Environmental Engineering Reference
In-Depth Information
There are many different types of closed systems, some of them are:
a.
Tubular photo bioreactors:
Tubular photo bioreactors consist of flexible plastic or glass tubes commonly
positioned parallel to one another or flat beyond the ground to increase surface
to volume percentage of the container. The pipes allow the penetration of light
and the developmental phase mingles from reservoir to reactor and back to the
reservoir. The blustery movement in the reactor permits the delivery of nutri-
ent, increases gas exchange, lessens the cell sedimentation and flow biomass for
equal enlightenment (Lee
2001
).
b.
Flat plated photo bioreactors:
These have large surface area which allows greater photosynthesis, low buildup
of oxygen being dissolved, and immobilization of algae. They are cheap but
great surface area roots for highly unacceptable problems, such as temperature
regulator, CO
2
diffusion frequency and affinity of the algae to wall adhering (Lee
2001
).
c.
Inclined triangular tubular photo bioreactor
:
Inclined triangular tubular bioreactor is similar to power plant using flue gas.
Flue gas enters reactor from the bottom. Gas bubbles move in the pipe producing
eddies for mixing and avoidance of entangling. The upper surface of pipe per-
mits absorption of solar energy. The mixing of the flue gas and the algae culture
allows growth to the extent that 15-30 % algae can be harvested each day (Ugwu
et al.
2008
).
d.
Continuous stirred tanks:
Continuous stirred tanks have wide, hollow, capped pipe, cylindrical in shape
which has low contamination risk and can be used both indoor and outdoor. The
light source and mechanical stirrer are placed at the top while draining canals
and gas injectors are placed at the foot of the reactor. The blustery movement
allows growth and avoids fouling (Kwiatkowski et al.
2006
).
iii.
Hybrid systems:
The hybrid system uses open and closed system in combination to obtain better
results. The hybrid system is the most reasonable option for cheap and more
crop growing strains for biofuel production. Open ponds are injected with
wanted strain of algae and is cultivated in bioreactor. The size of inoculum
should be larger than undesired species. To avoid contamination, cleaning and
flushing ponds must be a portion of aqua culture and are considered as batch
cultures (Kwiatkowski et al.
2006
; Sananurak et al.
2009
).
