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Advanced Oxidation Technologies for Wastewater Treatment: An Overview 183

3.6.2.1 Treatment of B-DWW Using HC
The B-DWW was subjected to HC pretreatment for which 6 L of waste-
water was taken in cavitation reactor. Cavitation was achieved using a cir-
cular venturi (shown in Figure 3.13). The experiments were conducted at
two different inlet pressures (low as well as high) and at different dilutions
over the time range of 50–150 min. At the end of each defined time
interval, the samples were withdrawn from the reactor through a sampling
port, centrifuged, and analyzed for pH, COD, BOD, and TOC. The
obtained results are reproduced in Table 3.3.
It has been reported that HC is capable of reducing the COD and TOC
of the B-DWW by about 34% and 33%, respectively, at 5 bar inlet pressure;
no further improvement was observed with increase in pressure from 5 to
13 bar. It can be observed from the values of COD and TOC that the dilu-
tion has no significant effect on the mineralization of distillery wastewater.
Although the percentage reduction is marginally higher at 50% dilution, the
total quantum (milligram of COD/TOC per unit volume) of COD and
TOC reduction is lower at 25% and 50% dilution as compared to undiluted
wastewater. But for the enhancement in the biodegradability of B-DWW,
the observed conditions are different. It was observed that at lower pressure
(5 bar) and zero dilution, the ratio of BOD/COD increases to the tune of
0.24, becoming 0.25 when the sample dilution is 25%. Thus dilution is again

Table 3.3 Effect of cavitation pretreatment on biodegradability index of
biomethanated distillery wastewater
Time BOD BI: BOD 5 /
Reaction Condition (min) COD (mg/L) (mg/L) COD
Pressure¼5 bar, 0 34391.00 4853.00 0.14
No dilution 50 23723.00 5120.00 0.22
100 23442.00 5500.00 0.23
150 23302.00 5500.00 0.24
Pressure¼5 bar, 0 28208.00 3666.00 0.13
25% dilution 50 19539.00 4170.00 0.21
100 18300.00 4250.00 0.23
150 18163.00 4500.00 0.25
Pressure¼13 bar, 0 33973.00 4756.00 0.14
No dilution 50 24128.00 5830.00 0.24
100 22325.00 6400.00 0.29
150 22325.00 6400.00 0.29
Pressure¼13 bar, 0 28754.00 3738.00 0.13
25% dilution 50 18795.00 6000.00 0.32
100 18374.00 5910.00 0.32
150 18363.00 5800.00 0.32