You may hear press accounts about an incident in Spencer, Massachusetts today where apparently too much of a water treatment chemical, sodium hydroxide, was added to the water system. Spencer is not part of the MWRA water system.

MWRA does not use sodium hydroxide to raise the pH of its water. MWRA raises pH and adjusts alkalinity at its John J. Carroll Water Treatment Plant in Marlborough by addition of sodium carbonate, a dry chemical, using weigh feeders that continuously monitor the amount of chemical being applied.

The system is further backed up with redundant on-line pH analyzers.  These analyzers tie back to a continuously staffed control room with two licensed water treatment operators.  If the chemical feed system malfunctioned, the operators would take the malfunctioning unit off line and place a back-up unit into service.

In addition to the process monitors, pH is also monitored at the point of entry into the MWRA distribution system.

Other water treatment chemicals used at the John J. Carroll water treatment plant have similar process controls and monitors.

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