Drinking Water Disinfection Techniques by Jyoti Kishen Kumar & Aniruddha Bhalchandra Pandit

Author:Jyoti Kishen Kumar & Aniruddha Bhalchandra Pandit [Kumar, Jyoti Kishen]
Language: eng
Format: mobi, azw3
Tags: Technology & Engineering, Environmental, Water Supply, General
ISBN: 9781439877418
Publisher: CRC Press
Published: 2012-12-13T23:15:25.310134+00:00

1.01

0.92

disinfection

HC (5.17 bar)

121,950

23.02

12.66

25.45

(CFU

without

killed/s) at

multiple-hole

the end of 15

orifice plate

min

treatment

Hydrodynamic

1,786,200

50.56

21.21

35.29

cavitation (1.72

bar) + US flow

cell (40 kHz)

TABLE 5.7

Combination of a Cavitation Method + A Chemical Disinfectant Disinfection

HPC

Total

Faecal

Faecal

Parameter

Method

Bacteria

Coliforms

Coliforms

Streptococci

Percentage

US bath

57

75

47

50

disinfection

US bath +

95

99

95.5

94.2

(% killed) at

0.5 mg/l O3

the end of 15

Hydrodynamic

56

66

57

40

min

cavitation (5.17

treatment

bar) 10 l setup

Hydrodynamic

66

80

88

74

cavitation (5.17

bar) 10 l setup +

2 mg/l O3

Overall rate of

1 mg/l O3

1508

0.83

0.39

0.55

disinfection

2 mg/l O3

2121

0.75

0.46

0.66

(CFU killed/s)

3 mg/l O

at the end of

3

3345

1.85

1.08

1.42

15 min

US horn +

2209

1.51

0.72

0.75

treatment

1 mg/l O3

Cavitation-Based Disinfection Techniques

151

TABLE 5.8

Combination of Acoustic + Hydrodynamic Cavitation + Chemical Disinfectant Disinfection

HPC

Total

Faecal

Faecal

Parameter

Method

Bacteria

Coliforms

Coliforms

Streptococci

Percentage

Hydrodynamic

99.6

85

60

57

disinfection

cavitation (1.72

(% killed) at

bar) + US flow

the end of 15

cell (40 kHz)

min

Hydrodynamic

99.7

92

75

70

treatment

cavitation (1.72

bar) + US flow

cell (40 kHz)

+ 5 mg/l H2O2

Hydrodynamic

56

66

57

40

cavitation (5.17

bar) 10 l setup

Hydrodynamic

66

80

88

74

cavitation (5.17

bar) 10 l setup +

2 mg/l O3

Overall rate

Hydrodynamic

1,786,200

50.56

21.21

35.29

of

cavitation (1.72

disinfection

bar) + US flow

(CFU

cell (40 kHz)

killed/s) at

Hydrodynamic

1,798,000

70.10

28.87

48.24

the end of 15

cavitation (1.72

min

bar) + US flow

treatment

cell (40 kHz) + 5

mg/l H2O2

Hydrodynamic

52,815

4.88

2.82

3.63

cavitation (5.17

bar) 10 l setup

Hydrodynamic

65,664

10.72

6.59

6.63

cavitation (5.17

bar) 10 l setup +

2 mg/l O3

compared to the individual methods. For example, at the end of 15

min of treatment, 99% HPC bacteria were killed using this hybrid method, whereas only 56 and 57% disinfections were obtained with the individual methods of hydrodynamic cavitation and acoustic cavitation, respectively. Similarly, the overall rate of disinfection obtained at the end of 15 min of treatment for hybrid methods was much higher (50 total coliforms/s) than the individual methods of ultrasonication (3 total coliforms/s) and hydrodynamic cavitation (23 total coliforms/s). This effect could be attributed to the synergism created when two cavitational techniques come together. In

152

Drinking Water Disinfection Techniques

other words, hybrid techniques lead to higher cavitational intensity, which is translated in the form of higher percentage and rate of disinfection than using any one method alone. Numerical simulations of the cavity dynamics equations (Moholkar et al., 1999a,b) have indicated that it is easier to generate a large number of cavities hydrodynamically, and it is efficient to collapse them acoustically, as the acoustic collapse was found to be more violent. This was exactly confirmed by the author’s work. It is now very clear that combining ultrasound and hydrodynamic cavitation results in improved generation of hydroxyl radicals when the distance between the transducer and the orifice is 5 to 10 mm (Amin et al., 2010).

• Cavitation-enhanced chemical disinfection efficiency: Cavitation, especially that produced acoustically, is known to enhance the efficacy of a chemical disinfectant (Senthilkumar, Sivakumar, and Pandit, 2000). The literature reports a spectrum of hypotheses and attributes this phenomenon to chemical bond rupture of microbial cell membranes, leading to increased permeability to chemical disinfectants, increased generation and activities of free radicals when hydrogen peroxide or ozone is used (Dahi, 1976), disaggregation of microbial flocs (Katzenelson et al., 1974, in Dahi, 1976; Burleson, Murray, and Pollard, 1975), or ultrasonic acceleration of diffusion, allowing more rapid penetration of the toxic gas molecule into the microorganism (Boucher et al., 1967), to name a few. Similar effects, such as those discussed here, were clearly observed by the authors in their hybrid experiments. For example, percentage reduction of faecal coliforms at the end of 15 min of treatment in US bath was 47%. However, addition of only 0.5 mg/l O3 substantially enhanced the percentage disinfection to 96%.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.