There is a lot of "wrong" going on here. An ro is not used for coliform reduction. Coliform is not "safe". It is an indicator of a potentially non dangerous issue, not a sure fire indicator. The same way e-coli is only a likely indicator of a dangerous issue...
Take care of the coliform issue. Please go to the line provided and read the article on coliform/e coli and sanitizing I wrote a while back, this may give you a little better insight to what is going on and how to solve it.
https://view.publitas.com/impact-water-products/2018-catalog-final/page/282-283
A home test kit is available, typically less than $15 and it only takes 24-48 hours. Ecoli and colifor are included in the same test, you use a UV light to determine if e coli is present.
https://view.publitas.com/impact-water-products/2018-catalog-final/page/278-279
calcium 109 mg/L
Iron 2.86 mg/L
High level, this should be treated... and you can double up on the coliform by chlorination/contact tank...
magnesium 5.7 mg/L
Manganese 0.020 mg/L
Potassium 2.6 mg/L
Silicon 10.6 mg/L
sodium 16.8 mg/L (MCL= 20 mg/L)
coliform positive (but no indication of how much)
Needs to be treated appropriately, redundant treatment recommended as is whole house sanitization
alkalinity (as CaCO3) 292 mg/L
bicarbonate (as CaCO#) 291 mg/L
carbonate (as CaCO3) 0.69 mg/L
clarity <100 mm
color 50 color units (MCM = 15)
Probably caused by the high level of iron, KL will usually take care of this. No real need for Big Blues in this application as the Hydra and KL backwashing system will negate these in most applications.
conductivity 611 micromhos/cm
aggressive corrosivity 12.3
Langelier corrosivity 0.4 S.U.
Ryznar corrosivity 6.5 S.U.
Hardness (as CaCO3) 296 mg/L (17.3 GPG)
High hardness, probably should treat this with a softener
Ph 7.4 S.U.
resistivity 1640 ohms/cm
salinity 0.306 ppt
silica 22.7 mg/L
high but not much you can do about this
sodium ads. ratio, adjusted 0.67
sodium adsorption ratio 0.42
turbidity 32.1 NTU (MCL = 0.3)
total dissolved solids 410 mg/L (MCL = 500 mg/L)
I dont really see anything too exciting here, a simple chlorine injection system with a baffled contact tank will take care of the majority of the iron, either a KL or Cat GAC backwashing system, I am more partial to KL since it does a better job of sediment reduction but either will do fine, followed by a softener and a whole house UV and you will have very nice water.
I would lean toward a higher rejection, higher quality RO rather than a high efficiency... a UV on the small RO would also be cheap insurance.