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Wastewater Treatment Plant cares for our dirty water

by Robin Benson — Commentary
| September 10, 2013 1:28 PM

The following is an overview of the process of the water flow from residents’ homes and businesses to the Wastewater Treatment Plant and its process before re-entering the environment via the Kootenai River. The intent is to communicate information and communicate to city residents this vital part of your city infrastructure.

The City of Libby Wastewater Treatment Plant was constructed in 1985 and was designed to treat an average flow of 511,000 gallons per day. Today, the average flow is 330,000 gallons per day.  Wastewater collection and treatment and disposal are regulated by the Montana Department of Environmental Quality (MDEQ) and the U.S. Environmental Protection Agency (EPA). A preliminary engineering report was done in 2010, which evaluates the wastewater collection and treatment system for the City of Libby. The report assessed the current condition, performance and capacity of facilities and established a recommended course of action and design for wastewater improvements to meet the needs of the city, and the requirements of state and federal regulations, for a 20-year planning period.

Libby maintains approximately 13 miles of sewer pipes and three lift stations, commonly called the collection system. The purpose of the lift stations is to change the elevation of the flow. The collection system and treatment plant consists of pump stations, headworks, oxidation ditch, two secondary clarifiers, and UV disinfection.  

In 2010, Libby upgraded from chlorine disinfection to UV disinfection. This was a state-mandated change to the treatment facility. A new dewatering sludge press system was also constructed at this time to address immediate concerns.  The  process is the same as nature uses but speeded up and controlled to be as effective as scientifically possible. Every stage is carefully monitored.  

The collection system carries the wastewater from homes and businesses to the treatment facility.  When the wastewater arrives at the treatment facility it flows through bar screens to remove large debris such as sticks, tree roots, rocks and rags to stop damage to equipment. 

Next, the water slows as it passes through grit tanks. Here sand and gravel settles to the bottom where it can be scraped out and sent to the landfill. It then flows through concrete channels into the oxidation ditch, where there is an abundance of lively bacteria and air is added to provide a favorable environment for the organisms. These micro-organisms are essential in digesting the dissolved material in the water using it as food for growth and reproduction. The micro-organisms and solids are then removed by settling in clarifiers and it is here the bacteria clump together to form a thick layer of sludge, which is easily separated from the clear water. 

The sludge is removed from the system and sent to the digester to be further processed. From there, the sludge goes to the screw press to be dewatered and sent to the landfill.  

The Wastewater Treatment Plant  processes approximately 56 metric tons of sludge a year. When the clear water leaves the clarifier, it goes to the contact basin where it passes through the ultraviolet lights for disinfection, before it is discharged to the Kootenai River.  

The Libby Wastewater Treatment Plant discharges about a quarter-million gallons of cleaned water a day to the river. Complex computer systems monitor this entire process.  Reports are sent monthly to state and federal agencies to make sure the treatment plant is in compliance with National Pollution and Discharge Elimination Standards. 

All of Libby sends its wastewater to the plant. Everything a resident flushes or send down the drain from your homes and businesses is processed. On average, approximately 70 to 150 gallons per person contributes each day to the wastewater flow.  This does not include added flow from rain water and storm drains.  

The work at the Wastewater Treatment Plant is continuous non-stop (24/7, 365 days a year) even when maintenance is required.   

One important note for the public is medicines and toxic chemicals should never be flushed or sent down a drain. This includes needles which pose a potentially unsafe environment to the employees.  Paper towels, baby wipes and rags are not biodegradable and cause undue wear on the pumps, increasing maintenance and time. Proper disposal of these items is the public’s responsibility.  

The employees at the Wastewater Treatment Plant welcome questions and would be happy to provide a tour of the facility.

(Robin Benson is a City Councilwoman who sits on the Water and Sewer Committee.)