 Last week, when waste treatment manager Bob Tackett offered a tour
of the waste treatment facility, some of the first questions to be
answered involved the rubicon.
By definition, the Rubicon is a small river in Italy that marks
the ancient boundary between Italy and Cisalpine Gaul. It is also
used as a term to mark a point of no return, as in once crossed, one
can never go back.
For the city, the definition fits, in that the rubicon is an
underground, man-made stream that catches waste and storm water and
delivers it to the waste treatment plant.
While severe storms and other elements can cause sewage to "back
up," for the most part, once waste enters the rubicon, there is no
point of return; everything goes south to the waste treatment plant.
The underground stream surfaces just to the north of the plant,
near the railroad viaduct on South to West Kickapoo. It continues
under the road and onto plant property, thus beginning the process
of waste treatment.
The rubicon is part of the city's combined sewer system. What
goes into the underground stream is raw sewage from toilet flushing,
dirty water from showers, sinks, dishwashers and washing machines as
well as runoff from city streets when it rains.
This spring the area has seen a lot of rain, but Tackett
explained that rain isn't always a bad thing. Naturally too much
rain can cause overflows, but a lack of rain can also cause more
incidents of odor, as sewage is not diluted along the way with storm
runoff and comes above ground at the plant in a more concentrated
form.
The cleaning process for sewage begins in a concrete pit called
the headworks. The large, deep pit has two levels. When needed,
workers can take stairs down to the floor area. To one side of that
space, the pit is deeper and waste passes through the pit on its way
to the next process. Above the deepest part of the pit where the
waste flows, there are two float arms, built by the plant crew, that
prevent waste from rising too high and covering the floor area.
After the headworks, the sewage passes through a trash collection
unit. This unit literally removes the garbage from the sewage. As
Tackett led the tour, he pointed out pieces of plastic and other
trash dropping out of a spout and into a dumpster. This is the stuff
that so many people toss out their windows as they are driving down
the street, or trash that gets away from the trash can and goes
traveling with the wind until it falls into the storm sewer.
Tackett explained that if these pieces of trash enter into the
pumps that are used throughout the plant, it would cause serious
damage, so the first step has to be to remove the garbage.
Tackett said that treating sewage, by and large, is a natural
microbial process that allows solids to separate from liquid and
gives the good bugs a chance to eat the bad bugs.
In the process the only chemical used is chlorine, with a
chemical composition comparable to bleach, and that is the last step
before water is released into Salt Creek.
From the headworks and trash collector, waste passes through a
blower building, where air is infused into the water to assist in
the growth of good microbial "bugs."
It then goes to a bank of concrete pits called aeration tanks.
Tackett explained that in this area, if all is going well, the
murky, grayish-black liquid will take on the color of chocolate
milk.
Leaving the aeration tanks, the waste then travels to the belt
filter press. Here the solids or sludge in the waste are filtered
out and the excess moisture removed.
When this process is completed, a solid waste product is left
behind. At the back of the plant is an open but roofed shed where
the sludge is stored
Tackett said the sludge is safe to use in much the same way
livestock manures are used as fertilizer for fields. He noted that a
few farmers in the area take the sludge product after it is dried
out and spread it on their fields. However, he also noted that there
are those who are wary of it, so even though it is a free product to
them, not everyone is anxious to take it.
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The final location of the waste before passing into Salt Creek is
the round clarifier ponds, where by now the product is all liquid.
At the ponds, Tackett pointed out two different pieces of
equipment that were fabricated at the plant. Both serve the same
purpose of moving on the surface of the water and collecting the
algae that form on the top.
Tackett said that right now they are testing both pieces to
determine which one works better. One is like a scraper blade that
travels around the outside edge of the pond collecting the algae,
and the other is a sweeper arm that rotates from the center to the
outside edge of the pond.
The final step to the waste treatment process is the addition of
the chlorine. Water moves out of the clarifiers and is treated with
the bleach-like compound, then exits the plant; going into Salt
Creek.
It goes out via a pit very similar to the headworks, but with one
major exception. The water is so crystal clear that it can hardly be
seen.
The oldest part of the Lincoln sewer plant was built in 1936, and
today that first building houses the laboratory. Inside, daily
testing is done on the wastewater, checking for chlorine levels, e.
coli and several other compounds. Even when water looks clear, it
can still hold harmful bacteria if not properly treated. Tackett
said the lab runs daily testing on water leaving the plant to assure
that it is safe for the environment.
Another part of the tour Tackett provided was a brief explanation
of the monstrous truck that is used to clean the sewers throughout
the city and the camera system that is used to snake down into sewer
lines and view what they look like inside.
The large truck is used to vacuum out and flush the sewers.
Tackett said there is a regular rotation of cleaning in the city,
and some may recall seeing it take place this spring at the
intersection of Keokuk and North Logan.
In addition, there are smaller, pull-behind rigs that are used
for tight areas, such as when crews have to work in a narrow
alleyway.
Also during the tour, Tackett showed the collection area for the
state-mandated combined sewer overflow testing. CSO monitoring has
been ordered by the Illinois Environmental Protection Agency because
the oldest part of the city sewer system is a combined collection of
storm water and raw sewage.
The city has to complete the CSO testing this year, and the
results will determine whether or not the city is going to have to
invest money in modifications at the plant.
Tackett said that based on his experience with waste treatment
plants, he thinks the system is in pretty good shape, and in a
worst-case scenario the EPA would require that the city enlarge the
overflow collection area.
[By NILA SMITH]
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