WEF Discussion Forums
Laboratory Management and Technical Issues
Sodium Bisulfite Residual
Hello to all,
At our WWTP we are required to constinuously monitor our de-chlorination agent (Sodium Bisulfite). In the event of equipment malfunctions, we need to acquire grab samples and run them ourselves.
Does anyone knows what type of equipment we would need for such purpose? We would prefer handheld meters, but it seems that there are none...
Thank you very much!!
There is a titration method to check for sulfite. Try SM 4500 SO3 B. It requires sulfuric acid, potassium iodide-iodate titrant, sulfamic acid crystals, EDTA reagent and starch indicator. I don't know what kind of levels you want in your process, but I think it is only good down to about 1 or 2 mg/L sulfite. Sulfite is about 80% by mass of the sodium bisulfite compound, so you could only measure about 2-3 mg/L of sodium bisulfite.
Thank you DSmith for your response!
Our limit for chlorine residual is 0.01mg/L, theoricatically any indication of bisulfite in our final effluent is an indication of the lack of chlorine residual.
Again, thank you.
Hach has a drop count titration method which makes it a simple analysis. Each drop is 1 mg/L so we make a 1/10 dilution of titrant so we can see 0.1 mg/L detection. This is for process control so we just want to be sure the procedure works. The result is in sodium sulfite so just adjust your units for sulfite or bisulfite as you would like to see them.
Are you required to check sulfite only when your TRC is <0.1?
Sorry, I meant <0.01 ppm
It is optional for us to either report bisulfite or chlorine residual values in order to support compliance of the NPDES permit.