How to oxidize sulphide in wastewater effluents of tanneries with hydrogen peroxide?

[Mayo89]

Hi, I have a question regarding sulphide removal from wastewater effluents of tanneries.
The effluent (300 mc/d) flows in a tank, where it stays for about 14 hours.
The sulphide value is very high: 610 mg/L; pH =12.
I would like to use hydrogen peroxide to oxidize sulphide to sulphate; I am, also, considering the possibility of install blowers at the bottom of the tank, in order to reduce the daily dose of hydrogen peroxide. The purpose is to obtain an effluent with 120 mg/L of sulphide.
There's something I was hoping you could clear up for me: what is the right concentration of dissolved oxygen to ensure a constant high-performance treatment? What is the correct dosage of hydrogen peroxide to be used with this concentration of dissolved oxygen?
Thank you so much!

 

[bimr]

Air oxidation of sulfide is a very slow process and peroxide is expensive. It may not be practical to oxidize sulfide with the proposed method.

I worked on a tannery wastewater treatment plant where a complete mix activated sludge lagoon process was used successfully to reduce the COD and sulfide. Here is a link to the proposed method:

Link 1

Note, this was a separate investigation and it was not involved with the facility where I was working.

 

[aljosa_90]

Hi Mayo,

Have you considered methods of precipitating the sulfide using ferric sulfate or ferric chloride? Given your parameters, it seems like you would get good results. Plus it would be way cheaper than oxidation.

 

[bimr]

Hi Mayo,

Have you considered methods of precipitating the sulfide using ferric sulfate or ferric chloride? Given your parameters, it seems like you would get good results. Plus it would be way cheaper than oxidation.

The method proposed would generate a very large and expensive sludge problem. A major concern with sulfide precipitation is the generation of metal-sulfide sludge. This sludge is considered toxic and hazardous under 40 CFR 261 (RCRA Waste Code F006). Sulfide precipitation produces more sludge (as much as three times) than does hydroxide precipitation. In addition, although sulfide precipitation processes do not produce significant air emissions, they must be controlled (pH must be high enough) to prevent the release of toxic H2S gas to protect workers’ health.