A look at the sewage treatment plant’s pending problems

Jan 16, 2024

As Dartmouth navigates school budget struggles and unforeseen capital needs, several big-ticket projects still loom on the horizon — namely, a new middle school and major renovations to the sewage treatment plant. 

Both projects are years down the line, but Department of Public Works officials say the treatment plant needs some immediate attention to handle the growing community. 

Specifically, plant manager Mike Arnold said the department needs an estimated $3 million interim upgrade to its aeration tanks, which will allow the plant to treat more wastewater in Dartmouth. 

The interim upgrade will buy the town a few more years to sort out an overall, long-term renovation plan, Arnold said. 

“I really believe the plant right now is taking everything we have,” Arnold said. “If we don’t do this interim upgrade, we’re going to have to worry about people flushing toilets in five years.”

The plant is currently able to process about 7,000 pounds of “biochemical oxygen demand.” BOD refers to the amount of oxygen required for bacteria to break down organic matter, such as poop.

Wastewater treatment plants essentially use BOD as a measure of how polluted the water is with organic matter — too much BOD means oxygen levels will dip, bacteria will die, and the waste will not organically decompose. At the moment, BOD levels are Arnold’s primary concern — the poor quality of incoming waste rather than the sheer quantity. 

New housing developments, in particular, present problems for the sewage treatment plant, Arnold said, as residents flush much more fecal waste and food waste than any commercial facility. 

And while Arnold said he can appreciate the intentions of modern, water-saving buildings, less water down the drain means a higher density of waste, meaning more BOD. 

The interim upgrade would pay for new “blowers,” which pump oxygen into the tanks, and new diffusers, which spread the oxygen out. These renovations would allow the plant to put its fourth, currently redundant tank online. 

With the interim plan, Arnold said the plant could sustain another 1,500 to 2,000 pounds of BOD, which will buy them “five years or more,” providing time to design a full renovation plan for the facility. 

The design for the interim upgrade, which was approved by Town Meeting in 2018 and 2019, is already underway. Part of the funding for the construction costs were approved at the 2020 Town Meeting, Barber said, but the cost of construction projects continues to increase. 

The Department of Public Works did already receive a large chunk of change from the American Rescue Plan Act — close to $6.7 million in total. However, Barber said the design for the interim upgrade will likely not be ready by the time the ARPA funding needs to be used — “But never say never,” he said. 

Instead, the funding was split between the drinking water and wastewater treatment operations, Barber said, including a “clear well” project meant to improve the town’s water supply quality. Other ARPA upgrades include “blowers” attached to the composting facility, a new compost press and ultraviolet light bulbs that treat the wastewater. 

Even after the interim project is designed and constructed, Arnold and Barber said the plant will require renovations across-the-board — from the electrical infrastructure to the aging pumps that the plant depends on. Some of the pumps require that external fan blows onto it to avoid overheating. 

“The entire operation of this facility is dependent on these 32-year-old pumps continuing to run,” Arnold said. “I’m not crying wolf, this is real.”

At the moment, Arnold said the plant is running very well and meeting all state regulations, but he sees the “warning signs” for the future. 

“I’m not going to say gloom and doom, but something has to be done to get us to the full plan,” Arnold said. 

The town’s newly formed long range capital planning committee is looking at ways to alleviate the impact that a full renovation plan would have on sewer ratepayers, but no decisions or recommendations have been made. 

In the meantime, Arnold and Barber said homeowners can help out by throwing away grease instead of putting it down the drain and never flushing bathroom wipes, even if they’re labeled “flushable” — the wipes are not biodegradable, they said, and one wipe can unravel and stop the plant’s pumps from working correctly.