Treatment method for reducing Cr<6+> in stainless steel acid wastewater

Abstract

The invention relates to a treatment method for reducing Cr<6+> in stainless steel acid wastewater. The treatment method comprises the following steps: feeding stainless steel mixed acid wastewater and sulfuric acid wastewater into a reducing pond; adding a reducing agent into the reducing pond and stirring, so that Cr<6+> in the wastewater is converted to Cr<3+> and leading effluent meeting an ORP (oxidation-reduction potential) requirement to flow into a neutralization pond; adding lime into the neutralization pond and carrying out oxygen blast aeration, so that Fe<2+> in the wastewater is oxidized to Fe<3+> and Cr(OH)3, CaF2, Fe(OH)3 and CaSO4 precipitates are formed; entering the effluent from the neutralization pond into a flocculation pond; adding 2-5 mg / l of PAM (polyacrylamide) into the flocculation pond so as to form large alum floc, and leading the effluent from the flocculation pond to flow into a precipitation pond for precipitation; and then entering the effluent after precipitation into a subsequent treatment facility so that the Cr<6+> in the effluent meets the emission requirement, and externally transporting sewage in the precipitation pond at regular intervals. The treatment method can meet environmentally-friendly requirement and is beneficial to subsequent biochemical treatment.

Description

technical field [0001] The invention relates to the field of iron and steel, in particular to a method suitable for reducing Cr in stainless steel acid wastewater 6+ The problem. Background technique [0002] Stainless steel wastewater includes acid wastewater and electrolyte wastewater, and the main component of electrolyte wastewater is Na 2 SO 4 and Cr 6+ 、Ni 2+ etc. Acid wastewater mainly contains HF, H 2 SO 4 、HNO 3 and iron ions, etc., because the electrolyte wastewater contains a large amount of Cr 6+ 、Ni 2+ etc. According to environmental protection requirements, acid wastewater and electrolyte wastewater are required to be treated separately, and the electrolyte wastewater is reduced, neutralized, precipitated, and filtered. 6+ 、Ni 2+ After reaching the standard, enter the acid wastewater. [0003] The stainless steel acid wastewater comes from the mixed acid (nitric acid and hydrofluoric acid) and waste sulfuric acid wastewater produced by the unit. Beca...

AI Technical Summary

Problems solved by technology

[0007] The technical problem to be solved by the present invention is: provide a kind of stainless steel acid waste water to reduce Cr 6+ method to solve stainless steel wastewater effluent Cr 6+ Problems that exceed the standard and affect the subsequent biochemical treatment operation

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