The Waste Water Treatment Plant (WWTP) of the City of Washington Court House is at the approximate mid-point of its three-year construction plan. The plant has been operating and will continue to operate while undergoing construction.
The challenge of rebuilding and bringing the WWTP up to Environmental Protection Agency (EPA) standards, according to Washington C.H. City Manager Joe Denen, is the WWTP must continue to operate throughout the construction process.
The engineering firm handling the project is Jacobs while the primary contractor for construction is Dugan and Meyers.
“The sewage from the community comes in from two influent sewers,” said Jacobs project manager Melanie Gamez. “One comes in from the west, one comes from the east, and they’re going to flow into the new influent pump station.”
Currently, the new influent pump station is in the process of having the lower level built which is a deep, rectangular structure built into the ground near Paint Creek. Once complete, Gamez explained it will be a single-story building with a basement that contains channels for the sewage and screens to screen out larger, solid items.
“If barbie doll gets flushed, we get it out at that point,” said Denen.
“It’s an influent pump station, so then it will get pumped up to the grit tanks and flows by gravity through the system—through the waste water treatment plant,” said Gamez.
What this means, is a person will not have to be inside the influent station to physically do the work. This differs from what it once was as Gamez explained “in the old days” people would have to use a rake to clean off the screens. With the newer equipment, the large screened items gets mechanically removed, cleaned and sent to the landfill.
The difficult part of being by the lake, according to Denen and Gamez, is with pressure from the ground water they had to consider how to balance that pressure/force to keep the building from rising—as it is like a boat in this situation.
Following the influent pump station, the waste water would go through aeration. Basically, there are long, rectangular structures that are reminiscent of a pool with walls separating lanes. Around these aeration tanks are metal rails blocking a person from accidentally walking or falling into them.
Air is blown from a building and through the tanks.
“It’s a bunch of biology. So, the micro-organisms that live in (the aeration tanks) break down the waste water, break down the solids,” said Gamez.
Denen explained, “if you didn’t pump the air, you’d limit the population of the micro-organisms you want to encourage. So you pump air into the sewage and it supplies them plenty of oxygen, so their population goes up and it breaks down the sewage. What you are trying to get to is that you separate water from all the stuff you don’t want in it.”
Following aeration, waste water goes to settlement tanks, also called secondary clarifiers. The settlement tanks are cylindrical structures. There are currently two in operation although there will be three.
According to www.aesarabia.com/clarifiers-systems/, clarifiers use gravity settling. Heavier, suspended solids settle to the bottom and are then “swept” to a center well by scraper blades for sludge collection.
To assist with getting rid of scum material that does not settle, a skimmer arm rotates slowly around the top of the water and pushes scum into a skimmer box for collection.
At this point the solids and water go to different locations.
The solids are pumped out to go to “digestion” which includes further aeration to assist with breaking it down. Four digestion tanks are a part of the plant—a primary digester, a secondary digester, and two storage tanks for the digested sludge.
Once the sludge is at the thickness it needs to be, the sludge goes to the new dewatering building. Within the dewatering building is a belt-filter press.
The purpose of the press is to remove or “squeeze” fluids further as the sludge is still mostly a liquid. The dry solids, now called “cake,” are moved by a conveyor belt and stored in a new Cake Storage Building. Although the storage building is open-air, there is a canopy over the building to keep precipitation out of the cake.
Following proper legal procedures, the cake can be used by local farmers as fertilizer.
Water that was removed during the pressing of the sludge goes back to the beginning of the system and starts over again.
Going back to the settling tank, water that was separated from the solids by settling and skimming has to remain for a certain amount of time within the settling tank. The design of weirs in the tank help to establish that detention time.
A weir, according to multiple sources, is used to raise water levels or divert water flow.
According to www.owp.csus.edu/glossary, “many circular clarifiers have a circular weir within the outside edge of the clarifier. All the water leaving the clarifier flows over this weir.”
Once the water, now called effluent, flows over the weirs, it then flows to a different area for disinfection—the Ultraviolet (UV) facility.
“This is the last spot the water hits before it goes out to Paint Creek,” said Gamez. “From May 1st to September 30th, they’re required to chlorinate the water. Right now they use chlorine gas. We’re switching to UV—ultraviolet—which provides a safe type of disinfection for the wastewater, but it’s much safer for the community and for the waste water treatment staff.”
Gamez further explained that the updated plant will be able to remove more phosphorus from the water than before. Phosphorus lowers the amount of dissolved oxygen in water. Basically, having less dissolved oxygen in water is harmful for aquatic life within that water. With the amount of dissolved oxygen able to be higher, water quality should be higher.
Another improvement, per EPA requirements, is new generators have been installed that will be able to run the entire plant. Prior to this addition, if power was to go out, something would need to be worked out with the utility company so the plant could continue to operate and to keep the micro-organisms alive.
With the updated facility, there will now be computer systems to help staff monitor the plant.
Wet weather tanks can be used when there is a big rain event as the capacity the plant needs to treat “goes up significantly,” according to Gamez. The updated plant can treat 15.9 million gallons a day. During a big rain event, when those wet weather tanks are in use, the plant will be able to treat 22.9 million gallons per day.
The old plant could treat approximately 12 million gallons before running into problems, according to assistant superintendent John Woodrow.
When asked what it is like working with construction happening, Woodrow said, “Well, right now it’s interesting. We have good operators here that’s been around for a while, and they’re able to work adjustments around all of it.”
Gamez said, “this upgrade, it touches on almost every aspect of the plant and will give Washington Court House a reliable waste water treatment plant for 20-plus years to come.”
More information will be shared on the WWTP as the project continues.
Reach journalist Jennifer Woods at 740-313-0355.