Workshop Alpi Biogas - Vorstellung der innovativen Forschungsprojekte zur Nachbehandlung von Gärrest.

1. Dipartimento di Ingegneria Civile Ambientale Meccanica
Corso di Laurea Magistrale
in Ingegneria per l’Ambiente e il Territorio
Indagine sperimentale sui processi di rimozione dell’azoto
dal digestato di origine zootecnica
Relatore Laureando
Prof. Dott. Ing. Gianni Andreottola Alice Limoli
University of Trento
Department of Civil, Environmental
And Mechanical Engineering
Soluzioni integrate
per il post-trattamento digestato: Case Study
BIOGAS IN AREE ALPINE
KLIMAENERGY 26-28 Marzo 2015
Prof. Dr. Gianni Andreottola
Ing. Michela Langone, PhD
Ing. Alice Limoli

2. UNITN research fields
 Anaerobic digestion and Co-digestion
OFMSW pre-treatment
Phytodepuration
Reduction of sewage sludge production
Respirometric techniques
Conventional biological treatments for carbon, phosphorus and nitrogen removal:
SBR, MBR, MBBR, etc
Innovative biological treatments: Partial Nitritation, Anammox, sulphate
reduction, autotrophic denitrification
Ammonia removal chemical processes: conventional and
nonconventional air stripping
Improvement of Sludge biodegradability for AD: Hydrodynamic cavitation system

3. Aim
CASE STUDY:
• Monitoring a post-treatment plant of manure
digestate
• The current post-treatment produces compost and
a liquid fraction applied to agricultural land
• Collaboration with AlpiBiogas, Atzwanger
(improvement of post-treatments), Univeristy of
Bozen and Innsbruck (management of the DENI-
DEMON pilot plant)

4. AGENDA
• Anaerobic digestion plant description
• Characherization of digestate
• Digestate post-treatment plant description
• Results and efficency of the current post-treatment
• Increase of ammonia removal efficiency proposal
• Introduction to DENI-DEMON pilot plant

5. ANAEROBIC DIGESTER
Cow manure
Cow slurry
Pig slurry
Poultry manure
Ingestate
Digestate
Biogas
INGESTATE
Biomass Type
ST
(%TQ)
SV
(%ST)
Biogas
(m3/t SV)
Methane
(%)
TKN
(% ST)
Cow manure 12 82 300,0 55,0 2,5
Cow slurry 8 68 400,0 55,0 4,3
Pig slurry 3,5 70 700,0 55,0 8,0
Poultry manure 25 56,8 644,0 57,1 7,9

6. ANAEROBIC DIGESTER
• CHP potential power 400kW
• 1.550.000 m3
biogas/year
• 865.000 m3
CH4/year
• Electric energy: 3270 MWhel/year
• Thermal energy: 3230 MWhth/year
Cow manure (29,0%)
Digestate
Biogas
ADCow slurry (29,7%)
Pig slurry (29,7%)
Poultry manure (11,6%)
Ingestate
Cow manure (28%)
Cow slurry (21%)
Pig slurry (16%)
Poultry manure (35%)
865.000 m3
CH4/year

7. CHARACTERIZATION OF DIGESTATE
DIGESTATE
Parameters value
ST (g/L) 73
SV (g/L) 46
CODtot (mg/L) 189.690
CODsol (mg/L) 39.350
TKN (mg/L) 6.803
N-NH4 (mg/L) 5.258
Norg (mg/L) 1.545
CODsol /N 7,48

8. DIGESTATE USES
• Monitored land application
Only if the ingestate
is composed of animal
wastesaters or waste
of fruit and vegetables
industry
 Nitrates directive
• Composting
Production of organic fertilizer that can
be sold according to the provisions of law
75/2010
• Sewage treatment
In sewage system or surface water

9. • Screw press
• Oxidation tank
• Centrifuge
• Equalization tank
• DAF (dissolved air flotation)
POST-TREATMENT PLANT SCHEME
• Compost
• Liquid fraction to agricoltural land
Two valuable products:

10. Digestate treatment plant scheme
Solid fraction
removal
efficiency
SCREW PRESS CENTRIFUGE DAF
ηST real 22% 48% 58%
ηST theoretical 32-35% 62% 60%
POST-TREATMENT PLANT EFFICIENCY
14.500 ton/year of solid fraction sent to composting plant
High use of coagulant (FeCl3)

11. Digestate treatment plant scheme
Nitrogen Removal
efficiency
OXIDATION TANK
WHOLE TREATMENT
PLANT
ηTAN 21% 51%
ηTKN 17% 59%
POST-TREATMENT PLANT EFFICIENCY
600 ha/year in NVZ (170 kgN/ ha year)
300 ha/year in OZ (340 kgN/ha year )

12. POST-TREATMENT PLANT EFFICIENCY
• Low nitrogen ( 20%) removal efficiency in the biological reactor, mainly
due to ammonia stripping:
 High solid content in the biological reactor
(45 gTS/L) and high temperature (30°C)
allow cell lysis, that increase the pH of the
reactor up to 8,5
 The high pH and the high temperature causes
the ammonia gas formation
NH4
+ NH3(gas) +H+
 The mixing and aeration conditions in the
biological reactor cause
ammonia stripping
• Ammonia removal in the in the whole system is higher than in the biological
reactor, due to ammonia stripping during the separation phases
Indagine!sperimentale!sui!processi!di!rimozione!dell’azoto!dal!digestato!di!origine!zootecnica!
!
!
Figura!3.!20!Aspetti!biochimici!e!termodinamici!dei!sistemi!ATAD!
!
La! Figura! 3.! 20! rappresenta! in! modo! schematico! le! reazioni! che! avvengono! all’inter
reattore!ATAD.!
Per! mantenere! il! regime! operativo! microaerobico! è! necessaria! un’elevata! effic
trasferimento! dell’ossigeno.! In! caso! di! trasferimento! troppo! basso! di! ossigeno! si!
formazione!di!condizioni!anaerobiche,!mentre!in!condizioni!di!eccessiva!aerazione!si!può
eccessivo!abbassamento!della!temperatura.!
Il! rilascio! in! atmosfera! di! anidride! carbonica! è,! nel! caso! della! digestione! termofila,!
• Low efficiency of solid remove in the centrifuge and a high use of coagulant (FeCl3)
that consume alkaninity

13. EFFLUENT FROM FLOTATION PROCESS
Parameters value
SST (g/L) 11
SSV (g/L) 6
CODtot (mg/L) 18.800
CODsol (mg/L) 2.560
TKN (mg/L) 2.813
N-NH4 (mg/L) 2.450
N-NO2 (mg/L) 0,4
N-NO3 (mg/L) 0
Norg (mg/L) 363
CODsol /N 1,04
Alcalinity (mgHCO3
- /L) 3.875
POST-TREATMENT PLANT EFFICIENCY

14. PROPOSAL FOR HIGHER AMMONIA
REMOVAL EFFICIENCY
PILOT PLANT Experimentation University of Innsbruck, Trento & Bozen
AIM:
 Reduce the agricoltural land necessary to application
or
 Discharge in sewage system
HOW? :
Innovative biological treatment  Partial Nitrification and Anammox
process
NH4
+ NO2
- NO3
-1.5O2
0.5O2
AOB
Autotrophic Bacteria
NOB
NH4
+
NO3
-
N2
Autotrophic Bacteria
1.32NO2
-
< 60% Oxigen consumption
Less sludge production
PARTIAL
NITRIFICATION
ANAMMOX

15. INNOVATIVE BIOLOGICAL PROCESSES
PILOT PLANT Experimentation University of Innsbruck, Trento & Bozen
DENI – DEMON Process
applied to the liquid fraction of digestate
(output of centrifuge or flotation)
• DENI tank
where denitrification
is performed to remove
the residual COD
• DEMON reactor
where Partial Nitrification
and anammox are performed
to remove NH4
• Discharge tank
DEMONDENI DISCHARGE
TANK

16. INNOVATIVE BIOLOGICAL PROCESSES
PILOT PLANT Experimentation University of Innsbruck, Trento & Bozen
DENI – DEMON Process monitoring
December 2014 - January 2015
DEMONDENI DISCHARGE
TANK

17. INNOVATIVE BIOLOGICAL PROCESSES
PILOT PLANT Experimentation University of Innsbruck, Trento & Bozen
DENI – DEMON Process
applied to the liquid fraction of digestate
(output of centrifuge or flotation)
TAN removal efficency TN removal efficency
18.12.2014 93% 92,7%
7.01.2015 86% 86,2%
14.01.2015 85% 84,5%
22.01.2015 81% 80,6%
TAN removal efficency TN removal efficency
18.12.2014 63% 63%
7.01.2015 44% 43%
14.01.2015 36% 34%
22.01.2015 51% 47%
Nitrogen Removal Efficiency
DENI-DEMON process
Nitrogen Removal Efficiency
DEMON process

18. INNOVATIVE BIOLOGICAL PROCESSES
PILOT PLANT Experimentation University of Innsbruck, Trento & Bozen
DENI – DEMON Process
• Several biological processes are involved simultaneously both in the
DENI and in the DEMON reactor: denitrification, anammox and
Nitritation, as can be observed from monitoring data.
• The biological processes involved did not reach a steady state and
Nitrite accumulation occurred in the DEMON reactor
• Disease causes:
- high solid concentration in the effluent to treat, that accumulate in
the reactor
- low alkalinity content, that limit biological processes due to ferric
chloride use in the centrifuge
• Possible improvement to the treatment scheme:
• Replace the centrifuge with a membrane module, avoiding the
utilization of polyelectrolyte. This can ensure a lower solid content
and a higher alkalinity content in the effluent to treat.

19. PROPOSAL FOR HIGHER AMMONIA
REMOVAL EFFICIENCY
AIM:
 Reduce the agricoltural land necessary to application
 Discharge in sewage system
HOW? :
Integration of sequential technological solutions  Two steps process
WHICH? :
First step: Conventional or nonconventional air stripping
(N removal efficiency 80-90%)
+
Second step: Conventional or Innovative Biological treatment
(N removal efficiency 60-90%)

20. AIR STRIPPING
First step
Lab - Experimentation at the University of Trento
CONVENTIONAL AIR STRIPPING
applied to the liquid fraction of digestate
Lower solid content=15g/L
“Packing” air stripping column
pH=11.5
T=20°C
Recycles n. 8
Ammonia efficiency average = 50-60%
NONCONVENTIONAL AIR STRIPPING
applied to the raw digestate
Higher solid content=50g/L
“Sequencing batch reactor” with a mixed phase
pH=10-11
T=20-30°C
HRT=3days
Ammonia efficiency average>90%

21. BIOLOGICAL TREATMENT
Second step
CONVENTIONAL BIOLOGICAL TREATMENT
NITRIFICATION + DENITRIFICATION + with external carbon sources
Disadvantages
High oxygen consumption;
High sludge production;
External carbon source required.
NONCONVENTIONAL BIOLOGICAL TREATMENT
PRE-DENITRIFICATION + PARTIAL NITRITATION + ANAMMOX
 DENI - DEMON PROCESS
Advantages
Low oxygen consumption, as the nitrification is stopped to nitrite;
Low sludge production, mainly autotrophic processes;
No external carbon source required.

22. CONCLUSION
 The DENI-DEMON process directly applyed to the
liquid fraction of the digestate did not reached the
stability due to the alkalinity limitation and the high
solid content. Further experimentation is needed.
 Dewatering system and N-removal have strong
interaction.
 In order to reach a high ammonia removal efficiency
(>90%) a sequential two step process is proposed,
composed by stripping and biological process.

23. THANKS FOR THE ATTENTION!
QUESTIONS?
CONTACT:
Prof. Gianni Andreottola
gianni.andreottola@ing.unitn.it
Ing. Michela Langone, PhD
michela.langone@ing.unitn.it
Ing. Alice Limoli
alicelimoli@yahoo.it
http://www.ing.unitn.it/~lisa/
BIOGAS IN AREE ALPINE
KLIMAENERGY26-28 Marzo 2015

24. • Mass balance
• Membrane
• Pilot plant monitoring
• Pilot plant analyses
• New plant scheme

25. MEMBRANE
• CERAMIC FILTER DISC
312 Kerafol
• Membrane pore size 0,5μm;
• Diameter 312 mm
• Thickness 6 mm;
• Filtering surface 0,14 m2 each
disc
Economic sustainability
is verifying

26. DIGESTATE TREATMENT PLANT MONITORING
Digestate treatment plant scheme
DIGESTATE
Sampling data Mass balance data
ST 74,9 65,1 g/l
TKN 6802,8 5058,6 mg/l
TAN 5258,4 4451,4 mg/l
SCREW PRESS LIQUID FRACTION
Sampling data Mass balance data
ST 58,5 48,0 g/l
TKN 6902,2 5263,7 mg/l
TAN 5236,6 4463,1 mg/l
Norganico 1665,5 800,6 mg/l
OXIDATION TANK
Sampling data Mass balance data
ST 45,4 50,0 g/l
TKN 5717,5 5265,5 mg/l
TAN 4151 4445,0 mg/l
Norganico 1566,5 1220,5 mg/l
CENTRIFUGE LIQUID FRACTION
Sampling data Mass balance data
ST 31,0 22,0 g/l
TAN 3043 4205,1 mg/l
EQUALIZATION TANK
Sampling data Mass balance data
ST 27,5 22,0 g/l
TAN 3445,0 4205,1 mg/l
DAF LIQUID FRACTION
Sampling data Mass balance data
SST 11,4 10,0 g/l
TAN 3020,3 3418,2 mg/l

27. PILOT PLANT MONITORING
(1) Feed
pH T Alk-tot NH4 NO2 NO3 COD sol SST SSV TKN CODtot
Date [°C] [mM CaCO3]
[mg
N/L]
[mg
N/L]
[mg
N/L]
[mg
O2/L]
mgSST/L %SST
[mg
N/L]
[mg O2/L]
18/12/14 54,57 2.090 <0,01 0,85 2.568 266 55
07/01/15 6,94 20,31 2.750 11,05 1,68 1.182 259 66 2.443 1.980
14/01/15 46,53 3.190 3,02 0,94 2.868 63 52
22/01/15 7,30 17,20 61,29 2.624 <0,01 0,83 1.998 252 56 2.780 2.238
(2) Deni pre-recirculation
pH T Alk-tot NH4 NO2 NO3 COD sol SST SSV TKN CODtot
Date [°C]
[mM
CaCO3]
[mg N/L] [mg N/L] [mg N/L] [mg O2/L] mgSST/L %SST [mg N/L]
[mg
O2/L]
18/12/14 13,1 580 <0.01 0,40 870 2.440,00 57
07/01/15 8,00 12,6 915 1,01 0,64 824 2.200,00 56 908 3.080
14/01/15 7,90 10,3 788 0,37 0,42 698 nd 63
22/01/15 7,70 10,4 13,3 1.070 1,92 0,26 856 2.290 20 759 1.698
(4) DEMON in settling (end of cycle)
pH T Alk-tot NH4 NO2 NO3 COD sol SST SSV TKN CODtot
Date [°C] [mM] [mg N/L] [mg N/L] [mg N/L] [mg O2/L] mgSST/L %SST [mg N/L] [mg O2/L]
18/12/14 2,29 214 <0.01 0,72 684 1.880 54
07/01/15 2,36 511 10,56 1,28 632 960 61 520 1.960
14/01/15 7,00 2,09 508 14,84 0,70 582 nd 56
22/01/15 7,10 23,10 2,36 523 46,55 2,15 716 990 27 487 1.148

28. PILOT PLANT MONITORING
(5) DEMON in mixing
pH T SST SSV TKN CODtot
Date [°C] mgSST/L %SST
18/12/14 11.100 51
07/01/15 9.400 60 908 10.060
14/01/15 6.930 56
22/01/15 7,0 24,6 10.400 46 725 6.760
(6) DISCHARGE TANK after DEMON discharge
pH T Alk-tot NH4 NO2 NO3 COD sol SST SSV TKN CODtot
Date °C [mM] [mg N/L] [mg N/L] [mg N/L] [mg O2/L] mgSST/L %SST [mg N/L] [mg O2/L]
18/12/14 1,90 152 <0.01 0,14 666 71 69
07/01/15 7,70 2,20 380 1,29 0,22 534 27 44 365 614
14/01/15 7,50 2,64 494 0,76 0,14 564 46 80
22/01/15 7,50 5,10 2,42 500 9,11 0,69 670 40 12 361 856
(7) DEMON (end of first aeration phase)
pH T Alk-tot NH4 NO2 NO3 COD sol
Date [°C] [mM] [mg N/L] [mg N/L] [mg N/L] [mg O2/L]
22/01/15 7,00 25,20 2,48 569 48,94 2,34 728

29. PILOT PLANT MONITORING
Number Name Description Sampling time Analyses
1 TQ InfluentTQ As weekly feeding indifferent SST, SSV, *
1 F InfluentF As weekly feeding indifferent N-NH4,N-NO2,N-NO3,COD, Alkalinity
2 TQ Deni pre-recirculationTQ Sampled before recirculation 09:10:00 - 09:20:00 SST, SSV, *
2 F Deni pre-recirculationF Sampled before recirculation 09:10:00 - 09:20:00 N-NH4,N-NO2,N-NO3,COD, Alkalinity
3 TQ Deni post-recirculationTQ Sampled after recirculation 09:40:00 - 10:00:00 SST, SSV, *
3 F Deni post-recirculationF Sampled after recirculation 09:40:00 - 10:00:00 N-NH4,N-NO2,N-NO3,COD, Alkalinity
4 TQ DEMON in settling TQ Mid-end of settling phase 15:15:00 - 15:20:00 SST, SSV, *
4 F DEMON in settling F Mid-end of settling phase 15:15:00 - 15:20:00 N-NH4,N-NO2,N-NO3,COD, Alkalinity
5 TQ
DEMON in mixing TQ during first
aerationphase
During mixing/ventilationphase
09:40:00 -15:00:00
SST, SSV, *
in ventilation
6 TQ Dischargetank TQ After DEMON discharge 15:35:00 SST, SSV, *
6 F Dischargetank F AfterDEMON discharge 15:35:00 N-NH4,N-NO2,N-NO3,COD, Alkalinity
7 F
DEMON F end first aeration (pH
7.88)
DEMON end first aeration (pH 7.88) 12:20:00 N-NH4,N-NO2,N-NO3,COD, Alkalinity
*TKNand COD 2° and 4° sampling

30. PILOT PLANT MONITORING
TAN removal
efficency
TN removal efficency
18.12.2014 93% 92,7%
7.01.2015 86% 86,2%
14.01.2015 85% 84,5%
22.01.2015 81% 80,6%
TN=TAN+N-NO2+N-NO3
-
500
1.000
1.500
2.000
2.500
3.000
3.500
mg/L
DENI- DEMON - DISCHARGE TANK
N-NH4 in
N-NH4 out
CODsol_in
COD sol_out
N-NO2 out
N-NO3

31. DEMON REACTOR MONITORING
TAN removal
efficency
TN removal efficency
18.12.2014 63% 63%
7.01.2015 44% 43%
14.01.2015 36% 34%
22.01.2015 51% 47%
-
200
400
600
800
1.000
1.200
mg/L
DEMON
N-NH4 in
N-NH4 out
CODsol_in
COD sol_out
N-NO2 out
N-NO3
TN=TAN+N-NO2+N-NO3
Nitrite N-NO2=46 mg/l

32. NEW PLANT SCHEME
• Membrane separation system
• Stripping treatment
• DENI-DEMON treatment
• Thermal drying treatment of the solid fraction