Hi Niels, thank for the update. Looks really interesting. 

I do wonder about the waterquality because - as i understand it - the groundwater is recharged by runoff water from the city. You mention that polluted recharge occurs from pitlatrines. But isnt there more pollution in a city? What about household chemicals like laundry detergent and paint which - in a city without a sewer - has to be spilled to the groundwater? What about petrolstations where gasoline and diesel leaks into the soil? What about heavy metals coming from garages and mechanical workshops?

Wont these factors influence the groundwater quality aswell? and if so, what are the potential consequences of it?