice straw could completely substitute glucose as substrate for (CBF) production. The maximum production was 87kg (CBF) per ton rice straws.Monosodium glutamate wastewater was applied as substitutive medium with gradient concentration. The optimum medium compositions was feeding 8 g/L of glucose into 20% glutamate fermentation wastewater without adding additional nitrogen source. This mudium could replace bioflocculant medium for producing bioflocculant and the flocculation rate can reach 95.4%. The optimal (CBF) fermentation conditions for flocculant-producing bacteria F2-F6 by wastewater medium were as follows:fermentation temperature 30℃, initial pH 7.0, rotation speed 140 r/min, seed inoculation concentration 8%, fermentation time 20h. Per litre glutamate wastewater produce 8.5g compound bioflocculant. During fermentation process, there were differences of DO requirement between the growth of flocculent-production bacteria and production of flocculation. Therefore, combined with the step wise oxygen supply strategy, the time of supply high concentrations of oxygen during the glutamate wastewater fermentation process was only 8h, while in the bioflocculant medium process was 21h. Obviously, using glutamate fermentation wastewater for (CBF) production was more energy saving.Production process of (CBF) was constructed and the main operating conditions and control strategies during the production process were confirmed. And product quality standard of (CBF) production was established. Technical and economic index, social and environmental benefit were briefly analyzed.Based on drinking source water and oily sewage, complex formulation flocculation tests and the effects of additives were carried out for (CBF) to find out the optimal addition method and dosage of flocculant. The results showed that the simultaneous application of (CBF) and its additives could reach the best results, which met the requirements of effluent quality and greatly reduced the total dosage.更多还原