The most economical approach ...

The most economical approach would be to use the aerobic species of microbe called Archaea.  They have a ph range of 5.5 to 10.0 . (test ph first, if 12, dilute, retest, continue).  This is what they use in the Alaska state park toilets. There is no odor= no flies etc. At the end of the year the water is tested by the state labs. Results are No pathogens found, no biosolids remain, no toxic compounds of any kind . Then instead of pumping out, taking it to a state authorized dumping facility, they can pump it out into the park area forest.  The only problem is where they dump it the trees grow at a much faster and healthier rate.  Mother nature at her best.  If business minded you can hook up a bio generator to have a small amount of electricity.  Note: labs indicate potable water in reports.  But most people do not have an education to understand what potable means.  So until they are dying of thirst this cure for all of the worlds water issues will only be for educated persons.