Water Related Regenerative Technologies at a Sustainable University Facility

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Water Related Regenerative Technologies at a
Sustainable University Facility

• Thomas Cathcart
• Biological Engineering

Center for Sustainable Design
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This presentation can be found athttp//abe.msst
ate.edu/csd/utah.ppt
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Introduction
The topics of this presentation are

• Constructed Wetlands - a regenerative
• technology to manage human waste products
• Rainwater Harvesting a regenerative
• technology to manage storm water runoff and
• meet human needs for water.

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Both constructed wetlands and rainwater
harvesting will ultimately be implemented at our
newly completed Landscape Architecture facility.
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• The building, completed in 2003, features
• Ground-source heating and cooling
• Large overhangs to prevent direct insolation of
  the walls in
• summer.
• High ceilings, high R value roofs, and thermal
  mass to keep
• the building thermally stable at comfortable
  temperatures.
• Photovoltaic electric power provided by TVA.
• Concrete floors inside the structures that
  assure there are
• no emissions of volatile organic compounds or,
  in some
• cases, floor coverings of either recycled
  rubber tire or
• natural soybean-based materials.
• Current measurements suggest that the building
  uses 75 less energy than other relatively new
  campus buildings.

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Artists rendering of building site showing
planned stormwater ponds.
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What is a regenerative technology?
A process that makes use of one or more
regenerative cycles
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What is a regenerative cycle?
A cycle in which the end product of one process
becomes the resource (raw material) of the next.
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Why are regenerative cycles and technologies good
things?

• They use solar energy (an unlimited and non-
• polluting form of energy) to operate.
• They function independently of humans
• (unless humans disrupt them).
• They are inherently sustainable.

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Why are regenerative cycles and technologies
important now?
Projected 9-12 billion by 2050
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There are enough of us now to adversely effect
the natural systems upon which we depend.

• 7000 sq. mile dead (anoxic) zone in
• the northern Gulf of Mexico.
• World wide loss of biodiversity.
• Global warming (?)

What is the carrying capacity of earth?
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No one knows for sure. But like a giraffe
growing up in a garage,
we will eventually have to consider our limits
and our options.
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We have lived by the assumption that what was
good for us would be good for the world. We
have been wrong. We must change our lives, so
that it will be possible to live by the contrary
assumption, that what is good for the world will
be good for us. And that requires that we make
the effort to know the world and learn what is
good for it. We must learn to cooperate in its
processes, and to yield to its limits.
Wendell Berry (Recollected Essays)
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In other words
We must learn to live within (and cooperate
with!) the assimilative and productive capacities
of our planet. Regenerative cycles are a model
for us to follow in our technologies (our methods
for meeting our needs). If our technologies are
consistent with the natural model, then there is
reason to hope that they are truly sustainable.
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This is why the word Regenerative figures
prominently in the title of our book.
(Constructed wetlands and rainwater harvesting
each got their own chapters!)
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There are 3 types of constructed wetlands

• Surface flow
• (Free water surface)
• Subsurface flow
• (Rock-Reed)
• Storm water

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The surface flow and subsurface flow constructed
wetlands are used for waste treatment and are
continually loaded. The Storm water wetland is
loaded like a storm water detention pond
(intermittently, following rain). Waste removal
mechanisms are similar for all three, but each is
also significantly different from the others.
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What is a wetland?
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A wetland is a site that has saturated soil for a
long enough duration each year so that its
primary population consists of plants especially
adapted to survive in saturated soils
Emergent wetland plants have specialized internal
tubes, called aerenchyma, that allow oxygen to
diffuse to their root zones. Aerenchyma allow the
plant to persist in anaerobic sediments when
other plants will die.
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Surface Flow Constructed Wetlands

• Don Hammer was one of the
• pioneers of surface flow
• constructed wetlands.
• SFCW emerged in the 1980s
• Excellent for removal of sediment,
• BOD, nitrogen.
• Has been used for heavy metals,
• treating acid mine waters, and pesticides.

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A constructed wetland is a wetland created where
one would not otherwise exist.
Its created To meet a human need (usually waste
treatment)
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Construction is pretty simple
Commonly, levees are pushed up from the inside
out (volume is partly dug and partly the raised
freeboard of the levees).
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If built on a site having relatively impermeable
soil, a lining may not be required. Alternately,
clay or a plastic liner may be used to prevent
groundwater contamination.
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An easy way to control hydraulic loading is using
orifice flow. For small systems, a simple and
cheap PVC orifice can be constructed.
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Here is a research wetland shortly after
planting at Mississippi State University.
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Influent is distributed using a manifold to
promote uniform flow.
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At the effluent end of small systems, water is
collected using a PVC manifold. Plugging can be
prevented using river gravel. Water elevation is
determined by the height of the outlet.
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In larger systems, concrete drop box structures
are used at the effluent end.
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• Emergent wetland plants fulfill a variety of
  roles.
• They promote microbial digestion of the
• wastes.

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• Friction from the stems promotes uniform
• flow.
• The plants shade the water (which reduces
• phytoplankton growth a source of BOD).
• The plants inhibit wind mixing (which
• also promotes uniform flow).

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Surface Flow Constructed Wetlands as a
Regenerative Technology

• Very low energy input (typically gravity flow
• may use lift pump in larger systems).
• Rich and diverse population of bacteria,
  insects,
• amphibians, and reptiles.
• Transforms organic wastes to carbon dioxide
• and water.
• Transforms organic nitrogen and ammonia to
• nitrate and then to nitrogen gas.

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• The second type of constructed wetland is the
• subsurface flow or rock-reed system.
• Developed by Bill Wolverton while at NASA.

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Subsurface flow system under construction.
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Subsurface flow
In a subsurface flow constructed wetland, the
wetland is filled with river gravel or similar
size stones. The treatment volume is the space
between the stones.
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Subsurface flow
The stones are a colonizing surface for
microorganisms. The root zones in SSF systems are
an important component of treatment, supplying
much of the oxygen required for aerobic treatment.
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• Subsurface Flow
• Sediment removal prior to the wetland is
• critical for SSF to prevent clogging.
• Subsurface discharge is common.
• Many systems appear to be zero discharge for
  much of the year.

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If you see water at the surface of a SSF wetland,
thats a good indication of plugging or some
other problem.
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Bill Wolverton is a member of the LA facility
design team. Shown here is a photo of an
indoor/outdoor plant treatment system in north
Mississippi.
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The building has been plumbed (and administration
approval has been received) for a small indoor
system and an outdoor rock-reed system for the
new building.
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Storm water wetlands differ from surface flow and
subsurface flow in that loading is neither
uniform nor continuous. These systems are
designed as shallow detention ponds or as
off-line first flush systems for treating runoff.
Design of storm water wetlands follows a process
similar to extended detention ponds which
brings us to the next topic.
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Stormwater detention pond capacity is usually
based on a hydrograph calculated from the
watershed and a design storm (a large magnitude
storm used to estimate maximum expected runoff).
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The hydrograph (left) and the detention pond
depth graph (right) were created using a package
called SMADA. The package is free and is used by
our engineering students.
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Shown below are links to the SMADA package and
well as 2 instructional html pages (SMADA has
little documentation) and 1 html document on
design storms.

• SMADA (installation file)
• Instructions for using SMADA, Part 1
• Instructions for using SMADA, Part 2
• Design storms

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Although useful for determining how big your pond
must be to accommodate the largest expected
storm, software such as SMADA does not help
predict how much water will be available if your
object is to use the impounded storm
water. Researchers in the Biological Engineering
Department at Mississippi recently attempted to
use historical meteorological data to predict
both the performance and water harvesting
capacity of extended detention ponds.
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• Here is how the model worked.
• A 30 year record of daily precipitation and
• class A pan evaporation was available from
• the National Climatic Data Center (see
• Instructions for getting historical daily
• precipitation and evaporation data to get
  similar
• data for your location)

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Water entered the pond as a result of runoff from
the roof (assume 90 capture) and runoff from 1
acre pervious material located off site (runoff
calibrated for storm size using SMADA). This
comprised the volume of water that entered the
pond during rain events.
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Pond discharge occurred whenever pond elevation
exceeded the height of the discharge weir.
Discharge occurred most frequently in the winter
months.
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A potable water cistern was placed in line with
the roof runoff. The cistern was filled first
before runoff reached the pond. Potable water
demand was 1 ft3 per student per day with an
equivalent amount drawn for non-potable student
uses from the pond. Student water use came from
Corbitt (1989). Students were assumed to be in
school 5 days per week from August 15 until May 6
each year 100 students were assumed to be in the
LA buildings all day.
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During the growing season (may 1 to September 30)
water was withdrawn from the pond for land
irrigation. The amount withdrawn was equal to 1
inch applied to a 1 acre irrigated area minus the
accumulated rainfall during the preceding 7 days.
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The elevation change in the storage pond was
equal to Elevation change daily runoff
direct precipitation - evaporation - irrigation
infiltration discharge indoor water use. The
elevation change was calculated each day and then
applied to the amount of water in the pond to
determine a new water height.
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A pond water balance was maintained to make sure
that water was mathematically conserved. Typical
balance values at the end of each simulation were
10-6 ft3. Shown here is the predicted water
elevation for a pond having a 6 ft average depth
over the 30 year period. Pond depth tended to
reach minima during the summer months.
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Results for 6 simulations are shown below. Pond
area is in acres, cistern capacity in cubic feet
and the 3 other columns are the number of days
the storage pond was empty, the number of says
that there was discharge from the pond, and the
number of days that city water had to be used
instead of cistern water.
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The simulation results shown here are
preliminary. This approach has been used and
validated for other pond related research. The
model is based on fairly simple geometry and the
water balance should be a good indicator of
problems. It appears that this approach may be a
promising method to predict with greater
refinement the amount of harvestable water
available from a given system.
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Tools and Reference Material (active links)

• SMADA (installation file)
• Instructions for using SMADA, Part 1
• Instructions for using SMADA, Part 2
• Design storms
• Instructions for getting historical daily
• precipitation and evaporation data.
• Water Related Best Management Practices
• Planning and Design Manual for the Control of
• Erosion, Sediment, and Storm Water.

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Class trip (BEs LAs) 1 week ago today!