Last year, the Village of Flossmoor, Ill. faced an unusual problem
at their Flossmoor Commons Sewage Pump Station as grease was accumulating at a
very rapid pace.
"The grease got to a point where it was five feet
deep," Alan Ohlendorf, a utility operator for the Village of Flossmoor
told Water & Wastes Digest.
According to Ohlendorf, the grease build-up occurred
approximately every eight weeks as the pump station collected the wastes from a
nearby strip mall, which included several restaurants. Following the discovery
of the grease, numerous attempts to determine the exact source of the grease
were unsuccessful.
Invariably, this grease caused a multitude of problems
including the clogged pump intakes, interference with level sensors, and a
blocked influent line.
Accordingly, the Village of Flossmoor made several attempts
with various products to reduce this grease level, finding little or no
success.
These unsuccessful attempts resulted in numerous emergency
calls and a tremendous amount of overtime maintenance for the village. The
resulting increase in costs quickly exceeded the village's maintenance budget.
Additionally, the village also began to incorporate regular
vacuum cleanings of the wet well in an effort to reduce the emergency calls and
additional costs. However, the collected waste had to be classified as
hazardous material, which resulted in extremely expensive handling and disposal
fees from the removal company.
Designed to mix
Per the variables mentioned previously, the village agreed
to install a Depth Charge Wet Well Mixing System, which was designed and
manufactured by Precision Systems. According to the manufacturer, the unit is
unique among wet well mixing systems in that it is the first system
specifically designed to mix floating/non-suspended solids within a wastewater
wet well.
Additionally, it is a self-contained system with no moving
parts in the wet well. The system operates using a series of injectors
installed on the wall of the wet well that inject high-pressure air around the
outside diameter of the wet well. The air is supplied by a compressor contained
in the system's control panel, which interfaces with the pump control panel.
Critical system
The pump station's level sensors control operation of the
system. When the wet well level reaches the lead pump "On Level," the
system's control panel delays the start of the pump to allow it to begin its
operation cycle. Following the end of the operation cycle, there is a short
pause cycle to allow the injected air to escape from the water. At the end of
the cycles, which takes a total time of less than 10 seconds, the lead pump is
allowed to start and operate as normal.
The operation is automatic and self-contained as it does not
require the addition of any chemicals or agents to achieve this mixing.
It is during the operation cycle that the effervescent
action of the injected air causes significant turbulence on the surface of the
wet well.
Solids floating on the surface of the water are mixed into
the water. But before the solids can escape their entrainment, the lead pump is
started and the suspended solids are removed from the station.
Since the Village of Flossmoor installed the system in
February 2002, the problems, and the according additional maintenance have been
eliminated.
"I no longer have any major maintenance at this station
and I am very happy with it," said Ohlendorf. "It's back to being
what I consider a normal lift station with normal maintenance."
For further information, contact Precision Systems at
708/891-4300.
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