What kind of chlorine solution do I use in water treatment system?
This looks very similar to a pool chlorine feeder - these could use cal hypo or sodium hypo, either way you would need to know the concentration to mix and the dosing for your qty of water to treat. Not sure we'll be able to answer those questions directly.

Sodium hypo - bleach - would be the cleanest option, but also will become ineffective the quickest.

Cal hypo is granular (and cheapest) and has the most shelf life, but you'd probably want to source food grade supply for long-term use.

Concentration of chlorine would be determined by the qty of water to be treated at one time, level of final level of chlorine needed for decontamination, how the chlorine solution is dispensed (continuous or on demand) and how much chlorine is dispensed at any given cycle.

Chlorine would only be used to correct organism growth not other chemical/mineral constituents of concern.

Due to the health risks, I 'm not sure how much I'd trust free advice at this point.  Spend the money and be sure this is set up properly.  Your health is worth it.