suphides removal from ww 1

[techv]

We are having an existing WWTP but with expansion, it needs to handle excess sodium suplhides. What is the threshold limit for this is bio-unit? If I can sufficiently aerate the sulhidis stream, thiosulphates can be formed which exert lesser BOD. These thiosulphates pose any problems in Biounit?
Pls advise based on your design/operating experience.

 

[mbeychok]

techv:

Are your sodium sulfides in the form of Na₂S or NaHS or both? Is your wastewater stream derived from a petroleum refinery? If so, does it contain other contaminants such as oil, sodium phenolates or sodium napthenates?

In my experience with sodium sulfides in refinery watewaters, it takes a good deal more than just simple aeration to convert them to sodium thiosulfates. It requires very good contacting of the wastewater with air and steam in a vertical contactor tower at temperatures of about 165 to 225 degrees Fahrenheit (74 to 107 degrees Celsius) and at a pressure of about 75 to 100 psia (517 to 737 kPa absolute). Some such units have also used CuCl₂ as a catalyst. Read pages 198 to 205 (especially Table 22) in this book: "Aqueous Wastes from Petroleum and Petrochemical Plants", John Wiley & Sons, 1967. Most good university libraries have a copy.

If your wastewater contains any oil, sodium phenolate or sodium naphtenate, that may cause problems with oxidizing the sodium sulfides.

As for whether or not sodium thiosulfate causes problems in a biotreater, I have no such knowledge.

If your wastewater contains only small amounts of sodium sulfides, I would suggest that you consider oxidation by dosing with hydrogen peroxide.

If your wastewater is what I call a "spent caustic" from a petroleum refinery, I would very strongly suggest that you contact the Merichem Company in Houston, Texas at this website:

http://www.merichem.com

for advice.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[bimr]

From memory, I believe that the best course of treatment is add a waste material like ferric chloride at a pH of 9-10. You must maintain an alkaline condition to prevent the release of H2S.

The iron will tie up the sulfide preventing the release into the atmosphere.

If you have an activated sludge treatment process the sulfide is rapidly ozidized to sulfate in the treatment process. The activated sludge process has a large capacity for sulfides.

This is a common treatment method for tannery wastewater where the tannery is using sodium sulfide to burn the hair off cowhide.

 

[bimr]

Here is still another method:

http://www.caruscorporation.com/pdf...per Sulfide Control in Tannery Waste 2006.pdf