Phosphate removal – a summary of the 5 years operation of the CoMag phosphate removal plant at Billerica, Massachusetts, USA

Kalmes, J. and Garabedian, D., Billerica Wastewater Treatment Plant, USA



The Billerica CoMag plant in the USA was installed 5 years ago to meet the more stringent consents for Phosphate discharge into the local water course, the River Concord. The innovative CoMag technology enhances conventional coagulation by utilising Magnetite as a ballast, which increases the weight of the flocs and this results in significantly improved effluent quality, in particular TSS and Phosphate. This paper will discuss why P removal technology was required at this location, the operational performance of the CoMag process and will continue by discussing the challenges of introducing then, an untried technology to an established Waste Water Treatment Works and how such challenges were solved.


The wastewater treatment plant (WWTP) in the town of Billerica, which is located 20 miles northwest of the city of Boston, was originally built in 1966. It has been upgraded several times, once in 1975 and then again in 1990. It was the 1990 upgrade that brought the plant to its current capacity of 21.25 ML/d (5.5 MGD). The treated wastewater is discharged into the Concord River. The discharge is regulated by National Pollutant Discharge Elimination System (NPDES) Permit. This Permit is generally updated every 5 years. In 2005 the Permit was revised to include lower limits for Phosphorus and Aluminium. Following notification of these revised permit limits, the Billerica waste water treatment plant had four years to develop a plan to reduce the phosphorus limits. The WWTP had an original summertime limit (April 1 to October 31) of 0.75 mg/l that was being reduced to less than 0.2 mg/l. The new wintertime (November 1 to March 31) limit was changing from a status of “report” to a reduced limit of 1.0 mg/l. In addition to this, the Town had been told to expect even more stringent limits by the Massachusetts Department of Environmental Protection (MADEP).


Keywords:  Billerica, Ballasted Clarification, CoMag, Evoqua, Phosphate, Wastewater

Please fill in your details to download the proceedings

For more information about how Aqua Enviro
can help you, contact us...

Aqua Enviro Ltd

T: 0113 8730728


c/o Tidal Accounting, HQ Offices, Radley House, Richardshaw Road, Leeds, West Yorkshire, LS28 6LE

  • By submitting this form, you agree that we may use the data you provide to contact you with information related to your request/submission and other relevant Aqua Enviro services. You can unsubscribe from Aqua Enviro marketing emails at any time by clicking the unsubscribe link in the email. To learn more, see our Privacy Policy