EPROBIO Foggia 10 July 2010 Environmental Aspects of AD of Sewage Sludge
Jan 31, 2016
EPROBIO Foggia 10 July 2010
Environmental Aspects of AD of Sewage Sludge
EPROBIO Foggia 10 July 2010
BIOSOLIDS
LANDAPPLICATION
ANAEROBICDIGESTION
DEWATERING
COMPOSTING
DEWATERING
THERMALDRYING
CO-DIGESTION
INCINERATION
GASIFICATION
LANDFILL
CLAY FACTORY
Ashes
LANDFILL
BIO-DRYING
OTHERORGANICWASTES
CEMENT FACTORY
ATAD
EPROBIO Foggia 10 July 2010
BIOSOLIDS
LANDAPPLICATION
ANAEROBICDIGESTION
DEWATERING
COMPOSTING
DEWATERING
THERMALDRYING
CO-DIGESTION
INCINERATION
GASIFICATION
LANDFILL
CLAY FACTORY
Ashes
LANDFILL
BIO-DRYING
OTHERORGANICWASTES
CEMENT FACTORY
ATAD
ANAEROBIC DIGESTION
• First application of AD
• Advantages
• Possibilities (heat / power)
• Configurations to improve the performance
• Co-digestion
EPROBIO Foggia 10 July 2010
Options to improve AD
EPROBIO Foggia 10 July 2010
Options to improve AD process
1) Hydrolysis: Pretreatments
• Thermal
• Mechanical (ultrasonic)
• Chemical (ozonation, H2O2,etc.)
• Biological (enzymatic)
2) Temperature: TAD
• Increase T of AD to reduce HRT and to incrase
OLR
3) Balance between acidogenic and
methanogenic step
• Two-phase digestion
4) Nutrient balance
• Co-digestion with other wastes
At any option, the improvement will depend on:
- Sludge characteristics (PS/SS)
- HRT used
- Temperature of operation (normally MAD)
EPROBIO Foggia 10 July 2010
Mechanical
Biological
Thermal
Chemical
Several effects:
-Solubilization
-Degradation
Improvent of biodegradability
Two interest: Increased biogas yield
Less residual sludge
Improvement options: 1) pre-treatments
EPROBIO Foggia 10 July 2010
Mètode Cond. de operació Desint. (%) Biogas incr (%)
Avantatges Desavantatges
Ultrasònic 10-15 106 J/kg ST 100 30 completa
desintegració intensiva energia
Tèrmic 150-200 ºC/ 30 min. 30-55 15-50 Procés flexible corrosió, olors
Termoquímic 80-150 ºC/30min NaOH (hasta pH12)
5-60 20-55 Relativament
simple
Corrosió, olor, subseguint
neutralització
Biològic* 5-10%; 37-55 ºC & 10-30 hr
5-50 10-20 operació simple,
baixos costs
baixos rendiments,
olors
Oxidatives O3 0.1-0.3g/gSV H2O2 0.5-2g/gSV
90 20-250 Alta eficiència
de desintegració
pH baixo, corrosió, alt cost
* recalcitrància de la part proteica
Improvement options: 1) pre-treatment
EPROBIO Foggia 10 July 2010
TREAMENTS ULTRASONIC vs THERMAL
Increase (%) on methane production
• More effectiveness:
- Mesofílic conditions - For secondary sludge
• Difference on Investment and operating costs.
PretreatmentUS
(11.000 kJ/kg)TT
(145ºC/ 30 min)
MAD PS 21.3 11.7
SS 30.0 17.9
TADPS 12.5 16.7
SS 21.4 18.3
Improvement options: 1) pre-treatments
EPROBIO Foggia 10 July 2010
9
PPCP’s
9(Esplugas, M. 2010)
EPROBIO Foggia 10 July 2010
*
AOX, LAS, PCB’s, PAH, DEHP, NP/NPE
Their removal has been studied under different operating conditions
* Results are complex as depend of the contaminant and
conditions
Removal or transformation (%) of NPE and DEHP with US (■) and TT (■) pretreatments
0
10
20
30
40
50
60
70
80
90
100
DEHP NP NP1EO NP2EO NPE
E(%
)
0
10
20
30
40
50
60
70
80
90
100
DEHP NP NP1EO NP2EO NPE
E(%
)
0
10
20
30
40
50
60
70
80
90
100
DEHP NP NP1EO NP2EO NPE
E(%
)
0
10
20
30
40
50
60
70
80
90
100
DEHP NP NP1EO NP2EO NPE
E(%
)
PS SS
55-71%53-65%
* In any case there is an improvement
Improvement options: 1) pre-treatments
EPROBIO Foggia 10 July 2010
0
20
40
60
80
100
TT-MAD TT-TAD US-MAD US-TAD
Treatment
E (
%)
0
20
40
60
80
100
TT-MAD TT-TAD US-MAD US-TAD
Treatment
E (
%)
(a) (b)
DEHP NPE
*
AOX, LAS, PCB’s, PAH, DEHP, NP/NPE
Their removal has been studied under different operating conditions
* Results are complex as depend of the contaminant and
conditions
* In any case there is an improvement
Improvement options: 1) pre-treatments
EPROBIO Foggia 10 July 2010
Improvement options: 2
Temperature
EPROBIO Foggia 10 July 2010
Thermophilic vs. Mesophilic AD
At low HRT TAD yields are much
higher
At high HRT yields are
similar
Values depend on type of sludge
-Pathogen removal higher in TAD (Biosolids Class A)
Better removal of Microcontamiinats % (AOX, LAS, PCB’s, PAH, DEHP,
NP/E)
- More VFA in supernatants
- Worse dewaterability
0102030405060708090
100
Mesophilicdigestion
Thermophilicdigestion
Substratesonication
Son+M_dig Son+T_digNap
htha
lene
and
pyr
ene
rem
oval
(%)
EPROBIO Foggia 10 July 2010
Temperature range alternance (Tartakovsky et al. 2007)
Incr. 50 % aprox. en CH4 prod.
TAD ranges are small to avoid methanogens
inhibition
Change of temperature
EPROBIO Foggia 10 July 2010
B A GRUP DE RECERCA EN
BIOTECNOLOGIA AMBIENTAL
DEPARTAMENT D’ENGINYERIA QUÍMICA
XARXA DE CENTRES
DE SUPORT
A LA INNOVACIÓ
TECNOLÒGICA
Improvement options 3) Two-
phase AD
EPROBIO Foggia 10 July 2010
To keep an equilibrium between acidogenic and methanogenic
phases
Can be considered as a biological
pretreatment of AD
Each phase has its own HRT and operting
Temperature
Keith et al., 2006
Acidogènic Methanogenic
Improvement options: 3) two-phase AD
EPROBIO Foggia 10 July 2010
M-M does not improve too much VS removal, but firts acidogenic phase reduces significantly the pathogenic
laod
Configuration HRT(d) VSrem (%)
Meso-Meso 3,5+6,5 50-55
Thermo-Meso 2,5+9 61
Thermo-Thermo 2,5 + 5 63
Improvement options: 3) two-phase AD
EPROBIO Foggia 10 July 2010
B A GRUP DE RECERCA EN
BIOTECNOLOGIA AMBIENTAL
DEPARTAMENT D’ENGINYERIA QUÍMICA
XARXA DE CENTRES
DE SUPORT
A LA INNOVACIÓ
TECNOLÒGICA
An example with hyperthermophilic conditions
was studied by Wang (1997) and Gavala (2003)
1st phase
70ºC
MAD
TAD
• Improvements: 30-50%
• For PS improvements for TAD
• For SS, improvements for MAD and TAD
HRT and T should be fixed for each
particular mixture
or
Improvement options: 3) two-phase AD
EPROBIO Foggia 10 July 2010
Improvement options: 4) Co-
digestion
EPROBIO Foggia 10 July 2010
Improvement options: 4) Co-digestion
• SS digesters are infra-used
• Biodegr. OM (High VS conc. Offers a good
opportunity) • A single infra-structure is
used
• Eventual nutrient deficit is
compensated
• Eventual inhibitors are diluted
Mata et al., 1989
EPROBIO Foggia 10 July 2010
Mata et al., 1989
IC
CAL
DIG
BIOGAS
MEZ
FD
SEL
FORSU
EFECTOS DE LA ADICION DE FORSU EN LOS FANGOS DE DEPURADORA SORE EL LA PRODUCCION DE GAS Y EL TIEMPO DE RESIDENCIA
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
160,0
180,0
200,0
0,0 2,0 4,0 6,0 8,0 10,0 12,0 14,0 16,0 18,0
PERCENTAJE DE INCREMENTO EN EL CAUDAL DE ENTRADA AL DIGESTOR
PO
RC
EN
TA
JE D
E IN
CR
EM
EN
TO
EN
LA
P
RO
DU
CC
IÓN
DE
BIO
GA
S O
DE
EL
EC
TR
ICID
AD
17,5
18,0
18,5
19,0
19,5
20,0
20,5
21,0Incremento biogas/electricidad
Nuevo Tiempo de Residencia
Improvement options: 4) Co-digestion
EPROBIO Foggia 10 July 2010
CONCLUSIONS
• DA can improve its yields (biogas productions and VS removal and digestate quality)
•Improvement can be carried out by pretreatments and a significant activity on this
field is underway.
• Improvement options are quite a few and should be carefully studied as many factors are
affecting
EPROBIO Foggia 10 July 2010
CONCLUSIONS
• Requirements of land application can favour TAD and possibly pre-treatmnes.
• Directive will have a high influence on these issues.
Co-digestion is a logical choice, depending on the surroundings, with
important benefits
EPROBIO Foggia 10 July 2010