1. Source of asbestos wastewater

A large amount of asbestos will be consumed in the diaphragm electrolysis process of caustic soda. As a diaphragm, these asbestos are used in the cathode net of the electrolytic cell, which consumes about 1.6 tons of asbestos per 10000 tons of diaphragm caustic soda. When the cathode net of the electrolytic cell is maintained, the asbestos will fall off by flushing out with high-pressure water, and the asbestos will be discharged with the wastewater, which will pollute the environment. The asbestos has been identified as carcinogen by IARC.

2. Treatment of asbestos wastewater

The test results show that it is feasible to treat the asbestos wastewater with horizontal decanter centrifuge. As long as the separation factor of the centrifuge is enough or flocculant is added, the asbestos wastewater can be directly treated by centrifuge to achieve the discharge standard.

In the wastewater, there are fine impurities such as asbestos lints and other metal hydroxides. These particles are negatively charged, not easy to agglomerate into large particles, so the wastewater will be a relatively stable suspension. If the chemicals with opposite charges can be used to absorb the negative charges, the particles will coagulate and settle.

3. Technological process

First, the asbestos wastewater will be sent to the water collecting tank, a plane artificial grid with mesh of 5×5mm is set on the top of the water collecting tank to remove the coarse slag. Then, the wastewater will be pumped into the horizontal decanter centrifuge, the solid substances will be pushed to the dewatering zone, and discharged from the slag outlet after dewatering, and the liquid will be discharged from the liquid outlet. And then, because there are NaOH in the separated liquid, so the liquid will be sent to the desalination section to remove salt and precipitate Mg3+, so as to realize comprehensive utilization of asbestos wastewater.

4. Practical operation result and conclusion

After long-term operation of horizontal decanter centrifuge, it has been normal and stable. The results show that: under the condition of adding flocculant, the effluent concentration can reach the national and local discharge standards.