The City of Grand Forks has a problem at its sewage treatment lagoons that needs attention. Sludge has built up in the large lagoon over many years to the point that it is now above the water line. It must be removed if the lagoon is to function efficiently. The question is: How and at what cost?
Sludge buildup in sewage lagoons occurs unless the concentration of enzymes is sufficient to turn the waste into water. Every Canadian community with a wastewater system that operates lagoons like those that serve Grand Forks will eventually have to dispose of sludge.
The very existence of the sludge is an indication that the system is not functioning at full efficiency. More effluent is entering the ponds than the existing enzymes can digest.
If the lagoons are to be restored to full operating capacity the sludge must be removed. The removal can either be done mechanically with an excavator or by natural means using an organic procedure. City council and staff must decide soon on which method to use.
Wastewater from households, industrial operations and the storm water system enters the sewage lagoons as a toxic mix of human waste, chemicals, pharmaceuticals, heavy metals and solids. When storm water from streets and roads is added to the mix becomes a potent product that should not be disposed of in a landfill or on agricultural land because the toxic materials could leach into the groundwater.
Over a couple decades, enzymes in the lagoons have digested the sludge through a process called anaerobic digestion. Bacteria consume the organic matter and break it into water and carbon dioxide. The process does not require oxygen.
Grand Forks city staff and council have been seeking a solution for handling the sludge and they have asked Urban Systems, a company based in Kelowna, to recommend a solution with costs. (Urban Systems has been retained by the city for a number of years to provide engineering expertise on infrastructure issues.)
In the fall of 2014, an engineer from Urban Systems addressed city council about the removal of the sludge from the largest of the sewage lagoons. He suggested that the material be removed, left to dry on site for a period of time and then be trucked to a suitable site where it would be spread as fertilizer. At the time, land adjacent to the airstrip was being considered as the disposal site.
The dried sludge cannot be disposed of at the RDKB landfill on Granby Road because of the toxins it contains.
A cost effective method for the removal of the sludge that has been proven to be effective in communities around the world is available to the city. However, because it is an organic approach, there is skepticism that it will not remove the sludge.
Measured quantities of enzymes that thrive on the organic material in the sewage can be added to lagoons on a regular schedule and in the right concentrations they will digest the solid material that can eventually become a source of odours and pollution.
The use of enzymes to digest sludge is a cost effective way of maintaining healthy sewage lagoons and there is no residue to take care of. Adding the right bacteria in proper proportions to the pond environment enhances the natural performance of the lagoons and that is the goal.
If the City of Grand Forks is going to meet government standards for the release of water from its lagoons into the Kettle River, it must clean up the system soon.
Should the more cost effective natural method be tried? Why not?
There is nothing to lose in doing so.