How does disinfection of drinking water relate to a culture of health:
In Colorado, all public drinking water systems are required to have continuous chemical disinfection, except for a few rare systems that meet strict standards to retain disinfection waivers and hand-pumped wells at campgrounds. Most folks understand that surface water sources used for drinking water are filtered and disinfected to remove and kill harmful organisms such as Giardia lamblia or Cryptosporidium. However, some may question the need to disinfect groundwater and spring sources. Why? Perhaps they believe that a groundwater source or a spring must be pure and free of harmful organisms by nature.
News Flash! Springs and groundwater can be contaminated with viruses and bacteria from any number of sources - from animal waste, septic systems, from the influence of a stream just across the road, from a dead animal 100 yards upstream, and on and on. Even if the water from the well or spring is not contaminated, contamination can enter the distribution system due to line breaks, leaks in pipelines, low pressure events, backflow events, or storage tank contamination, just to name a few. Yuck!
Additionally, there are regions in Colorado where nitrate, arsenic, uranium and other acute or chronic contaminants are known to occur naturally in groundwater. Thus, it would be a mistake to assume that it’s safe to consume untreated water from a well or a spring. Arsenic and E. coli are “natural” but they can also be harmful or even deadly.
Some common examples of unprotected openings are inadequately protected access hatches, overflow pipes and air vents at storage tanks as well as unprotected well caps (check for holes or cracks in electrical conduits and vents where critters could enter).
The photos below show an unprotected opening into a storage tank (left) and a well cap with unprotected openings (right).
Multiple Lines of Defense:
Disinfection of drinking water supplies effectively inactivates bacteria and viruses. Continuous disinfection of drinking water sources is one of the best lines of defense in the multiple barrier approach to providing safe drinking water. Even if water from a groundwater source meets safe drinking water standards, unprotected openings can allow contamination to enter storage tanks, wells, spring boxes or distribution systems. Frequently, unprotected openings and sanitary defects are found at storage tanks and wells by Field Service Section staff during sanitary surveys.
Disinfection with chlorine or chloramines provides a persistent disinfectant residual. Maintaining a sufficient disinfectant residual throughout the distribution system is an important second line of defense against harmful organisms that can unknowingly enter a water system at unprotected openings.
The photos below show a storage tank with significant deficiencies.
Positive total coliform (TC) samples were collected from the distribution system of a previously unregistered community water system in Costilla County, indicating contamination in the water system. Upon investigation it was found that the system was using two wells which were not being properly disinfected. In addition, unprotected openings into the supplier’s wells and storage tanks were found during a sanitary survey. Although the exact source of the contamination was not determined, it is noteworthy that the supplier’s TC samples came back clean after the supplier began disinfecting the system with chlorine.
The photo to the right is a close-up of a significant deficiency - the tank’s overflow pipe is unprotected.
Conclusion:
Lack of appropriate disinfection can lead to positive bacteria (TC) samples in the distribution system, which points to a source of bacteriological contamination and a pathway for contamination to enter the water. Chemical disinfection is a critical part of the multiple barrier approach to providing safe drinking water and is a safe and effective way of protecting our communities and promoting a culture of health.
The photo below demonstrates another significant deficiency - the tank has an inadequately protected access hatch with debris inside the tank.
Guidance & Resources:
- Quick guide: Disinfectant residual and
- Quick guide: Minimum disinfection for groundwater
- Additional information about disinfection is available at the division's Revised Total Coliform Website
- Please feel free to reach out to the field services section at cdphe_wqcd_fss_questions@state.co.us with any related questions.
