15.2 Photobiological Agents and Methods Used in PhotoBiological Reactors

233

15.2.2

Use of Photolytic and Photochemical Methods in Various

Photobiological Reactors for Treatment of Wastewater

15.2.2.1

Photo-Enhanced Degradation of Contaminants of Emerging Concern

in Wastewater

Emerging pollutants are posing serious global threats to the environment due

to their diversity, unruly nature, and bioaccumulation. More worrying is the

fact that present wastewater treatment systems do not have the volume to deal

with these classes of compounds. The mission to develop new technologies to

lessen the adverse effects of these pollutants has led to new research attention

on photo-enhanced processes. Photo-enhanced processes, with the possibility of

mineralizing environmental pollutants, currently seem to be the main feasible

technologies for dealing with emerging contaminants. The process of contaminant

degradation could proceed through either oxidation or reduction courses, men-

tioned as advanced oxidation processes (AOPs) and advanced reduction processes

(ARPs) respectively. As the danger of emerging contaminants continues to increase

globally, the strength of research on measuring their negative environmental impact

and the examination of new and improved methods for effecting their removal

continues to be on the rise. Photo-enhanced degradation processes have shown

huge potential for degrading evolving contaminants. Hence, it is very important

to carry out more studies for better consideration and flexibility of the process

particularly for industrial-scale applications. Since, most processes still rely on UV

light sources; there is the need to develop degradation systems that could use direct

sunlight for degradation process. This, in a way, will recover the economic viability

and environmental friendliness of these processes [18]. Various photobiological

agents and methods used in photobiological reactors for treating wastewater are

shown in Figure 15.3.

15.2.2.2

Pond Reactors (Photo-Fenton Process)

Currently, iron oxides have been planned as low-cost heterogeneous photo-Fenton

catalysts for the concurrent disinfection and discount of micro-contaminant load

from urban wastewater in channel pond reactors at near-neutral pH. The objective

was not finding the best working conditions but understanding the mechanisms

of iron oxide (FeOx)-driven disinfection and the insinuations presented by the

matrix constituents, namely organic matter and carbonates. Another objective was

to explore the possibility to apply this system after different secondary treatments

in continuous flow mode. Prominent bacterial inactivation was obtained in both

batch and continuous flow modes by any iron oxide used, with total inactivation

(5-log reduction) in the case of hematite.

The heterogeneous photo-Fenton process was confirmed to be the heavy bacterial

inactivation force in urban wastewaters. Additionally, nursing the elimination of 25

emerging contaminants in the secondary effluents was done. The operation mode

(batch or continuous) was assessed and a minimum of 35% micropollutant removal

was attained. This study presents the first attempt to use natural iron oxides (FeOx)