Marana Water News: Chlorine and Coliforms - Water Quality Testing

Water quality is one of the most vital parts of the job here at Marana Water. Our Water Quality staff work each day to ensure that the water delivered to our customers is safe to drink at all times.

Marana Water's water quality inspector in the field testing the water system.

Marana Water's water quality inspector in the field testing the water system.

As you can imagine, there is a lot of testing involved to check that water is safe for customers. Established in 1974, and amended in 1996, the Safe Drinking Water Act under the Environmental Protection Agency (EPA) establishes the allowable levels of elements in the drinking water. Approximately 90% of Americans are served by a public water system similar to Marana Water. The guidelines from the EPA require public water systems to test to be sure that the water system is not being contaminated by bacteriological sources, specifically Total Coliforms.

Close up of total coliform bacteria

Close up of total coliform bacteria

Total Coliforms are used as an indicator of fecal contamination from animals and humans. These tests are scheduled to be completed monthly throughout the water system. Each sample is sent to the lab where a "present" or "absent" result can occur. Absent means no total coliform was identified in the sample, while present would indicate a positive sample. Should there ever be a "present" result, Marana Water has plans in place to conduct a second test, notify the public, and determine if the result was a sampling error or there is a defect in the system. Be sure to sign up for notifications from Marana Water by clicking here to keep up to date with all Marana Water news by clicking here.

In order to safeguard against a potential total coliform result, Marana Water provides minimal treatment to the water system. Chlorine is added to protect against bacterial contamination. Water can come from a variety of sources such as lakes, rivers, and wells. Water from these sources can be contaminated with microbes that can make people sick. Marana Water uses 100% groundwater, which is less susceptible to contamination, the chlorine is an added precaution to protect public heath. Chlorine kills many microbes that cause waterborne diseases like cholera, dysentery, and typhoid fever. It was first introduced to a public water system in 1908, and since has been considered a major public health achievement. Tests are also done for chlorine to be sure there are safe levels. These tests are called chlorine residuals. Some amount of chlorine is expected and necessary to keep the water safe. Chlorine residual tests are done throughout the system on a weekly rotation.

Example of a sample bottle used for testing for total coliforms

Example of a sample bottle used for testing for total coliforms

All other elements that require testing are done on individual schedules with the Arizona Department of Environmental Quality (ADEQ). Tests for synthetic organic compounds (SOCs), inorganic compounds (IOCs), volatile organic compounds (VOCs), radiochemicals (RADs), lead and copper, disinfection by-products (DPBs), and microbial contaminants. The staff even perform tests to show the water hardness. In the next few weeks customers should receive a report in the mail outlining the testing results for that water system. Be sure to check back to Marana News for more information on these reports. Marana Water works closely with this department to plan all necessary testing and reporting. For more information on water quality information, check out the this page of the website.