Drinking Water Nutrification Surveillance Program

State: FL Type: Model Practice Year: 2004

Nitrification is not addressed by the current Safe Drinking Water Act regulations, but it can significantly deteriorate water quality in a public drinking water distribution system. It is a two-step biological process that first converts ammonia to nitrite, and then converts nitrite to nitrate. The second step generally does not occur or occurs very slowly in drinking water, resulting in a buildup of nitrite. Nitrite can accumulate in the drinking water and exceed the maximum allowable contaminant level. Nitrite in drinking water poses an acute health concern, causing serious illness and sometimes death in infants less than six months old from methemoglobinemia (blue-baby syndrome). Nitrification can also cause a loss of the disinfectant residual in the water, leading to other bacteriological problems. The American Water Works Association estimates that nitrification occurs to some degree in two-thirds of the public drinking water systems that practice chloramination disinfection. The number of water systems practicing chloramination is expected to dramatically increase in the near future due to new disinfection by-product regulations. Lee County’s nitrification surveillance practice easily and rapidly monitors for, detects, and confirms nitrification occurrence in a drinking water distribution system, thus allowing a public water utility to execute timely countermeasures. Although nitrification countermeasures are known and available, an easy, fast, and inexpensive early warning system was sorely lacking. This practice fills that void. The cost to implement this practice is insignificant because the labor is attached to the routine microbiological sampling programs that all public water utilities are already required to perform. The benefits of i this practice include protecting infants under six months old from methemoglobinemia and preventing consequential bacteriological problems.
Nitrification within a drinking water distribution system poses a public health threat that is not addressed by the current Safe Drinking Water Act regulations. Current regulations require water systems to sample for nitrite and nitrate only at the entry point to a water distribution system. The formation of nitrite or nitrate within the water distribution system will not be detected. The model practice will quickly and easily detect nitrification within a drinking water distribution system and provide an early warning to the water system so that the water system can carry out appropriate countermeasures before the nitrite level exceeds the maximum allowable contaminant level. Although nitrification countermeasures are known and available, an easy, fast, and inexpensive early warning was not in place until the inception of this program. Compliance with current regulations will not result in detection of nitrification within a water distribution system. The scientific literature contains recommendations that water systems can voluntarily implement to monitor for distribution system nitrification, but these recommendations normally involve using inconvenient, slow, or expensive techniques such as monitoring of heterotrophic bacterial populations throughout the water distribution system or developing an accurate nitrogen mass balance along with specific biological monitoring for ammonia-oxidizing bacteria and nitrite-oxidizing bacteria throughout the water distribution system. Lee County’s program can confirm or refute nitrification occurrence using an inexpensive (less than one dollar) one-minute field test in conjunction with the water system’s standard routine microbiological monitoring.
Agency Community RolesThe primary collaborative partners will be the public water utilities that practice chloramination disinfection. The local public health agency role can vary depending on the working relationship it has with the public water utilities. The practice is flexible along a wide continuum of shared roles. At one extreme, the local public health agency could simply share this model practice with the appropriate public water utilities and encourage them to adopt it or something similar. At the other extreme, the local public health agency could develop a working relationship with the public water utilities in which the local public health agency conducts all of the water system’s standard routine microbiological monitoring and implements this practice at the same time. The latter approach is the current one in Lee County. A local public health agency could also adopt some middle ground whereby the agency conducts periodic spot checks while encouraging the water utility to implement the model practice. Public water utilities normally want to do the right thing to protect the health, safety, and welfare of their customers. The key point is that the local public health agency should work with and educate the utility managers and operators and explain: What nitrification is, why it is important, and where and when it can occur.  How to detect and confirm nitrification occurrence.  How the utility can prevent and fix nitrification problems.  Once all the facts are on the table, the local public health agency and the utility can decide, on a case-by-case basis, the most efficient and effective way to monitor for nitrification and protect public health. There is ample scientific literature on nitrification (see below, under “replication”). Costs and ExpendituresThe only costs of this practice, over and above the costs of routine required microbiological monitoring, are the cost of the water quality test strips and the cost of occasional laboratory analyses for nitrite and nitrate. The program spends about $100 per year for water quality test strips, and about $100 per year for extra laboratory tests. Furthermore, additional staff time is negligible. ImplementationIn the community, the health department cultivated a working relationship with most of the public water utilities whereby the health department conducts all of the water system’s standard routine microbiological monitoring. The water utilities reimburse the health department for the cost of this service. It is standard procedure to conduct field tests for pH and total chlorine residual at the same time that routine microbiological water samples are collected. The health department trained field staff to watch for symptoms of nitrification, such as a sharp, unexpected decrease in total chlorine residual or an unexpected decrease in pH. If such symptoms are observed, then staff conducts a one-minute nitrate/nitrite field test using water quality test strips. If the test strip qualitatively confirms nitrification, then staff immediately notify the water utility so that they can 1) take countermeasures and 2) collect a water sample to obtain a certified laboratory analysis of nitrite and nitrate. The certified laboratory results are used to determine whether public notification is warranted.
In 2003, the program staff detected and confirmed two independent episodes of nitrification in the water distribution systems of two different water utilities. After confirmation of nitrification with the water quality test strips, certified laboratory analyses for nitrite showed a level of 0.4 mg/L in one case and 0.8 mg/L in the other case. The maximum safe allowable contaminant level for nitrite is 1 mg/L. Both incidences of nitrification in 2003 were detected, confirmed, and corrected, before exceeding the maximum safe allowable contaminant level. In the absence of the practice, the nitrification occurrences would not have been detected until they worsened and resulted in loss of disinfection, an increase in bacteria and nitrite levels possibly exceeding the maximum safe allowable contaminant level. Program staff monitored regularly and detected nitrification early. Early detection provided the water utilities with a greater number of control and countermeasure options. This practice is considered to be successful if it detects and confirms nitrification occurrence in a water distribution system. This program effectively, efficiently, quickly, and inexpensively accomplishes its goal of rapid detection and confirmation of nitrification occurrence within a public water system distribution system. Early detection allows water utilities to prevent significant deterioration of the water quality in their distribution systems. This practice can minimize or eliminate the risk that nitrite in drinking water might become a serious threat for infants less than six months old. It also reduces the risk of consequential bacteriological problems.
SustainabilityThe water system partners are very committed, and based on the local experience, they take nitrification very seriously. When nitrification is discovered, the water system partners take prompt and effective corrective action without hesitation. The cost of the practice is so low compared to the public health benefits that they do not foresee any reason to discontinue monitoring for nitrification. Lessons LearnedProgram staff learned to use the water quality tests strips only for the qualitative purpose of confirming the occurrence of nitrification, and not for determining quantitatively the actual level of nitrite or nitrate in the water. If the water quality test strip confirms the occurrence of nitrification, then a water sample for nitrite is collected and nitrate analyses by a certified laboratory. The certified laboratory result should be used to determine whether a public notice is warranted.  Key Elements ReplicationRead the available scientific literature on nitrification in water distribution systems to better understand the issue. A succinct publication is available on the web from the American Water Works Association Research Foundation at: