September 30, 2010 at 9:14 a.m.
The Chisago Lakes Joint Sewage Treatment Commission (CLJSTC) recently approved construction of two small structures that will house filtration devices and ancillary equipment, and the commission is also sinking a small well near Hwy. 8 and County Road 36 so the new filter has water to operate.
People started complaining to the commission in 2006.
Sampling of odors showed high concentration of hydrogen sulfide. Whenever the lift station pumps activated, the stagnant material in the pipeline would be stirred-up and odors released to offend anybody nearby. Commuters stopped at the traffic light on Hwy. 8 near the Bonnie Glen part of town, could even catch a wiff.
The commission did attempt to alleviate odors over the last few years, especially at the Hwy. 8 site; but initially an activated carbon "scrubber" system proved to be insufficient and filters were being replaced too frequently. Subsequent use of a chemical additive costing about $12 per pound was not cost-effective.
The new approach requires the construction of buildings to house a bio-filter. This unit uses a media mixture to provide "habitat" for naturally occurring bacteria that remove the offending gasses. The biological unit requires a water supply to provide moisture and warmth to support its compost-like culture.
The odors develop from a three mile long forcemain carrying waste from the city of Wyoming to the highway corridor, that cuts off any interaction with air. CLJSTC engineers estimated 14 hours "detention time" of the sewer product, giving time for anaerobic bacteria to convert the sulfates in the wastewater to sulfides.
The Hidden Forest housing development, which is in Chisago City also contributes to the flow, so there was lengthy debate on how Chisago City and Wyoming would split the odor response costs. The other odor emitting site being addressed is near west Liberty Lane in Chisago City.