煤化工高盐废水零排放处理全流程的水质变化特征研究
- Study of the water quality variation in a full-scale zero-liquid discharge system for high salinity coal chemical wastewaterZHAO Pengfei1, XU Yuanhao2,3, FU Zhixiong4, JIAO Jianye2, GU Qingqing2, ZHENG Libing2,5*, ZHONG Hui2, WEI Yuansong2,5
- 基金项目：国家重点研发计划(2021YFC3201403)；北京市科技新星计划项目(20240484679)
- 摘要：废水回用与零排放(ZLD)是缓解水资源短缺和水生态影响的关键途径，已成为我国煤化工行业可持续发展的重要方案。煤化工废水盐度高、成分复杂、可生化性差，盐离子主要为Na+、Cl-和SO42-，难降解有机物主要为腐殖质和芳香族化合物。但煤化工废水的水质组成复杂，因此其ZLD处理的工艺流程长，其各流程的污染物的组成与变化特征尚不明确。本研究考察了煤化工ZLD系统各阶段的水质变化特征，并提出针对性优化建议，为系统的稳定运行提供支撑。研究发现：ZLD系统整体运行情况较好，预处理过程可以有效除硬并同步实现硅去除，反渗透(RO)和纳滤(NF)保障高效水回用和盐回收。废水中溶解性有机物(DOM)以色氨酸类和类腐殖质类物质为主，其主要通过RO去除，但RO对腐殖质类有一定的选择性截留，产水中主要为色氨酸类物质，表明膜表面存在一定的有机物和微生物污染。因此，建议后期强化有机物和硅的预处理，并结合精准投药来促进系统的长期高效稳定运行。本研究系统分析了ZLD系统的水质变化特征，解析其潜在的问题并提出解决方案，可为煤化工行业可持续发展提供支撑。
- Abstract：Water reuse and zero-liquid discharge (ZLD) of coal chemical wastewater are key strategies to alleviate the water shortage and ecological degradation issues, which have become the key to the sustainable development of the coal chemical industry. Coal chemical wastewater exhibits high salinity, complex composition, and low biodegradability, the predominant salt ions are Na?, Cl?, and SO?2?, while the organic pollutants are primarily composed of humic and aromatic compounds. The ZLD process for coal chemical wastewater is long for its complicated composition, thus the pollutants distribution and transformation during the ZLD process remain less understood. This study systematically examines the water quality in different stages of the ZLD system, based on which we offering some optimization strategies, whcih provide a scitific support to the stable and efficient operation. The ZLD system showed a good performance, during which the high-efficient hardness removal and synchronous silica removal can be achieved by the pretreatment stage; the water reuse and salts recovery can be guaranteed by the following RO and NF processes. Tryptophan and humic-like substances are the main DOM in the wastewater, which can only be removed in the RO stage. However, the RO membrane showed high retention for humic-like substamces, while tryptophan-like substances appearred in the RO permeate. These results demonstrates the high potential of organic- and bio-fouling of the membrane. Therefore, it is recommended to strengthen the pretreatment of organic matter and silica at the pretreatment stage, together with the precise chemicals dosage to modify the system. This study systematically analyzes the water quality variation in the full-scale ZLD system and discusses its potential problems and optimation strategies, which has potential to provide support for the sustainable development of the coal chemical industry.
