What is the downside of using carbon dioxide to reduce the pH of alkaline waste water from an anodizing plant?

We are considering switching from acid to carbon dioxide since we're rejecting too much sulfate according to the environmental regulations. The only information we are getting about this new technology is from commercial people, but we are interested to know practical and actual information about the disadvantages of using carbon dioxide in the pH reduction process. If you have used this method then please describe the advantages and disadvantages of adopting carbon dioxide in pH reduction process.