Underground Infrastructure - May 2023 - 30

Rehab Technology
Until then, the most effective cleaning practices used huge
amounts of water and had to be followed by an expensive, hot
caustic soda solution, which created unusable waste product
with the added cost of disposing it.
The types of solid pigs common to energy pipelines at the
time were impractical for the food systems, but Quarini had
an idea: what if there was a type of pig that could flow through
pipes like liquid but apply significantly more shear to clean its
inner surface with less water than flushing?
Quarini's solution was ice pigging, and its top U.S. evangelist,
Paul Treloar, was working for the Suez-owned water supply
company in Bristol when it began collaborating with Quarini
on developmental testing of his process.
pipes. But, in time, we learned that the flushing wasn't getting to
as much of those metals as we wanted to remove. "
When a contamination problem drew sharp attention to
the issue a few years ago, the city sponsored a Water Research
Foundation (WRF) project that began with the engagement of
Confluence Engineering Group, a Seattle-based firm specializing
in water distribution system quality, as principal investigators.
That led to a 2021 pilot test that, for the first time, pitted
lesser-known ice pigging against foam swabbing and the unidirectional
(water) flushing method that Park City had concluded
was insufficient for its challenging mineral conditions.
" And we found that the more advanced technologies like
ice pigging and foam swabbing were generally greater than 90
percent effective at removing all of the accumulated material,
where we were getting more in the realm of 20 to 30 percent at
most out of flushing, " De Hann said.
While the end results were in line with foam swabbing, ice
pigging was the more expensive of the options. However, De
Hann and her team ultimately favored ice pigging for the ease
of its less-invasive application.
" We're pretty confident it was an easier application for us,
especially as it related to working with fire hydrants, because
when you foam swab, it's a little more invasive, " she said. " You
have to actually remove the barrel and the guts of the hydrant
when you put it in, and sometimes those haven't been removed
for a lot of years, and you may have to completely replace it or
replace portions of it. Some of the older hydrants don't play
very nice in this environment.
" So, there were some limitations there, where it was a lot easier
to inject the slurry from ice pigging. We didn't have to think
about changing out as many hydrants, " De Hann added. " And
just the manpower itself generally felt like an easier lift. "
Because ice pigging is a proprietary solution with only one
U.S. supplier, she noted, it's costly. " But it was worthwhile for
us from a cost-benefit analysis to go forward with it. "
Bristol born
Nearly 30 years ago at the University of Bristol in England,
Professor Joe Quarini came up with a novel approach to cleaning
pipes in the food industry.
30 MAY 2023 | UndergroundInfrastructure.com
" Professor Quarini came to the company and said, 'Hey,
I have this idea to use ice to clean water pipes,' and people
thought he was a bit nuts at the time, I think, " Treloar recalls.
" But he wanted to use our underground network to practice
and develop the technique. Once they developed the different
practices and saw that it was going to be a good tool, they had a
good sense then to take patent out on it. "
Suez was licensed as the sole provider of ice pigging worldwide,
and the method migrated along with Treloar from the
U.K. in 2012 when Suez sent him to introduce the service to the
U.S. market. Suez continues to offer ice pigging in many parts of
the world but decided to exit the United States in 2020, when
American Pipeline Solutions (APS) bought the equipment
from Suez and hired Treloar to head the group.
Since its arrival in the United States, ice pigging has been
used on more than 410 projects and cleaned over 1,100 miles
of water pipes in 42 states, according to Treloar, who currently
serves as regional head of business development for APS.
Ice pigging explained
When people hear about ice pigging for the first time, it may
conjure different images. Those who are familiar with conventional
pigs used in oil and gas pipelines may picture a solid slug
of ice passing through a pipe like conventional pigs made of
foam, polycarbonates or other materials.
Simply put, ice pigging is a cleaning method for potable
water distribution mains and wastewater force mains that involves
pumping a slurry of ice into a main through a hydrant or
other existing fitting and using normal operational flows and
system pressures to push the ice " pig " downstream, where it
exits through a similar fitting.
The ice slurry, filling 20-30 percent of a pipe's volume,
cleans with shear forces up to 1,000 times greater than with
water alone, provides more effective cleaning, and uses 35-50
percent less water than UDF.
Treloar uses the analogy of a glacier to explain why ice pigging
is guaranteed not to cause blockages.
" When the ice pig goes through a water main, it doesn't
push all the sand, sediment, fats, oils and greases up front, but
it more picks them up in the body of the ice, just like a glacier
picking up stones and rocks as it's moving through valleys, "
Treloar explains. " If the pipe is heavily sedimented, you're
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