1. Anaerobic Co-digestion Of Organic Fraction Of Municipal
Solid Waste And Municipal Sludge
EFATH ARA
M.A.Sc

2. Anaerobic Digestion Basics
Waste
Anaerobic digestion occurs in absence of O2
Hydrolysis
rate
limiting
30%
70%
BACK

3. Bio-solid Cell Basics
•A large part of the organic matter in bio-solid is enclosed inside microbial cells
•Cell walls are barriers that resists degradation preventing release and
degradation of organic matter present inside
• This cell wall is very thin in most of the OFMSW so they degrade
faster

4. Biological Methane Potential (BMP) of
Waste
• OFMSW(Organic Fraction of Municipal Solid Waste)
• TWAS (Thickened Waste Activated Sludge)
OFMSW is
rapidly
degradable
TWAS is
tough to
degrade
0
50
100
150
200
250
300
350
400
450
0 10 20 30 40 50 60 70 80
Cumulativebiogasproduction(ml)/gofvs
added
Days
ofmsw TWAS
Biological Methane Potential (BMP) of waste

5. Objectives of the Study
Evaluate effect of anaerobic co-digestion of
OFMSW and TWAS/PS (Batch and Semi-
continuous flow study) on
– Biogas production
– Energy recovery from the waste
– Improved process control

6. Literature Review

7. Material Used
• OFMSW (Organic Fraction of Municipal Solid Waste) ( 28% TS)
• TWAS (Thickened Waste Activated Sludge) ( 5% TS)
• PS (Primary Sludge) ( 3.5% TS)
OFMSW/Kitchen Waste contained :
•Rice 17.5%
•Cooked Pasta 17.5%
•Apple 11%
•Carrot 11%
•Banana 11%
•Cabbage 11%
•Ground beef 10%
•Dog food 10%
•Biodegradable plastic bags 1%

8. Experimental Work Plan
Co-digestion
of OFMSW,
TWAS and
PS
Co-digestion
of OFMSW
& TWAS
Semi-continuous Test
Batch Test
Effect of co-digestion

9. BMP Experimental Setup
OFMSW
25%
TWAS 75%
OFMSW
50%
TWAS
25 %
OFMSW
75%
OFM
SW
25%
PS
37.5%
TWAS
37.5%
PS
12.5
%
OFMSW
75%
TWAS
12.5%
PS
25%
OFMSW
50%
TWAS
25%
Setup (1)
Setup (2)
All bottles
have the
same
organic load
(3.5% VS)

10. Parameters Tested
• Total Solid
• Volatile Solid
• Total COD/Soluble COD
• Volatile Fatty Acids
• Alkalinity
• Hydraulic Retention Time =Solid Retention Time
• Biogas, Gas composition/Methane production
• Reactor Stability Test

11. Co-digestion Results OFMSW:TWAS 25:75
TWAS OFMSW
Expected gas
production =Weighted
avg. of gas production
of individual substrate

12. Co-digestion Results OFMSW:TWAS
50:50
TWAS OFMSW
1/4
1/4
1/4
1/4
76 % Increase

13. Co-digestion Results OFMSW:TWAS
75:25
TWAS OFMSW

14. Experimental Setup 2
OFM
SW
25%
TWAS 75%
OFMSW
50%
TWAS
25 %
OFMSW
75%
TWA
S
37.5
%
PS
37.5%
OFMSW
25%
PS
12.5
%
OFMSW
75%
TWAS
12.5%
PS
25%
OFMSW
50%
TWAS
25%

15. Anaerobic Tri-digestion of
OFMSW:TWAS:PS Results
OFMSW:TWAS:PS 25:37.5:37.5

16. Anaerobic Tri-digestion of
OFMSW:TWAS:PS Results
OFMSW:TWAS:PS 50:25:25

17. Anaerobic Tri-digestion of
OFMSW:TWAS:PS Results
OFMSW:TWAS:PS 75:12.5:12.5

18. Anaerobic Tri-digestion over Co-
digestion Results

19. Potential Tri-digestion Benefits to
MWWTP
0
100
200
300
400
500
600
700
800
900
0 10 20 30 40 50 60 70 80
Cumulativebiogasproductionml/gofvsadded
Days of digestion
TWAS:PS:50:50
MSW:TWAS:PS::25:37.5:37.5
MSW:TWAS:PS::50:25:25
MSW:TWAS:PS::75:12.5:12.5
Control
TWAS:PS
:50:50
OFMSW:TWAS:
PS:25:37.5:37.5
OFMSW:TWAS:
PS:50:25:25
OFMSW:TWAS:
PS:75:12.5:12.5

20. A time sliding diminishing supply of
OFMSW in AD co-digestion with
TWAS/PS in MWWTP

21. Effect of MW Heating Time on Biogas
Production
Biogas Production=3559+140 x %OFMSW in Mix - 0.9 x (%OFMSW in Mix)2

22. Effect of MW Heating Time on Biogas
Production
Biogas production=5637.3+40.5 x (% OFMSW in mix)

23. Conclusion for Batch Results
BIOGAS
PS/TWAS
%
OFMSW %
Clockwise rotation is
considered increase
• Co-digestion of TWAS/PS/OFMSW has a positive synergistic effect
on specific biogas production
• Specific biogas production improved during co-digestion of
TWAS/PS/OFMSW with higher percentages of OFMSW in the mix

24. Semi-continuously Flow Reactor
Design

25. Daily Biogas Production Results
15 days and 10 days HRT
7 days HRT

26. Semi-Continuous Reactor Efficiency
Biogas
yield
mL/gV
S
added

27. Reactor Stability Test
Reactor name HRT days
OLR
gVS/L/d TVFA mg/L Stability Ratio(=IA/TA)
OFMSW:TWAS:PS
15 2
1312±178 0.25
TWAS:PS 500±90 0.09
OFMSW:TWAS:PS
10 3.5
625±119 0.3
TWAS:PS 188±96 0.09
OFMSW:TWAS:PS
7 4.5
1750±142 0.25
TWAS:PS 437±101 0.07
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28. Conclusion
• Co/tri-digestion has a synergistic positive effect on specific
biogas production (batch/cont.)
• Specific biogas production increased with increasing percentages
of OFMSW (batch/cont.)
• Higher biogas production for OFMSW:TWAS:PS mix than
OFMSW:TWAS mix (batch/cont.)

29. Some of the new technology available for
BMP test

30. Few studies on Anaerobic Co-digestion
and Aerobic Composting

31. Flow Diagram for Integrated Solid Waste
Management

32. Benefits of AD/Aerobic Composting
• The whole process produce two end product which leads
to the ultimate use of the carbon/energy source
• Aerobic composting stabilizes Anaerobic digested in
terms of pathogen removal, so compost end product can be
considered as Category A type
• Digested provides the water/ moisture source in the
composting
• Reduces volume of AD end product