sedimentation had affected quality of biomass produced, they switched on shortly to
other harvesting methods like centrifugation.
Due to sluggish process that resulted in deterioration of biomass quality, they
later switched to centrifugation as a harvesting method. For the quick harvesting
technique and to evade biomass deterioration, it is important to have high
settling rate.
7.2.2 Centrifugation
Centrifugation is extensively used for microalgae that produce high-value products,
as it involves more energy and cost. There are various types of industrial centrifuges
exist. Some of the key benefits of harvesting via centrifugal methods are it is rapid, it
involves no added harmful chemicals, and also it won’t degrade the biomass quality.
On the other hand, use of this technique has some drawbacks like elevated investment cost and high demand of energy. Some of the following approaches to a certain
extent can able to reduce the energy demand of the centrifugation method.
In a study, Evodos (the Netherlands) have developed a spiral plate centrifuge
which increased the surface area by means of decreasing the distance travelled by
settling microalga. Even though the harvesting efficiency is low, this technique has
significantly consumed very little energy for harvesting per unit of biomass
[50]. Another approach relies in pre-concentration of biomass, which significantly
reduces volume of culture and thus resulting in reducing energy demand for centrifugation. This can be achieved through flocculation, which increases the particle
size, thereby enhancing easy separation.
7.3 Filtration-Based Separation Technologies
Filtration, a physical process performed by using semipermeable membrane like
filter cloth, screens for the separation of solids. The pressure drop across the
membrane formed due to vacuum, gravity, or pressure acts as the driving force of
filtration method. High recovery efficiency, reuse of filter permeate, separation with
no added chemicals, and capability to separate shear-sensitive species all these
factors make filtration an attractive option for harvesting microalgal biomass. However few drawbacks like clogging and fouling of membranes and high investment
costs of pumps and membranes make filtration a costly process [51–53]. For effective microalgal biomass filtration, clogging and fouling must be avoided, and
membrane cost should also be reduced. The harvesting process can be made costeffective by performing combined harvesting techniques. A novel solution is to
combine flocculation with a lamella settler and then use a filter press to dewater the
sludge. Another method is filtration of the membrane for pre-concentration of
biomass shared with centrifugation to produce an algal paste. Because of their
heterogeneous existence, every form of microalgae needs different harvesting
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B. Srinivasan and G. Kulshreshtha
other harvesting methods like centrifugation.
Due to sluggish process that resulted in deterioration of biomass quality, they
later switched to centrifugation as a harvesting method. For the quick harvesting
technique and to evade biomass deterioration, it is important to have high
settling rate.
7.2.2 Centrifugation
Centrifugation is extensively used for microalgae that produce high-value products,
as it involves more energy and cost. There are various types of industrial centrifuges
exist. Some of the key benefits of harvesting via centrifugal methods are it is rapid, it
involves no added harmful chemicals, and also it won’t degrade the biomass quality.
On the other hand, use of this technique has some drawbacks like elevated investment cost and high demand of energy. Some of the following approaches to a certain
extent can able to reduce the energy demand of the centrifugation method.
In a study, Evodos (the Netherlands) have developed a spiral plate centrifuge
which increased the surface area by means of decreasing the distance travelled by
settling microalga. Even though the harvesting efficiency is low, this technique has
significantly consumed very little energy for harvesting per unit of biomass
[50]. Another approach relies in pre-concentration of biomass, which significantly
reduces volume of culture and thus resulting in reducing energy demand for centrifugation. This can be achieved through flocculation, which increases the particle
size, thereby enhancing easy separation.
7.3 Filtration-Based Separation Technologies
Filtration, a physical process performed by using semipermeable membrane like
filter cloth, screens for the separation of solids. The pressure drop across the
membrane formed due to vacuum, gravity, or pressure acts as the driving force of
filtration method. High recovery efficiency, reuse of filter permeate, separation with
no added chemicals, and capability to separate shear-sensitive species all these
factors make filtration an attractive option for harvesting microalgal biomass. However few drawbacks like clogging and fouling of membranes and high investment
costs of pumps and membranes make filtration a costly process [51–53]. For effective microalgal biomass filtration, clogging and fouling must be avoided, and
membrane cost should also be reduced. The harvesting process can be made costeffective by performing combined harvesting techniques. A novel solution is to
combine flocculation with a lamella settler and then use a filter press to dewater the
sludge. Another method is filtration of the membrane for pre-concentration of
biomass shared with centrifugation to produce an algal paste. Because of their
heterogeneous existence, every form of microalgae needs different harvesting
150
B. Srinivasan and G. Kulshreshtha