Hey:)
Bottled water is definitely not a long-term plan.
Reducing the water consumption does not really solve the problem.
Store the rain water is a nice choice, but you cannot drink the rain water directly, it needs to be filtered.
Since the contamination is only caused by N and P, it should be easy to filter out, but still, it depends on the type of the compound of N and P.
I would choose the last option.
