MERIDEN — Public utilities officials say the city’s ongoing efforts to reduce levels of phosphorus in treated wastewater before it is pumped into the Quinnipiac River have already delivered promising results.
Frank Russo, manager and chief operator of Meriden’s Water Pollution Control Facility on Evansville Avenue, and Public Utilities Director Richard Meskill on Thursday showed the Record-Journal the system now in place to filter out phosphorus and nitrogen from wastewater before it is treated and discharged into the river. That system has been operational since the fall of 2021.
It has already reduced the amount of phosphorus present in treated wastewater from previous levels of around 0.7 micrograms per liter, to 0.094 micrograms.
The computerized system, which pushes water through a series of filters, pipes and pumps, is housed in a brick building and a large rectangular concrete structure next to it. That concrete structure consists of 128 individual sand filter bowls, all of which use sand to filter out phosphorus that had been solidified with chemicals from the water during the overall treatment process before it is discharged into the river.
Russo in explaining the process of removing phosphorus often referred to the mineral as “phos.”
“And the dirty water with the phos comes in from the bottom,” Russo said. “And that water just works its way up and filters its way through the sand. As it goes up through the sand, because we’ve added that chemical that turns the phosphorus into solids, those particles get trapped in the sand. So the clean water comes out on the top and carries.”
That clean water is backwashed to get rid of the phosphorus particles and is returned to the head of the plant for more treatment, Russo explained.
Russo said the sand filtration system in Meriden is probably one of the largest in operation across New England.
Russo said Meriden has one of the strictest limits on phosphorus in the state. And wastewater isn’t the only source of phosphorus, which also can be found in rainwater and in fertilizers.
Russo said one of the main issues with phosphorus is that it helps to grow algae very quickly.
“One pound of phosphorus will help support the growth of 16 pounds of algae. That’s a problem in a river like the Quinnipiac,” Russo said.
When that algae starts to decay, that decay draws oxygen from the water, which Russo said can kill large populations of fish.
“That’s why you want to keep it out of there so you don’t grow all that algae and you don’t harm the river or the wildlife,” Russo said.
The project to reduce phosphorus from wastewater dovetailed with another project intended to prevent the discharge of untreated wastewater into the Quinnipiac River during significant, high rain weather events.
Officials said such storms may happen once or twice a year.
In 2018, the city received an administrative order issued by the U.S. Environmental Protection Agency, after the federal agency found the city non-compliant with its wastewater discharge permit. The EPA found that over a four-year span there had been eight instances when discharges of untreated sewage from the Harbor Brook Pump Station exceeded the limits the city is permitted to discharge by the agency and by the state Department of Energy and Environmental Protection.
So city officials embarked on a bond-funded project, which is also covered in part by state Clean Water Fund monies. The city issued a $50 million bond for the project. Now officials are seeking a $5.65 million change order to enable that project’s completion. The cost of the project has increased because of ongoing supply chain issues spurred by the COVID-19 pandemic, according to officials. The requested change order is scheduled to be taken up by the City Council’s Finance Committee.
To prevent wastewater discharges into the Quinnipiac, officials have devised a plan to divert water into two large concrete digesters located at the Evansville Avenue facility. They are capable of holding more than two million gallons of water.
Meskill, the public utilities director, said the plan is to try to capture water that accumulates during large rain events.
“The plant cannot necessarily handle all that flow, which is mostly rainwater,” Meskill said. But officials need to be cautious because that rainwater mixes with the wastewater in its collection system.
The plant’s design is to put a relief point in the piping allowing water that can’t flow into the plant to be directed into the digester. The plan also calls for the relining of pipes to reduce leaks both into and out of the system.
That project is still around 18 months from completion.
“We’re dealing with a very old system, which was first started in the 1800s,” Meskill said. “And because of the age of it, it has leaks in it. It’s not leaks necessarily out of the pipes, but water leaking into the pipes — groundwater and surface water. So during these big storm events you see very high flows that exceed the capacity of the plant to treat.
“So there’s been leaks there that allow this water to go out,” Meskill said. “The whole plan of this change order is to try to capture this water into storage tanks on site. The capacity of those tanks can hold quite a bit of water.”