Lead-zinc Smelting Waste-water Treatment Technology Research

In 2007, Cheng Zhou Zinc co. LTD. Gansu Province,(Cheng zhou Zinc) invested 440 million 50000 t/a new electrolytic zinc production capacity in the original 50000 t/a production scale, which increased the zinc smelter reconstruction total production scale to a capacity of 100000 t/a zinc ingots, sulfate 180000 t/a. Due to the large consumption of water during the production and the lack of water resource in Cheng zhou Zinc industry, it is important to reduce the water consumption, and to achieve wastewater "zero emissions" '. Valuable groundwater resource can be saved by treating the acidic waste-water through advanced treatment, which can also reduce the sourht country ricer water body pollution in order to lead the zinc smelting waste water recycling.There are three steps in Lead-zinc smelting waste-water treatment technology. First, neutralizaiton by limestone to treat acidic wast-water; Second, vulvanization treatment to contral a pH value 2-3 remove the heavy metal mercury(such as arsenic, mercury); Third, lime-ferric salt-micro filter-sodium filter-industrial reverse osmosis treatment of sewage. The first step is based on sulfuric acid purification process which is use limestone neutralization to control pH value 2-3. The second step contains three sections. The pH value of the first section is no greater than 5, in order to reduce the heacy metal arsenic. The second section is to reduce the heavy metal mercury with a pH value no greater than 9. The pH value of the last section is no greater than 12 for precipitation. The third step is Neutralization-Oxidation- Microfiltration-NanofiltrationReverse Osmosis processing with a pH value 8-9, in order to remove heavy metals(such as lead, zinc) from the sewage, then the final recycling water can be reused for all the production system.The project was constructed in March 2010. The total water consumption is 2755.8×104m3/a with the new 100000t/a electrolytic zinc production capacity, which include fresh water consumption 31.082×104m3/a, circulating water consumption 2619.309×104m3/a, and waste water emissions 104.9×104m3/a. According to different water quality requirements, the new process reduced a 3178.13m3/d waste-water emission, increased the water recycle utilization rate up to 95%. It also reduced the emission of suspended matter 7.60t/a, chemical oxygen demand(cod) 9.72t/a, fluorine 0.05t/a, 0.12t/a zinc, cadmium, lead, 0.03t/a 0.01t/a, 0.01t/a copper and arsenic 0.01t/a.A 1.049 million m3/a fresh water consumption can be saved by using the project at Cheng Zhou Zinc(330day/a), which eliminate pollution of heavy metal waste water to the surface water.