7/29/2019 BEVAT 1
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Ater extensive research, we reached the conclusion that the
most
suitable blackwater treatment system or the situation we
were
working with was the Evapotranspiration Basin.
Blackwater ows in through an inlet
into an impermeable tank containing
a tunnel o tires and layers o
rubble, gravel, sand and soil. On the
last layer waterloving plants are
present.
Sewage stays in the system or 3
days during which it seeps rom the
tunnel o tires and ows up through
the dierent layers. Eventually the
euent is absorbed by the plants
and released into the atmosphere
through transpiration.
The dierent layers o materials
act as flters and provide an
environment or the development o
anaerobic bacteria which help break
down and decompose sewage.
Principles o theEvapotranspiration Basin
Inlet
Rubble
Gravel
Soil
SandOverow
pipe
Tire tunnel
Water loving plants
(Banana trees, taioba, etc)
ADVANTAGES
Risk o groundwater
contamination is reduced
Can be used in many types o
terrain
Low costs
Can be used occasionally
Aesthetically appealing
Used to increase soil
absorption
No need to pump
sludge out o system
Produce grown on
the system can be
consumed or used
as source o
income
7/29/2019 BEVAT 1
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usaf ModularEvapotranspiration Basin
Groundwater
Septic TankRubble
Gravel
Sand
Soil
Inlet
Overow
Pipe
SPECIFIC PARAMETERS
Design a blackwater system or a daycare o 30
children and 5 adults
Blackwater and Greywater are already separated
Very high groundwater table: so system must be
not be more than 50 cm below surace (Normal ET
requires 1m depth) System should not require a secondary
treatment or
its blackwater: should be enclosed
STEPS FOR OUR DESIGN:
1. Calculate amount o blackwater that will need to be treated
daily
2. Choose a septic tank that can hold one days worth o waste
3. Ensure that there is an adequate amount o land or the ET
system
4. The piping should have at least a 2% decline to make sure
solids do not
clog the pipe5. I horizontal ET, the two tanks should have the
same volume, 40 cm deep
6. All the materials should be washed beore insertion in the
system so that
dirt does not disrupt the fltration process
Water loving plants
(Banana trees, taioba, etc)
CONTINUITY
An easy to use construction manual
was produced to be used in educational
projects in partnershup with
NGO and to aid in the
implementation o
Evapotranstpiration systems
in the community
The separation o modules allowed us to
design a sel-sufcient system adapted
to the geographical situation o the NGO
