LAWTON –The Notice of Violation that the state Department of Environmental Quality issued April 18 against Lawton’s wastewater treatment plant was blamed on a cascade of problems and an industrial user’s discharge of effluent “in excess of typical concentrations.”
The City of Lawton “has been working diligently… over the past three years” to correct “issues” with the 47-year-old wastewater treatment plant, Public Utilities Director Rusty Whisenhunt wrote in a May 13 letter to David Mercer in the Municipal Wastewater Enforcement Section of the DEQ’s Water Quality Division.
Those measures included an equipment replacement project that was completed in November 2022 and a construction project currently underway, Whisenhunt said. Those two projects have involved an investment of more than $100 million “dedicated to theWWTP.”
Lawton’s sewage treatment plant discharges treated wastewater into Nine Mile Creek, which merges with East Cache Creek, which in turn empties into the Red River. The discharge rate from theWWTP is “anywhere from 14 million to 16 million gallons per day,” the city’s communications manager told Southwest Ledger.
What is emitted from the treatment plant is commonly referred to as “gray water:” wastewater from which biowaste has been removed but is nevertheless unfit to drink. Treated effluent discharged into Nine Mile Creek is appropriately labeled as gray water.
The DEQ issued a Notice of Violation against the City on April 18 because of numerous “apparent violations” of the state Environmental Quality Code by the wastewater treatment plant.
The DEQ reported receiving a complaint Jan. 18 that Nine Mile Creek “had the odor of sewage.”
Jeff Lawler, environmental programs specialist for DEQ, investigated the site and observed that theWWTP effluent “had the gray appearance and odor of sewage,” which indicated that the treatment facility was providing “only partial secondary biological treatment.”
Lawler visited Nine Mile Creek again on Feb. 26 and “again observed that the discharge” from theWWTP was “gray in color and had the odor of sewage.”
When he went to the site again on April 11, Lawler reported the wastewater was again gray “but had no sewage odor.”
Perhaps that could be explained, at least in part, by the City of Lawton having raised the dam gate at Lake Lawtonka spillway three inches on April 8, City Manager John Ratliff reported. “That significantly increased the flow and decreased the stagnation throughout the creek system.”
From Feb. 26 to April 10, the DEQ received six more complaints “regarding the ability of the WWTP to provide sufficient wastewater treatment and/or the adversely impacted state of Nine Mile Creek and/or East Cache Creek.” The complaints were made about locations in both Comanche and Cotton counties, wrote Shellie R. Chard, director of the DEQ’s Water Quality Division.
A consent order the DEQ issued to the City of Lawton in May 2021 is one of two that are still active. The 2021 mandate requires the city to “take steps to make improvements/repairs to theWWTP to bring it into compliance with its Oklahoma Pollution Discharge Elimination System permit requirements.”
The city’s monthly wastewater discharge monitoring reports are to include effluent monitoring results for ammonia, biochemical oxygen demand, E. coli bacteria concentrations, total residual chlorine, and total suspended solids sampling.
In the April 18 notice the city was cited for 19 infractions that occurred between December 2023 and February 2024. Those violations involved ammonia concentrations, carbonaceous biochemical oxygen demand, total suspended solids and dissolved oxygen.
The notice informed municipal officials that the City of Lawton had been discharging pollutants “in excess of your OPDES permit limits…” Ammonia concentrations were three to five times allowable limits; CBOD, as much as five and seven times greater than permissible limits; TSS, 9.8 times higher than acceptable limits.
‘Significant challenges’ atWWTP The “unanticipated equipment failures” in January “while the plant was in a vulnerable state” because of the construction project, and the industrial user’s effluent that exceeds “typical concentrations,” created “significant treatment challenges over the last several months” that resulted in “the non-compliance” outlined in the NOV, Whisenhunt informed Mercer.
• Aeration basin blowers at the WWTP are “obsolete and no longer reliably serviced by the manufacturer.” After the blowers failed, the aeration basins “turned septic, thus compromising the performance of the activated sludge process.”
The manufacturer’s inability to keep the machines operational led to a decision to replace three unserviceable blowers with four new ones, at a cost of $1 million.
• Also during Phase 1, each trickling filter “is to be taken offline for cleaning and rehabilitation.” After one of the filters was taken out of service, the three remaining filters “struggled due to age and obsolescence,” Whisenhunt lamented.
When they’re operating “effectively,” the trickling filters reduce biochemical oxygen demand upstream of the aeration basin. “Their reduced performance compounded the issues experienced with the blower failure in the aeration basin,” he explained.
• One of Lawton’s “significant industrial users,” Republic Paperboard, is experiencing failures at its pretreatment WWTP, Whisenhunt wrote. Consequently, the BOD concentration at Lawton’s WWTP “has been more than four times the permitted concentration typically received” from Republic.
On Oct. 31, 2023, the DEQ issued a Notice of Violation to Republic Paperboard for exceeding biochemical oxygen demand and total suspended solids “from Oct. 17, 2023, onward.”
The City of Lawton sent a letter to Republic on Dec. 7, 2023, stating that the notice would “remain open until consistent compliance has been achieved.” BOD results for the last seven months have been elevated.
Because of these issues, the aeration basin at theWWTP “has not been able to maintain an adequate mixed liquor concentration to treat sufficiently,” Whisenhunt wrote. The combination of increased BOD loading and a compromised activated sludge process “is the greatest contributor to the recent non-compliance,” he said. “The quality of the sludge from the aeration basin upset the clarifiers, further resulting in a solids loading that was non-compliant.”
Another problem, according to a city report, is that sludge from Lawton’s Southeast Water Treatment Plant is causing “overloading” at the wastewater treatment plant.
In addition, “numerous equipment procurement delays have presented themselves” during Phase 1 of theWWTP renovation. Temporary solutions City staff initiated several temporary solutions, Whisenhunt reported.
• After an aeration blower failed in December, “We brought in two rental blowers in January at a cost of $22,000 per month until new blowers can be installed,” said Caitlin Gatlin, the city’s communications manager. The four new, permanent blowers have been ordered “and are expected to be installed and commissioned” by August 2025, Whisenhunt said.
• City staff made temporary modifications to improve operation of the trickling filters.
• Temporary chlorination and dechlorination “have been mobilized to bolster the ultraviolet disinfection system.
• The aeration basins have been “reseeded.”
In sewage treatment, the aeration basin is used to break down organic matter into simple elements like nitrogen gas and carbon through aeration of the wastewater to promote microbial growth.
On Feb. 16, city staff “augmented” the basins with 30 bags of supplementary bio-seed.
From March 28 through April 4, trucks containing 6,000 gallons of activated sludge from Fort Sill’s WWTP were sent to Lawton’s WWTP aeration basins. And since April 15, Whisenhunt wrote, city staff have transported three 6,000-gallon trucks loaded with waste activated sludge five days per week from Duncan’s WWTP to Lawton’s, to reseed the aeration basins.
City officials have requested “an in-person meeting” with DEQ officials “to discuss actions taken to date, the path forward on the Notice of Violation items,” and an extension requested on the Phase 1 project.