By: ANJALI KRISHNAN

Department of Botany

The Institute of Science,Mumbai,India

Open pond system

Closed pond system

Air-lift method

Marine /Open Ocean cultivation

Desert cultivation

Photobioreactors

• Types of photobioreactors

Reference

Open pond systems can be categorized

into two :

Natural waters(lakes, lagoons & ponds).

Artificial ponds or containers .

The most commonly used systems include

shallow big ponds, tanks, circular ponds

&raceway ponds

This method have been employed since

1950s.

The ponds in which the algae cultivated are known as “raceway ponds”.

In these ponds, the algae, water, nutrients, circulate around a race track.

With the paddle wheels providing the flow, algae are kept suspended in the water,& are circulated back to the surface on a regular frequency.

The ponds are usually kept shallow because the algae needs to be exposed to sunlight ,&sunlight can only penetrate

the pond water to a limited depth .

The ponds are operated in a continuous

manner with CO2 & nutrients being

constantly fed to the ponds, while algae

containing water is removed at the other

end.

The algae cultivated are:

o Anabaena

o Nostoc

o Chlorella

o Dunaliella

o Arthrospira

ADVANTAGE

• One of the major advantages of open

ponds is that it is easier to construct

&operate than the closed ponds.

DISADVANTAGE

• There is poor light utilization by the cells,

evaporative losses, diffusion of CO2 to the

atmosphere and requirement of large

areas of land

An alternative to open pond system.Control over the environment is much

better than the open ponds.A closed pond is to close it off, to cover a

pond or pool with green house.Takes care of problems associated with an

open system. It allows more species to be grown &

remain dominant. The growing season can be extended by

heating.

It is possible to increase the amount of

CO2 in these quasi-closed systems, there

by increasing the rate of growth of algae.

The closed systems are usually

constructed using plexiglass.

Horizontal photobioreactors.

Vertical systems.

Flat plate reactors.

This system includes tubes laid on the

ground to form a network of loops.

Mixing of microalgal suspended culture

occurs through a pump that raises the

culture vertically at timed intervals into a

photobioreactor.

These reactors use vertical polythene sleeves hung from an iron frame.

Glass tubes can also be used alternatively.

Microalgae are also cultured in vertical alveolar panels (VAP)which a type of photobioreactor .

2 main types of vertical photobioreactors are the Flow through VAP & the Bubble Column VAP.

Flat plate reactors(FPR)are built using

narrow panels & are placed horizontally to

maximise sunlight input to the system.

The concept behind FPR is to increase

the surface area to volume ratio such that

the sunlight is effectively used.

It reduces oxygen build up.

This method is used in indoor cultivation &

production of microalgae; where air is moved

within a system in order to circulate water

where microalgae is growing.

The culture is grown in transparent tubes that

lie horizontally on the ground & are connected

by a network of pipes.

Air is passed through the tube such that air

escapes from the end that rests inside the

reactor that contains the culture & creates an

effect like stirring.

Spirulina spps

Marine algae comes in two forms, some

marine algae are small &only be seen

under microscope while others are very

large called macroalgae or seaweeds such

as macrocystis, a species of kelp.

The most common name of marine algae

is “seaweed”.

Isochrysis galbanaTetraselmis sppsChlorococcum littoraleSynechococcus sppsChlamydomonas sp.Nanochloropsis salinaPheodactylum tricornutumDunaliela tertiolectaChaetoceros muelleriBotryococcus brauniiEmiliania huxleyi

Algae can be grown in salt water ponds in

the deserts.

Algae cultivation in desert is done for

biodiesel production.

Haematococcus pluvialis

Microcoleus vaginatus

Chlamydomonas perigranulata

Synechocystis

A bioreactor is an installation for the

production of microorganisms outside their

natural but inside an artificial environment.

The prefix “photo” particularly describes the

bio-reactors property to cultivate

photoautotrophic microorganisms, or

organisms which grow on by utilizing light

energy like microalgae, macroalgae ,

mosses & cyanobacteria.

It is a closed equipment which provides a

controlled environment & enable high

productivity of algae.

PBRs facilitate better control of culture

environment such as CO2 supply, water

supply, optimal temperature, efficient

exposure to light, culture density, pH

levels, gas supply rate mixing regime, etc.

1. From the feeding vessel, the flow progress

to the pump which moderates the flow of

the algae into the actual tube.

2. The PBRs itself are used to promote

biological growth by controlling

environmental parameters including light.

The tubes are made up of acrylic & are

designed to have light & dark intervals.

3. The PBR has an built–in cleaning system that internally cleans the tube without stopping the production.

4. After the algae have completed the flow through the PBR, it passes back to the feeding vessel. As it passes through the hoses ,the oxygen sensors determine how much oxygen has been built up in the plant. It is also at this stage that the optical cell density sensor determines the harvesting rate,

5. When the algae is ready for harvesting,

they pass through the connected filtering

system. This filter collects the algae that

are ready for processing, while the

remaining algae passes back to the

feeding vessel.

6. The flow continues.

1. TUBULAR PBRs

Made up of plastic tubes, tubular

PBRs consist of straight, coiled or looped

transparent tubing arranged in various

ways for maximizing sunlight capture.

2. Christmas Tree Reactor

This reactor is built in a tapered

geometry which carries a helically

attached , translucent double hose circuit

system. The result is a layout similar to a

christmas tree.

A location is not crucial ,& therefore non-

arable land is suitable as well.

3. Flat Plate ReactorsFlat-plate photobioreactors are made of

transparent materials for maximum utilization of solar light energy. Accumulation of dissolved oxygen concentrations in flat-plate photobioreactors is relatively low compared to horizontal tubular photobioreactors. It has been reported that with flat-plate photobioreactors, high photosynthetic efficiencies can be achieved.

Flat-plate photobioreactors are very suitable for mass cultures of algae

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