Petri-disks by 3M are cheap ...

Petri-disks by 3M are cheap and easy.  You need to incubate the samples to show presence of e-coli which is easy to do in Columbia, just find a warm but not hot room.  Sensafe has bottles you fill that check for both coliform and e-coli.  They are more expensive than the Petri-disks but real handy.  Here is their website.  https://sensafe.com/waterworks-ez-cult-bacteria-absence-of-coliform-with-e-coli-using-uv-light-extra/