The most effective technologies for purification of rain water for drinking and cooking purposes

We are working on a project for countries with severe hygiene and sanitation issues like India and Africa. I am working in the water purification division and we need to find a low-cost rain harvesting method which is feasible and cost-effective to implement in poor and developing countries inside their house. Currently, the filtration technologies are among the most common ones which are not quite accessible in these areas and it is hard to supply different parts such as the filtration cartridges. Hence, we need to find the easiest way of purification.  I would be so thankful if you kindly share any useful information regarding the most effective and cost-effective technologies for purification of rainwater for drinking and cooking purposes .  Thank you for your consideration and kind attention.   Regards, Mehrzad Pakzadeh