Total coliform bacteria are microorganisms in soil, sewage, surface water and very shallow groundwater that is under the influence of surface water.  

The presence of coliform bacteria in drinking water indicates a possible sanitary defect in the drinking water system that could provide a pathway of entry for contamination into the well or distribution system (plumbing into the home). This pathway may provide an opportunity for harmful material to enter the drinking water creating a potential health hazard. As surface water percolates through the soil, a natural filtration process takes place which normally removes microorganisms (including coliform bacteria) unless a pathway exists which bypasses this natural filtration process. 

Escherichia coli (E.coli) bacteria are a type of total coliform bacteria which are present in sewage.  

The presence of E.coli bacteria in drinking water indicates a pathway exists to the water system from a waste source, such as an animal feedlot, septic tank, cesspool leakage, etc. This indicates that the water may be contaminated with microorganisms that can cause serious illness, such as Salmonella or enteric viruses or parasites. 

• If the total coliform bacteria and E.coli test results are ABSENT, or the most-probable-number is <1, the water is bacterially safe for drinking purposes. 

• If total coliform bacteria are PRESENT, the water is unsafe with potential health concerns.   

• If total coliform and E. coli bacteria are PRESENT, the water is unsafe with serious health concerns. 

Short term:  Disinfect water by boiling it for one minute or use an alternative source of water that is known to be safe, such as bottled water or water from a public water supply.  Do not consume water or brush teeth with water that has total coliform or E. coli bacteria unless it is properly disinfected.  Wash dishes and utensils with disinfected or known safe water or run the sanitation cycle on a dishwasher. 

Long term:  The best approach to ensuring safe water is to determine how and where contaminants are entering the system and eliminate the entry pathway. A sanitary survey of your water system and remediation assistance may be available from your local county health department, Iowa State University extension services, and certified well drillers and pump installers. 

There are three areas to evaluate if you had a positive coliform result: sample collection, distribution system, and finally the well as outlined in the coliform action response flowchart in the SHL Well Water Quality and Home Treatment Systems Guide. 

First, review the sample collection procedure. If the sample was collected correctly and represents the drinking water supply, then schedule an inspection of the complete water system (well and distribution plumbing system) and area surrounding the well for possible sanitary defects or pathways. If defects are found, they should be corrected accordingly. 

Strategic sampling for coliform bacteria (in the most-probable-number (MPN) result format) collected at various locations (e.g. at the well, before or after treatment systems, etc.) may be necessary to pinpoint the source of the problem. For example, if the samples taken closest to the well and before the softener are negative and the sample after the softener is positive, this indicates that the softener may be contaminated (e.g.biofouled) and is the source of the coliform problem. In this case, contact a reputable water treatment professional for remediation guidance. 

With older wells, this defect may include structural problems in the well such as pits, cracks in the casing, inadequate grouting, brick or concrete wells, or cisterns. 

With new wells, the defect is more likely a problem with the distribution system such as cross-connections, broken or contaminated distributions lines or treatment systems, faulty pressure tanks, contamination from repairs or new construction without proper disinfection, etc. 

A sanitary survey of your water system and remediation assistance may be available from your local county health department or certified well driller and pump installers.

Nitrates are chemical compounds composed of nitrogen and oxygen. Nitrate contamination is more likely to occur in shallow wells and in wells which are poorly located, constructed, or maintained and are generally an indication of contamination from nitrogen fertilizers, sewage disposal systems or animal manure. 

Nitrate levels greater than 10mg/L as N may pose a serious health hazard for infants. Do not use water with elevated nitrate in infant formula or juice. Infants who are fed formula or juice with elevated levels of nitrate could develop a life threatening illness called methemoglobinemia, or “blue baby syndrome,” which results in blue-gray coloring of the skin due to a lack of oxygen in the blood.  Recent research studies suggest potential health hazards for adults following long-term consumption of elevated nitrate levels. 

Short term: Use an alternative source of water that is known to be safe, such as bottled water or water from a public water supply 

Long term:  The best approach to ensuring safe water is to determine how and where contaminants are entering the system and eliminate the entry pathway. A sanitary survey of your water system and remediation assistance may be available from your local county health department, Iowa State University extension services, and certified well drillers and pump installers.  It is also possible to remove this contaminant using an appropriate treatment device such as distillation, reverse osmosis, or anionic exchange (ion exchange).

Arsenic is a naturally occurring element found in rocks and soil. There are two types of arsenic: inorganic and organic.  ​Inorganic arsenic compounds are found in soils, sediments, and groundwater. Organic arsenic compounds are found mainly in fish and shellfish.  Organic arsenic, in general, is much less toxic than inorganic arsenic and some organic arsenic compounds are not toxic at all.    

In Iowa, arsenic is a common water contaminant.  Arsenic may enter groundwater through the rocks and soil that surround the water. The depth of the well and the well design can affect the presence of arsenic in the well water. Arsenic may also be present in some foods (including seafood, rice and rice-based foods, and some fruit juices), herbal medicines and Ayurvedic products.  Arsenic is used in some pressure treated woods (use of arsenic in pressure treated woods was phased out in the US in 2003), some pesticides, and some paint pigments.  Arsenic is no longer produced in the US but continues to be imported.

Studies have shown that chronic or repeated ingestion of water with arsenic over a person’s lifetime is associated with increased risk of cancer (of the skin, bladder, lung, kidney, nasal passages, liver or prostate) and noncancerous effects (diabetes, cardiovascular, immunological and neurological disorders).  

Bathing with water that contains arsenic is not a significant health risk because arsenic is not readily absorbed through the skin. Some ingestion of arsenic may occur when brushing your teeth. Although the amount ingested is minimal, using a clean source of water for brushing your teeth is advisable. 

Short term: Use an alternative source of water that is known to be safe, such as bottled water or water from a public water supply.  Arsenic cannot be removed from water by boiling.  

Long term:  Arsenic can be removed by treatments such as distillation, reverse osmosis, activated alumina and anionic resin. If you have total arsenic present in your well water, you may also want to test for arsenic speciation at the State Hygienic Laboratory. The speciation of arsenic determines how easily it can be removed, and what will be the most effective treatment option.

Because flood water is contaminated with microorganisms that can cause disease, you should not drink the water from a well that has been flooded. Obtain water from a known safe public water supply or buy bottled water.  Wait until the flood waters recede, then contact your local county health department or certified well driller/pump installer for well shock-chlorination guidance. Perform this procedure (include flushing the well) before testing for bacteria (total coliform and E.coli) to determine if the water is now safe to drink. Shallow wells (less than 100 feet deep) may become contaminated from nearby flooding and should also be tested even if the well head was not submerged.  

Directions for collecting a sample for coliform bacteria and nitrates are included in the collection kit, along with specially prepared sterile bottles. Please follow the instructions carefully; it is easy to contaminate the sample with coliform bacteria using improper sample collection techniques. Please review the Drinking Water Collection Instructions for collecting a sample and the How to collect a drinking water sample video for guidance. 

The white powder is a chlorine-neutralizing chemical since some well water is chlorinated. Neutralizing any chlorine is necessary to obtain a valid coliform test. The chemical will not interfere with the coliform analysis even if chlorine is not present. However, this chemical can interfere with the nitrate test so a different sampling bottle  is needed  for this test which does NOT contain this agent. 

Where the sample is collected depends on the purpose for sampling. In general, the sample should be collected from the tap most frequently used for drinking water.  

If you are troubleshooting a coliform bacteria problem, you may need to collect numerous samples at strategic locations in your system as outlined in the coliform action response flowchart. Sampling locations may include various areas of the distribution system. These include near the well, at the connections from the well and at points before and after water treatment devices. This approach helps determine the source of the coliform bacteria problem so that appropriate remedial action can be taken.. 

No. The coliform and nitrate bottles are specially prepared for this testing. You must use the container supplied by the laboratory for the purpose intended.

No. The State Hygienic Laboratory can test for a variety of organic, inorganic, radiological and microbiological contaminants in drinking water. Each contaminant will require its own type of container, sample volume or preservative. The laboratory can help determine what tests are necessary based on your circumstances and needs.  

Requesting that your coliform result be reported in numbers (called Most-Probable- Number or MPN) is usually not necessary if you are collecting only one sample and you just want to know if your water is safe to drink. If you are troubleshooting a coliform problem and collecting numerous samples to pinpoint the problem, numbers may be helpful in that situation. Because of the uneven distribution of bacteria in a water system, the most probable number is only a semi-quantitative estimate of the number of bacteria in the water sample. You can only compare the numbers in ballpark terms; for example, total coliform MPN results of 20 and 40 are considered similar for bacteria testing. 

The sooner you can get the samples to the laboratory, the more accurate the test results will be. The required time between collection and receipt at the laboratory is 48 hours, so mail or ship samples the same day of collection to avoid delay. Avoid shipping samples on Friday, during the weekend, and prior to major holidays. 

Yes, sampling kits for coliforms and nitrate can be sent outside of Iowa. However, the sample must be received by the laboratory within 48 hours of sample collection.

If you live within the city limits, you probably receive your water from the city public water supply that is routinely tested by the water department for many parameters, including total coliform bacteria and nitrate. It is usually not necessary for private individuals to test this water. If you have concerns about the city’s water quality, we encourage you to consult your city water department or the Iowa Department of Natural Resources Field Offices.