Treatment plant upgrades had been anticipated for years
Warren City Council approved a financing package for upgrades to wastewater treatment facilities Monday, but what does the project encompass?
The city’s present facilities include a return activated sludge plant, built in 1956. An upgrade done in 1972 added secondary biological treatment equipment and work done in 1982 added two aerobic digester tanks.
Essentially, the current plant operates by aerating waste sludge in a tank or basin to develop a biological solution which reduces biodegradable organic content in wastewater. The sludge in the liquid is then allowed to settle and liquid portions of the solution are passed on for further treatment. A portion of the remaining “activated”, or biologically impregnated, sludge is sent back to the aeration area to serve as a “seed” in development of the biological solution in further incoming wastewater. Excess sludge is removed from the treatment process to keep wastewater solution levels balanced.
City Director of Public Works Mike Holtz noted that, while some upgrade work has been done since, parts of the plant date to original construction.
“We’ve gotten a lot of use out of it,” Holtz said.
As part of the upcoming project, the majority of the plant, with the exception of a few digester and storage tanks, will be demolished.
In place of the old system, the city will be installing an oxidation ditch plant.
While an oxidation ditch system still utilizes activated sludge to reduce biodegradable organics, it uses a circular channel rather than a basin or tank for aeration and provides better treatment of sludge through extended aeration times. Extended aeration time allows a greater variety of microorganisms to develop in the biological solution and eat the sewage contents. Greater diversity of microorganisms in turn, mean less of the original input material ends up as waste sludge.
Oxidation ditch systems are also able to handle variations in sewage flow more readily than tank systems, a feature Holtz said the city took into consideration when choosing a design.
According to Holtz, the city is permitted to allow combined sewer overflows in times of increased flow through the system, such as when there is heavy rainfall. This means that during high-flow periods when wastewater exceeds system capacity, some discharge can be made directly into the Allegheny River. However, the Pennsylvania Department of Environmental Protection is now encouraging wastewater systems to limit combined sewer overflow events as much as possible.
According to Holtz, daily flow rates vary between approximately 1 million gallons on an especially dry, summer day and can reach up to 5 or 6 million gallons during a rainy, spring day.
“Back in the 50s, that was how they did it,” Holtz said. “The rules have changed. That’s one of the reasons we’re doing the project.
The other is because it’s old. The equipment is tired. Some of it’s from the 50s. Some of the electric is that old.”
“It’s a much needed project,” City Manager Nancy Freenock said. “I’m happy the state is partnering with the city to do this.”
The project will encompass a new headworks/control building as well. the headworks and accompanying pump system are used to raise wastewater to a level at which passage through the treatment plant can be accomplished by gravity flow rather than pumping.
The project will also see the installation of a sludge dewatering system. At present, the city contracts the process out.
“We’re looking to save a few bucks by doing it in house,” Holtz said. “Also, we can do it on our schedule rather than the contractors.”
The city’s pump stations on Clark and Pine Streets will also be seeing an upgrade.
“We’re basically gutting them and installing bigger pumps,” according to Holtz. “Roughly 70 percent of the sewage gets transported across the Allegheny River to be treated. We’ll also be replacing the force mains that run under the river with bigger pipes to handle the increased flow. That’s an additional few million dollar construction project.”
Project work is anticipated to take three years. During the first approximately two years, Holtz said work would focus on the treatment plant itself, with pump station work to follow once the plant his capable of handling a higher capacity.
The project will affect sewage bills, but, according to Holtz, it already has.
“The city, over the last eight to ten years, has been raising sewer rates in anticipation of needing to fund this project,” Holtz pointed out. “Getting a new sewage project is something that’s been talked about for 15-plus years. The city has really been very proactive.”
The previous rate hikes, Holtz said, will alleviate the sting of a sudden, sharp increase. He said the city plans to continue the incremental raises of 8 to 10 percent in 2014 and 2015.
“The first loan payment isn’t for a few years yet. We’ll then be taking a look in 2015 or 2016 at what we need to make this work,” Holtz added,
He noted a rate increase of up to 30 percent could be in store when loan payments begin, far less than the 60 or 80 percent increase which would have been needed had the city not stretched the increases over time.
After total increases, Holtz estimated a family of three, using approximately 4,000 gallons of water per-month, “will be paying around 40 bucks a month.”
Holtz noted the system serves residents of Pleasant, Glade and Conewango Townships in addition to city residents.