Evaluation of Anaerobic digestion by Influent of Ammonia Nitrogen

Concentration and Nitrogen Loading Rate

Park Hyun Chul • Kim Sung Jin • Oh Yong Keol • Park Chul Hwi

University of Seoul

Background

2

3

Food Waste Water(Leachate) ?

Water(wash water, settling water) that is produced by course of the

treatment and recycling of food waste or part of food waste.

separate discharge

Food waste water

HOME Food

Waste tank

Particle

Dumping / Incineration

Breaking food

waste

Settling water

Food waste water

Steam condensate

water

Dewatering Dryer

Composting

Ocean Dumping

Prohibit London Dumping

Convention

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Food Waste Water(Leachate) ?

Anaerobic digestion

Dumping of food waste water is prohibited by London Dumping

Convention , anaerobic digestion is in the limelight for land treatment.

Anaerobic digestion produce sludge smaller than aerobic treatment, also

it can produce methane from organic matter.

It produced approximately 9,000 ton per day, concentration of BOD is

about 74,000 mg/L.

The cost of food waste water treatment is high because concentration of

organic matter is too high.

Thus, an average of approximately 5,000 tons per day or more was

dumping at sea.

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Anaerobic digestion using food waste water

For efficient and reliable operation of anaerobic digestion, it is

important that operater maintain the operating conditions.

Operating factors are pH, temperature, alkalinity, ammonia

nitrogen, etc., and each has a deep relevance.

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Anaerobic digestion using food waste water

For efficient and reliable operation of anaerobic digestion,

anaerobic digestion need to maintain the appropriate

concentration of ammonia nitrogen.

NH4+-N Concentration Effects

50~200 mg/L Beneficial

200~1,000 mg/L No adverse effect

1,500~3,000 mg/L Inhibitory at high pH value

Above 3,000 mg/L Toxic

• Anaerobic digestion is reduction process that convert organic nitrogen to

ammonia nitrogen.

• In anaerobic digestion, the accumulation of ammonia nitrogen is inevitable.

• In anaerobic digestion, food waste water which containing high concentrations of

organic matter and nitrogen much more convert organic matter and nitrogen to

ammonia nitrogen than sludge

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Anaerobic digestion using food waste water

Optimal concentration of ammonia nitrogen can lead to maintain

alkalinity and pH

• When concentration of ammonia nitrogen is high in digester, ammonia

combines with carbon dioxide to generate HCO3- and NH4

+. Accordingly, pH

increase due to alkalinity supplement.

NH3 + H2O + CO2 -> NH4+ + HCO3

-

In anaerobic digestion, the accumulation of ammonia

nitrogen is inevitable.

In order to maintain the concentration of ammonia nitrogen,

process is required which means removal and maintaince of

ammonia nitrogen.

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Anaerobic digestion using food waste water

In this study, for stable operation of the anaerobic digestion

using food waste water, operational characteristics were

investigated by nitrogen loading rate.

• In order to investigate the behavior of the ammonia

nitrogen, anaerobic digestion is studied without feed.

• Investigation of behavior of ammonia nitrogen by

nitrogen loading rate.

• To maintain the appropriate concentration of ammonia

nitrogen, the experiment of anaerobic digestion using

watering and sludge recirculation process was conducted.

Materials & Method

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Characteristics of food wastewater (S landfill food wastewater) Items Unit Value

pH - 3.9

TS % 11.5

VS % 9.1

TCODcr mg/L 182,642

SCODcr mg/L 99,119

T-N mg/L 3,583

NH4+-N mg/L 528

Items Unit Value

pH - 7.44

TS % 2.1

VS % 1.34

SCODcr mg/L 886.1

T-N mg/L 1,505

NH4+-N mg/L 451

VFAs mg/L 138.2

Alkalinity mg/L as CaCO3

2,404

Characteristics of seed sludge (N sewage treatment plat digestion sludge)

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Schematic diagram of anaerobic digestion process

System Single anaerobic digestion

Total volume Anaerobic digestion(35L), Gas storage(50L)

Temperature 35◦C , mesophilic

Substrate S landfill food wastewater

Seeding sludge N sewage treatment plant digestion sludge

System of experiment

Gas collector

Gas collector

Gas collector

Food waste water tank

R2 R3 R4 R1

Gas collector

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The experiments were carried out with two different operating conditions. 1. Test of no loading

• Without feed, it is conducted test to investigate about change concentration of ammonia nitrogen during 30 days

2. Test of loading

• The investigation of behavior of ammonia nitrogen by nitrogen loading

rate.

• To maintain the appropriate concentration of ammonia nitrogen, the

experiment of anaerobic digestion using watering and sludge recirculation

process was conducted.

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Watering and sludge recirculation process(R1)

Condition Purpose Solution

Case 1 ․ NH4

+-N 700mg/L ≤ R1

․ TS 2.2% ≤ R1

․ TS and NH4+-N

control

· effluent digested sludge

(3L) and replace DW (3L).

Case 2 ․ NH4

+-N 700mg/L ≤ R1

․ TS 1.9~2.2%

․ NH4+-N

control

Centrifuge 1L digested sludge for

5min.

Pour off supernatant and replace DW.

Case 3 ․ NH4

+-N 700mg/L

․ TS 2.2% ≤ R1

․ TS

control

· Stop mixing and concentrating

digester.

Effluent concentrated digester.

Items R1(control) R2 R3 R4

Nitrogen Loading rate

(NLR, kg N/m3•d)

0.075 0.075 0.15 0.3

SRT (d) HRT

70 70 35 17.5

Internal TS control (%) 1.9~2.2 - - -

NH4+-N control (mg/L) 500 - - -

VFAs control (mg/L) 300 - - -

Condition of experiment

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Gas collector

Sedimentation and

stabilization

Treated water

WWTP

River

Q : 500 mL

Qe : 1,500 mL

Qe’ : 1,200 mL Qw : 300 mL

Qr : 1,000 mL (300+700)

Qx : 700 mL

Results & Discussion

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Time (Day)

0 5 10 15 20 25 30 35

Concentr

ation (

mg

/L)

200

400

600

800

1000

1200

1400

1600

T-N

NH4+-N

NH

4+

-N/T

-N (

%)

0

20

40

60

80

100

NH4+-N/T-N

Nitrogen was decreased slightly

Ammonia nitrogen was increased from 451 mg/L to 1,060 mg/L

Alkalinity and pH was increased 4,800 mg/L and 7.9 respectively.

Time (Day)

0 5 10 15 20 25 30 35

Alk

alinity(m

g/L

as C

aC

O3)

2000

2500

3000

3500

4000

4500

5000

Alkalinity

pH

7.0

7.5

8.0

8.5

9.0

pH

17

Time(Day)

0 5 10 15 20 25 30 35

Co

nce

ntr

atio

n (

%)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

TS

VS

VS

/TS

(%

)

40

50

60

70

80

VS/TS

Time (Day)

0 5 10 15 20 25 30 35

VF

A c

on

ce

ntr

atio

n (

mg/L

)

0

20

40

60

80

100

120

140

160

180

VFA

Accu

mu

lative

bio

ga

s p

rod

uctio

n(L

)

2

3

4

5

6

7

Biogas production

Concentration of TS and VS was decreased from 2.1 ~ 1.8 and 1.4 ~ 1.1

respectively

VS/TS ratio was decreased from 65% to 50%

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Time(Day)

0 50 100 150 200 250

Concentr

ation o

f N

H4+

-N (

mg/L

)

0

500

1000

1500

2000

2500

R1

R2

R3

R4

NLR

(kg N

/m3/d

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)NLR(R3)NLR(R1 R2)

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Time(Day)

0 50 100 150 200 250

pH

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

R1

R2

R3

R4

NLR

(kg N

/m3

/d)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R3)NLR(R2)

NLR(R1)

NLR

(kg N

/m3

/d)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R3)NLR(R2)NLR(R1)

Time(DAY)

0 50 100 150 200 250

HC

O3- ,

Alk

alinity (

mg/L

as C

aC

O3)

0

2000

4000

6000

8000

10000

12000

14000

R1

R2

R3

R4

pH was increased consequently during experiment due to increasing of

ammonia nitrogen and it leads to increase of alkalinity

Bicarbonate alkalinity and pH was increased in proportion to nitrogen loading

rate.

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Time(Day)

0 50 100 150 200 250

VF

As (

mg/L

)

0

500

1000

1500

2000

2500

3000

3500

4000

6000

8000

R1

R2

R3

R4

NLR

(kg N

/m3/d

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)NLR(R3)

NLR(R1 R2)

Time(Day)

0 50 100 150 200 250

SC

OD

cr

0

500

1000

1500

2000

4000

6000

8000

10000

12000

R1

R2

R3

R4 NLR

(kg N

/m3

/d)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)NLR(R3)NLR(R1 R2)

The difference in speed between acidogenesis and methanogenesis occurred

and then VFA was accumulated.

The tendency of SCODCr is similar to VFAs

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Time(Day)

0 50 100 150 200 250

VS

(%

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

8.0

10.0

R1

R2

R3

R4

Feedstock

NL

R (

kg N

/m3

/d)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)

NLR(R3)

NLR(R1 R2)

NLR

(kg

N/m

3/d

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)NLR(R3)

NLR(R1, R2)

Time(Day)

0 50 100 150 200 250

TS

(%

)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

8.0

10.0

12.0

R1

R2

R3

R4

Feedstock

TS and VS increased gradually except R1

Excessive increasing of TS and VS inhibits microorganism activity

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Time(Day)

0 50 100 150 200 250

Bio

gas y

ield

(m

3/k

g V

Sre

mo

ve

d)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

R1

R2

R3

R4

NLR

(kg N

/m3/d

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R4)NLR(R3)NLR(R1 R2)

Time(Day)

0 50 100 150 200 250

VS

re

du

ctio

n (

%)

0.75

0.80

0.85

0.90

0.95

R1

R2

R3

R4

NL

R (

kg N

/m3/d

)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

NLR(R3)NLR(R2)NLR(R1)

R1,R2 biogas yield was 1.0~1.2 and 0.9~1.1 respectively.

Biogas yield of R2 was not decreased in spite of accumulated VFAs.

VS reduction in R1 is higher than R2

Thank you

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