污泥电渗透脱水过程中导电机理的研究

Electroosmosis technique is very effective for deeper dewatering of sludge from municipal wastewater plant, but higher energy consumption has hampered its widespread distribution. Aiming to the problem that higher energy consumption caused by increasing sharply resistance of sludge near the anode, it is established that the relationship between electrical conductivity of sludge and the boundary conditions of electroosmotic dewatering and dewatered layers and un-dewatered layers of sludge by analyzing the variation of structure of sludge layers and water morphology during electroosmotic dewatering. It is made clear that the electric conductivity mechanism of sludge and the criterion of electroosmotic dewatering amount by controlling it by means of investigating the evolution of sludge structure, surface adsorbed layers of sludge, electroosmotic flow behavior of water molecular and specific resistance of sludge. Moreover, the coupled mathematical model between the electric conductivity of sludge and electroosmotic flow of water along the pore and fracture of sludge was established, and it was solved using finite element method namely introducing the equivalent unite about the isotropy in a unite and the nonconformity among the unites and dynamic dewatering unite. The operating parameters was optimized during electroosmotic dewatering of sludge, providing the theoretical basis and technical support for industrial application of electroosmotic dewatering technology.

电渗透技术对于城市污水厂污泥的深度脱水是有效的，但相对较高的能耗制约了它的广泛应用。针对电渗透脱水过程中阳极区污泥电阻迅速增大引起能耗高的问题，项目采用实验研究、理论分析和数值模拟相结合的方法，研究电渗透脱水过程泥层结构、水分形态变化特征，建立含水层、脱水层与电渗透脱水边界条件与污泥导电能力之间的关系。考察电渗透脱水过程中污泥结构、污泥表面吸附层、水分子的电渗流特性以及污泥比电阻随时间的变化规律，探索污泥导电机理并建立污泥导电机理对电渗透脱水调控的判据。建立电渗透脱水过程污泥导电-水沿污泥孔隙-裂隙电渗流耦合的数学模型；引入单元内各向同性、单元间非协调等效单元和动态脱水单元，进行有限元法求解；优化污泥电渗透脱水的操作参数，为电渗透脱水技术的工业化应用提供理论基础和技术支持。

电渗透脱水技术对于污泥深度脱水具有经济性优势，尤其适用于机械脱水后的污泥，但脱水后期能耗的急剧升高制约了它的广泛应用。针对阳极区污泥电阻迅速增大引起能耗高的问题，项目采用实验研究、理论分析和数值模拟相结合的方法，考察了电渗透脱水过程不同床层污泥电阻率、水分形态、金属离子、水分子电渗流特性以及其他污泥理化性质随时间的变化规律；探索了电渗透脱水过程污泥物理形态的变化以及影响电渗透脱水的污泥关键性因素；研究了电极两侧污泥胞外聚合物EPS的特性以及污泥导电机理并建立其对电渗透脱水调控的判据；建立了电渗透脱水已脱水层与含水层的边界条件及污泥导电-水沿污泥孔隙-裂隙电渗流耦合的数学模型；同时对阳极结构进行优化以减小阳极侧污泥电阻。.结果表明，阳极侧污泥电阻率快速增加的主要原因为电化学产生的气体屏障，其次为污泥含水率的下降；而其他层最显著的影响因素为含水率，且随含水率的减小呈指数型增加。影响电渗透脱水的污泥关键性因素为电导率、VS/DS和zeta电位，而粒径及结合水含量对其影响较小。通过增多电化学反应活性点的波浪面阳极提高了电渗透流量，降低了气体阻隔层对阳极与泥饼电接触的影响。电化学反应促使污泥中的TB-EPS转化为LB-EPS和S-EPS，由于阴极侧氨基酸的二级结构存在大量支链导致该侧污泥蛋白质疏水性增强。.当污泥含水率大于84%，污泥电导率较低时污泥本体导电为传导电流的主要方式，电渗透脱水效果较好；当污泥含水率小于84%，污泥电导率较高时，离子导电为传导电流的主要方式，电渗透脱水效果恶化。污泥电导率与电渗透脱水后其最终含水率呈线性相关，电渗透脱水程度的判据可根据污泥电导率进行判定。.基于不同污泥层间的导电模式，提出了电渗透脱水双导电模型。该模型描绘了污泥电阻与水分沿污泥孔隙-裂隙电渗流间的关系。该模型可以用来预测和优化操作条件，为电渗透脱水的实际应用提供理论和技术支撑。.