Biological water treatment effective in Saddle Lake
Three transparent pipes connected to a network of hoses and gauges stretch from the floor to the 14-foot ceiling in a back room of the Saddle Lake water treatment plant. Water burbles through the pipes, mixing with a material that looks like black sand.
The particles are actually expanded clay aggregates that provide the surface needed for water-cleaning bacteria to live on. The bacteria remove nutrients and energy that could sustain disease-carrying microbes.
This integrated biological treatment component of Saddle Lake’s pilot project is a pre-treatment of the water so it can pass through a reverse osmosis membrane.
Hans Peterson, the scientist who designed the system, explains that manufacturers of RO membranes only guarantee their product if the water passing through it contains less than three milligrams of organics per litre. Saddle Lake has between 20 and 25 milligrams of organics per litre.
“First we have to get rid of all the particles. Once that’s done, there’s no problem with reverse osmosis,” said Peterson.
In reverse osmosis, water passes through a membrane, leaving viruses, protozoa, parasites and organic material on the waste side, and clean water on the other side.
Peterson explains this system removes organics, while treatments like ozonation in St. Paul’s water treatment plant kill the organisms. However, he says that if any nutrients aren’t destroyed, they remain in the water and can be food for slow-growing organisms.
In a few weeks, the Saddle Lake pilot project will be testing membranes to find out which works best under the conditions at the