Where in Pakistan do you ...

Where in Pakistan do you work? Sindh? You may consider looking for deeper groundwater, which tends to be less mineralized; a household-level demineralization is hardly possible. Arsenic, depending on its chemical form in your specific water, may be removed by aeration (oxydation) and iron "saw dust" in the water, followed by a simple filtration; however, you have practically no control over the remaining As content on household level. You would have to test each shallow well inidividually and several time after starting to use it, since frequently As contents develop only after some months of operation. In Sindh, deep seated groundwater (explorable through handpumps) is frequently found, but it needs careful well construction for safe exploration. This is dafer and less costly on village level, than inividual purification installations on household level.