超声波用于净水沉淀污泥无害化处理及污泥回流强化低浊水源水混凝特性研究

45~50 percent of lakes and reservoirs are characterized with low turbidity, as the common source water of urban drinking water treatment plants in our country. Drinking water precipitated sludge recycling is an effective method to improve the low turbidity water treatment, which is research and application focus in recent years, as well as a critical form of sludge resources reutilization. The ideas that innocuous treatment of drinking water precipitated sludge by ultrasonic is advanced for the first time, for the enrichment problem of poisonous and deleterious substances in the sludge. The pathogenic microorganism inactivation and decomposited efficiency of poisonous and deleterious substances in the sludge by sonolytic irradiation technology, including the impacts of different process factors and mechanisms, will be systematically investigated to optimize the performance parameters. Flocs formation, breakage and regrowth will be discussed due to the breakage of sludge flocs in recycling process. In order to reflect sonolytic conditions, the characteristics of denatured sludge flocs will be studied with respect to charge distribution, surface morphology, size, sedimentation rate and specific surface area. The coagulation performance and mechanism of recycling denatured sludge will be investigated during the low turbidity source water treatment. Meanwhile, the safety evaluation of treated water quality in accumulation of heavy metals, microorganism, disinfection by-products formation potentials and biodegradable dissolved organic matters, will be carried out. This project is provided with exploratory and innovative significance. The conclusions will provide theory and technology supports for the low turbidity water treatment and sludge resources reutilization, and will be a promising implication in wide applications.

我国45~50%城镇生活用水水源属于湖泊和水库低浊水，沉淀污泥回流作为低浊水强化混凝处理有效技术，是近年来研究和应用的热点，也是污泥资源化的重要形式。课题针对污泥回流中有毒有害物质积累问题，首次提出将超声技术用于净水沉淀污泥无害化处理的思想，系统地研究超声作用对污泥中病原微生物灭活、有毒有害污染物降解效能、影响因素及作用机制，优化出最佳工艺运行参数；针对污泥回流中絮体破碎对混凝效能的影响问题，研究絮体的形成、破碎及再絮凝的动力学过程，从絮体表面电荷分布、形态、粒度、沉降速率和比表面积等方面评价超声作用对沉淀污泥絮体特性影响；研究超声作用后污泥回流对低浊水混凝效能的影响及作用机制；从重金属积累、微生物量、消毒副产物生成势及可生物降解有机物含量方面综合评价污泥回流工艺出水水质安全性。本研究是探索性和有创新意义的，研究成果将为低浊水源水处理及污泥资源化提供理论和技术支持，并将具有广阔的应用前景。

污泥回流是有效的强化混凝技术，也是污泥资源化的重要形式。课题针对净水厂污泥回流工艺中消毒副产物前体物、重金属和病原微生物等累积问题，采用超声波预处理技术提高回流污泥的化学安全性和生物安全性。研究了单频/复合超声作用对病原微生物灭活和有机物降解效能的影响，优化出超声工艺条件和最佳参数。系统研究了超声作用后污泥特性的演变规律和混凝特性与作用机制，提出了污泥回流工艺安全性的运行策略。结果表明，随着功率的增加，大肠菌群灭活率趋于稳定；在相同作用时间和功率条件下，40kHz的杀菌效果优于25kHz。在槽式反应器中，双频复合超声的杀菌效果最好，有机物去除效果均优于单频超声。40kHz单频超声对隐孢子虫和贾第鞭毛虫的灭活效果最优，且对隐孢子虫灭活效果优于贾第鞭毛虫。基于空化泡动力学模型的结果表明，超声频率较低时，气泡崩溃压强较大，超声频率较高时，气泡崩溃压强减小。高声能密度下空化气泡最大压强较高，且气泡成长时间较长，利于空化效应。铝箔腐蚀试验表明，超声波频率越小、声能密度越大，则越有利于空化效应发生；与槽式超声装置相比，探头式超声装置更易发生瞬态空化。二维DLA模型结果表明，超声频率和声能密度较低时，絮体破碎以剥蚀作用为主；声能密度超过3W/mL或频率大于40kHz时，以大规模破碎为主。0.03W/mL低声能密度超声作用就会使污泥破解，造成蛋白质、多糖和类腐殖质等有机物溶出，低频率（25/40kHz）和较高声能密度（5W/mL）的超声作用会使得污泥破解程度更高，蛋白质和多糖释放量更多。超声作用对pH值和表面电荷影响不显著，但污泥粒径降低、BET比表面积增加。较低频率和较高声能密度作用后污泥脱水性明显恶化，但沉降性显著改善。无溶出物的污泥回流混凝效果有明显改善，有溶出物的未得到提高，甚至变差。超声波预处理不能有效地解决Cd2+和Cu2+的累积问题，但可提高出水微生物安全性。本课题研究成果可为低温低浊水的污泥回流强化混凝技术、以及净水污泥资源化提供理论和技术支撑。