Some net info. on well water evaluation / corrective actions below.
As per previous posts and for the ideal case of a controlled system / residual chlorinated water, one would expect that all 3 parameters being discussed would be undetected in routine samplings. If unknown, unchlorinated, unfiltered, any prediction is inevitably more complex. However the local legal micro. requirements are usually well defined if the water is to be used for food-related purposes, typically the water must be "potable" as defined by local rules and/or via international / destination standards where relevant.
Five random but, IMO, reasonably coherent overviews of ground wells/drinking water capabilities, problems are linked/attached below.
IMEX, one practical difficulty is that the reliable (ie validatable) measurement of certain relevant micro. parameters, eg E.coli, requires quite lengthy and precise control of specific conditions + proper sampling procedures. The methods available can vary which may complicate interpretation / comparison of data. Additionally quantitative microbiological data is almost invariably of significantly wide confidence limits, albeit never meaningless in the case of a positive detection of a specific species from a valid sample-technique.
Nonetheless, on basis of previous posts so far, it is presumably logical to, at least initially, assume a worst-case scenario and act accordingly.
Interpretation of Results / Corrective Actions
Predictably these also vary in location, stringency and detail. The environmental-usage situation, legal requirements, microbiological history of source and repeatability / specificity of data are 4 obvious parameters.
I have attached 4 (random) official responses and 1, more generic, example (cor5).
Hopefully of interest but it will obviously depend on the actual situation.
Rgds / Charles.CGo to the full post