oh an after thought look into slow sand filter, plans and info free on net and also info on " activated carbon" how to make or more often called activated charcoal, how to make the basic is first make charcoal ( coconuts shell is best they say ) then take the charcoal and 2nd step is to " activate it " most use i think battery acid, but i did see something on using steam under pressure to activate it, the activated charcoal is used for medicen can be sold as a business idea using steam would be more expensive i think as you need a container to hold and regulate the steam under pressure but is more natural and safe as long as you dont blow up the pressure vessel, there is info on the net regarding toxins that can be filtered with activated charcoal try a search on toxins removed with activated charcoal might find that info, same with slow sand filter, hope this is usefull info, if you try slow sand filter look into ferrocement water tank construction, if you choose ferrocement construction you might have another part time business to help others in construction of tanks ferrocement dot com has tons of info on this. very helpfull people including low cost building methods using bamboo and bio fiber, hey if you grow bamboo in waste water you , and gain knowledge in ferro cement you can make a side business building with bamboo ferrocement, they show how to make low cost panels etc and bio fiber with acrylic cement is really cool stuff also this has all been used in africa also