Sulfuric acid, being less ...

Sulfuric acid, being less expensive than other industrial acids, is usually preferred, I have seen it fed through a drizzle line fed by gravity directly into the basin (this is the least preferred means), pumped into a mixing trough (preferred by me due to the low pressure involved), pumped into a header under controlled pressure (below 20 psig is better) with static mixer in line.  The only time sulfuric acid treatment could be considered to be a problem is when the calcium levels in the make-up water are high at the start, not lowered by softening, and high cycles of concentration of the water is attempted.  The real problem there could be Calcium Sulfate scale (not so easily reversed). Use of an eductor with chemical feed is only allowed when positive cutoff of the chemical is available automatically, otherwise a likely over feed could result, although if a small enough restriction valve is utilized, and steady flow is preferred, this can be done with reasonable control.

CO2 injection can not really lower the total alkalinity of cooling water, but it can shift the pH to slightly lower values.  

Hydrochloric acid is not my preferred choice to add to any system (other than possibly upstream treatment of RO feed water) due to the corrosion issues from fugitive vapor.