Wastewater System Infrastructure Improvements
The East Moline Regional Wastewater Treatment Plant serves five communities, East Moline, Silvis, Carbon Cliff, Hampton and Rapid City. The treatment design average flow (DAF) is 11.1 million gallons per day (MGD) and has a design maximum flow (DMF) of 27.8 MGD. The average flow for the last two years has been 3.5 MGD. Prior to that, the average flow has been 5.5 MGD. This reduction in flow can be attributed to a couple of different things; one – water conservation by residents; two – the closing of the Case IH plant. With the Case IH property now vacant we have the capacity to accommodate future development on this property as well as other new business, industry and residential grow with in the communities.
Operations of the wastewater plant revolve around treating waste solids and wastewater. The treatment plant is an activated sludge treatment plant, which means a bacterium is used to break down and reduce solids in the waste.
The last major equipment improvements at the wastewater treatment plant were completed in 1976, with some of the equipment dating back to the 1950's, the original construction of the plant. Equipment within a wastewater treatment facility has a design life of 25 years due to the environment in which the equipment operates. With equipment that is between 30 and 50 years old, this equipment is operating 5 to 25 years beyond its useful life, there have been many problems keeping the plant operational due to mechanical failures.
With this in mind, East Moline contracted with Howard R. Green Company to complete a comprehensive study of the wastewater system during the fall of 2005. During Howard R. Green's evaluation, East Moline received a notice of violation from the I-EPA for exceeding discharge limits due to operational problems caused by equipment failures.
(Hot button to HR Green's Report)
An I-EPA requirement for correcting this violation was a commitment to a plan of action for improvements at the treatment plant to insure discharge limits would not be exceeded in the future.
Improvements planned are to comply with I-EPA requirements, replacing mechanical equipment to protect the integrity of the treatment process. The first item that is being addressed is the bar screen.
The bar screen strains incoming flow to remove large debris that can cause other equipment failures. In March of 2006 during a high flow incident damaging the bar screen, causing a large opening in the screen and leaving the rest of the plant's mechanical equipment unprotected.
To improve the treatment processes a constant, steady flow is required. In order to achieve this, installation of a smaller pump is required along with improvements to the existing pumps, piping and replacement of check valves, which are failing.
At right, you can see the hole in a failed check valve in the main lift station after 50 years of wear.
Much of the mechanical equipment is inefficient, and obsolete; parts cannot be found to repair the equipment when breakdowns occur.
1955 era pump
The grit chambers remove grit from the influent flow to the treatment process. These were installed with the original treatment plant in the mid 1950's and require extensive labor and human contact with waste in addition to numerous mechanical failures.
Cleaning grit chambers
Improving the treatment process will require upgrades to the aeration basins. The aeration process introduces oxygen (air) to activate the biological process. As you can see from the picture below this basin is very turbulent with very large air bubbles. A more effective and efficient process is a fine bubbler system, which is required to meet EPA regulations.
Six clarifiers remove solids from the wastewater, the mechanical equipment on five the six are operating beyond their useful life. One clarifier has already failed, and required emergency repairs. The remaining clarifiers are operating on barrowed time. The bearings, bearing raceways, and gears are very worn and can fail at any time.
Mechanical equipment being installed in a clarifier during emergency repairs
Repair and replacement of the wastewater system infrastructure has been delay as long as possible. In order to insure discharge limits are maintained on a regular basis, the EPA is requiring improvements.
There is no option these improvements have to be done and need to be done in the immediate future. East Moline cannot wait any longer.
(Hot Button to Wastewater Collection System Improvements)