Over 55 municipalities located in Massachusetts fall under the jurisdiction of the Massachusetts Water Resources Authority (MWRA) for industrial wastewater discharge. Among the various requirements, the MWRA prohibits wastewater with a pH lower than 5.5 or higher than 12 from being discharged to the sewer system.
Neutralizing the pH is typically needed to meet these discharge requirements. This is most often accomplished using a pH neutralization system which treats highly acidic or alkaline wastewater through the addition of sulfuric acid or caustic sodium hydroxide to adjust the pH to an acceptable MWRA value.
Any discharge outside of the permissible pH range (5.5 – 12) is considered to be an excursion if it is an unintentional and temporary incident. Excursions below a pH of 5.5 are permitted only if all of the following are true:
- The total time during which the pH values are below 5.5 shall not exceed seven hours in any calendar month.
- No individual excursion from the range of required pH values shall exceed 60 minutes.
- The excursion may not be below a pH of 5.
If these criteria are not met, then the MWRA must be immediately notified of any discharge outside of the acceptable pH range by calling the MWRA emergency phone number. The notification should include the location, date, and time of the discharge as well as it’s characteristics and volume. Any corrective actions taken should also be communicated.
In addition, within 15 calendar days, a written notification must be submitted to the MWRA describing the causes of the discharge and the measures being taken to prevent it from recurring. The report must include the following items:
- A description of the discharge, and the type, concentration, and volume.
- A statement of the duration of noncompliance caused by the accidental discharge.
- An explanation of all steps taken to reduce, eliminate, and prevent recurrence of the accidental discharge.
It’s important to note that pH excursions may not be related to the facility putting highly acidic or basic material into their process wastewater as part of laboratory or other operations. Excursions can be the result of a pH neutralization system malfunction. For example, a faulty sensor or pump could allow the system to flood with acid or caustic, and issues with the agitator shaft may cause an uneven distribution of the neutralization chemicals in the tank.
When these issues arise, they can be highly concerning, but we are here to help navigate responding to the excursion and communicating with the MWRA. Please contact us.
This blog was written by Beth Graham, Director of Quality, Research, and Training