To have a chemical free pool?? If so, how? If not, what is the "least chemical" method?

We are installing a liner pool. We have a special needs child and to this point have pretty much kept her chemical free. She has a very rare genetic disorder (1 in 117 known cases in the world). We would like to keep her enviroment chemical-free, but the pool will be a HUGE part of her therapy. She is very tiny and will remain small. She already has a compromised immune system, lung/airway problems.

Our pool people are trying to help us research safe alternatives for our family.

However, I figured you guys know as much or more than them anyway. We are researching Nature2, Ecosmarte, Stigma, oxyfree, etc.

We would appreciate any help or insight into this. Pls feel free to contact us anytime.

I guess lots of ppl generally ask for ideas. However, we feel this is something very important for our daughter. I was on a swimteam for 7 yrs.... chlorine is no big deal to me, my husband or even our son. We just need it to be safe for our daughter as well.

Thanks for any help/insight....