Chlorine or Sodium Hypochlorite as Disinfectant

WOW!!!! You are about to treat potable water for 20 million people and you need to ask a bunch of strangers if what you want to use is safe?

At least he knows that Engineers have saved more lives then doctors.

Using gas chlorination or hypochlorite has the same effect of forming the disinfectant HOCl or hypochlorous acid. It makes a lot of sense to augment gas chlorination with hypochlorite in areas where residual chlorination is difficult. Gas chlorination is fraught with many safety hazards; whereas, hypochlorite can be safely transported and operated with minimum training. The one difference that may be a potential problem is that gas chlorination tends to lower pH at the point of injection while hypochlorination will raise pH at the point of injection. The net result is usually a little more maintenance for hypochlorination to make sure the precipitates from the water do not clog the point of injection. Clogging is easily resolved with routine maintenance. I would opt for hypochlorination as the method of augmentation under many circumstances.

Purchasing Hypochlorine is generally 3x the cost of gas chlorine. That is likely why the main source is gas when other infrastructure costs are minimal. A new injection boost will require significant risk training and infrastructure costs over and above the same costs for hypochlorination.

A detailed analysis of the demands, water quality, and all other costs need to be evaluated and generally are under such circumstance.