Getting rid of coliform?

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bluefish67

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Hi everyone,

I'm having problems with my well and would appreciate any help you can offer. Here's the short version of the story.

A year and half ago we found out the well had coliform bacteria (no fecal coliform). It was shock treated and tested OK. Last month it tested positive again. I shock treated it twice, but it still tests positive. From the smell and visual inspection, we also have a problem with iron and/or sulphur bacteria.

There are three septic tanks on the property. The inspections said they were sited far enough from the well.

My questions:

- Where is the coliform coming from? Why is it returning?

- Could a septic be the cause? Some people have said that since there is no fecal coliform, the problem is not coming from a septic. One person said this might not be true.

- Why did the shock treatment not work?

- Do we need a new well?

- Would the new well become contaminated?

- Is the iron/sulphur bacteria interfering with the shock treatment?

- Given the problems we've had, does it make more sense to just treat the water after it comes out of the well?

- Are there other options than a new well or water treatment? Did I do the shock treatment wrong?

Below are more details for those with the patience. Sorry for the length, but I want to give enough info to people who might be able to help.

Thanks,

-Scott

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The details:

The well is 150 feet deep, 4 inch casing. The well feeds three houses on the property. I don't know the age, but the well company says it will probably need to be replaced soon. Even though it's old, getting several more years of life out of it would help, given our current financial situation.

We bought the property a year and a half ago. During the sale, the well was tested and came back positive for coliform. I assume that the previous owners did not know of the contamination, or else they would have treated it before they put it on the market. Why risk undermining a sale, when they knew they would have to treat it anyway. So, I'm assuming the contamination has been there for some time. They owned the house for the previous 15 years.

The well company treated the well. I didn't pay too close attention, but I believe they used some kind of dry, granular chlorine, not pellets. I ran the water through all the fixtures, as directed by the well company. I had a hard time telling by smell whether enough chlorine was coming out, especially after doing three houses. But after finishing, the water tested fine.

Last month, we did a follow-up test. It tested positive for total coliform. I did the shock treatment myself, using several quarts of 6% household bleach, in a single application. This was calculated to give a concentration of about 50 ppm. I flushed the water down the casing, ran it through the fixtures, and let it sit. Again I had difficulty knowing there was enough chlorine. The water still tested positive for coliform.

I repeated the shock treatment. This time I used high range chlorine test strips. I added chlorine then cycled it through the system using a hose for about 20 minutes. The strips showed 300+ ppm. I ran it through the fixtures, checking the chlorine level each time. When the level dropped below 300 ppm, I added more chlorine and cycled. When I finished, I added more and cycled it, so that there was a high level left in the well. It sat for about 15 hours. All told, I used about 2 gallons of 6% bleach in four applications.

After all this, it still tests positive.
 

Gary Slusser

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Shocking a well is at best a temporary solution which treats the symptom rather than the cause of the contamination. As proved by your experience.

Shocking a well can cause expensive water quality, pump and/or power cable and drop pipe problems.

Bacteria contamination can come from any direction any distance and it can come and go in days.

Of course the best and all but impossible choice would be to find and prevent the source of the contamination but.... that usually is expensive and impossible. While it may take years to clear the groundwater of the contaminated water... So, the next best is to drill a new well BUT, that does not guarantee non-contaminated water. So, treating the water usually is the best doable choice with minimal expense and it comes with a guarantee of bacteria free water as long as you maintain the equipment; which is easy and takes little time.

There are a number of ways to treat bacteria but you have have to meet pretreatment needs for some, like UV lights. You have iron abd possibly SRB/IRB so UV is out. I dont like chlorine but, it is usually the best when other parameters limit the use of UV, like your situation plus... you have other people using the water, which makes you a water company if you like the idea or not... and the guvmint guys love chlorine.

So, I would propose my relatively inexpensive inline pellet chlorinator and special mixing tank followed by a correctly sized for the SFR (service flow rate) the houses would require Centaur carbon filter.
 

Raucina

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First of all you dont have fecal coliform so you can relax and take time to fix this. Prior to the days of labs, most water had a large dose of the same [non fecal at least] and we did not care because we did not know. If kids lived past 1 year, then they were immune forever. All kinds of things can show coliform on a test and it seems to me that about all wells do unless it has been recently chlorinated. Then it slowly returns, and we drink it for several years with no ill effects, until some lender tests it and makes us chlorinate it. Then the cycle starts again.

Lets assume big brother is right for once and we dont want ANY coliform. On the last cycle you did the right stuff. Lots of chlorine [dont worry about the pump] and recirculated it. I assume that means you sent the water back down the well seal for some time.

The key question now is where are you testing? With three houses you have a myriad of issues, so you should test only at the well head until that comes clean, then move to the kitchen faucets in the houses after that result. Well head - not at pressure tank.

Lets say some kid dropped his pet hampster in your well, or maybe his cockroach collection. Maybe the renter didnt like his cleaning deposit not being returned and dropped his leftover kentucky fried chicken in the hole...
I would try some more oxidizer before giving up.

Now about the iron bacteria, that can create a slime that does not allow the chlorine to penetrate - so on the next round, try some acid treatment [with good instructions and safety info] first, then one more round of chlorine. [see some recent posts in this regard]

With three families that can be a real chore to schedule. Do not risk a new well unless its thousands of feet uphill from the septics. Treatment is cheaper.
 
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