water disinfection

WATER DISINFECTION

WATER TREATMENT AND PURIFICATION SYSTEMS

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water treatment

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment To print in Adobe Reader
    Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment      

Jin Xin

University of Science and Technology Beijing

School of Civil and Environmental Engineering

Centre for Sustainable Environmental Sanitation

Xueyuan Road 30 / Haidian District

Tu Mu Huan Jing Lou - Office 1214 - Beijing, 100083 - P.R. China

Phone / Fax +86 10 6233 4378 website: www.susanchina.cn

Background

Introduction

Materials and Methods

Results and Discussion

Conclusions

1. Background

Infectious diseases

Highly pathogenic avian influenza

Epidemic situation of SARS

Epidemic situation of H1N1

Cause problems

Ecological safety

Environmental sanitation

Other aspects.

The environmental safety of WWTPs tail water plays an important role in the whole ecological environment protection, thus tail waters disinfection became a significant defense line in both protecting the receiving waters ecological safety and preventing the epidemic situation from being spread out.

People have been pay more attention on the disinfection of wastewater treatment plants effulents. Traditional disinfectants have many disadvantages, finding new safety and efficiency disinfection technologies became more and more important. The work was carried out based on project of Research on Mechanism of Ultrasonic Synergy Disinfection----- which supported by NATURAL SCIENCE FOUNDATION of CHINA (NSFC).

2. Introduction

The project Research on Mechanism of Ultrasonic Synergy Disinfection-- (NSFC) focus on studying the synergy disinfection effect. The main work :

• Find out the mechanism of ultrasonic disinfection as a pre-treatment method; Chanel - . .

• How it works with other disinfectants;

• The key influence factors in ultrasonic disinfection.

The objective of this work is

• To evaluate the newly proposed method of applying a ULTRASONIC (US) as a pretreatment step in combination with ultraviolet irradiation to improve the disinfection efficiency of wastewater by breaking up the large particles;

• To explore the fundamental characteristics of how particles and bacterias in wastewater respond to ultrasonic (US);

• To find the mechanism of synergistic disinfection.

3. Materials and Methods

Ultrasonic generator and transducer are made according to our specially need. Ultrasound frequencies are 21.51kHz (horn) and 83.03kHz (column); UV light: SJD-I desktop UV germicidal lamp, AC220V-50HZ, quartz tube lamps power is 15W.

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

Lab scale experiment equipment

3. Materials and Methods

Main Elements:

• CODcr (potassium dichromate method)

• SS

• E.Coli (multiple-tube fermentation technique)

• Energy Consumption

 4. Results and Discussion

a.CODcr

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

Ultrasonic has gteat effect on CODcr during the first 50 seconds, The value of CODcr increasing rapidly with time increase.

b. SS

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

The experimental results show that, SS concentration decreaseing with the increase of US acting time. The size of big particle became smaller, samples became turbid.

c. E.coli

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

The number of E.coli increased with disinfection time in the initial stage of the experiment, and then decreased rapidly, it will below the initial value after 20 minutes.

d. E.coli

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

The number of E.coliform decreased with time increasing of ultraviolet irridiation.

The total coliform number reduced by 2.8 log units when UV light disinfect for 30S, the total coliform number reduced by 3.4 log units when UV light disinfect for 40S, sterilization rate reach to 99.9%. However, the number of coliform became more and more during the following two days. Some bacterias which seem be killed reappeared.

d. Synergy effect

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

In the synergy disinfection experiment, US can improve the UV disinfection effect noticeably. With US pretreatment it only takes about one-third of the ultraviolet light exposure time to achieve the same disinfection results as ultraviolet treatment.

The results of Orthogonal test:

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

e. Energy consumption

Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment

The energy consumption is large when only using ultrasonic for disinfection. Very short time of US pretreatment, It can not only improve the disinfecton effect of ultraviolet radiation, but also achieve the same premising effects take shorter UV radiation time. At the same time, the energy consumption is smaller than UV alone.

4. Conclusions

• Ultrasonic working as a pre-treatment method and followed by UV radiation for disinfection is a much better way in practice;

• The experiment results revealed that the particle size distribution (PSD) in the test samples were apparently shifted toward the small size range;

• The synergy effects can raise the disinfect efficiency compare with single UV. It can reduce radiation time in reaching the same disinfect efficiency;

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• The application of a US step might also be beneficial in terms of costeffectiveness.

• During the follow-up monitor, the phenomenon of photoreactivation was under control.

The experimental results in this study showed some degree of variation for similar experiments. This is not unusual for this kind of study, due to many uncontrolled factors,such as:

Characteristics of tested samples, Random error in the microbiology tests.

However, these experiments clearly showed that the proposal of using the US to pre-treat wastewater could be a very attractive alternative to enhance ultraviolet disinfect efficiency.

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Russian version
2002 JSC "SVAROG"                           Phone / Fax: +7(495) 617-1945, +7(499) 795-7786
E-mail:   E-mail:svarog@svarog-uv.ru