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Water vs. wallets; Assabet River facilities find a way.

Byline: Lisa Eckelbecker



While the Upper Blackstone Water Pollution Abatement District fights federal orders to wring more phosphorus from treated wastewater, four smaller treatment plants stretching from Westboro to Maynard are successfully meeting similar requirements with the water they send to the Assabet River.

Facilities in Westboro, Marlboro, Hudson and Maynard have spent millions of dollars on different technologies, and their experience offers a glimpse into what it takes to reduce pollutants flowing into troubled rivers.

"Communities really deserve congratulations for making these investments in their wastewater treatment, which is really an investment in the future of the rivers," said Alison Field-Juma, executive director of OARS, the Organization for the Assabet, Sudbury and Concord Rivers.

A product of human waste, phosphorus feeds plants in slow waterways. Microbes that feed on the plants suck oxygen out of the water, and without oxygen, fish die. As recently as September, the Upper Blackstone's treated water contained 0.2 to 0.8 milligrams of phosphorus per liter of water. The U.S. Environmental Protection Agency has ordered the Upper Blackstone to bring phosphorus levels down to 0.1 milligrams per liter of water.

Wastewater treatment plants on the Assabet River are attaining that level by adding chemicals and thickeners to treated water. The agents bind to phosphorus, creating flocculation particles, or floc, big enough to settle out or skim away.

In Westboro near the Assabet River's headwaters, the Westboro Wastewater Treatment Facility started operating an ActiFlo system from Veolia Environnement SA's water division in March as part of a $50 million plant upgrade.

Plant operators add an iron salt known as ferric chloride to wastewater that has already gone through screening, settling and biological treatment. Then the system injects ultrafine sand that binds to floc and drags it to the bottom of a tube-lined tank. The sand then wrests away from the particles and gets reused, while the system removes the floc as sludge.

The Marlboro Westerly Waste Treatment Works uses a Blue PRO system that was installed as part of a $32 million upgrade. The system from Blue Water Technologies Inc. uses cone-shaped sand filters to remove floc from water. Pumps then wash the floc off the sand.

"Since we started it up in January, we're below our 0.1 milligram per liter average," said Harry P. Butland Jr., chief operator of the plant.

Hudson's wastewater plant installed an AquaDAF system by Suez Environnement's Degremont business in 2009 as part of a $16 million upgrade. The AquaDAF process allows floc to float to the surface of a tank of water, where a long piece of metal skims the fluffy brown material into a trough for removal as sludge.

"There are electrical costs, but the advantage of it is I'm using about the same number of chemicals I was before the permit changed," said Mark L. Concheri, the plant's chief operator.

Maynard's Wastewater Treatment Facility uses a CoMag system from Cambridge Water Technology, now part of Siemens AG, that was installed as part of an $11.4 million upgrade in March 2011. The system mixes treated wastewater with a thickener called polyaluminum chloride, which binds to phosphorus, and then adds a heavy form of iron called magnetite. Particles settle as sludge to the bottom of a tank. The sludge goes to a magnetic drum that draws off the magnetite for reuse.

"My rolling average this year, I believe, is 0.07 (milligrams of phosphorus per liter of treated water), but I've had results show 0.05," said David A. Simmons, project manager with engineering company Weston & Sampson Inc., the contractor that runs the facility. "I'm researching what can be used to give me less than 0.05."

Assabet River plants are not a perfect model for the much bigger Upper Blackstone facility. They handle smaller volumes of wastewater, and some do not treat stormwater. The Assabet River is also shorter than the Blackstone River and flows through a less urbanized area.

In at least one way, the rivers are similar. It's not clear how upgrades at facilities will impact either waterway.

Study of the Assabet River has shown "the main source of phosphorus is from the wastewater treatment plants, and that phosphorus is the main cause of the problem," said Ms. Field-Juma of OARS. "What isn't clear is when you lower the phosphorus concentration, at what point is it no longer a cause?"


CUTLINE: (1) Christopher W. Pratt holds an Imhoff settling cone to show the layers in a sludge/sand mixture sample at the Westboro Wastewater Treatment Plant. (2) Mark Concheri, chief operator at the Hudson Wastewater Treatment Facility, walks over the intermediate clarifer pool. (MAP) Wastewater treatment plants and the Assabet River

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Publication:Telegram & Gazette (Worcester, MA)
Date:Dec 6, 2012
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