A primary goal of enhancing biological treat- ment led to another important goal of con- trolling overfows for the 2015 Shamokin
Coal Township (Pa.) Joint Sewer Authority’s treatment
plant upgrade and expansion. Adding sequencing batch
reactors (SBRs) to the plant’s existing trickling flters
suffciently improved the effuent quality to lessen the
eventual impact on the Chesapeake watershed. However, the addition required upgrading the existing headworks to fully protect the new SBRs.
Grit removal was historically a problem at the plant,
which operated an Archimedes screw device that augured
grit from two chamber wells. During wet weather events,
incoming grit included sediment and other fne particles
especially harmful to plant pumps and processes. The older grit system was unable to remove
the large amount of grit entering the
system during these overfow events,
requiring costly, multi-day cleanouts
four times a year.
“It was very labor intensive,” said
Paul Petrovich, general manager of the Sewer Authority.
Designers from Great Valley Consultants evaluated
various grit removal technologies for the expansion
project based on two key criteria: grit particle removal
effciency and ability to handle surge events. They visited real installations nearby and spoke with operators.
Ultimately, the PISTA® 360™ with V-FORCE BAFFLE™
from Smith & Loveless was selected because of its high
effciencies, high turndown and low life cycle cost.
Unlike conventional vortex-type systems, the
PISTA 360 maintains ideal velocity during low-fow and
surge events, ensuring consistent grit removal at all times.
The system’s patented hydraulic design is comprised of a
carefully positioned inlet fume and integral fow control
baffe inside a 360-degree, fat-foor grit chamber. This
design creates a forced vortex fow path that sweeps the
incoming grit along the chamber foor toward the center opening for removal. As fows fuctuate, the baffe
causes the water level to properly adapt to maintain ideal
velocities. It features a 10: 1 turndown with no additional
downstream control devices.
The upgraded Shamokin Coal Township Joint Sewer
Authority plant was offcially commissioned in 2015.
Project leaders report exceptional service from the system, which has provided more than a year of dependable
grit removal with minimal O&M requirements, including
during combined sewer overfow events.
“It’s removing 99 percent of the grit, pre-storm and
during storm events,” Petrovich said. “We don’t see
any grit downstream, including in the motors where grit
can tear them up.”
That’s signifcant because of the heavy fows encoun-
tered during wet weather.
“We are a combined sewer system so during storm
events fows can actually reach 13. 5 MGD,” Petro-
vich said, adding that the new 12 MGD grit chamber
“wasn’t missing a beat. It pulls out all of the grit.”
The performance of the system is especially impres-
sive, according to Petrovich, when you consider that it
requires signifcantly less O&M than the previous unit.
The recommended maintenance schedule consists pri-
marily of periodic lubrication, he said.
“There has been very little trial and pain,” Petrovich
remarked. “After start-up, we had to adjust certain settings, but since then we have had basically no other
To learn more about Smith & Loveless, visit smithandloveless.com.
(Above) The Sewer Authority’s space-saving PISTA® 360™ Grit Removal
System operates out of a new headworks building alongside complete
grit pumping and dewatering equipment.
(Right) The grit system is removing
99 percent of incoming grit, even during wet weather surge events.
BY MICHAEL MICROBI
Presented by Smith & Loveless