黄河流域典型铅锌冶炼企业重金属废水管控与碳排放协同研究

Collaborative Study on the Heavy Metal Wastewater Control and Carbon Emission of Typical Lead Zinc Smelting Enterprises in the Yellow River Basin

黄河流域作为国家生态安全的重要屏障,重金属污染一直以来备受关注.为提升重金属重点排放源铅锌冶炼行业废水排放管控水平,本文聚焦黄河流域中上游典型地区某铅锌冶炼企业,研究了不同产污环节排放废水中重点重金属排放特征及达标情况,并从行业绿色低碳发展方面测算了不同冶炼工艺流程碳排放强度、不同产污环节排放废水处理过程碳排放强度.结果表明:(1)采用氧化法+硫化钠除汞+石灰中和+生物制剂法+除铊稳定剂的组合处理工艺,污酸废水中总铅、总镉、总汞和总砷的排放浓度均可稳定达到《铅、锌工业污染物排放标准》(GB 25466-2010)特别排放限值要求,以处理后各重金属日最大检出浓度的90%分位数作为参比浓度,该处理工艺对总铅、总镉、总汞的去除率分别为98.2%、99.8%、99.9%.(2)铅锌冶炼企业污酸车间地面冲洗水应全部纳入污酸车间污水处理系统进行集中处理,避免铅、镉、汞、铊等重金属废水稀释排放,长期汇入黄河干流富集造成潜在环境风险.(3)锌冶炼过程重金属主要富存于固相颗粒和液相颗粒中,污酸废水(废气洗涤制酸废水)中总铅、总镉、总汞、总砷产污系数分别为4.83、4.33、7.02、0.01 g/t(以产品计),较实际流向废气中相应重金属产污系数低10^(3)量级.(4)鉴于污酸废水处理碳排放强度约为一般性生产废水的7.93倍,建议加强评估并推广应用2022年《国家先进污染防治技术目录(水污染防治领域)》提出的有色冶炼烟气洗涤污酸废水治理与资源化利用技术,研究提出基于资源化利用途径的污酸废水排放控制要求.(5)湿法炼锌工艺碳排放强度为3.08 t/t(冶炼1 t锌的CO_(2)排放量),相对属于绿色低碳冶炼工艺.研究显示,黄河流域中上游部分典型铅锌冶炼企业已采用相对绿色低碳冶炼工艺,鉴于黄河流域的国家战略定位,需进一步提升末端重金属废水风险管控和减污降碳协同治理力度,引领沿黄冶炼产业高质量发展.

As an important shields for national ecological security,the heavy metal pollution in the Yellow River Basin has always been a concern.In order to improve the control level of wastewater discharge from lead-zinc smelting industry,this research takes a lead and zinc smelting enterprise in the middle and upper reaches of the Yellow River Basin as the research object to study the discharge characteristics and standards of key heavy metals in wastewater discharged from different pollution production links.The carbon emission intensity of different smelting processes and wastewater treatment in different pollution production links were measured from the aspect of green and low-carbon development of the industry.The results showed that:(1)By using the combined process including oxidation method+sodium sulfide removal of mercury+neutralization+biological agent method+thallium removal stabilizer,the concentration of total lead,total cadmium,total mercury and total arsenic in acid wastewater could reach the special discharge limits stipulated in the Emission Standard of th Pollutants for Lead and Zinc Industry(GB 25466-2010).When the 90 centile of the highest daily detected concentration of each heavy metal after treatment was used as the reference concentration,the removal rate of total lead,total cadmium and total mercury was 98.2%,99.8%and 99.9%,respectively.(2)The ground washing water from the waste acid workshop of lead and zinc smelting enterprises should be discharged into the wastewater treatment system in the waste acid workshop for centralized treatment to avoid potential environmental risks caused by dilution discharge of wastewater containing lead,cadmium,mercury and thallium into the Yellow River.(3)During the zinc smelting process,heavy metals mainly exist in solid and particles.The pollutant-producing coefficient of total lead,total cadmium,total mercury and total arsenic in acid wastewater(generated during exhaust gas washing process)were 4.83,4.33,7.02 and 0.01 g/t 3(calculated by product).respectively.It was 10^(3) orders of magnitude lower than the corresponding heavy metal pollutant-producing coefficient in the waste gas.(4)In view of the fact that the carbon emission intensity of acid wastewater treatment was about 7.93 times that of general production wastewater,it was recommended to speed up the research on the management and control requirements for the resource utilization of contaminated acid wastewater,evaluate and promote the application of the treatment and resource utilization technology of non-ferrous smelting flue gas washing-polluted acid wastewater proposed in National Advanced Pollution Prevention and Control Technology(Water Pollution Prevention and Control field)released in 2022,in order to propose requirements for controlling the discharge of acid wastewater based on resource utilization approaches.(5)The carbon emission intensity of zinc hydrometallurgy process,a green and low-carbon smelting process,was 3.08 t/t(CO_(2)emissions during the process of smelting 1 ton of zinc).The typical lead and zinc smelting enterprises located in the middle and upper reaches of the Yellow River Basin have adopted relatively green and low-carbon smelting processes.Given the national strategic positioning of the Yellow River Basin,it is necessary to further improve the risk control of terminal heavy metal wastewater and the collaborative governance of pollution reduction and carbon reduction,so as to lead the high-quality development of the smelting industry along the Yellow River.