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15 Photobiological Reactors for the Degradation of Harmful Compounds in Wastewaters

is far advanced than the rate of bio-adaptability. As a result, conservative treatment

arrangements are facing problems in recent times.

Nowadays, using microalgae and other microbes in large wastewater systems has

revolutionized wastewater treatment [1, 2]. Apart from the microbial-based photo-

biological reactors, there are other reactors that use photolytic and photochemical

methods such as photo-enhanced degradation, photo fermentation, photo-activated

(chemical) degradation and photocatalytic methods, membrane-based separation

techniques, and nanotechnological approaches. Currently, anaerobic treatment is

used for sludge management after aerobic treatment in many cases and management

of sludge is shown in Figure 15.1.

Aerobic treatment stages include:

1. Pretreatment: Large-size solids arriving at the water treatment plant are first

removed. If not disposed of effectively, these materials can lead to serious equip-

ment failure.

2. Primary treatment: It involves sedimentation of solid waste within water and

is done after filtering out larger contaminants within the water. Wastewater is

passed through several tanks for removal of contaminants.

3. Secondary treatment: It is the portion of sewage treatment sequence removing

dissolved and colloidal compounds measured as BOD. It is traditionally applied

to the liquid portion of sewage after primary treatment.

4. Tertiary treatment: Depending on the quantity of the effluent obtained, its final

destination, and relevant legislation, tertiary treatment may be applied to remove

residual organic load and other pollutants not removed after the secondary treat-

ment, such as nutrients, phosphorus, and nitrogen. Any combination of treat-

ment processes can be used, whether physical, chemical, or biological.

Anaerobic treatment: Anaerobic microbes transform organic matter in the

wastewater into biogas that contains large amounts of methane gas and CO2. It is

an energy-efficient process used for treating wastewater.

Different methods for the treatment of wastewater using photobiological reactors

are discussed in this chapter. Studies on the use of microbes as photobiological agents

for the degradation of various harmful compounds such as phenol, alkane, hex-

adecane, oil, etc., in wastewater and sewage have been reviewed. The chapter also

discusses the different treatment methods such as photobiological, photochemical,

membrane, and nanotechnology methods.

15.2

Photobiological Agents and Methods Used

in PhotoBiological Reactors

15.2.1

Microbes Acting as Photobiological Agents in Various

Photobiological Reactors for the Remediation of Wastewater

15.2.1.1

Olive Mill Wastewater Treatment by Immobilized Cells of Aspergillus

niger

Apart from using as sources of phytotoxic and antimicrobial agents, the oil mill waste

(OMW) can be used as raw material and fertilizer since it contains up to 11 kg of