ENGINEER TO ENGINEER
Progressive cavity pump specialist
Seepex has developed a new system
that is said to improve dewatered
sludge handling, enabling long-distance
transfer with reduced operational costs
by using a combination of progressive
cavity (PC) pump technology and densephase
conveying. The technology has
been trialled by Thames Water at its
Reading Sewage Treatment Works (STW),
pictured above, and is now being installed
as part of the new Thames Water
Riverside project, said to be providing
an energy-e cient, high-performance
alternative to conventional sludge
handling systems.
Following a visit by Thames Water
representatives to observe smart air
injection (SAI) in action in Sweden,
the company decided to measure the
potential energy savings it could make by
installing a trial SAI system at its Reading
STW. This site had previously used
piston pumps, but as a result of process
limitations and high operating costs,
Thames Water switched to Seepex’s
multistage PC pumps in 2014. This
solution halved Thames Water’s energy
use, as well as reducing transport and
maintenance costs. Four years on, it was
time to see if SAI could improve things
further.
The SAI Reading trial set out to not
only prove the technology, but to quantify
the additional energy savings that could
be delivered by pumping the dewatered
biosolids from the centrifuge discharge
to the storage silo. An SAI trial unit,
including full controls and monitoring,
was installed on the Seepex multistage
PC pumps for a trial period and the
results were recorded.
During the trial, energy use and
discharge pressure measurements were
taken. Using these gures, together with
the volume and height of the discharge
pipework, Seepex engineers could
then calculate the optimum amount
of air required. The
trial concluded the
energy saving with
SAI compared to a
multistage PC pump
without air injection
was 15%. Compared
to the original piston
pumps, the energy
saving was 61%.
However, there were even greater
savings to be made by switching to
a single stage SAI pump tted with
Seepex’s Smart Conveying Technology
(SCT) (www.is.gd/akituj), instead of the
multistage pumps currently in use.
Air usage data from a working SAI
installation using SCT pumps in Belgium,
enabled Seepex to produce an estimate
for Thames Water, based on the trial
results from Reading.
It concluded that, if SCT single stage
pumps were used in place of multistage
pumps, the energy saving at Reading
STW would be approximately 40%. When
compared to the original piston pumps,
an SAI system with SCT pumps would
reduce energy consumption on this
application by approximately 75%.
As a result of the Reading trial, Thames
Water has procured several of Seepex’s
SAI units for its Riverside project. Paul
Fountain, senior consultant for biosolids
at Thames Water, explains: “We were
faced with a particularly tough challenge
at Riverside. Replacing a problematic
conveyor system with proven PC pumps
was the preferred solution, but due to
very tight space constraints, low access
walkways and a labyrinth of pipework to
work around, the traditional multi-stage
pump was not going to be possible.
“Working with Seepex, we decided
to purchase several single stage
Smart Conveying Technology PC
pumps, coupled with Seepex Smart Air
Injection innovation. This allowed us to
signi cantly reduce the pump length
and installed motor powers, and has the
added bene t of ease of maintenance.”
Sludge solution
for Thames Water
Seepex says that its smart
air injection technology is an
alternative to conventional
sludge handling systems
30 www.operationsengineer.org.uk June 2019
/akituj)
/www.operationsengineer.org.uk