Fixing a Weird Smell or Oily Sheen in Well Water - why I regularly chlorinate my well

Some of the weirdest water problems turn out to be iron bacteria. Generally, iron bacteria produce unpleasant tastes and odors commonly reported as: "swampy," "oily or petroleum," "cucumber," "sewage," "rotten vegetation," or "musty." The taste or odor may be more noticeable after the water has not been used for some time and are not easily explained by other causes. There is often a discoloration of the water with the iron bacteria causing a slight yellow, orange, red or brown tint to the water. It is sometimes possible to see a rainbow colored, oil-like sheen on the water. Though the most classic symptom of iron bacteria is a rust colored slime, it may be yellow, brown, or grey. A quick screen for iron bacteria would be to feel the rubber flapper in your toilet tanks. The iron bacteria tends to accumulate there.

About six or seven years ago I tested my well water for iron bacteria. Though I test my well water each year during the annual water clinic the Prince William Extension Office hosts and every few years for all primary and secondary pollutants, iron bacteria is not part of those suite of tests. The standard bacteria tests do not test for iron bacteria. Iron bacteria assay test can be purchased from National Testing Laboratories for $59.99 these days (excluding shipping). My test found “Iron Related Bacteria” present with an estimated population of 2,300 cfu/mL.

Iron bacteria once introduced into the well will not get better, but continue to get worse destroying your pump and ultimately fouling the well. Iron bacteria can grow on pump intakes and screens openings causing plugging, corrosion, and reducing the yield and efficiency of the well. The iron bacteria can reduce well yield and damage well equipment. In addition, the slime produced by the iron bacteria reduces the ability of regular chlorine treatments to kill disease-causing organisms. Finally, though, there is no health risk associated with the bacteria, ultimately it will make the water unpleasant.

Iron bacteria can be introduced into a well during drilling, repair, or service if tools, equipment, or devices used during well drilling or pump servicing were not properly disinfected. It is believed that the bacteria must be introduced into the aquifer and cannot infect the water without human help.

Elimination of iron bacteria once a well is heavily infested can be extremely difficult. Iron bacteria cannot be eliminated by most common water filtration methods or water softeners. However, though it is difficult to eliminate, it is actually very easy to control – just oxidize the heck out of the well.

Normal treatment for a problem such as this would be to chlorine “shock,” but iron bacteria can be particularly persistent and chlorine treatment of the well may be only partly effective. Typically, a chlorine concentration of 50-200 parts per million is used for decontamination of a well impacted by coliform bacteria. A significantly higher concentration of chlorine is recommended by the literature for iron bacteria. Recommended concentrations are between 500-1,000 parts per million. Be warned that too high a concentration can make the well alkaline and reduce effectiveness, so don’t go crazy. In addition high concentrations of chlorine may affect water conditioning equipment, appliances such as dishwashers, and septic systems, so do not pull the heavily chlorinated water through equipment and the plumbing system.

The recommended strategy is to treat the well with a 500-1,000 parts per million chlorine hold for 12 hours and then dilute the remaining water in the well. This can be accomplished by allowing a significant amount of the water to runoff to a safe disposal location using hoses until the water runs clear. Use chlorine test strips to verify that there is still residual chlorine in the water and allow the well to refill and then introduce the water into the house water system to disinfect the household treatment units, appliances and piping with lower concentrations circulated through the water system and hold for an addition 12 hours. Flush the system completely using hoses not your drains and septic system.

The Idaho Water Resources Research Institute recommends an initial treatment at 1,000 ppm including scrubbing and disinfecting the pump and an annual maintenance disinfection of 500 ppm leaving the pump in place. My initial treatment was about 600-800 ppm with the pump in place for 12 hours and then running off the slimy rust colored crude that came out for a few hours, topping up the chlorine concentration to about 200 ppm and pulling the chlorinated water throughout the household plumbing system.

I chlorine treat the well ever couple of years to keep knocking back the iron bacteria. I gave up testing for the iron bacteria because it did not seem worth the expense. Because you never really get rid of iron bacteria, prevention is the best safeguard against the bacteria and their accompanying problems. The bacteria will eventually grow back so be prepared to repeat the shock treatments from time to time. With my well that translates to even years.

Chlorination for iron bacteria can also rehabilitate the well. As a water well ages, the rate at which water can be pumped (commonly referred to as the well yield) tends to fall. This can be caused by Incrustation from mineral deposits or bio-fouling by iron bacteria. The most common methods to rehabilitate a water well are: acids or chlorine to dissolve the encrusting materials and bacterial slime from the well; and physically cleaning the well.

Chlorination can dissolve the encrustations and extend pump function. These days regularly treating a well with chlorine is the recommended strategy to extend the life of a well and equipment and can improve the taste of the water. See well maintenance tips from Penn State University Extension. Last week with the help of someone who wanted to see how a well was chlorinated I chlorine shocked my well. Just in time before the cold weather.