【作者】 田侠；

【导师】 林国林； 史衍玺；

【作者基本信息】 沈阳农业大学 ， 农业环境与生态， 2013， 博士

【摘要】 甘薯淀粉加工时间短,废水具有量大、有机物浓度高、集中处理难度大等特点,废水处理已成为制约甘薯产业发展的瓶颈；亟待研发适合中小型甘薯淀粉加工企业的废水处理技术。甘薯生产废水中含大量的蛋白质,由于缺少有效的分离提取技术,蛋白质只能随废水排放,不仅造成资源浪费,而且成为甘薯废水排放的主要污染物质。本文以提取甘薯淀粉生产废水中的蛋白质为目标,采用膜材料制备、预处理、中试评价等相结合的研究方法,确定了以聚氯乙烯为原料制备中空纤维超滤膜纺丝的最佳工艺条件,摸清了铸膜液组成、成孔剂、改性剂等对中空纤维超滤膜性能的影响,明确了中空纤维超滤膜改性的机理,制备了具有高效、抗污染的改性中空纤维超滤膜组件。筛选了甘薯废水预处理的工艺,获得了与膜分离技术相结合的蛋白质提取工艺参数。通过中试,评价了改性中空纤维超滤膜组件对蛋白质的截留及COD等污染物的去除效果。新型抗污染的聚氯乙烯(PVC)中空纤维超滤膜被自主研发。获得最佳铸膜液配方,聚氯乙烯、二甲基乙酰胺(DMAc)的质量百分含量分别为16、80wt%,最佳凝胶温度为25℃,最佳预蒸发时间为30s,同时获得中空纤维超滤膜最佳纺丝条件为：芯液流量20ml/min,计量泵转速42r/min,绕丝机卷绕速度20r/min,凝胶浴温度20℃。在聚氯乙烯中空纤维超滤膜铸膜液中适量添加纳米粉体改性剂,可明显改善膜的抗污染性能。其改性机理是改性剂比表面积大,表面富含的羟基与聚氯乙烯分子链产生吸附作用,从而形成机械性能稳定的大分子网络结构,改善了聚氯乙烯的亲水性,增加膜丝韧性,增强膜的抗污染能力。添加一定量改性剂时,膜的空隙率取得最大值,且膜的通量和截留率改性效果最好,膜丝性能稳定。当工作压力从0.04MPa上升到0.2MPa时,随工作压力的增大,膜通量逐渐增大,而截留率变化平缓,考虑膜丝耐受压力,聚氯乙烯中空纤维超滤膜的工作压力选择0.18MPa。对比研究酸化沉淀、冷藏、离心、化学絮凝、生物絮凝等预处理工艺,筛选出酸化沉淀、离心和生物絮凝是较好的预处理工艺,将筛选出的预处理工艺联合改性聚氯乙烯中空纤维膜处理甘薯淀粉生产废水,获得最佳组合工艺运行参数和处理效果。最后设计组装中试规模设备回收企业实际生产废水中蛋白来评价超滤膜改性效果。采用改性聚氯乙烯中空纤维超滤膜回收甘薯淀粉生产废水中蛋白质,膜通量恢复率92.5%,比未改性超滤膜提高5.8%；蛋白截留率83.2%,比未改性超滤膜提高2%且运行稳定,实验结果表明聚氯乙烯中空纤维超滤膜改性效果良好。大量实验数据明确在酸化沉淀、冷藏、离心、化学絮凝、生物絮凝等几种预处理工艺中酸化沉淀是最佳预处理方式。酸化沉淀后废水经过超滤处理,透过液COD浓度去除率为14.2%,蛋白截留率为95.7%。应用改性PVC中空纤维膜制成内压式超滤膜设备处理山东威海某淀粉厂实际生产废水,设备连续运行10周期(天),每个周期工作10小时,设备运行基本稳定。超滤设备连续运行10小时后废水COD的平均去除率仍为15.3%;可溶性蛋白平均截留率83.3%；连续运行10天,超滤出水COD平均去除率20.8%;可溶性蛋白平均截留率83.6%；总氮和总磷的平均去除率为21.2%和8%。实验证明,改性聚氯乙烯中空纤维超滤膜能高效截留甘薯淀粉生产废水中的可溶性蛋白。更多还原

【Abstract】 Content:Environmental pollution has become the bottleneck of the development of sweet potato starch production because the wastewater has the characteristics of containing high concentration of organic substance, concentrated of discharging time and difficult to be treated. The new treat technique is expected and which fit for Chinese middle and small starch fabrication enterprise. The sweet potato starch has a rich source of protein, however, they have to be discharged in the wastewater because of lacking of effective separation technology, so large amount of protein resources are wasted and the environment is polluted. The object of this paper is extracted protein from wastewater of sweet potato starch production. The optimum conditions are determined of spinning conditions of hollow fiber membrane with polyvinyl chloride (PVC).The influences of dope solutions composition, Pore-forming agent and modifier on properties of such modified ultra filtration membrane are investigated through the methods of preparing hollow fiber membrane, Pretreatment and field experiment evaluation. The mechanism of membrane modification was discussed. The anti-fouling and high efficiency hollow fiber membrane modules with polyvinyl chloride (PVC) are prepared by phase-inversion. The pretreatment of sweet potato starch production wastewater has been filtered out. The extraction parameters were determined through combing membrane separation technology. The effect for protein retention and contamination removal are evaluated though pilot test.The experimental results show that a new anti-pollution that nanometer powder was added into PVC hollow fiber ultrafiltration membrane was developed. The optimum membrane formula is determined. The PVC, DMAc, content were16,80wt%, the best coagulant bath temperature is25℃, the best pre-evaporation time is30s.At the same time, the optimal conditions for preparing the hollow fiber membrane spinning is core liquid flow rate20ml/min, speed of metering pump42r/min, the winding speed of wire machine20r/min, coagulant bath temperature20℃. The membrane performance is significantly improved because of the modifier moderately to be added in the casting solution of PVC hollow fiber UF membrane. The specific surface area of modifier was large, the adsorption was produced between hydroxyl groups and PVC molecular chain, mechanical stability and hydrophily were increased because of large molecular network structure was formed,were the main mechanisms of modification. It was shown that the modified membranes expressed better anti-fouling ability in the ultrafiltration. When the moderate modifier concentration was added, membrane flux and the rejection of the modification effect is best. The pressure increased from0.04MPa to0.2MPa, the membrane flux increases and rejection is stable with the increases of pressure. So we choose0.18MPa as the working pressure of PVC hollow fiber ultrafiltration membrane. Then, the processes of hydrolysis acidification precipitation, cold storage, centrifugal, chemical flocculation and biological flocculation were studied as pretreatment methods for sweet potato starch production wastewater. The best pretreatment process was screened out through comparison. Sweet potato production wastewater was treated by the best pretreatment method and UF process, and the optimum process parameters and processing was obtained. Finally, pilot scale treatment device is designed and assembled for treating actual production wastewater from enterprises, operating parameters, the combined process treatment effect and protein retention effect were further evaluated.The protein from wastewater of sweet potato production was recoved with modified PVC hollow fiber ultrafiltration membrane. The membrane flux recovery rate is92.5%,and retention of protein is83.2%。The modified ultrafiltration membrane increased by more5.8%and2%compared with that of unmodified membrane. Experiments show that the optimal pretreatment is hydrolysis acidification precipitation. Wastewater was pre-treated by hydrolysis acidification precipitation, after that, Effluent was treated by ultrafiltration. The removal rate of COD and soluble protein is14.2%and95.7%. The inside-out hollow fiber ultrafiltration equipment was made by modification of PVC hollow fiber membranes. Wastewater from starch factory in Weihai was treated by this equipment. Equipment operated continuous period (10days),10hours of work per cycle. The average removal rate of COD is15.3%when Ultrafiltration equipment run10hours. The average removal rate of COD and soluble protein is20.8%and83.6%. The average removal rate of total nitrogen and total phosphorus is21.2%and8%.when ultrafiltration equipment continuous operated10days.The test results show that, the soluble protein in wastewater can be efficient intercepted by ultrafiltration equipment of modified PVC hollow fiber membrane.更多还原