Question:
After some research on the internet, I found some sites which referred to "Brown Algae" which can grow in the dark in nutrient-rich wells. Our well, for some reason, has a high coliform content (not fecal coliform though - which is below the measurable limit, and we have a UV filter to sterilize the water). Recently, I saw a small fibrous plant of some kind floating just below the surface of the well. Does that mean the yellow is caused by Brown Algae? Even if that's true, why won't the Manganese Greensand filter remove the iron? Does the algae (if it's there) somehow prevent the filter from working properly?

Answer: That seemed to work each time when the water went clear for a day or so. Then the water returned to its normal disgusting yellow colour. The iron level remained high when we next measured it.

The supplier of our Manganese Greensand filter has now begun to suggest that our problem might be caused by Tannin Lignins. After some research on the internet, I found several websites which referred to "Heme Iron", which apparently is iron bound up in a complex with molecules from decayed vegetation. Apparently, this can cause a yellow colour, somewhat like the colour of weak tea.

Well, first I'd say that you have to realize that the drinking water guidelines are just a measure of whether the water is safe for human consumption. They don't mean you'll have clean, clear, mineral free water. Frankly, all throughout reading your tale of woe, the words "deep bored well" kept drifting through my mind.

I'm not too keen on shallow wells. The water doesn't receive enough natural filtration to suit me. Deep water usually (not always) means clean water. My water here comes from a 180 foot bored well. The water is clean, clear, and cold. There is also a shallow dug well on the property, and while it never lacks for water, the water is, well the best word is "icky". I wouldn't drink it even though the health department says it is safe.