Alternate Alkali for Neutralization in Effluent Treatment System.

[Designer80]

Hi All

We have been operating a chemical plant coupled with an effluent treatment plant to reduce effluent COD load within desired limits before discharge to Govt. drainage system.Our plant effluent is acidic in nature with a ph of 4-4.5 and we have to neutralize it before feeding to our effluent treatment plant and we increase ph to aprox 7.0 using caustic soda ( its strength is aprox 25 % ).We have biological treatment plant using activated sludge. Cost of operation is very high and one of the major contributor in cost is caustic soda. Can anybody suggest us the alternate option to replace caustic ?

 

[Compositepro]

Limestone.

http://butane.chem.uiuc.edu/pshapley/GenChem1/L26/3.html

 

[moltenmetal]

First of all, the activated sludge will reduce COD- increasing the pH won't affect the COD one way or the other.

Lime (calcium hydroxide) is cheaper than caustic but also a great deal less convenient because it's a slurry.

 

[ashtree]

Do you have to get to pH 7.0 anyway or are you only doing this for the activated sludge process?
Activated sludge once acclimatised will work at a pH well below 7, so if you don't have to go that high to meet the discharge requirements just slowly lower the pH by reducing the caustic dose. I think operation at 6.0 pH would be possible.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[moltenmetal]

Discharge pH requirements are usually 6-9 if the product is going to a POTW- tighter than that if it's going to surface water. Limestone is slow to react, and doesn't achieve as high a pH as easily as lime, but it's also cheaper.