The Cause
Plagued by cyanobacteria, Cascade Reservoir was dying. Cyanobacteria
produced a toxic bloom that caused twenty-two cattle that had access
to the reservoir to die in 1993. Owners had to keep their dogs away
from the water, afraid that the animals would die from the toxins.
These bacteria caused the EPA to forbid human contact with the reservoir.
Excess nutrients, such as phosphates, in the water were cited as the
cause of the blooms, resulting in the Division of Environmental Quality’s
restriction on phosphate contributions to the reservoir. The largest
contributor to these nutrients was the McCall Sewage Treatment Facility.
The treatment plant was designed to be a secondary treatment system,
which removes solids and small amounts of nutrients through sand filters.
This kind of system is inadequate in filtering and reducing phosphates,
nitrates, and ammonium. The plant then discharged its waste into the
North Fork of the Payette. The river empties into the reservoir and
contributed to eleven percent of the phosphate entering the reservoir.
Being the largest contributor to these phosphates, the McCall Sewage
Treatment Facility was asked to reduce its contributions of phosphates,
nitrates, and ammonium to the reservoir. The local Division of Environmental
Quality required that the total phosphate entering the reservoir be
reduced by at least 30%. With the elimination of McCall’s phosphate
contribution, a large part of the requirement would be met. McCall
hired an engineering firm to propose solutions to the problems the
effluent was causing in the reservoir. The alternatives planned had
costs raging from $9.5 million to $14.9 million, with extra costs
that continually rose. Seeing the numerous flaws present in the alternative,
a group of girls from the advance biology class in Cascade, soon to
be known as the Sewage Sisters, came to the conclusion that a cost-effective
and environmentally sound alternative to the proposed solution could
be found. In their research, three important criteria needed to be
met: scientific goals, economic expectations, and political boundaries
and obstacles.
The Sewage Sisters
The Sewage Sisters began to run tests to see what the major causes
of the algae blooms. They ran tests on the reservoir, including oxygen,
phosphorus, orthophosphate, total phosphate, carbon dioxide, pH, nitrate,
total coliform, fecal coliform, BOD’S, temperature, ammonium,
and turbidity. With the results of their tests they discovered the
conditions in the reservoir to be ideal for cyanobacteria. The Sewage
Sisters decided on trying to eliminate the phosphates, nitrates, and
ammonium through a process of altering the sewage plant and adding
a phosphate-removal system at the end of the treatment process. The
Advanced Integrated Pond system, AIPS, was developed by SOA Inc.,
a consulting engineering firm based in California. AIPS is an integrated,
multi-stage biological reactor system. The reactors are in forms of
open ponds. Introducing the AIPS to the McCall treatment facility
would require simple retrofitting of the existing ponds. The system
would consist of five ponds, which consist of a facultative pond,
a high-rate pond, a settling pond, and the last two are the maturation
ponds. Effluent completing the AIPS process will travel to a phosphate,
nitrate, and ammonium removal system, the Biocoil. Lee Robinson, who
was also the founder of Biotechna Environmental International Ltd,
invented the Biocoil Photobioreactor. Biotechna is a biotechnological
company based in London, England. The Biocoil is a revolutionary photosynthetic
bioreactor that provides an environment for biological organisms to
grow in a controlled manner. Uncontrolled algae growth can lead to
unattractive toxic blooms, yet under simple controlled conditions,
may produce beneficial results. In this situation, Chlorella growth
is used to remove nutrients from secondary effluent in an environmentally
and economically sound manner. Construction of the Biocoil is simple
and inexpensive, and operating costs are low as a result of its simple
design. Phosphate is reduced by 92% and nitrates by 97%. Land requirements
are significantly lower than for conventional facilities, and excess
Chlorella can be dried for use as animal feed, fertilizer, and fuel.
The Biocoil is cutting-edge technology, and upon its installation
in McCall, it would be the first operational system in the United
States. Implementation of the AIBPS in McCall would focus national
attention to this community in a positive way. The chlorella culture
is maintained in suspension at a high concentration, causing the culture
to become nutrient deficient. It is then mixed in a tank called the
contact tank. When the nutrient-deprived culture is exposed to the
secondary effluent, it absorbs and incorporates nitrates, phosphates,
and ammonia in large amounts. The algae then pass through coils of
tubing to allow complete nutrient absorption. These tubes consist
of clear, food-grade PVC and are wound horizontally around a vertical
frame. The tubing consists of several sections instead of one main
system, preventing an anoxic condition from developing. They are illuminated
primarily by sunlight and on cloudy days by artificial lighting to
provide conditions necessary for photosynthesis. The design of the
Biocoil enables maximum photosynthesis to occur. The cultures are
able to grow because of high turbulence and efficient light usage.
However, unwanted toxic blooms are unable to survive. Within 24 hours
a complete nutrient replacement is necessary; however, there is no
need for renewal of the biomass. A peristaltic, centrifugal pump that
produces compressed air is incorporated into every separate section.
The circulation of air prevents algae build-up. A build-up in algae
would inhibit the overall productivity of the Biocoil. Each section
of tubing contains a cleaning system to remove any algae build-up.
The cleaning system consists of a scouring pad that travels through
the tube and scrapes the sides when the flow is reversed. After they
have completed the cycle, the pump is then turned off and the flow
resumes its original direction. The algae then settle out in a settling
tank where it concentrates and is easily harvested or recycled. The
biomass is removed in a liquid form and then dried in an oven to be
used as animal feed, fertilizer, or fuel.
Mobility and Variables
As the Sewage Sister graduated a new class took up the care of the
Biocoil. Their goal was to build a mobile unit of the Biocoil. The
construction of the Biocoil consisted of a few major differences than
either Biotechna’s original design or the Sewage Sister’s
plans. This new mobile unit had a height of eight feet and a circumference
of thirty feet. With the mobile Biocoil the new group started to test
the Cascade sewer lagoons that included several experiments of variables
affecting the Biocoil’s efficiency. These tests included the
amount of time the algae is exposed to light in the tubing, the amount
of water that can be treated in the shortest amount of time, the effect
different trace elements have on the growth of the algae culture,
the ratio of phosphate and nitrate for best removal rates, and the
time the algae spends in the contact tank. A final test the 1996-1997
group planned was to see how well the Biocoil worked as a sewage treatment
system for home use to replace septic systems and drain fields.
Freezing
In the year of 1997-1998 the Biocoil group tried to find a solution
to prevent the Biocoil from freezing. To withstand the cold weather,
the group wrapped the Biocoil from top to bottom in transparent greenhouse
plastic. This helped to maintain the heat inside the Bocoil, while
still allowing sunlight to penetrate the tubing. The vents were plugged
in the fall and winter with foam rubber, and a wall-mounted thermostatically
controlled electric heater was installed. Halogen lights were used
instead of the fluorescent ones in Biotechna’s design, because
of the greater light and heat output. The Biocoil became an efficient,
nearly maintenance free system to cycle the water, and the tanks and
the tubing of the Biocoil wouldn’t freeze, as they were contained
within the Biocoil itself.
The Manifolds
A manifold was designed next, so that the direction of the flow of
water could be reversed and so that the pressure from the pump would
be divided equally among the sections of tubing. The manifolds also
allowed the sections of tubing to be shut off, so that the pressure
in the other tubes would increase. It also allowed for sections of
tubing to be joined together, increasing the amount of time the algae
remained in the sunlight. The manifold was built out of PVC plastic
pipe, valves and connectors.
Controlling the pH
In order to keep the pH of the system down and provide a source of
carbon, carbon dioxide was bubbled into the system. An electronic
pH probe was placed into the holding tank, which monitors the pH level
of the water in the tubing and holding tank. If the pH level fell
below 6.5, a solenoid valve would open and allow carbon dioxide from
a tank to bubble into the holding tank.
Rebuilding
When the group of 2004-05 inherited the Biocoil, it was beginning
to fall apart. The group then began to start to rebuild the Biocoil
by first replacing the Biocoil’s tubing. The next year, 2005-06,
began to replace and fix the pump, the CO2 tank, and the roofing making
the Biocoil function properly once again. Unfortunately the manifolds
broke during the winter giving the group another project to work on.
The BioSub
During that same winter a man in Australia named Lloyd Godson contacted
the group and created a partnership with him. He is designing a BioSub,
which allows him to live underwater temporarily. He asked the group
if they could create the same system, but measure the amount of CO2
being used and the amount of O2 being released, instead of measuring
the amount of nutrients. Now in the year of 2006-07 the group is creating
new designs to fit a system that would fit Lloyd’s.
