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15 Photobiological Reactors for the Degradation of Harmful Compounds in Wastewaters

15.2.4

Nanotechnology in Photobiological Reactors for the Treatment

of Wastewater

15.2.4.1

Potential of Nanotechnology in the Treatment of Wastewater

Nanomaterials become crucial in water treatment plants because of their strong

antibacterial activity, photocatalytic response for a broad light spectrum, highly

effectual adsorbence, reusability, recyclability, and easy operation. Currently,

metals and their oxides, carbon nanomaterials (CNMs such as nanocomposites,

nanotubes), metal organic frameworks (MOFs), and zerovalent NPs are discussed.

They possess increased surface area and more porosity, which enhances the

efficiency of NPs. Magnetic nanoparticles agglomerate due to van der Waals forces.

Cytotoxicity fallouts due to carbon nanotubes, quantum dots, TiO2, silver, and gold

NPs make the use of nanomaterials in wastewater treatment with greatest care.

Hence, the protective and risk studies of nanomaterials have to be assessed before

their application [24].

15.2.4.2

Moving Bed Biofilm Reactor

The pure bacterial culture will form a biofilm adhered to specific large surface sup-

porters (filters fill), which are submerged and moving in the biological reactor. Paints

and sunscreens contain TiO2 NPs, which also act as catalyst in the wastewater treat-

ment. The TiO2 NPs will exhibit toxic effects on an anaerobic bacterium, Macrococ-

cus caseolyticus, isolated from the activated sludge of a wastewater treatment. The

cytotoxicity inspection was performed under both light and dark conditions, and it

showed decreased feasibility on exposure to light, and it was dose-dependent. The

formation of exo-polymeric substances (EPSs) is dose-dependent, and maximum

EPS release was observed under UV-A. When treated with TiO2 NPs, the accretion

tendency of biofilm was more marked. The acceptance of TiO2 NPs by the biofilm

could be due to remediation of the NPs in wastewater by the organisms. The inter-

action of TiO2 NPs with M. caseolyticus under UVA, visible light, and dark condition

was observed [25].

15.3

Conclusion

Various modern emerging methods of wastewater treatment such as activated

sludge, oxidation ditches, UASB, activated carbon, nanoparticles; microbial fuel

cells are currently well developed. These advanced methods are of less sustainability

but have high efficacy in treating wastewater. High-efficiency reactors that use

various photobiological methods are pond reactors, flow reactors, anaerobic sludge

reactors, hybrid reactors, membrane reactors, moving-bed biofilm reactors, and

they are industrious in wastewater management.

Acknowledgment

The authors are very much thankful to N. Venkateswarlu, President, P. Lakshmana

Rao, Secretary SAGTE, Dr. G. Devala Rao, Principal, and Dr. Buchi N. Nalluri HOD,