Page 199 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Oxidation Technologies for Wastewater Treatment: An Overview 173

Figure 3.8 Typical schemes used for the combinatorial effects of UV and ultrasonic
irradiations: Batch reactors.

T1
T6 T2 Quartz
tube
Effluent
UV light
T5 T3 source
T4
Effluent out

UV tube
Ultrasound
transducers
Quartz
tube
Effluent in
Triple frequency hexagonal flow cell
Figure 3.9 Typical schemes used for the combinatorial effects of UV and ultrasonic
irradiations: Continuous reactors.

(continuous reactors). For wastewater applications, it is important to design
continuous reactors rather than batch reactors or at least reactors operating
inrecirculatingmode,becauselargequantitiesofeffluentswillhavetobetrea-
ted. The sonochemical element should be designed with power dissipation
over a wider area (more energy efficiency and also larger cavitational yield);
hence, ultrasonic bath-type reactors or parallel plate reactors with multiple
transducers are recommended (Gogate et al., 2001, 2003). Multiple-
frequency reactors have also been found to generate more intense and
spatially uniform cavitation as compared to reactors with single frequency
and/or single transducer operations; thus, these give better destruction effi-
ciency (Sivakumar et al., 2002). For the photocatalytic element, usually