Tour Time

May 15, 2014

About the author: David Coppes is director of water works for the Massachusetts Water Resources Authority. Coppes can be reached at [email protected] or 508.424.3645. Elisabeth Lisican is managing editor of Water & Wastes Digest. Lisican can be reached at [email protected] or 847.391.1012.


The water supply for 42 communities in the metropolitan Boston area currently is treated at the Massachusetts Water Resources Authority’s  (MWRA) 405-million-gal-per-day (mgd) John J. Carroll Water Treatment Plant in Marlborough, about 25 miles west of Boston. The plant is one of the featured facility tours of AWWA ACE14. Here Managing Editor Elisabeth Lisican discusses the facility with David Coppes, director of water works for the MWRA. 

Elisabeth Lisican: What is this plant’s infrastructure? What makes it unique? 

David Coppes: It is the second-largest unfiltered treatment plant in the country. It uses four separate disinfection processes: ozonation, ultraviolet (UV), free chlorine and chloramines.

Lisican: Please provide a summary of this plant’s history. How was it funded?

Coppes: The plant was completed in July 2005 as part of an overall modernization of the MWRA’s water system, which also included a new 17.6-mile-deep rock tunnel and seven covered storage facilities. The initial cost of the ozone plant was $145 million, and the addition of UV was $32 million. These projects were funded through state revolving fund loans and municipal bonds, paid for by the ratepayers in the cities and towns that are served by the plant.

Lisican: What can visitors expect when they tour this facility?

Coppes: Visitors will be able to see the ozone generators used to turn pure oxygen into ozone. Ozone originally was used at the plant for regulatory compliance with a 3-log (99.9 %) inactivation of Giardia as well as a voluntary target of 2-log Cryptosporidium inactivation based on site-specific criteria. 

Ozone also was found to be extremely effective at improving the clarity and taste of the water. With the addition of UV disinfection, the plant now is able to meet the U.S. Environmental Protection Agency’s requirements for two primary disinfectants as well as the now mandatory 2-log inactivation of Cryptosporidium. The use of ozone upstream of UV increases the clarity and transmissivity of the water, increasing the cost-effectiveness of UV and decreasing total energy use.

Lisican: What changes or upgrades are ahead for this facility?

Coppes: In addition to the recently completed UV facility, MWRA is about to begin construction on a 240-mgd zero net energy backup raw water pumping station. The plant also hosts a solar field to reduce it use of electricity and improve its carbon footprint. 

Lisican: How does MWRA integrate public education and outreach into its operations?

Coppes: MWRA has a dedicated school education program that visits classrooms in the 61 cities and towns in its service area to teach kids about their role in the water cycle. This helps students see the links between their daily lives and important environmental issues like water conservation and pollution. 

Each year, MWRA hosts a poster, essay and video contest on current issues facing the water and sewer industry. Last year’s topic was “Bottled Water vs. Tap Water.” For this year, the topic is “It’s a Toilet, Not a Wastebasket,” aimed at raising awareness of the increasing number of wipes and other non-flushable items that have been clogging pipes and pumps across the country.

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