Global: Why some test kits show high nitrate readings

Global Water officials provided Maricopa customers with a possible explanation of why some residents using water quality test kits are finding high nitrate levels in the city’s water system. 

The water company began investigating the issue after a local business posted a Facebook message Friday that claimed the city’s water contained nitrate levels that exceeded a federal limit. The message on MegaAquarium’s Facebook page stated that after conducting water quality tests, results showed nitrate levels at 40 parts per million – above the 10 ppm limit set by the Environmental Protection Agency.

According to the EPA, drinking water that contains nitrate levels exceeding the limit can cause serious illness for infants below the age of 6 months, and could lead to death.

A message from another Facebook user was subsequently posted Friday on the “Maricopa buy sell trade mobile” page, which has more than 1,500 members. The posting had a photo showing the results from a test kit, which also appeared to indicate an excess of nitrates. Both postings received scores of comments, and many local residents wrote about their own test results on the social media site.

Global officials responded to customers' concerns and conducted testing Friday that showed a nitrate level of 6.6 ppm.

In a recently issued customer notice, Global officials provided a possible explanation for why Maricopa customers testing the water from the local utility, Santa Cruz Water Company, are seeing high nitrate levels.

The notice explains the EPA’s 10 ppm limit is for nitrate-nitrogen. However, some aquarium test kits measure nitrate ion, or “total nitrate,” and will give results 4 to 5 times higher.

A description of a total nitrate test kit on the website MarineDepot.com explains that other kits that measure nitrate-nitrogen give readings 4.4 times less.  

The EPA’s limit for total nitrate is set at 45 ppm.

“When reading test results for water quality, be sure to note whether test kits are for (nitrate-nitrogen) or total nitrate,” the notice reads.

Nitrate in drinking water is caused by a number of sources, including runoff from fertilizer use, septic tank leaks, sewage and erosion of natural deposits, according to Global Water’s website. A water system that exceeds 10 ppm is required to issue a public notice within 24 hours. The site also states that if a public water system exceeds 5 ppm, it “is required to increase their monitoring.”

The customer notice also states that Santa Cruz Water Company “is required to test for (nitrogen-nitrate) annually, but conducts more frequent tests to ensure (nitrogen-nitrate) levels are maintained below 10 ppm.”
 

The local utility uses a third-party laboratory to conduct testing and reports the results to the Arizona Department of Environmental Quality monthly.

According to an annual report on Global Water’s website, the lowest level of nitrate-nitrogen reported in 2012 was 4.9 ppm, and the highest was 6.2 ppm. Since 2009, levels have not exceeded 8 ppm.

An administrator of the MegaAquarium Facebook page wrote another post Sunday that said “both my house faucet and the store faucet just now and both locations tested NEGATIVE for Nitrates!!”

The post goes on to state: “I’m guessing both suppliers acted promptly to all our backlash … Thank you All, without your independent testing they would od (sic) kept telling me it was impossible to have Nitrates that high. Makes you wonder why the sudden spike and how was it corrected so … quickly?”

The notice from Global Water said the company contacted the business owner of MegaAquarium. The company also alerted ADEQ and the Arizona Corporation Commission.

In comments on the social media site over the weekend, many Facebook users made mention of the city’s water rates – an issue that remains contentious as Global Water nears the end of rate case with the ACC.

The city, Global Water and other parties involved in the case reached an agreement this month about phasing in higher rates for Maricopa customers in the years to come.

Global Water asks customers with questions or concerns about water quality to call the company at 520-568-4452.

Check back this week on InMaricopa.com for follow-up stories about water quality.