Process method of a selenium-containing discharge water

Abstract

The invention provides a process method capable of recovering a selenium, a heavy metal from a selenium-containing discharge water containing a large amount of suspended materials such as a stack desulfurization discharge water of a coal fired power plant and separating and processing the selenium and heavy metal at the state of being suitable for recycle and a process method for recovering the selenium, the heavy metal in the discharge water and effectively recycling the resources, characterized in that: a first flocculation separation step is that: a polymeric flocculant is added into the selenium-containing discharge water and the precipitate of the selenium-containing flocculant is separated; a second flocculation separation step is that: the pH of the discharge water without the precipitate is adjusted to 4-9 and the polymeric flocculant is added to make the flocculant precipitate, therefore the aluminum, the silicon, the sulfate ion and the ferrum are separated from the discharge water and the discharge water after the second flocculation separation step is guided into a heavy metal removing step: a reducible ferrum compound containing a mixture of patina and ferrum ferrate is formed in the alkaline and non-oxidizing atmosphere, thus the heavy metal enters into the precipitate and is removed outside the system.

Description

technical field [0001] The present invention relates to the recovery of selenium and heavy metals from selenium-containing wastewater containing a large amount of suspended matter and dissolved salts, such as exhaust gas desulfurization wastewater from coal-fired thermal power plants, washing wastewater from heat exchangers, etc. etc., a method of separating and treating them in a state suitable for reuse, and a treatment method that can recover selenium, heavy metals, etc. contained in these wastewaters and effectively reuse resources. Background technique [0002] Flue gas desulfurization wastewater from coal-fired thermal power plants, heat exchanger washing wastewater, and the like contain a large amount of suspended particles (Suspended Solid: called SS) generated from fly ash, etc., and the fly ash contains selenium. Most of the selenium in the drainage is tetravalent selenite ion (SeO 3 2- ), or hexavalent selenate ion (SeO 4 2- ) state exists, it is difficult to ...

AI Technical Summary

Problems solved by technology

[0010] The concentration of floating particles and dissolved salts in the flue gas desulfurization and drainage of coal-fired thermal power plants is high, and it is difficult to remove selenium if they are not treated

In the conventional treatment method, the suspended matter is treated by adding a flocculant to the wastewater to form a floc of the suspended matter and performing solid-liquid separation before removing selenium by adsorbing it on iron hydroxide precipitates. , but since selenium is adsorbed at a high concentration on the floc, it is difficult to effectively utilize the recovered sediment as cement raw materials and other resources

[0011] Furthermore, the existing treatment methods all make the wastewater contact with metallic iron to dissolve iron ions, and the iron ions reduce selenium and adsorb on the ferric hydroxide precipitate, but the volume of the ferric hydroxide precipitate is large, and it is subjected to solid-liquid treatment problems such as the need for large installations

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