To the editor:
As an outlying coastal community, Gloucester has a unique challenge to modernize infrastructure and plan for the future while adapting to the challenges of fishing, tourism, businesses, residents, and industry to provide compliant and sustainable services at the best value.
In regard to recent water quality complaints, they largely relate to the record warm 2011-2012 winter, and will be explained. First, a few details of the water treatment process must be summarized to explain water quality complaints and actions.
Chlorine is used for primary disinfection at the two main water treatment plants (WTPs), Babson and West Gloucester and the smaller limited capacity Klondike water treatment plant. Following the 2009 boil order, immediate emergency upgrades were performed in 2010 to the WTPs and other components of the public water system that continue and will be complete in 2013 that consist of upgrades at WTPs, storage tanks, pumping stations, and water mains.
This includes the July 2010 switch of secondary water distribution system disinfection from chlorine alone to a combination of chlorine and ammonia that creates monochloramine, a milder disinfectant than chlorine alone. Monochloramine and chlorine alone are the two main accepted federal Environmental Protection Agency and state Department of Environmental Protection secondary disinfection practices that communities are required to maintain in the distribution system that brings water to homes and businesses.
Monochloramine produces fewer disinfection byproducts and maintains a longer lasting residual disinfectant level than chlorine alone in the water distribution system.
The winter of 2011-2012 was a record warm winter and most of the city’s drinking water reservoirs did not ice over, warmed up far earlier than normal following most winter, and were warmer than usual through summer months. In 2012, the water distribution system experienced July and August water temperatures starting in May, nearly two months early. Warmer water is more chemically and biologically active.
With elevated distribution system water temperatures and increased water age in the fall following reduction from peak summer water demand, nitrifying bacteria can reduce the ammonia in the monochloramine (a process called nitrification), which in turn reduces the concentration of the monochloramine and its disinfection properties.
When nitrification occurs it makes the water smell musty, which is a water quality concern as it does not taste good. The danger can be from the loss of disinfection properties which can lead to an increase coliform bacteria levels, a health concern that led to the 2009 boil order.
In the fall of 2012 we started to see evidence of nitrification at the fringes of the water distribution system where we have the most aged water in terms of the time since leaving the WTPs.
This was most evident at Eastern Point, which has a large proportion of summer residents and where water demand dramatically decreases in the fall. We started receiving numerous complaints of musty smelling water from Eastern Point and other outer areas of the city.
We hoped that cooler water temperatures would help control the nitrification that the city was experiencing, which it did not, so we switched to the use of chlorine alone in the distribution system just after Thanksgiving 2012.
The switch was effective in controlling nitrification and stopped consumer complaints of musty smelling water. We converted back to monochloramine as the distribution system disinfectant in April 2013. Throughout this process, we were in contact with MassDEP.
The MWRA and other communities also experienced nitrification in the fall of 2012. What we learned from Taunton, which has been using monochloramine for distribution system disinfection since 2006, is that when its reservoir water temperatures reaches 70 degrees or higher, officials routinely incorporate a switch to chlorine and then back to monochloramine with their fall water main flushing program.
With monochloramine the majority of the chlorine is combined with ammonia so there is less uncombined or “free chlorine” available, so generally there is little to no chlorine taste to the water since the end of April.
If you have water related concerns please contact the DPW’s Water Compliance Office at 978-281-9792.
LAWRENCE A. DURKIN
City of Gloucester