The Application of UASB-MBR With Partial Nitrification-Denitrification in Wastewater Reclamation in Warm Climate

8/10/2019 The Application of UASB-MBR With Partial Nitrification-Denitrification in Wastewater Reclamation in Warm Climate

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The Application of UASB-MBR with PartialNitrification-Denitrification in Wastewater

Reclamation in Warm Climate

F.S. Wong,W. Fang, Y.P. Moy, S. Lin

WATERREUSE2011Barcelona, 26-29 September 2011


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Background

Experimental

Results and Discussion

Conclusions


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Background

30% of Singapores total water demand is from recycledwater (Newater)

Projected to meet 50% of Singapores future water

demand by 2060.

Growing concern over the carbon footprint of treatmentprocesses

A more effective wastewater treatment is desired Lower energy consumption

Reduced land use

Reduced sludge production


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Municipal/Industrial

Wastewater

Conventional Technology

Effluent

CAS: Conventional Activated Sludge Process

MBR: Membrane Bioreactor

High Cost, Long HRT & Large Footprint, CO2

Emission, Sludge Production

MBR

CAS

Activated sludge process - an aerobic condition for oxidation of C-source

Nitrification - an aerobic condition for oxidation of ammonia

Denitrification - an anoxic condition in the presence of electron donors


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EffluentMunicipal/Industrial

Wastewater

New Approach- Combined UASB-MBR

Shortcut Nitrification Denitrification

Anaerobic-Reduced Energy via

Reduced AerationBiogas

Smaller Footprint

Reduced Emission

MBRUASB

Less SludgeMembrane

HRT/SRT


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Combined UASB/MBR Concept

UASB

-+C,NH4-N

MBRUASB

Effluent-UASB Effluent-MBR Biogas

CH4,N2,CO2

Recycle (R)Influent (F)

membrane

Aerobic

Biodegradat

ionM

ethanogenesis

Denitrification

Nitrification

C,NOX-N

UASB MBR air

UASB designed for

methanogenesis

denitrification via nitrite

MBR designed for

partial nitrification


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AdvantagesCombined UASB/MBR System

Less oxygen demand ---- 25% reduction in oxygen via nitriterather than nitrate

Saving carbon source ---- 40% carbon saving in denitrification

Conventional nitrification/denitrification

NH4++ 2O2-------------->NO3

-+ 2H++ H2O

6NO3-+ 5CH3OH------->3N2+ 5CO2+ 7H2O + 6OH

-

Shortcut nitrification/denitrification

NH4++ 3/2O2-------------->NO2

-+ 2H++ H2O

6NO2-+ 3CH3OH------->3N2+ 3CO2+ 3H2O + 6OH

-


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Objective

To develop a simultaneous carbon and nitrogen removal

process with:

low energy consumption

low sludge production

a high effluent quality for NEWater production


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Lab Reactor System


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Wastewater Characteristics

Wastewater CODsolu

(mg/L)

TSS

(mg/L)

NH4+-N

(mg/L)

CODsolu/

NH4+-N

UPWRP 40-70 50-100 27-38 1-2.4

JWRP 220-1000 90-310 50-90 2.4-18.8

Real Wastewater

Ulu Pandan Water Reclamation Plant (UPWRP)

Jurong Water Reclamation Plant (JWRP)


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Operation Conditions

Parameters Water Reclamation Plant

Ulu Pandan Jurong

Operation stage UPWRP JWRP1 JWRP2

HRT of UASB/MBR(hrs) 3.5/5 8.4/12 4.7/6.7

Recirculation ratio (MBR

to UASB)

200%

pH 7.8-8

Dissolved oxygen (mg/L) 3.5-4 and 0.5-1

Temperature (C) 30

Membrane module 0.22 um, hydrophobic PVDF, flat Sheet


12/21CODsolu removal performance in UASB and MBR (a) UPWRP (b) JWRP1 (c) JWRP2

COD Removal

-69% for UASB

-85% & 86% for JWRP1 and JWRP2

Bulk of COD removed in UASB (46% / 71-76%)

Cf

MBR (23% / 14-10%)

Time (days)

0 5 10 15 20 25 30 35

CODConcentration(mg/L)

0

200

400

600

800

1000

1200

RemovalEfficiency(%)

0

20

40

60

80

100

Influent

UASB effluent

MBR permeate

Total efficiency

(b)

Time (days)

0 20 40 60 80 100 120 140


0

10

20

30

40

50

60

70

80


0

20

40

60

80

100Influent

UASB effluent

MBR permeate

Total efficiency

(a)

Time (days)

0 10 20 30 40 50


0

200

400

600

800

1000

1200

1400


0

20

40

60

80

100

Influent

UASB effluent

MBR permeate

Total efficiency

(c)


13/21NH4+-N removal performance in UASB-MBR system (a) UPWRP (b) JWRP1 (c) JWRP2

Feed NH4+-N:

30 mg/L for UPWRP

50-70 mg/L for JWRP

Removal at steady state:

96%

Average permeate conc:

3 mg/L

Time (days)

0 20 40 60 80 100 120 140

NH4

+-NConcentration(mg/L)

0

10

20

30

40


0

20

40

60

80

100

Influent

MBR permeate

Efficiency

(a)

Time (days)

0 5 10 15 20 25 30 35

NH4

+-NConcentration(mg/L)

0

10

20

30

40

50

60


0

20

40

60

80

100

Influent

MBR permeate

Efficiency

(b)

Time (days)

0 10 20 30 40 50

NH4

+-NConcen

tration(mg/L)

0

20

40

60

80

100


0

20

40

60

80

100

Influent

MBR permeate

Efficiency

(c)


14/21Nitrite accumulation in UASB-MBR system (a) UPWRP (b) JWRP1 (c) JWRP2

Shortcut nitrification optimised at:

pH 7.8-8

Temperature 30C

DO3-4 mg/L

In later tests, higher nitrite achieved at 0.5-

1 mg/L

Time (days)

0 20 40 60 80 100 120 140

Concentra

tion(mg/L)

0

2

4

6

8

10

12

14

NO2

- -N/N

Ox

- -N(%)

0

20

40

60

80

100

NO2--N

NO3--N

NO2--N/NOx

--N

(a)

Time (days)

0 5 10 15 20 25 30 35

Concentration(mg/L)

0

1

2

3

4

5

6

7

NO2

- -N/NOx

- -N(%)

0

20

40

60

80

100

NO2--N

NO3--N

NO2--N/NOx

--N

(b)

Time (days)

0 10 20 30 40 50

Concentration(mg/L)

0

1

2

3

4

5

6

7

8

NO2

- -N/NO

x- -N(%)

0

20

40

60

80

100

NO2--N

NO3--N

NO2--N/NOx

--N

(c)


15/21TN removal performance in UASB-MBR system (a) UPWRP (b) JWRP1 (c) JWRP2

TN removal:

56% for UPWRP

80% & 73% for JWRP

COD/TN ratio:1.9 for UPWRP

13.2 & 7.6 for JWRP

Low organic carbon could limit

denitrification in UASB for UPWRP

Time (days)

0 20 40 60 80 100 120 140

TNConcentration(mg/L)

0

10

20

30

40

RemovalEf

ficiency(%)

0

20

40

60

80

100Influent

MBR permeate

Efficiency

(a)

Time (days)

0 5 10 15 20 25 30 35


0

10

20

30

40

50

60

70

RemovalEf

ficiency(%)

0

20

40

60

80

100

Influent

MBR permeate

Efficiency

(b)

Time (days)

0 10 20 30 40 50


0

20

40

60

80

100

120


0

20

40

60

80

100

Influent

MBR permeate

Efficiency

(c)


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System Performance Results: UPWRP Wastewater

System Unit Parameters

(mg/L)

Influent Effluent/permeate Removal

(%)

UASB CODsolu 68 31 54

TOC 20 10 50

UASB + MBR CODsolu 68 20 70

TOC 20 5 75

NH4+-N 31 4 87

TN 29 13 55

Lab-scale system

C/N ratio = 2-3


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Biogas Production

Biogas production rate:

--- 1L/m3wastewater for UPWRP

--- 25 to 76 L/m3wastewater for JWRP (~0.23g CH4/g COD)

Methane composition in the biogas varied between 50% to 75% at differentstages of operation.

The extremely low biogas production in the treatment of UPWRP:

--- Low feed carbon concentration

--- Low C/N ratio

--- Loss of methane via dissolution in effluent from UASB


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Conclusions

The combined UASB/MBR with partial nitrification is:

feasible for treating municipal wastewater for carbon/nitrogen removal withmethane production

more suitable for treating higher strength wastewater where higher carbonand nitrogen removal can be obtained with higher energy recovery fromhigher methane production

a process with potential for further development for higher strengthmunicipal wastewater or high strength industrial wastewater for positive

energy balance, reduced footprint and reduced greenhouse gas especiallyin countries with warm climate.


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Acknowledgment

Environment & Water Industry Development

Council (EWI), Singapore for financial support to

the project

PUB, Singapore for its strong support to the project


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Documents

The Application of UASB-MBR With Partial Nitrification-Denitrification in Wastewater Reclamation in Warm Climate