混凝型胶质气泡的形成及其对发酵废水中致色有机物的去除机理研究

Organic colorants in fermented wastewaters are difficult to be removed by biological treatment due to their complex composition, anti-oxidant and anti-microbial. Thus, decolorization has become a worldwide research-focus in the treatment of fermented wastewaters. As one of the most widely used decolorization techniques, the coagulation-flotation process is still facing problems of excess chemical dose, great sludge generation and low treating efficiency, significantly limiting its color removal effect. Considering this context, this project will firstly explore characteristics of organic colorants in certain fermented wastewaters via the analysis and identification of their composition, and accordingly, proper coagulants can be decided. Subsequently, coagulants will be loaded on the surface of colloidal gas aphrons (CGAs) which are featured by the high stability and rigid structure, and the coagulative CGAs are expected to form. The novel aphrons will be pumped into the flotation tank as soon as being prepared so as to remove colored organic matters. In this continuous technique, dosing coagulant into influent is unnecessary, and less chemical dosage may be needed and the chemical residue in effluent will be decreased. The flotation performance may no longer be limited by the critical micelle concentration of surfactant. In this project, through the analysis and characterization of organic colorants, novel bubbles, floats and effluent, the interfacial interaction of gas-solid-liquid can be clarified; flotation mechanisms of coagulative CGAs will be figured out, providing both of the theoretical and technical support for the decolorization of fermented wastewater by novel flotation process.

发酵液中的致色有机物因其结构复杂、抗氧化性强而难以被传统的生化方法去除，发酵废水的有效脱色已成为当前国内外的研究热点。混凝-气浮是最为常用的深度脱色方法，但耗药量高、污泥产量大、处理效率低等问题严重影响着其脱色效果。本课题通过对废水致色组分的解析与识别，揭示特定发酵废水中致色有机物特性；据此选用适宜的混凝剂，负载于具有多层表面活性剂分子层的刚性胶质气泡的表面，形成“混凝型胶质气泡”；气泡在改进的气泡发生器中一经生成立即泵入气浮池，分离去除致色有机物。该连续工艺无需向原水投药，能解决一般的泡沫气浮中表面活性剂用量大、出水引入二次污染的问题，且过程不受表面活性剂的临界胶束浓度制约。本研究将致色有机物解析、混凝型胶质气泡性质、气浮出水和浮渣特性三者综合分析，理解气浮过程中气-固-液三相的界面过程，探索气浮特性和特定发酵废水中的脱色机制机理，为新型气浮工艺的发酵废水脱色研究提供实验和理论支持。

本研究首先以木薯酒精废水生化处理出水为研究对象进行致色有机物污染物的解析与识别。该废水中溶解性有机质（DOM）呈强亲水性，此处采用不同分子量级别的超滤膜对木薯酒精废水生化出水进行物理分级，分析原水中有机物的分子量分布，并对其进行了官能团和荧光特性表征。结果表明，木薯酒精废水生化出水中1-5 kDa分子量区间的有机物占比最大，以DOC和色度计分别为51%和52%；<5 kDa的有机物中的荧光发色基团对总荧光响应强度的贡献最大。不同分子量区间的主要有机物均为木质素衍生物，含有较少类黑精或不含有类黑精，其含碳官能团以芳香族碳和脂肪族碳为主。. 随后，本研究采用表面活性剂（十二烷基二甲基甜菜碱和十六烷基三甲基溴化铵）和无机混凝剂（Al系和Fe系简单无机混凝剂及其对应的高分子混凝剂）复配制备气泡发生液。CCGAs通过高速机械搅拌复配溶液制备得到。结果表明，复配溶液可保证溶液的起泡性，混凝剂与表面活性剂在气泡发生液中的结合。CCGAs表面携带稳定正电荷，具有表面性质可控、稳定性好、气含率高、比表面积大等有点。混凝剂可能通过吸附，静电吸引及架桥作用将气泡网络于其中。. CCGAs气浮技术可作为一种深度处理工艺，用于酒精废水中抗生化有机物的分离去除，将好氧出水初始pH值调为7.0-9.0，可达到最佳处理效果——色度和DOC去除率分别达到93.0%和79.0%。与仅投加混凝剂的过程对比，在达到相同的处理效果的前提下，混凝型胶质气泡气浮过程在脱色和去除有机物方面分别可以降低约46.8%和34.0%的混凝剂使用量。这可能是由于将混凝剂负载于胶质气泡表面，可以使混凝剂与污染物充分接触、令二者更有效结合。混凝型胶质气泡气浮过程中，形成了大而蓬松的浮渣，有利于污染物的气浮分离。混凝剂的投加可以有效去除木质酚、木质素降解产物等有机物. 将微气泡进行混凝功能修饰并用于气浮技术这一新思路有望克服常规的气浮法药剂使用量大、易在气浮出水中引入二次污染物、成本高的缺陷，为不同污染物的强化分离去除以及气浮工艺的发展提供理论依据和技术支持。