June 2018 Pipeline

weeks, the WWTP Operators continued
to pump out the trench on a regular
basis, as dewatering continued well
after the Lambourne crews had left.
What do we do with them now? Well,
as pointed out, they can be used again
with little prep work to remove more
sludge if desired. If left alone, and the
solids are allowed to dry, there are
different ways to dispose of the
material.
any seepage, a poly liner was put in place
under the Geotubes as they were
unrolled. A collection sump was dug at
the northeast corner of the laydown area
so that all decanted water could be
easily pumped back into the lagoon. It
had been determined during the initial
survey that the City would need 6
Geotubes, each 30m long x 11m in
diameter.
The Lambourne crew arrived on
September 18th and lowered the
dredge into the lagoon. Once all the
pipe connections had been made and
the polymer trailer was prepped,
pumping began on September 21st. It
was essential that the dredge not get
too close to the WAS (waste activated
sludge) line that runs out approximately
50 m into the lagoon. Damage to this
pipe could be disastrous in the ability to
pump the WAS to the lagoon at all. The
dredge ran along a cable secured on
both sides of the lagoon, enabling the
machine to stay true and not allow
doubling up on areas that had already
been pumped. Two separate crews ran
12 hour shifts as a delay at their previous
job had put them slightly behind
schedule. Fortunately the mild weather
held well into October and work was
done in plenty of time to avoid winter
temperatures. Two Geotubes were filled
in succession, that meaning as one was
“Once the biosolids have rested for a period of time, the Geotubes® are cut
open and the dried material can be taken away and disposed. The
Geotubes® can be left for as long as needed, even several years. Once the
material is dried, landfills receive this dried product, as it will pass their
paint-filter test requirement and can be used as top cover.”
www.lambourne.ca/what-we-do/lagoon-desludging/dewatering/
filled to capacity, a second began filling
as the first dewatered and slowly shrank
in size. Then once the second was filled,
the first was topped up. This was
repeated several times until it was
almost entirely sludge that filled the
Geotubes. Once two were filled, the next
two were filled, and so on until all six
Geotubes were filled to capacity. During
the month the sludge was being
pumped, the Lambourne operators took
several samples from the Geotubes to
confirm that the quality was as
expected.
After 21 days (with several small
shutdowns) the dredge had pumped
45,668 cubic meters of sludge from the
lagoon cell, and all six Geotubes were
full. The estimated removal was
approximately 913 dry tonnes of
biosolids. By the time the last Geotube
was filled, the first two had shrunk in size
considerably due to effective dewatering.
This reduction in tube size
allows the same vessels to be reused at a
time in the future if further dewatering is
required. Each of the six units may have
another 1/3 of their original space filled
and dewatered will little or no prep work
at all. Over the course of the next few
It has been suggested that if the
sludge is stabilized during its curing
process, it can be added to compost
and used as a soil conditioner due to its
high organic content.
As far as the City of Swift Current is
concerned, further testing needs to be
done before any decision can be made
as to the use of the biosolids. After
approximately 10 months, a core
sample will be taken and analyzed for
pathogens and nutrient quality. If no
conclusive results are found, then the
solids can remain in the Geotubes to
dewater further. This began as a short
term solution, and in reality is the first
step in solving a bigger issue. But the
first step has been taken, what the next
step will be remains to be seen. Stay
tuned.
Tim Cox, Superintendent WWTP
Swift Current, Saskatchewan
What do
we do with
them now?