Abstract: Based on the optimized parameters in achieving the in situ salt reduction, the evaluation of coking wastewater treatment process in Shaogang Steel Plant was conducted with special emphasis on the evolution of conductivity. The analysis of water quality, operation parameters, types and quantity of reagents were carried out to examine the variation of conductivity in each unit, and then to elucidate the influencing factors for salinity changes. The influence of biodegradation of coking wastewater, the applied reagent dosage and the coagulation process on the concentration evolution of main anions were investigated and the fate of salt residual in water as well as sludge during biochemical and physiochemical process were studied. The results showed that the optimized biodegradation and physiochemical degradation of coking wastewater can lead to partial reduction in salinity. The increase of salt concentration is mainly attributed to the addition of phosphorus and alkalinity in the biochemical process, the employment of coagulation in physiochemical process, as well as the mineralization of organics. The reduction of salt was resulted from the transformation of N, S constituent and strong electrolyte C₆H₅O^- into N₂, H₂S, CH₄, CO₂, H₂O. Also, the complexing precipitation, insoluble salts of coagulation sedimentation coming from the combination of Fe²⁺ with CN^-, S^2-, SCN^-, OH^-, CO₃^2-in the physicochemical process contributed to the decrease of salt. The separation of refractory organics in biochemical procedure, the dosage and the order of chemical reagent, the optimization of pH were found to be beneficial for in situ reduction of salt. It was suggested that the choice of process principle, reaction control and optimization of conditions are the significant factors that influence the changes of salt during coking wastewater treatment.

Key words: coking, salt reduction, conductivity, coagulation, biodegradation, optimization

摘要： 基于优化工艺单元参数实现原位盐分削减的构思，以广东韶关钢铁厂一期和二期焦化废水处理工程为例，用电导率表征废水中盐分的含量，通过水质和运行参数、投加药剂的种类和浓度讨论工程工艺各单元的电导率变化规律，分析影响盐分变化的因素，再分别从生物降解实验、药剂用量实验、混凝条件实验深入分析生化过程及物化过程水样、泥样中的主要阴离子浓度变化及其对盐分归趋的主要作用途径。研究发现：焦化废水的生化处理工艺与物化处理优化的工艺均能实现盐分浓度的部分削减，过程中，盐分的主要来源是有机物的矿化以及生化过程磷盐和碱的投加所致，此外还有物化过程混凝剂阴离子的引入，盐分的削减包括生化工艺废水中表现为盐分的N、S元素及强电解质C₆H₅O^-转化为非电解质N₂、H₂S、CH₄、CO₂和H₂O以及物化工艺以Fe²⁺与废水中CN^-、S^2-、SCN^-、OH^-、CO₃^2-结合为弱电解质或难溶性盐的混凝沉淀、络合沉淀共同作用的结果，两方面比较，来源量小于削减量，导致废水电导率下降；生化过程之前的有机物特别是难降解有机物的预分离，物化过程的投药量、投药顺序和pH控制的优化均有利于盐分在废水处理工艺中的原位削减。上述结果表明了基于某一性质的焦化废水其工艺原理选择、反应原理与条件优化控制成为了影响水处理过程中盐分变化的重要因素，原位削减盐分对于废水零排放具有重要工程学指导意义

关键词: 焦化, 盐分削减, 电导率, 混凝, 生物降解, 优化