ITHACA, N.Y.—The Ithaca Area Wastewater Treatment Facility’s (IAWWTF) primary digester suffered severe damage in March of 2021 and the emergency funds to get it back online have proven to need another bump. The damage is more extensive than previously estimated, so another $1.15 million has been allocated for repairs on top of the $1.65 million granted in April.
The digester system is sort of gross, pretty cool, and plays a big part in keeping people’s water and sewer bills down.
Scott Gibson is the Acting Assistant Superintendent of Water & Sewer at the City of Ithaca. The facility has two digesters, one of which is out of commission. Gibson said that the Ithaca area facility is running at about half capacity right now. While the facility is still able to meet the needs of the communities it serves, it’s turning away outside waste that it normally can generate revenue off of.
Often that extra waste is runoff from landfills, which Gibson said turns into about $500,000 a year for the plant. That’s somewhere around half the annual revenue the facility takes in and uses to offset people’s utility bills.
The system will likely be back in full operation in February. That’s Gibson’s tentative guess, who said that this bad dream likely began with a blockage in the digester’s overflow pipe.
He told the City of Ithaca’s Common Council that $1.15M is the maximum estimate for the remaining work, and added that he’s hoping to use just half of that, “but we don’t want to come back to this body in case it’s not enough money.” The cost for repairing the digester is coming from the City as well as the Town of Ithaca and Dryden, all of which share use and ownership of the facility.
‘Turnin’ poop into gold’
The digester system at the IAWWTF is basically two large tanks with a series of specialized piping connecting them to the plant and each other.
Wastewater gets piped into the tanks, where it’s heated. To prevent too much from filling the tanks, an overflow pipe is in place to drain out excess wastewater. When this pipe was blocked in the facility’s primary digester, it caused liquid levels to surge.
At the IAWWTF, Gibson said the digester’s cover was busted open by about a foot and a half, and the tank’s anchor bolts, mounts and cement base were all damaged. The system’s sludge piping was damaged as well.
The primary digester’s overflow was likely blocked by some material that was never supposed to reach it. The screening system at the plant’s headworks was outdated until a few years ago, said Gibson, but the plant was able to invest in upgrading it’s screening system, and “grit” removal systems, which take out sand, rocks and dirt.
When things are running as designed in the digester system, the metabolic activity of anaerobic bacteria breaks down the waste inside the heated tanks.
During this process, solids separate from the wastewater and collect at the bottom of the tank; phosphorus and heavy metals get removed; and methane gas is produced from the waste in the digester. That gas is used to generate energy for the wastewater facility, saving big bucks on the cost of operations.
“We’re turnin’ poop into gold, we like to say,” said Gibson.
The sludge that collects at the bottom of the primary digester is normally passed through the facility’s 2nd digester for a rinse-and-repeat of the whole process, drawing out more waste and methane. But the facility is stuck using just one digester to do the job of two, meaning it has to buy more energy off the grid.
Repairs on the primary digester are going to be completed soon, said Gibson, but it’s been an arduous project. Gibson said the contractors who were hired to clean and repair the digester system ran into “excessive material” in the pipes, which was more than their equipment could handle. Contractors were apparently seeing their gear break, which slowed work down, and additional costs began piling up.
“Before we knew it the budget was getting eaten up pretty quickly,” Gibson said.
The new round of funds will go toward finishing repairs on the primary digester, and also cleaning the secondary digester. When the primary is operational, the secondary digester will go offline while crews work on it. Gibson said taking care of the second digester now, while crews are already at the facility, will save money in the long run. It’s also right about time for it to be cleaned too.
The recommended length of time for cleaning a digester is every 6 to 8 years. Gibson said that the wastewater treatment facility was almost at the 8 year mark from when it last had the digester system cleaned, and was getting ready to schedule the next cleaning when the disaster at the primary one happened back in March.
With the screening upgrades, Gibson assured that the facility should not see a repeat scenario. To his knowledge, only one other digester system in New York State has ever seen a similar disaster.