It must be a certain minimum degree to kill bacteria. 

Treat the goop as full of bacteria...

I would have the water tested for pressure, minerals, metals and bacteria.

I do have some concern about helping build a better bacteria that is more resistant.

My question now is what exactly should the well /septic inspection include (bacteria testing, arsenic, e-coli etc)?

As an example, the last meeting was fascinating as we discussed brownfield properties and were introduced to a company who cleans up contaminated properties, bringing them back back to organic certification by reactivating natural occurring bacteria.  

As the wrigglers are processing your soil, it will slowly convert as sand is actually an extremely vast array of different soil types and mineral compositions, and as it is processed in the digestive tract of the worms, the soil will be broken down by the bacteria on the molecular level, amd then excreted, leaving more microlife behind. 

If you want nicer, remember that wood holds bacteria so try to go with something solid.

We’re awfully tired of lukewarm showers, the inability to use our tub & the possibility of there being bacteria in the water — hence the code.I still cannot imagine behaving like this with our tenants. 

You should check the well water for chloroform and bacteria, contaminats etc.