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After a dream run in
its Californian trials, QED’s new air-driven piston pump has arrived in
Australia. By Richard Collins.
Landfills and
environmental clean-up sites are harsh environments and often have
conditions, such as volatile gases, that must be factored into operating
specifications.
The new Iron Horse
line-up of air-driven piston pumps is designed to handle landfill leachate,
methane condensate and groundwater clean-up pumping. The piston pumps
made by US firm QED Environmental Systems have been launched in Australia
by Enviroequip.
They are engineered for
extreme durability, low maintenance and serviceability, important in tough
environments. QED vice president David Mioduszewskisaid: “Large landfills
which have been burdened with frequent service of previous piston pump
models could realise substantial savings in maintenance costs.”
Electric submersibles are
often used for pumping leachate as they are fairly cheap, economical and
easy to maintain. But there are disadvantages to such systems. For a
start, they can be affected by leachate with high temperatures – of 40-50
deg C – and need to be specified to take this into account.
Most electric pumps also
require some external level control, which can be difficult if access is
restricted. Some models do have internal levels control or use
electronics to detect level based on loading of the pump, but this can be
expensive.
With electricity cables
running across a landfill site and the chance of creating a spark which
could ignite vapours, safety issues are paramount. There are
explosion-proof electric pumps but these are expensive. Corrosion is
another issue to note.
Some sites also use
eductors, a pressurised wellpoint system which uses a venturi (based on
pressure differences) to draw groundwater into the well screen and up to
the surface. These are finely engineered and detractors say they can be
difficult to keep running, especially if there is any particulate matter
in the leachate, which could require daily backwashing of the system.
Air Vs Electricity
The pneumatic option
solves many of these problems, says Matt Scaddan of Enviroequip. For a
start, it is easier and cheaper to lay 20mm plastic air pipe than it is to
get electricity to the pumps. The approach is also low maintenance as
there are no fast moving parts and the pumps can handle high temperatures
and all kinds of corrosive environments.
Air-powered submersible
pumps, however, have higher capital cost than electric pumps and lower
flow rates and depths (<100m). On top of this, air comes into contact
with liquid, which could lead to precipitate formation.
Scaddan says the Iron
Horse piston pumps while more expensive than other options, offer
considerable further advantages. They can operate in slanted and
horizontal bores, have extremely low drawdown (will only leave 145cm of
water in the bore) and allow higher flow rates and depths (>100m) than
other pneumatic pumps.
QED has conducted field
testing at two difficult sites in California, the Puente Hills Landfill in
Los Angeles County and Waste Management Inc’s Bradley Landfill in Sun
Valley. The Bradley site had experienced difficulties dating back to
1999, with sumps silting in at depths to 75m. The landfill had not been
able to achieve the required flow rates with limited liquid levels at
these depths. The Iron Horse system was installed in the worst well to a
depth of 62m, with good results. The liquid levels were lowered from more
than 40cm over the inlet to less than 8cm.
At the Puente Hills
Landfill, four demonstration pumps have been operating since June last
year, working “essentially flawlessly” according to QED. The previous
system required new seals and valves every 2-10 days, a problem avoided by
the Iron Horse range’s seal-less piston design. The downwell pumping
mechanism uses an oversize, all stainless steel piston manufactured to
close tolerances that require no seals, eliminating the most frequent
cause of pump breakdowns and service.
This extended pump duty
capability produces major savings on labour and repair parts and limits
the exposure of service personnel to hazardous leachate or contaminated
groundwater. Finally, key components such as the liquid check valves and
the drive air cylinder are field serviceable rather than throwaway.
For more information
on the QED Iron Horse Pump, contact your local EnviroEquip office. |
