emily learns to make (almost) anything

In rural India, millions of people access drinking water via hand pumps, such as this one:

The water that comes out of these pumps is neither filtered nor treated; whatever is in the groundwater goes into the users' bodies (it is rare in typical Indian villages for people to filter, add chlorine to, or boil their water after collecting it from the pump). Groundwater conditions vary throughout India, but it is usually contaminated. My idea, then, is to create a filter that can be attached to the outlet of the pump so that villagers can have easy access to clean water. Using SolidWorks, I developed the following model:

The filter is 35 cm long, so hopefully it would fit between the end of the pump outlet and the user's pot. Here is an exploded view:

A filter can act pretty slowly, so I thought it would be annoying for the user to pump once, wait for the water to pass through the filter, pump again, wait again, etc. I thought it would be more convenient for the user to pump water into a reservoir and then leave her bucket or pot to fill up while she does something else. The reservoir can hold up to ten liters of water, which is a typical bucket/pot size that rural Indian women use (their pots and buckets are usually between 5 and 20 L). The reservoir would be made of clear plastic so the user can see how much water is inside. The top of the container would plug into the pump's outlet and be sealed by an o-ring (but I still need to think about the best way to firmly attach the filter system to the outlet so that it does not fall).

I did not model the contents of the filter because, admittedly, I do not know much about filters. I would utilize existing technology, which I need to research further. One idea would be to emulate the bio-sand filter (taken from Practical Action):

Hand pumps are generally shared by several households, and filters would need to be replaced regularly. The filter would be inserted into the bottom of the filter container. When the water passes through the filter, a green LED would light up to indicate that the water is potable or a red LED would light up to indicate that the water is not clean and the filter must be replaced. Because pure water is a poor conductor of electricity, few ions should be present in the water if it is clean. I thought sensors could run an electric current through the water after it exits the filter and detect the amount of ions present. If electricity conduction is below a certain threshold, the water would be considered clean and the green LED would turn on; if the amount of ions is above this threshold, the red LED would turn on. However, I know absolutely nothing about electronics, so I did not plan out any of those components yet.

The electronics would be powered by a mobile phone battery. Almost every Indian household owns and operates a mobile phone--even in villages without electricity. Somehow, people are figuring out how to charge their mobile phones. Therefore, it should be possible to charge a mobile phone battery for use in this water filter. Again, I do not know anything about electronics yet, so I did not model the battery components.

If you have any experience with water filters, I would greatly appreciate your advice! Thank you.