Nonferrous metal smelting wastewater treatment process

In recent years, the frequency of pollution incidents in my country is gradually increasing, and the reason for this is closely related to non-ferrous metal smelting. Therefore, it is necessary to analyze the water quality characteristics of non-ferrous metal smelting wastewater according to the actual situation of non-ferrous metal smelting, and innovate the existing wastewater treatment methods to reduce the impact of non-ferrous metal smelting wastewater on people’s normal production and life, so as to protect my country’s non-ferrous metal industry. can truly achieve sustainable development.

Basic principle and process flow

1.1 Process flow

After the lime neutralization treatment, the harmful components of the non-ferrous heavy metal wastewater will be effectively reduced. After drying, the sediment should be returned to the production system, and the valuable non-metals should be recycled. After the treatment, the clear liquid after precipitation should be put into the second-stage neutralization tank. The supernatant is subjected to secondary treatment, and the treated liquid is put into the inclined plate for sedimentation treatment, and the harmful substances in the supernatant will settle into the pool. in the Xiangjiang River.

In this process, part of the supernatant should be filtered again, and a corrosion and scale inhibitor should be added to the supernatant during the treatment. This part of the supernatant is put into the production system for recycling.

1.2 Basic principles

In the treatment of non-ferrous metal wastewater, neutralized lime milk should be added to the wastewater. Lime milk can effectively reduce the acidity of heavy metal ion wastewater. In an alkaline environment, heavy metal substances in heavy metal wastewater will precipitate. The principle of this method can effectively separate harmful substances in heavy metal wastewater, and it is difficult for heavy metal ions to form soluble precipitates. Valuable heavy metal ions in heavy metal wastewater can be effectively recovered by precipitation. Adding compound effect agent to the supernatant can effectively control the corrosion rate of heavy metals and ensure that the corrosion rate of heavy metals is within the specified range, so as to achieve the purpose of effective control of smelting heavy metal wastewater. The formulating agent prevents the formation of scale components, so as to avoid the adhesion of the scale components, so that a crystal structure is formed. In the case that the crystal particles do not grow, they are suspended in water, and the scale is removed in this way.

Production results of wastewater treatment

2.1 Production process route

When treating wastewater, it is necessary to put the wastewater into the neutralization reaction tank. In this way, the wastewater is controlled, and lime is used to fully react with it, and the wastewater is put into the inclined plate tank, and the wastewater is sedimented and separated. Treatment, put the supernatant of the wastewater into the second-stage neutralization tank, and put polyferric sulfate in the neutralization tank. After mixing the supernatant and ferric sulfate, the wastewater is effectively controlled to ensure the pH of the wastewater. Between 8.5 and 7.0, the sedimentation tank is scientifically separated through the inclined plate. After two separations, the supernatant is also tested. After the detection is completed, it is discharged. In addition to this, the sediment is dried, the valuable metals are recovered and put into the production system and then sent to the production system for recycling.

2.2 Wastewater treatment practices and discussions

The wastewater treated by the new process has been sampled by the non-ferrous metal quality supervision and inspection authorized station, and the external drainage fully complies with the national comprehensive sewage discharge standard (GB8978-1996). Industry, the water quality comparison after one-stage neutralization and two-stage neutralization treatment of wastewater. The concentration of Ca, Pb, Cd, Zn and other ions in the wastewater after the first-stage treatment is lower than that of the untreated wastewater. %, 64.15%, the effect is obvious, and the Ca also decreased. After the wastewater is treated by the new process, the qualified rate has increased, and the metal recovery rate has been significantly improved. Statistics on the reuse of purified water. A variety of systems use the new process to purify the backwater with better effect, and no obvious scaling occurs.

Economic benefit analysis

According to the annual wastewater discharge of 900×104 m3 and reuse of 380×104 m3: the zinc recovery rate is increased by 17.19%. According to the average zinc content of the wastewater from 2017 to 2018, the average zinc content is 180mg/1, and the value of extra metal zinc recovered each year: 180×10-6× 17.19%×90×105m3×4000 yuan = 1.114 million yuan, the cost of purified water is 0.4 yuan/m (after comprehensive accounting), the cost of purified water reuse is reduced to create benefits: 380×104m3×(1.20 yuan/m3-0.40 yuan/ m3)=3.04 million yuan, reducing the efflux of heavy metals in Xiangjiang River every year: zinc: 900×104m3×6.86mg/1(-900×104m3-380×104m3)×1.76mg/1=51.52t, lead: 900×104m3×1.32 mg/1(-900×104m3-380×104m3)×0.47mg/1=9.41t, Cadmium: 900×104m3×0.30mg/1-(900×104m3-380×104m3)×0.069mg/1=2.34t Reduce environmental pollution discharge fees by 2 million yuan.

Originally, it paid 4 million yuan of sewage charges to Zhuzhou City every year. After adopting the new wastewater treatment process, the environmental protection departments of the province and municipality monitored all discharges up to the standard, and the sewage charges were 2 million yuan. Avoid the loss of 3 million yuan for the company to stop production. Auxiliary material consumption cost and labor wage increase cost: 0.111 yuan/m3>900>104m3+4 people>2 yuan/person=1.08 million yuan In summary, the direct economic benefit can be calculated as: 1.114 million yuan + 3.04 million yuan + 3 million yuan Yuan + 2 million yuan – 1.08 million yuan = 8.074 million yuan. The first stage of lime neutralization → second stage of polyiron recovery → corrosion inhibition and scale formation → purification and reuse of new technology to treat wastewater, the process is scientific, reasonable, simple, reliable technology, low investment, stable production and operation, and the treatment effect has reached the domestic advanced level.

Conclusion

To sum up, when innovating existing non-ferrous metal smelting methods, it is necessary to understand the discharge characteristics and water quality characteristics of non-ferrous metal smelting wastewater, understand the hazards of smelting metal wastewater, clarify the nature and source of non-ferrous metal smelting wastewater, and understand the characteristics of smelting metal wastewater. Harmful, and adopt a targeted wastewater treatment process to purify the wastewater to ensure that people’s health will not be affected.

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