Evaluation of Pathogenic and Indicator Microorganisms Removal by Membrane

Bioreactor

1Yamashita, N., 1Sugita, D., 1Hata, A., 1Tanaka, H., 2Mori, N., 2Okuma, N. 1Research Center for Environmental Quality Control, Kyoto University

2Water Reuse Promotion Center

Background

2

Bacteria: E. coli O-157, Cholera, Shigella

Protozoa: Cryptosporidium, Diardia

Virus: Norovirus, Rotavirus, Adenovirus Small size Disinfection tolerance

Reuse of sewage treatment water

Microorganisms in sewage water become problem

Is MBR effective to remove microorganisms?

Background

3

Contact facility Excess sludge reduction Water quality improvement Water Reuse

Knowledge of microorganisms removal by MBR is not enough.

Especially, virus removal data is important.

Breaking of membrane module in MBR would be observed occasionally.

What is appropriate indicator microorganism?

Advantages of MBR

4

→Evaluation of microorganisms removal by MBR

→Relashinship between microorganisms removal and membrane condition

２．Evaluation of indicator microorganisms

Purpose

1．Removal of microorganisms by MBR

Selection of appropriate indicator microorganism

Comparison between MBR and CAS

Materials and methods

5

6

Membrane Bioreactor (MBR)

Anaerobic tank Anoxic tank

Screen

Aerobic tank

Return sludge

Return sludge

Effluent

1

2

Influent

Membrane module replacement Since breaking of a few hallow fiber membrane was observed, membrane modules were replaced in January 2015.

Comparison microorganisms data between before and after replacement of membrane modules

1 2 Sampling point

Sampling period: Aug 2014 - March 2015, twice a month

hollow fiber type membrane

module

MLSS concentration: 6000-8000 mg/L

7

Conventional Activated Sludge (CAS) system

Disinfection

Chlorination 1

3

2

Returned sludge

Excess sludge

Sedimentation tank

Sedimentation tank

Conventional treatment

Deep shaft aeration treatment

Sedimentation tank

Influent

1 2 3 Sampling point

Sampling period: September 2014 - March 2015 Once a month

MLSS concentration: 1200-1500 mg/L

Effluent 2

Effluent 1

8

Sampling

9

Target Microorganisms

Norovirus (GI,GII-NoV)

Rotavirus(RV)

F-phages (GI~GIV-FPH)

Aichi virus (AiV) Pepper Mild

Mottle Virus (PMMoV)

Pathogenic virus Indicator virus

Indicator bacteria

E. Coli Coliforms

10

Bacteria

Culture method Plaque assay Concentration with electro-negative filter

Virus F-phage

genotype

Detection

Water samples

RT-qPCR TaqMan®

probe

Results and discussion

11

12

Effluent concentration from MBR was 101-102.

Bacteria removal by MBR was 5-6 logs.

E. coli was detected in effluent from MBR.

Bacteria concentration in MBR

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

Con

cent

ratio

n (C

FU/1

00m

L)

Influent

effluent

E. coli was detected.

E. coli concentration in influent and effluent in MBR (Before membrane module replacement)

Aug. Sep. Oct. Nov. Dec.

13

Bacteria concentration in CAS

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

Con

cent

ratio

n (C

FU/1

00m

L)

Influent

effluent 1

effluent 2

High concentration

Effluent concentration from CAS was about 104.

Bacteria removal by CAS was 2-3 logs.

Concentration of E. coli in effluent from CAS was relatively high.

E. coli concentration in influent and effluent in CAS

Sep. Oct. Nov. Dec. Jan. Feb.

0

1

2

3

4

5

6

7

8

Log

Rem

oval

14

Bacteria removal by MBR

E.coli Total coliforms

Bacteria removal by MBR was much higher than that by CAS.

E. coli and total coliforms removal by MBR was 5-6 logs.

E. coli and total coliforms removal by CAS was 2-3 logs.

Removal by CAS

0

1

2

3

4

5

6

7

8

Log

Rem

oval

15

Virus removal by MBR

AiV: Aichi virus, PMMoV: Pepper Mild Mottle Virus, GI, GII GIII-FRNAPH: GI, GII GIII F-RNA phage, GI-NoV: GI Norovirus, GII-NoV: GII Norovirus

AiV

PM

MoV

GI-F

RN

AP

H

GII-

FRN

AP

H

GIII

-FR

NA

PH

GI-N

oV

GII-

NoV

Virus removal by MBR was 3-4.2 logs. Virus removal fluctuated depending on samples and viruses.

(Before membrane module replacement)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00

AiVPMMoVGI-FRNAPHGII-FRNAPHGIII-FRNAPHF-PHGI-NoVGII-NoVRV

16

Comparison between MBR and CAS removal

CA

S s

yste

m L

og R

emov

al

MBR Log Removal

Virus removal by MBR was 3-4.2 logs as average.

Virus removal by CAS was 1-3 logs as average.

MBR will be effective to remove viruses in water.

17

Membrane replacement

Since breaking of a few hallow fiber membrane was observed, membrane modules were replaced in January 2015.

Lifting up membrane modules Setting new membrane modules

Compare microorganisms removal between before and after

18

Bacteria removal by MBR – Membrane replacement

0

1

2

3

4

5

6

7

8

Log

Rem

oval

E.coli Total coliforms

Bacteria removal by MBR was 6-7 logs.

Bacteria removal was improved after replacement.

Before replacement

After replacement

Rejection by membrane will be the important role.

19

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

Con

cent

ratio

n (C

FU/1

00m

L)

Influent

effluent

Bacteria removal by MBR was improved after replacement.

E. coli was not detected in effluent from MBR.

E. coli was not detected.

E. coli concentration in influent and effluent in MBR

Bacteria concentration in MBR – Membrane replacement

N.D. N.D. N.D. N.D. N.D.

E. coli would be used as a indicator to evaluate membrane condition.

Jan. Feb. Mar.

0

1

2

3

4

5

6

7

8

Log

Rem

oval

Virus removal by MBR – Membrane replacement

Before replacement

After replacement

AiV

PM

MoV

GI-F

RN

AP

H

GII-

FRN

AP

H

GIII

-FR

NA

PH

GI-N

oV

GII-

NoV

Virus removal fluctuated depending on samples and viruses.

Virus removal by MBR was not improved after replacement.

Rejection by membrane will not be important for virus removal. 20

21

Conclusions

Removal of microorganisms by MBR

Evaluation of indicator microorganisms

Bacteria removal by MBR was 5-6 logs and virus removal was 3-4.2 logs.

MBR will be effective to remove microorganisms in water.

Microoranisms removal by MBR was higher than that by CAS.

Bacteria removal was improved after membrane replacement.

E. coli would be used as a indicator to evaluate membrane condition.

Virus removal was not improved after replacement. E. coli was not detected in effluent from MBR.

Thank you for your kind attention