Pretreatment of sulfates before wastewater treatment

[jerryvo]

I have a 100 gallon per day batch waste stream that contains residual sulfuric acid (about 5%) and formaldehyde(about 2%). I want to minimize the sulfates going into my biological waste treatment area by pre-treating this stream. I will experiment with raising the pH with soda ash and then making a floc by adding CaCl2. I will then be able to decant the clear supernatant into the bio-treat area (then dispose of the greatly reduced volume of solid residue). Any other cost effective, proven suggestions? Any additives to enhance the floccuating properties? I read some pretty wild economically INfeasible suggestions on these forums, so please make any suggestions practical and not textbook!

 

[kenvlach]

Instead of "raising the pH with soda ash and then making a floc by adding CaCl2," why not use Ca(OH)₂ to do both?
The vast majority of the sulfate will precipitate out by the time you reach pH 7. You may be able to get [SO₄] down to about 810 ppm; see thread161-50054, although this depends upon temperature and common ion effects, too.