The original plan to clean both the Water storage tank as well as the Detention tank during the previous boil order were unable to be completed due to further inspection of the Detention tank and more work needing to be done as well as a safety hatch cut into the side of the tank.
The water in Tiskilwa is high in iron and hydrogen sulfate. The Village utilizes a detention tank, that was constructed in 2010, at our water treatment plant to help clean the water. Water from the well is pumped to the top of the aerator and falls through the media where it is formed into a thin film on the surfaces of the media and where air is blown in from the bottom and makes contact with the film of water oxidizing the iron and stripping the hydrogen sulfate. The oxidized iron forms a precipitate and settles out in the detention tank. The water with the precipitated iron then moves through the sand and gravel pressure filters where the iron particles are filtered out in the media and clear water is then disinfected and sent to distribution.
The aeration media used in the tank are sections of pvc piping and can after time get caked with iron particles and become plugged and ineffective in the removal process. Iron also settles out to some extent in the detention tank and since iron is corrosive, as the coating system wears or any minor imperfections exist the iron attacks and the steel substrate begins to rust and fail. Keeping the media clean to do its job and periodic inspections to maintain the coating system intact would keep the treatment system working for many years. It is recommended to perform cleaning and preventative maintenance on this tank every 3-5 years. Since its installation it has never been cleaned or maintenance performed on it.
Once the tank was taken offline and drained there were many issues that were found. The aerator motor and fan were broken and not performing so there was no air going into the system to have any impact on the treatment of the water. The aerator nozzles were plugged with iron sludge, this is a tray that is designed to disperse water evenly across the pipes through holes. With the holes being plugged this caused raw well water to overflow the tray and deposit iron sludge on the pipes throughout the aerator chamber. The inside of the tank also had rust along the sides of the walls that needed to be sandblasted and cleaned properly and then painted.
Currently the aerator motor and assembly have been disassembled and replacement parts have been ordered. The interior has been cleaned of iron deposits. The piping will be cleaned or new piping installed. Sand blasting of the tank interior is nearly completed and painting is to follow. Allowing for paint cure time and replacement materials to arrive, reassembly of the tank and aerator is set for next Wednesday (5/29). Once the tank is reassembled, samples will have to pass testing before being put online. The exterior of the tank will also be cleaned and painted during this time as well.
The tank is currently isolated from the Village water supply, residents may experience some slight discoloration during this time. We apologize for the late notice on the work being performed and for any inconvenience this may have caused. We are working hard to try and resolve the issues and get the tank back to proper working condition. Thank you for your understanding.