COMBATING COLIFORM

A small system was dealing with some serious water quality issues when they reached out to Rural Water Association of Utah (RWAU) Circuit Rider Jake Wood. Samples taken from the system tested positive for coliform bacteria multiple times. This bacteria indicates potentially harmful bacteria may also be present. Jake has also had run-ins with Coliform Bacteria in the past. One of these experiences was featured in the January Newsletter.

January Newsletter Article

As we’ve seen time and again, the best way to tackle any problem is to start with a proactive plan. Following the creation of a plan, a date was set for maintenance in hopes of clearing up the bacteriological samples.
In order to begin draining and cleaning the storage tank, the tank needed to be taken offline. Once offline, the entire distribution system would then lose pressure, due to the systems hydraulics. The customers receiving water were going to experience an interruption in service as soon as the tank was taken offline. It was imperative for the operators in the system to get the word out before they took the tank offline. According to plan, the system operator handed out notices to all the customers several days before the work would begin on the system, explaining what work was being done and why, along with an approximation of how long their water service would be interrupted. Cases of bottled water were also made available to all customers that requested them. They had also prepared boil advisory notices to hand out. These were hand-delivered to all customers the day the work was done just before the distribution system was re-pressurized. The operator explained to the customers that the advisory would stay in effect until two separate rounds of clean bacteriological samples were reported.

After the storage tank was drained and cleaned, the interior structure was inspected and documented. The operators then began filling the tank along with a dosage of high test hypochlorite that, once full, would meet a dose of close to 4.0 parts per million (ppm). The tank was filled and left used until the required contact time was met. This allowed the chlorine to remain in contact with any remaining bacteria that may be present and to ensure the storage tank was completely sanitized. They then flushed the water mains until a chlorine residual was detected. At that point, they moved to the next hydrant, repeating the process until the ends of the system were reached and a residual was detected. This left a residual close to 2.0 ppm in the systems distribution lines. Several bacteriological samples were then taken throughout the system and were delivered to the local health department. The chlorine was allowed to dissipate until there was no longer detectable chlorine residuals. The second group of bacteriological samples were then taken. After all the samples were reported to be negative of bacteria, the boil advisory was lifted. It was agreed upon that this process would be made part of the systems annual maintenance program to ensure that the customers water quality would be safe and sanitary throughout the years to come and that the systems approval rating with the State would not be jeopardized in the future.