polyelectrolytes (e.g., Dow C-31) initiated flocculation of algal cells while nonionic
as well as anionic polymers demonstrated ineffectiveness.
Flocculation is often achieved by smearing upright ultrasound waves and by
flocculating the electrocoagulation. While the use of hanging ultrasonic waves works
well in the laboratory, its large-scale handling is very difficult, and the high amount
of metal ions in the end result is a disadvantage of flocculating electrocoagulation.
1.3.6.5 Electroflocculation/Electro-Coagulation/Electrolytic
Aggregation
The need for an electrical field to change the surface characteristics of the algal cells
and to induce flocculation carries the ability for better harvesting because, in
principle, the process does not entail the addition of chemicals and could effectively
be performed as a continuous process. The obstacles to the general applicability of
these techniques are the development of electrodes that do not connect metals to the
device and the cost of the requisite electricity.
Electrophoresis is one of the harvesting processes in which no chemical substance
is added for segregation of substances. Charged algae in the solution escape due to
electric field. Hydrogen, generated water electrolysis, sticks to and takes to the
surface of the microalgae flocks. Compatibility with environmental, flexibility,
security fussiness, energy efficacy, and cost-effectiveness are a few profits of this
method. The major drawback of this approach is the fouling of cathodes and devices
that are impaired by high temperatures due to higher amount of power required
(Pragya et al. 2013).
1.3.7 Flotation
It is a process in which algal particles and air froths are exposed to one another and
the buoyancy of the air froth brings to the surface and it can be the algae. Flotation
methods can catch particles below 550 μm, these methods are made especially
suitable for single-cell microalgae. There are a few alternative approaches used for
harvesting such as flotation: dissolved air flotation (DAF), electrolytic flotation,
dispersed flotation, and flotation of ozone.
1.3.7.1 Dissolved Air Flotation (DAF)
DAF is based on the introduction of coagulants or flocculants, but the harvest is
enhanced by the use of fine bubbles from the bottom of the DAF device to collect
small aggregates and to carry them to the tank surface. The froth containing the cells
is skimmed off at the tank surface and deposited in a far more concentrated solution
(100-fold rise in solids) (Milledge and Heaven 2013). This supersaturates the culture
22
A. Shrivastava et al.
as well as anionic polymers demonstrated ineffectiveness.
Flocculation is often achieved by smearing upright ultrasound waves and by
flocculating the electrocoagulation. While the use of hanging ultrasonic waves works
well in the laboratory, its large-scale handling is very difficult, and the high amount
of metal ions in the end result is a disadvantage of flocculating electrocoagulation.
1.3.6.5 Electroflocculation/Electro-Coagulation/Electrolytic
Aggregation
The need for an electrical field to change the surface characteristics of the algal cells
and to induce flocculation carries the ability for better harvesting because, in
principle, the process does not entail the addition of chemicals and could effectively
be performed as a continuous process. The obstacles to the general applicability of
these techniques are the development of electrodes that do not connect metals to the
device and the cost of the requisite electricity.
Electrophoresis is one of the harvesting processes in which no chemical substance
is added for segregation of substances. Charged algae in the solution escape due to
electric field. Hydrogen, generated water electrolysis, sticks to and takes to the
surface of the microalgae flocks. Compatibility with environmental, flexibility,
security fussiness, energy efficacy, and cost-effectiveness are a few profits of this
method. The major drawback of this approach is the fouling of cathodes and devices
that are impaired by high temperatures due to higher amount of power required
(Pragya et al. 2013).
1.3.7 Flotation
It is a process in which algal particles and air froths are exposed to one another and
the buoyancy of the air froth brings to the surface and it can be the algae. Flotation
methods can catch particles below 550 μm, these methods are made especially
suitable for single-cell microalgae. There are a few alternative approaches used for
harvesting such as flotation: dissolved air flotation (DAF), electrolytic flotation,
dispersed flotation, and flotation of ozone.
1.3.7.1 Dissolved Air Flotation (DAF)
DAF is based on the introduction of coagulants or flocculants, but the harvest is
enhanced by the use of fine bubbles from the bottom of the DAF device to collect
small aggregates and to carry them to the tank surface. The froth containing the cells
is skimmed off at the tank surface and deposited in a far more concentrated solution
(100-fold rise in solids) (Milledge and Heaven 2013). This supersaturates the culture
22
A. Shrivastava et al.