nickel smelting wastewater treatment
Nickel smelting is the process of recovering nickel from its ores. Nickel Smelting is a major industrial process and a major source of water pollution. All nickel smelting operations, regardless of the type of process used, produce large amounts of wastewater containing metals and other pollutants. The discharge of this wastewater, if uncontrolled, can be damaging to surface and subsurface waters, wetlands, and aquatic life, resulting in the need to control wastewater discharges from this industry.
Treating nickel smelting wastewater requires an understanding of the types and concentrations of the contaminants present and their impact on the environment. Analysis of the wastewater is conducted to determine the types of parameters present, the concentrations of the contaminants, and the types of treatment required to reduce the risk associated with their discharge. Once the parameters of the effluent have been determined, a treatment system design can be developed and implemented.
Primarily, nickel smelting wastewater contains precipitated heavy metals, suspended solids, and salts, all of which require removal. To reduce the amount of suspended solids and nickel in the wastewater, flocculation is the most effective treatment solution. Flocculation involves the addition of a coagulant, such as aluminum sulfate or calcium hydroxide, to the wastewater. This causes the suspended particles and dissolved metals in the wastewater to agglomerate into larger particles known as “floc”, which can then be easily separated from the wastewater. After the floc is separated, it is often processed further with a series of physical, chemical or biological treatments, or a combination of all three.
Chemical treatments are often used to remove heavy metals from wastewater, as well as to neutralize acidic or basic components of the effluent. Chemical precipitation is one method of removing heavy metals from nickel smelting wastewater. In this process, chemicals such as calcium oxide, calcium hydroxide, or aluminum sulfate are added to the wastewater to cause the heavy metal ions to form insoluble metal hydroxides, which can then be separated from the water. Ion exchange is another method of removing metals from nickel smelting wastewater. In this process, metal ions are either exchanged for those of some other metal, or adsorbed onto an anion exchange resin.
Finally, biological wastewater treatment is often used to treat nickel smelting wastewaters. This process harnesses the natural activity of aerobic and anaerobic bacteria, which are added to the wastewater, to convert the contaminants into harmless byproducts. The bacteria digest the organic material, metals, and other pollutants, converting them into carbon dioxide, water, and other harmless compounds.
Overall, nickel smelting wastewater requires careful management in order to reduce the impact of pollutants on the environment. Analysis of the effluent parameters, followed by careful design and selection of the treatment system, can provide the necessary mitigations for protecting surface and subsurface waters, wetlands, and aquatic life from the role of this industry in contamination.
