Chemical-free technology cleaning up landfill leachate
Whaddon Water Management
(WWM), located in Bois-de-
Filion, Québec, is an
advanced water and
wastewater treatment company specializing
in chemical-free technology
for municipal drinking water and
medium to large industrial wastewater
treatment. Its wastewater applications
range from pulp and paper to pig waste
to the food and beverage industries.
For the past fifteen years, WWM’s
research and development department
has focused on its Oxycair line, a
multi-media technology treating
municipal surface and ground water to
ensure bottled-water quality in drinking
water. Now, based on these
advanced principles, the Oxycair XPM
technology has evolved to the point
where the same water quality standards
can be produced from sources as
severe as landfill leachate. XPM technology
offers companies the option of
the reuse of treated wastewater within
the plant, as well as direct discharge
into the environment.
The pilot project
A full-scale demonstration of the
Oxycair XPM technology has been
underway for one year at a pulp and
paper mill. The wastewater stream is
created at the mill’s landfill site where
all pulp and paper process waste is
dumped. Once the waste is saturated
by rain and melting snow, it is collected
and stored in cistern holding tanks.
Until now, the leachate has been
trucked to a secondary treatment facility
located many kilometres from the
landfill, incurring significant and
unnecessary transportation costs.
The challenge
The influent wastewater consists of
a number of contaminants consistently
found in raw leachate. Since these are
typical pollutants, the demonstration
study will be relevant to most industrial
effluent streams subject to environmental
pollution standards.
Depending on the amount of raw
water to be treated per day, the specific
XPM, manufactured in various
sizes, can be selected. The model used
in the pulp and paper leachate demonstration
project has a nominal treatment
capacity of 600 m3 per day.
Recovery of treated water is high - up
to 95% - and virtually pure, permitting
environmentally safe discharge or
industrial reuse of the product water.
The remaining 5% is rejected as a by-product
concentrate.
During the study, all influent, effluent
and concentrate analyses have been
performed using standard methods
performed at university laboratories
and at commercial, government certified
environmental laboratories.
Generally speaking, the treated
leachate is in full compliance with the
environment discharge standards set
by the legal authorities.
The above graphs demonstrate influent and effluent
water results.
How it works
This chemical-free technology is
based on mechanical processes occurring
simultaneously in several reactor
vessels. Within the main drive pump
housing, solids entering with the raw
water are broken up and mixed by the
extreme rotational forces of the multistage
raw water pump. Three similar
pumps boost the process stream pressure
to as high as 1500 psi through a
series of in-line screen and membrane
housings. The heat and pressure generated
by these submersible motors and
pumps increase the solubility of salts
in solution, and the membrane elements
produce higher quantities of
product water at higher temperatures.
The in-line screens provide
mechanical filtering to separate suspended
solids from the process stream
to ensure that large particulates are
removed or broken up prior to entering
the membrane housings. The process
stream through the screens is reversed
every few minutes. While in the backflow
position, the screens, supports,
and housings are designed to produce
mechanical resonance and pressure
waves to loosen and remove solids and
crystals from the screen surfaces.
Dissolved air in the process stream is released from solution
near or at areas of plugging and works as a scrubbing
agent to aid the removal of solids from the screens.
The concentrated return flow from the membranes and
inline screens goes through a set of venturis, which drop
the pressure and induct large quantities of ambient air.
Incoming raw water mixes with this highly oxygenated
and supersaturated stream and enters the concentration
chamber at high velocity. Metals, salts and organic solids
contained in the raw water are rapidly oxidized and
sheared from the process stream and are collected in the
concentration chamber. Volatile and low solubility gases
contained in the raw water stream are also oxidized or displaced
in the high pressure, super-saturated environment,
and collect in an air cap at the top of the concentration
chamber.
As the process stream slows across the concentration
chamber to a still zone at the opposite end from the intake,
gases are released, the temperature decreases, and salts
that are at, near or above saturation levels solidify and settle
to the bottom. Final settling of most solids occurs
throughout the still zone within the chamber, preventing
them from reentering the process stream. Following a production
cycle, the pressurized air cap is used to rapidly
and completely empty the liquid, solid, and gaseous contents
of the concentration chamber through a blow down
port.
Clean product water extracted by the membranes enters
a product accumulator at the top where it passes through
an air cap, assisting the
degassing process. Water
leaves the product accumulator
from the bottom of the vessel
where the lowest concentration
of gases exists.
Degassing at atmospheric
pressure reduces the aggressiveness
of the product water
and pH increases while dissolved
C02 is released from
solution.
Three dimensional view of
the XPM processor unit.
The membrane technology
The use of thin-film membranes
may be necessary for
the treatment of certain kinds of wastewaters,
as is the case in the treatment
of leachate from a pulp and paper landfill
site. The new XPM technology
resolves conventional thin-film drawbacks,
i.e. plugging, blinding, biofouling,
mechanical stress. In this case
the membranes reduce or eliminate the
toxicity of off gases in the effluent,
maximize treated water recovery, and
minimize concentrate discharge volumes.
The technology allows for further
development and evolution, and
improvement patents are being added
as a result of ongoing research and
development.
Overall, the technology is proving
to be a very attractive, economical
alternative to other leachate treatment
strategies. Transportation alone, from
the landfill site to a mill’s wastewater
treatment plant, may cost $500,000 or
more, depending on the distance from
a landfill site to the secondary treatment
facility. Without the need for
additional treatment facilities, a company
will also save the chemical costs
usually associated with the treatment
of leachate.
Most important, third party results
demonstrate that the XPM is meeting
the most restrictive of government
standards, allowing direct discharge
into the environment at the demonstration
site.
With rising energy costs, water
reuse within a plant for washing,
cleaning, sanitizing, boiler processes
and cooling towers is of high priority
and, with the XPM technology, can
now be realized. The ability to close
the loop within an industry eliminates
additional water usage, saving companies
the rising cost of water as well.
The small footprint of the XPM
reduces or eliminates the need for new
construction at most companies’wastewater
sites. Because the XPM processor
is fully automated it can be remotely
operated, reducing manpower costs.
Contact, Ed Philion, Whaddon Water
Management Inc., at e-mail: ephilion@wmint.ca.
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