Engineering report recommends new $17.5 million wastewater treatment plant
An engineering report is recommending replacement of the city of Whitefish’s existing wastewater treatment plant with a $17.5 million new treatment plant that would comply with state requirements.
Public Works Director Craig Workman said the city is looking to construct a new wastewater treatment plant to meet new state standards issued in the city’s latest discharge permit.
“New requirements for removal of ammonia, nitrogen and phosphorous were included in this permit,” he said. “The city’s lagoon system was originally constructed in 1979, and has served the residents well. However, the existing treatment facility has reached the end of its useful design life and cannot be made to meet the state new standards without major reconstruction.”
City Council last month accepted the preliminary engineering report for the wastewater plant design and authorized its submittal to the Montana Department of Environmental Quality. The city anticipates comments from the state on the plan by the end of the year.
DEQ in 2012 issued the city of Whitefish an administrative order on consent as the result of several violations of the city’s wastewater discharge permit. Last year the order was updated to incorporate a compliance plan detailing the completion dates that must be met in order to bring the treatment plant up to the new standards by November 2021.
Anderson-Montgomery Consulting Engineers was hired by the city to conduct an assessment of the area, an evaluation of the existing treatment plant and analysis of treatment alternatives.
The preliminary engineering report looked at three treatment alternatives — Biolac lagoon treatment system, oxidation ditch, sequencing batch reactor.
The recommended project includes replacement of the existing treatment facility with the sequencing batch reactor.
“We looked at a number of factors for these systems and the sequencing batch reactor came out on top,” Workman said. “The system will be capable of removing ammonia, nitrogen and phosphorous to fully comply with the requirements of the current discharge permit. The system will also be capable of meeting anticipated standards — we anticipate future standards to get more rigid. It is a technology that will keep current with standards.”
The capital cost for the sequencing batch reactor is $15.9 million, the Biolac system is $15.9 million and the oxidation ditch is $21 million.
The city estimates including construction, engineering, administration costs and a 15 percent contingency for the selected sequencing batch reactor system will bring the project to a total of $17.5 million. Annual costs for operating the facility is estimated at $780,000, which is roughly $440,000 more than current operation costs.
The sequencing batch reactor is an activated sludge process designed to treat wastewater in batches.
“It is a process that is designed to run with variable conditions like we have in Whitefish with seasonal variable flow,” Workman said.
The Biolac lagoon treatment system consists of a lagoon-based sludge treatment system that uses bacteria, aeration and other processes to treat wastewater. The oxidation ditch uses a variation of the activated sludge process that uses aeration through mixing of the wastewater to treat it.
Residents on Whitefish’s southeast side this summer complained about foul odors wafting from the city’s plant. Neighbors said the smell was bad enough to force them to stay inside their homes with the windows shut.
At the time the city said the odors were being caused by unusually warm spring temperatures and the city hired an expert to troubleshoot the situation.
Workman said when the city moves from its current lagoon system to the new sequencing batch reactor system it should be able to better control odors.
“There is many more areas where we can control odor,” he said. “In an ambient system it is essential at the whim of the weather, but with the sequencing batch reactor there is a variety of techniques we can use to control odors. Some of the areas of the new plant where the more odoriferous process take place would be covered, while right now those are open.”
The city has been working for months to prepare for the construction of a new wastewater treatment pant. A timeline for the compliance plan sets a deadline of February 2018 for design plans to be submitted to the state. Construction of a new facility is estimated to be complete in 2021.
To fund the upgrades, the city is applying for grants and loans from the Department of Natural Resources and Conservation Renewable Resources Grant and Loan program, the Montana Department of Commerce Treasure State Endowment Program and the USDA Rural Development grant program. The rural development grant could provide up to 30 percent of the total cost of the project. The city may also have to increase wastewater rates to help pay for the new plant.