For the treatment of desulfurization wastewater, oxidation, neutralization, flocculation, sedimentation and other methods are widely used, mainly including the following steps:
1. Cod treatment
Most of COD in desulfurization wastewater comes from ferrous salts or sulfur compounds with s2o6 as the main body. For divalent iron salt, Fe (OH) 3 can be oxidized in air by adjusting pH to 8-10. Sulfur compounds with s2o6 as the main body are difficult to be treated below 10mg / L if they are only treated by oxidation-reduction and activated carbon adsorption. Therefore, at present, the main method is to add synthetic adsorbent for treatment, that is, to further use synthetic adsorbent for adsorption treatment and drug desorption, and then take out COD in the form of concentrated solution for further treatment.
2. Treatment of heavy metals
Heavy metals are mainly treated by precipitation. First, add Ca (OH) 2 slurry to adjust pH to about 9. The purpose of this operation is to adjust the pH to meet the discharge standard, precipitate the metal ions in the form of M (OH) n to remove the metal ions in the wastewater, and use the characteristics of CAF precipitation formed by the reaction of Ca (OH) 2 and F - to remove the F - in the wastewater. The results show that when the mass concentration of Ca (OH) 2 in the wastewater reaches 900 mg / L, the fluoride ion concentration can be reduced to 5-8 mg / L or even lower, which can meet the requirements of the discharge standard. For cadmium, mercury and other heavy metals, sulfide precipitation method should be used to remove them by producing mnsm which is more difficult to dissolve (with smaller ion product constant).
3. Suspended solids treatment
The treatment of suspended solids is mainly realized by flocculation, that is, coagulant and coagulant aid are added to react in the water body. After the flocculant is dispersed under stirring, the hydrolysis reaction and destabilization are accelerated, and the colloidal suspended solids in the water are destabilized to form fine alum. With the weak agitation, alum flocs grow into large flocs, and the addition of coagulant aids further promote the growth of flocs and increase the precipitability. After complete reaction, the sludge is precipitated and discharged through inclined plate sedimentation tank to achieve the purpose of removal.