Environmental Aspects of AD of Sewage Sludge filegasification landfill clay factory ashes landfill...

EPROBIO Foggia 8-23 June 2010

Environmental Aspects of AD of Sewage Sludge


BIOSOLIDS

LANDAPPLICATION

ANAEROBICDIGESTION

DEWATERING

COMPOSTING

DEWATERING

THERMALDRYING

CO-DIGESTION

INCINERATION

GASIFICATION

LANDFILL

CLAY FACTORY

Ashes

LANDFILL

BIO-DRYING

OTHERORGANICWASTES

CEMENT FACTORY

ATAD


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


Options to improveAD


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 betweenacidogenic and

methanogenic step

• Two-phase digestion

4) Nutrient balance

• Co-digestion with otherwastes


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 betweenacidogenic and

methanogenic step

• Two-phase digestion

4) Nutrient balance

• Co-digestion with otherwastes

At any option, the improvement will depend on:

- Sludge characteristics (PS/SS)

- HRT used

- Temperature of operation (normally MAD)


Mechanical

Biological

Thermal

Chemical

Several effects:

-Solubilization

-Degradation

Improvent ofbiodegradability

Two interest: Increased biogas yield

Less residual sludge

Improvement options: 1) pre-treatments


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


TREAMENTS ULTRASONIC vs THERMALIncrease (%) on methane production

• More effectiveness:

- Mesofílic conditions - For secondary sludge

• Difference on Investment and operating costs.

Pretreatment US (11.000 kJ/kg)

TT (145ºC/ 30 min)

MAD PS 21.3 11.7 SS 30.0 17.9

TADPS 12.5 16.7SS 21.4 18.3



10

PPCP’s

10(Esplugas, M. 2010)


*

AOX, LAS, PCB’s, PAH, DEHP, NP/NPE

Their removal has been studied underdifferent 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


E(%

)

0

10

20

30

40

50

60

70

80

90

100


E(%

)

0

10

20

30

40

50

60

70

80

90

100


E(%

)

PS SS

55-71%53-65%

* In any case there is animprovement



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 underdifferent operating conditions

* Results are complex as depend of the contaminant and

conditions

* In any case there is animprovement



Improvementoptions: 2

Temperature


Thermophilic vs. Mesophilic AD

At low HRT TAD yieldsare 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

(%)


Temperature range alternance (Tartakovsky et al. 2007)

Incr. 50 % aprox. en CH4 prod.

TAD ranges aresmall to avoidmethanogens

inhibition

Change of temperature


BAGRUP DE RECERCA EN

BIOTECNOLOGIA AMBIENTAL

DEPARTAMENT D’ENGINYERIA QUÍMICA

XARXA DE CENTRES

DE SUPORT

A LA INNOVACIÓ

TECNOLÒGICA

Improvement options 3) Two-

phase AD


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


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



BAGRUP 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: 4) Co-

digestion


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


Mata et al., 1989

IC

CAL

DIG

BIOGAS

MEZ

FD

SEL

FORSU

Improvement options: 4) Co-digestion


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


CONCLUSIONS

• Requirements of land application can favour TAD and possibly pre-treatmnes.

• Directive will have a high influence onthese issues.

Co-digestion is a logical choice, depending on the surroundings, with

important benefits


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Environmental Aspects of AD of Sewage Sludge filegasification landfill clay factory ashes landfill...

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