International Seminar - University of Palermo 20 May 2016
Donatella Caniani 1
Università di Palermo
Dipartimento di Ingegneria Civile,
Ambientale, Aerospaziale, dei
Materiali (DICAM)
Innovative wastewater
treatment technologies
for energy saving and
environmental
protection
May 20, 2016 - Palermo
Innovative wastewater
treatment technologies
for energy saving and
environmental
protection
May 20, 2016 - Palermo
Emissioni di gas serra dalla
digestione aerobica dei
fanghi: risultati
sperimentali e modellistici
Donatella Caniani
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
Outline
1. GHG emissions in wastewater utilities1. GHG emissions in wastewater utilities
4. Biological processes for GHG production4. Biological processes for GHG production
6. 6. Aerobic Digestion (Aerobic Digestion (AeDAeD) ) ModellingModelling
77. . Experimental resultsExperimental results
22.. LiteratureLiterature AnalysisAnalysis
33.. AttentionAttention towardstowards aerobicaerobic digestiondigestion
55.. BiologicalBiological processesprocesses forfor NN22OO productionproduction
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
Schematic diagram of the modified
BSM2 plant and sources of modelled
GHG emissions.
(C. Sweetapple et al., 2013)Off – site emissions
(indirect emissions)
1. 1. GHG emissions in wastewater utilitiesGHG emissions in wastewater utilities
On – site emissions
(direct emissions)
•• ONON--SITE EMISSIONS: BIOLOGICAL PROCESSES DURING WASTEWATER TREATMENT.SITE EMISSIONS: BIOLOGICAL PROCESSES DURING WASTEWATER TREATMENT.
•• OFFOFF--SITE EMISSIONS: ENERGY CONSUMPTION,CHEMICALS SITE EMISSIONS: ENERGY CONSUMPTION,CHEMICALS PRODUCTION AND PRODUCTION AND TRANSPORTATION, TRANSPORTATION, SLUDGE SLUDGE
TRANSPORTATION, DISPOSAL OR TRANSPORTATION, DISPOSAL OR REUSE.REUSE.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
Impossibile v isualizzare l'immagine. La memoria del computer potrebbe essere insufficiente per aprire l'immagine oppure l'immagine potrebbe essere danneggiata. Riavviare il computer e aprire di nuovo il file. Se v iene visualizzata di nuovo la x rossa, potrebbe essere necessario eliminare l'immagine e inserirla di nuovo.
Nitrous oxide is a
POWERFUL GREENHOUSE GASPOWERFUL GREENHOUSE GAS
GWP (Global GWP (Global WarmingWarming PotentialPotential))
Carbon dioxide(CO2) = 1
Methane (CH4) = 24
Nitrous oxide (N2O) = 289 (IPCC, 2006)
WHAT IS NITROUS OXIDE ? WHAT IS NITROUS OXIDE ?
1. GHG emissions in wastewater utilities
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 2
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
2. LITERATURE ANALYSIS. STRENGTHS & WEAKNESSES..
4. The knowledge on modelling about
activated sludge processes (ASM) with
nitrous oxide emissions is increased.
STRENGTHSSTRENGTHS WEAKNESSESWEAKNESSES
1. The knowledge on CO2 and CH4 formation during biological
processes is very rich.
2. The knowledge N2O formation during nitrification,
denitrification and nitrifier denitrification processes is
increased.
3. The infleunce of design variables on amount of emissions is
clear.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
STRENGTHSSTRENGTHS WEAKNESSESWEAKNESSES
1. Lacking of a standard protocol for gas sampling and
measurement in liquid and gas phase, including aerobic
digestion
2. Lacking of a model for sludge aerobic digestion
3. Lacking of experimental measurement at pilot scale and full
scale of aerobic digestion
Attention towards aerobic digestionAttention towards aerobic digestion
2. LITERATURE ANALYSIS. STRENGTHS & WEAKNESSES..
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
3. Attention towards aerobic digestionBiologicalBiological Systems: Systems: ActivatedActivated sludgesludge tank (AS) and tank (AS) and AerobicAerobic digestordigestor ((AeDAeD))
WWTP in Rionero in Vulture (Pz)
AA fractionfraction ofof nutrientsnutrients andand organicorganic pollutantspollutants areare removedremoved throughthrough thethe biologicalbiological activityactivity ofof bothboth
heterotrophicheterotrophic andand autotrophicautotrophic bacteria,bacteria, whichwhich survivesurvive inin thethe tanktank underunder specificspecific biochemicalbiochemical andand
physicalphysical conditionsconditions..
SubmergedSubmerged
aerationaeration devicesdevices
The AS is the core unit of a WWTP where
the actual contaminants biological removal
takes place.
The microorganisms (generally bacteria,
called activated biomass) are able to digest
the wastewater under aerobic conditions,
reducing the organic carbon and nutrients
(N and P) loads.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
BiologicalBiological Systems: Systems: ActivatedActivated sludgesludge tank (AS) and tank (AS) and AerobicAerobic digestordigestor ((AeDAeD))
In AeD the excess sludge is maintained in
aerobic conditions with retention time of
approximately 20 days without feeding
exogenous organic substrate. In this way, a
decrease in the sludge concentration is
observed due to its endogenous
respiration.
DECAY RATE
SubmergedSubmerged
aerationaeration devicesdevices
SurfaceSurface aerationaeration
devicesdevices
WWTP in Rionero in Vulture (Pz)
3. Attention towards aerobic digestion
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 3
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
AttentionAttention towardstowards the the AerobicAerobic DigestionDigestion ((AeDAeD). ). WhyWhy??
WWTP in Rionero in Vulture (Pz)
Experimental measurements of direct GHG emissions from
aerobic digesters (AeD) were yet not available in literature.
Estimating the contribution of AeDs to the WWTP eFP and CFP is
important for knowing their impact through CO2 equivalent
(CO2,eq)emissions, in particular regarding N2O.
The interest towards the contribution to the WWTP CFP of AeD
is linked to its popularity in small to medium sized WWTPs
(5000-50000 IE) in Italy as excess sludge treatment.
Small to medium sized plants normally characterized by
conventional treatment schemes are usually neglected in
scientific literature, even though they are very popular in
isolated villages, especially in rural areas.
Similarly to what occurs in biological tanks, CO2 is produced by
bacterial endogenous respiration, accumulates in the liquid
phase and is then stripped during aeration . N2O is also
generated and its production depends mainly on nitrogen (N)
availability.
3. Attention towards aerobic digestion
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
AerobicAerobic DigestionDigestion vs vs AnaerobicAnaerobic DigestionDigestion
AeDAeD advantagesadvantages.
1. High VSS removal efficiency
2. Sludge reuse in agriculture
3. Better management conditions
4. Low cost in construction
AeDAeD disadvantagesdisadvantages.
1. High energy demand for aeration
2. No energy recovery
3. Sensitive to operational conditions (T, pH, TSS..)
4. High cost in management
3. Attention towards aerobic digestion
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
4. Biological processes for GHG production11.. OrganicOrganic CarbonCarbon OxidationOxidation byby meansmeans ofof heterotrophicheterotrophic aerobicaerobic bacteriabacteria
CCxx(H(H22O)O)xx + O2 → CO2 + H2O + e-Red.Ox.
ATPATP
CCxxHHyyNNzzOOtt
(C(C55HH77NONO22,, asas suggestedsuggested byby
HooverHoover && PorgesPorges inin 19521952))
Cx(H2O)x electron donor
O2 electron acceptor
ATP energy needed for generation
CxHyNzOt new cells
CO2 product of the reaction
catabolic
pathway
anabolic
pathway
N, P, S, K,
Ca, Mg
22.. EndogenousEndogenous decaydecay
CxHyNzOt + O2 → CO2 + NH3 + H2ORed.Ox.
C5H7NO2 + 5O2 → 5CO2 + NH3 + 2H2O
(organic
substrate)
The organic substrate in wastewaters is represented by:
ProteinsProteinsCarbohydratesCarbohydrates OilsOils, , fatsfats and and greasesgreases
Fossil carbon from soaps,
detergents, petroleum
derived ecc..
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
NN22O O emissionsemissions fromfrom activatedactivated sludgesludge reactorreactor duringduring BNR (BNR (BiologicalBiological NitrogenNitrogen RemovalRemoval) )
processesprocesses. . TheyThey are are classifiedclassified asas on on –– site site emissionsemissions , or , or directdirect emissionemission. . (C. Sweetapple et al., 2013; J. Porro et al., 2011; X. Flores – Alsina et al., 2013)
33.. OrganicOrganic CarbonCarbon OxidationOxidation byby meansmeans ofof autotrophicautotrophic aerobicaerobic bacteriabacteria
CO2 + H2O + E → Cx(H2O)x + O2
NitrificationNitrification pathwaypathway: oxidation of NH4+ to NO3
- via NO2-
N2O from secondary chemical reactions
44.. OrganicOrganic CarbonCarbon OxidationOxidation byby meansmeans ofof heterotrophicheterotrophic anoxicanoxic bacteriabacteria ((DenitrificationDenitrification))
Cx(H2O)x + NO3- → CO2 + N2+ H2O + e-
Red.Ox.
ATPATP
CCxxHHyyNNzzOOtt
(C(C55HH77NONO22))
Cx(H2O)x electron donor
NO3- electron acceptor
ATP energy needed for generation
CxHyNzOt new cells
CO2 product of the reaction
catabolic
pathway
anabolic
pathway
N, P, S, K,
Ca, Mg
e-
N2O as intermediate
4. Biological processes for GHG production
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 4
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
5. 5. BiologicalBiological processesprocesses for Nfor N22O productionO production
NITRIFICATIONNITRIFICATION DENITRIFICATIONDENITRIFICATION
Nitrification is the oxidation of NH4+ to NO3
- via NO2-, as represented by following
reactions:
AutotrophicAutotrophic aerobicaerobic bacteriabacteria..
The inorganic carbon is their only carbon
source.
The energy for their growth is taken from
reactions (chemoautotrophicchemoautotrophic bacteriabacteria).
NH4+ + 3/2 O2 NO2
- + 2H+ + H2O
NO2- + ½ O2 NO3
-
IT IS PERFORMED BY:
Secondary nitrifiers or nitrite –
oxidizing bacteria (NOB)(NOB) that
oxidize the NO2- to NO3
-
Primary nitrifiers or ammonium
– oxidizing bactiera (AOB)(AOB) that
oxidize the NH4+ to NO2
-
NitrosomonasNitrosomonas
NitrobacterNitrobacter
REACTION REACTION
ENVIRONMENTENVIRONMENT
Aerobic
nono == -- 33 nono == ++33
nono == ++ 55
NH3 + 3/2 O2 HNO2 + H2O
HNO2 + ½ O2 HNO3
Red.Ox.
Red.Ox.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
5. 5. BiologicalBiological processesprocesses for Nfor N22O productionO production
NITRIFICATIONNITRIFICATION DENITRIFICATIONDENITRIFICATION
NH4+ + 3/2 O2 NO2
- + 2H+ + H2ONitrosomonas
NH4+ + ½ O2 NH2OH + H+
NH2OH + O2 NO2- + 2H+ + H2O
Reazioni Reazioni
intermedieintermedieIntermediate:
NH2OH
HYDROXYLAMINE
N2O is formed during the chemical
decomposition of intermediates,
such as hydroxylamine and nitrite.
N2O is also produced during the
incomplete oxidation of NH2OH
because of formation of nitrosyl
radical (NOH).
Outline of the pathway and enzymes involved. (N. Wrage et al., 2001)
ENZYMES CATALYSING
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
5. 5. BiologicalBiological processesprocesses for Nfor N22O productionO production
NITRIFICATIONNITRIFICATION DENITRIFICATIONDENITRIFICATION
The denitrification is è the stepwise reduction of NO3- to N2. Denitrification involves
several types of heterotrophic microbes that reduce the nitrate to nitrogen gas, producing
nitrite, nitric oxide (NO), and nitrous oxide (N2O) as intermediates .
HeterotrophicHeterotrophic facultativefacultative bacteriabacteria ((PseudomonasPseudomonas)).
The organic carbon is used for both anabolic and
catabolic pathways.
The NO3- is used in place of oxygen as an
electron acceptor in anoxic conditions.
REACTION REACTION
ENVIRONMENTENVIRONMENT
Anoxic
IT IS PERFORMED BY
C10H19O3N + 10 NO3- 5N2 + 10CO2 + 3H2O + NH3 +10OH-
Red.Ox.
NN22O O isis anan intermediate in the intermediate in the denitrificationdenitrification
pathwaypathway. . ItIt isis notnot a a productproduct of of chemicalchemical
reactionsreactions!!Outline of the denitrification pathway and enzymes
involved. (N. Wrage et al., 2001)
ENZYMES CATALYSING
DENITRIFICATION - 4 4 STEPSSTEPS
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
NITRIFIER DENITRIFICATIONNITRIFIER DENITRIFICATION
More than 35 years ago, it was proposed that same nitrifiers (AOB) could not only nitrify,
but denitrify as well; this pathway of nitrification, called nitrifiernitrifier denitrificationdenitrification, might
contribute to a major part of the loss of ammonium in the form of NO ed N2O.
It is a pathway in which the oxidation of NH3 to NO2- is followed by reduction of NO2
- to
N2O and N2, withoutwithout NONO33-- productionproduction.
Nitrifier denitrification: hypotetical pathway and probable enzymes. (N.
Wrage et al., 2001)
This sequence of rections in
perfermed by autotrophicautotrophic
ammoniumammonium –– oxidizingoxidizing bacteriabacteria;
Nitrosomonas europaea is the
best studied.
5. Biological processes for N2O production
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 5
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
The two pathway model (Poquet et al., 2016)
OXIDATIONOXIDATION PROCESSESPROCESSES
oror
HYDROXYLAMINEHYDROXYLAMINE PATHWAYPATHWAY
REDUCTIONREDUCTION PROCESSPROCESS
oror
NITRIFIER DENITRIFICATION NITRIFIER DENITRIFICATION
PATHWAYPATHWAY
Red.
Ox.
2e-
O2Red.
3e-
Byproduct of incomplete oxidation
Final product of AOB
denitrification
Aerobic environment, O2 as electron acceptor Anoxic environment, NO2- as electron
acceptorENZYMES:
AMO – Ammonia monooxygenase
HAO – Hydroxylamine oxidoreductase
Nor – Nitric Oxide reductase coupled with copper ions
NirK – Nitrite reductase coupled with copper ions
Major contributor to
nitrous oxide production
in WWTPs.
H2O
Ox.
Red.
oxidation
red
uct
ion
1e-
2e-
1e-
1e-
NITRIFIER DENITRIFICATIONNITRIFIER DENITRIFICATION
5. Biological processes for N2O production
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
6. AeD modellingAEROBIC DIGESTORAEROBIC DIGESTOR
Basic concepts of ASMN (Hiatt & Grady, 2008) Basic concepts of ASMN (Hiatt & Grady, 2008) –– 2 steps nitrification, 4 steps 2 steps nitrification, 4 steps denitrificationdenitrification
++
PoquetPoquet Model (Model (PoquetPoquet et al., 2016) et al., 2016) –– NitrifierNitrifier DenitrificationDenitrification
AEROBIC DIGESTORAEROBIC DIGESTOR
Basic concepts of ASMN (Hiatt & Grady, 2008) Basic concepts of ASMN (Hiatt & Grady, 2008) –– 2 steps nitrification, 4 steps 2 steps nitrification, 4 steps denitrificationdenitrification
++
PoquetPoquet Model (Model (PoquetPoquet et al., 2016) et al., 2016) –– NitrifierNitrifier DenitrificationDenitrification
The wastage flow rate is 385 m3d-1
Few modifications were performed for the necessities of the study: 18 components and 19
processes were modelled.
MODEL LAYOUTMODEL LAYOUT
MatlabMatlab--SimulinkSimulink
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
6. AeD modelling. Basic concepts of ASMN (Hiatt & Grady, 2008) STATE VARIABLES – AeDMG1
1 SS
M(COD) L-3
Readily biodegradable substrate
2 SI Soluble non – biodegradable (inert)
organic matter
3 XS Slowly biodegradable substrate
4 XI Particulate non – biodegradable (inert)
organic matter
5 XB,H Active heterotrophic biomass
6 XB,A
OB
Active AOB biomass
7 XB,N
OB
Active NOB biomass
8 XD Inert particulate from biomass decay
9 SO Dissolved oxigen
10 SNO3
M(N) L-3
Nitrate
11 SNO2 Nitrite
12 SNO Nitric oxide
13 SN2O Nitrous oxide
14 SNH Ammonia nitrogen
15 SNS Soluble biodegradable organic
nitrogen
16 XNS Particulate biodegradable organic
nitrogen
17 SALK Molar units Alkalinity
PROCESSES – AeDMG1
R1 Aerobic growth of heterotrophs
R2 Anoxic growth of heterotrophs, nitrate to nitrite
R3 Anoxic growth of heterotrophs, nitrite to nitric oxide
R4 Anoxic growth of heterotrophs, nitric oxide to nitrous
oxide
R5 Anoxic growth of heterotrophs, nitrous oxide to nitrogen
R6 Decay of heterotrophic
R7 Aerobic growth of autotrophic, AOB
R8 Aerobic growth of autotrophic, NOB
R9 Mixotrophic growth of NOB
R10 Decay of autotrophic, AOB
R11 Decay of autotrophic, NOB
R12 Ammonification of soluble organic nitrogen
R13 Hydrolysis of entrapped organics
R14 Hydrolysis of entrapped nitrogen organic
4 4 StepsSteps
forfor
DenitrificDenitrific
ationation
4 4 StepsSteps
forfor
DenitrificDenitrific
ationation
2 2 StepsSteps
forfor
NitrificatiNitrificati
onon
2 2 StepsSteps
forfor
NitrificatiNitrificati
onon
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
Poquet Model (Poquet et
al., 2016)
NEWNEW POCESSESPOCESSES ANDAND STATESTATE VARIABLESVARIABLES
Five steps for nitrifier denitrification were added, as show below.
The model is more complex than the proviuos one. However it is able to describe the
proceses for N2O production in a better way, without understimations in emission
evaluation.
The new state variable is
the Hydroxilammine
(NH2OH).
It is fundamental in N2O
emission evaluation.
6. AeD modelling
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 6
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
6. AeD modelling
SensitivityClasses
Index
Sensitivity
I 0.00≤|I|<0.05 Small or Negligible
II 0.05≤|I|<0.20 Medium
III 0.20≤|I|<1.00 High
IV |I|≥1.00 Very High
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
RANKINGRANKING
MO
DE
L M
OD
EL
PA
RA
ME
TE
RS
PA
RA
ME
TE
RS
MODEL OUTPUTSMODEL OUTPUTS
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
mu_H
Y_H
etaAOB_ND0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
COD
COD
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
6. AeD modelling: sensitivity results
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
mu_H
Y_H
etaAOB_ND0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
TSS
TSS
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
6. AeD modelling: sensitivity results
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
mu_H
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
NH4
NH4
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
6. AeD modelling: sensitivity results
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 7
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
mu_H
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
NO3
NO3
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
6. AeD modelling: sensitivity results
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
mu_H
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
NO2
NO2
MODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
6. AeD modelling: sensitivity results
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
6. AeD modelling: sensitivity resultsMODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
mu_H
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
N2O
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
6. AeD modelling: sensitivity resultsMODEL CALIBRATIONMODEL CALIBRATION
SensitivitySensitivity AnalisysAnalisys –– MorrisMorris MethodMethod
mu_H
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Si
di
NH2OH
Serie1
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 8
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results.
EVALUATE THE N2O EMISSIONS FROM BIOLOGICAL TANKS USING THE OFF-GAS METHOD. Rionero in Vulture WWTP (Pz), March 2015Activated Sludge Tank
At least the 2% of the entire surface must be covered with
the floating hood to obtain a representative result.
Aerobic Digestor
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
77.. ExperimentalExperimental resultsresults.. Rionero in Vulture WWTP (Pz), March 2015.
EVALUATE THE N2O EMISSIONS FROM AN ACTIVATED SLUDGE TANK
A reinforced polyethylenepolyethylene floatingfloating hood (1 x
0.7 x 0.4 m, L x W x H) with a cross sectional
area of 0.7 m2 was used to capture the gas
fluxes. Dissolved gases within the liquid are
transported by aerationaeration strippingstripping into the gas
in the hoodhood headspaceheadspace.
SuperSuper--Inert Multi Foil bags (4 L volume)Inert Multi Foil bags (4 L volume) were used to collect off-gas samples and carry
out off-line measurements of NN22O and COO and CO22 concentrations (Gori et al., 2015). The gas bags
were equipped with a vacuum pump vacuum pump and connected to the hood headspace to collect a
gas sample. The main advantage of Multi Foil gas bags was the good sample storage
properties allowing a safe transporsafe transportation for reliable GC-ECD and GC-FID laboratory gas-
chromatographic analyses.
The hood headspace was connected to an
off off –– gas analyzer gas analyzer and the gas flow rates gas flow rates
were measured by a hot wire anemometer.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
EVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR WITH SURFACE AERATORS
Impossibile v isualizzare l'immagine. La memoria del computer potrebbe essere insufficiente per aprire l'immagine oppure l'immagine potrebbe essere danneggiata. Riavviare il computer e aprire di nuovo il file. Se v iene visualizzata di nuovo la x rossa, potrebbe essere necessario eliminare l'immagine e inserirla di nuovo.
The off-gas hood was used to collect the exhaust gas in the hood headspace but
due to the presence of surface aeration, there was no relevant off-gas flow rate
leaving the liquid surface and was impossible to collect gas samples immediately.
Therefore, the floating hood was positioned in one location. In order to measure
the relative flux of the gases leaving the liquid volume, a portion of the Teflon tube
was siphon shaped and filled with water.
After about twenty hours keeping the hood in one position, the displacement of
the water level was measured and gas bags were sampled. This methodology
allowed to accumulate a measurable amount of gas in the hood headspace for
both GHG concentrations and flux.
Rionero in Vulture WWTP (Pz), March 2015.
7. Experimental results.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. 7. Experimental results. Experimental results. Rionero in Vulture WWTP (Pz), March 2015.
Nitrous oxide emissions in wastewater treatment plants: biological processes, methods for
sampling and measurement, decision support systems for planning and management.
From electricity
generation
From organic
matter oxidationFrom N2O
Total CO2,eq
emissions
Plant
CFP
AS 0.26 0.14 0.007 0.4070.47
AeD 0.063 3·10-10 4·10-9 0.063
Gori et al. 2010 0.60.6 from AS
0.4 from AeD0.1 - 1.7
Corominas et al.
20100.524
0.376 from AS
0.389 from AD0.384 from AS - 1.673
Total plant CFP (all values in kgCO2,eq/ kgbCOD) and comparison with literature data
From electricity
generation
From organic matter
oxidationFrom N2O
AS 0.294 0.158 0.007
AeD 0.071 3·10-10 4·10-9
Flores-Alsina et al. (2011) -
scenario A0
0.311 without energy
recovery
0.380 from AS
0.079 from AD0.236 from AS
Flores-Alsina et al. (2011) -
scenario A1
0.276 without energy
recovery
0.398 from AS
0.078 from AD0.146 from AS
Flores-Alsina et al. (2011) -
scenario A2
0.276 without energy
recovery
0.380 from AS
0.079 from AD0.158from AS
Flores-Alsina et al. (2011) -
scenario A3
0.287 without energy
recovery
0.398 from AS
0.078 from AD0.202 from AS
Plant CFP (all values in kgCO2,eq/ m3 of treated wastewater) and comparison with literature data
Emission factor: 0.00032 kgN2O-N/kgNH4-N Daily rate AS: 70 gN2O/d
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 9
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. 7. Experimental results. Experimental results. Rionero in Vulture WWTP (Pz), March 2015.
• The value obtained for the emission factor is 0.00032 kgN2O-N/kgNH4-N, corresponding to
0.032%. The obtained value is inside the range indicated by Chandran (2011) for
AS, nevertheless closer to its lower bound. This is not because the plant is designed and
managed towards a low-emissions configuration, but most probably because many anoxic
zones are generated in the aerobic tank due to the poor performance of the aeration system.
• The daily rate of N2O emitted from the aeration tank is 70 gN2O/d that is a value typical
obtained for anoxic tanks, as shown for example by Ahn et al. (2010) for a Modified Ludzack -
Ettinger (MLE) configuration.
• The emissions from the AeD are smaller than those from AS mainly because of low off-gas
flow rates due to the installation of surface turbines instead of submerged diffusers.
However, the poor management of the AS compartment implies that the AeD receives higher
NH4 loads than in normal operative conditions and could become potentially the main
contributor to N2O emissions: nitrogen compounds accumulated in the AS are the potential
source of emissions along the sludge line (e.g. during following sludge treatment steps such
as thickening, dewatering, transportation and disposal).
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plantEVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
� IN 60 mL
� OUT 60 mL
� At first, 6 L of secondary sludge from the settler underflow of
the WWTP located in Potenza (Italy), serving 120000 PE, were
introduced in the digester was fed.
� Diffusers were introduced inside the tank to ensure an
adequate amount of DO to the microorganisms’ activities; a mixer
was also useful to avoid sludge sedimentation and consequently
the clogging of diffusers.
� The testing was performed in a 20-days monitoring campaign,
in order to reach the equilibrium conditions regarding the
biological activities. To ensure a discontinuous feeding, 60 mL of
new sludge were introduced every day.
� Analysis regarding COD, nitrogen compounds, TSS and VSS on
the influent and the underflow were performed during the testing
days.
Palermo 21/05/2016
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plantEVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
� A simplified off-gas technique was used to
collect the off-gas.
� A hood was used to collect and conveying
the off-gas towards the flowmeter. The off-
gas flow rate was measured. However, at the
same time, Tedlar sampling bags were used to
take gas samples from the hood headspace:
eight bags a day were analyzed, one every 15
minutes.
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plantEVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
mg/l COD TSS VSS NH4+ N-NO2
- N-NO3-
Influent sludge at first day test 6141.23 10720 8240 2.28 1.13 132.87
Discharged sludge after 20 days 5130.55 6780 4045 3.03 1.77 277.50
A 50.9 percent decreasing in VSS concentration and a
36.7 percent decreasing in TSS concentration were
observed, respectively, after 20 days, which are values
closer to the literature range for well performed systems
(38 - 50 per cent in VSS and 30 - 50 per cent in TSS,
Metcalf and Eddy, 2003).
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 10
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plantEVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
NN22OO coverscovers thethe 7272 percentpercent ofof thethe totaltotal COCO22 equivalentequivalent emissionsemissions andand COCO22 onlyonly thethe 2828
percent,percent, consideringconsidering aa conversionconversion factorfactor ofof 289289 kgkgCOCO22/kg/kgNONO22 forfor NN22OO (IPCC(IPCC 20062006))..
testing days
CO2
kgCO2/kgbCOD·m2
N2O
kgN2O/kgbCOD·m2
CO2,e
kgCO2e/kgbCOD·m2
7/13/15 53.03 0.093 79.87
7/14/15 31.65 0.071 52.09
7/15/15 65.20 0.372 172.73
7/16/15 67.69 0.732 279.26
7/17/15 78.23 0.164 125.65
7/20/15 58.71 0.290 142.59
7/21/15 43.89 0.159 89.85
7/24/15 35.38 0.886 291.45
7/27/15 39.94 0.183 92.95
7/28/15 42.33 0.871 294.10
7/29/15 43.90 1.491 474.84
7/30/15 28.30 0.079 51.12
7/31/15 30.35 0.184 83.62
Assuming a conversion factor of 0.74 kgbCOD/kgCOD (Henze et al., 2000), the quantified emissions
from pilot AD are summarized in Table 2, showing an average value of 171171 kgCOkgCO22,e,e//kgkgbCODbCOD··mm22..
TheThe emissionsemissions areare
lowerlower thanthan thosethose
anan ASPASP andand higherhigher
thanthan thosethose anan
anaerobicanaerobic digester,digester,
inin whichwhich thethe
producedproduced COCO22 isis
convertedconverted inin
biogasbiogas withwith thethe
possibilitypossibility toto
recoverrecover energyenergy forfor
thethe plantplant..
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plantEVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
testing days
Flux
(kgN2O/m2·d)
Emission fraction·10-3
kgN2O/kgNH4
7/13/15 468 0.018
7/14/15 317 0.009
7/15/15 1545 0.055
7/16/15 2909 0.102
7/17/15 612 0.022
7/20/15 1121 0.051
7/21/15 770 0.022
7/24/15 4190 0.131
7/27/15 879 0.027
7/28/15 4255 0.133
7/29/15 7150 0.210
7/30/15 396 0.010
7/31/15 867 0.025
Table 3 shows that the daily amount of N2O emissions depends of BNR processes,
computing the N2O emission fraction by means the normalization of the flux to the daily
influent Total Kjeldahl Nitrogen (TKN).
OnOn average,average, thethe calculatedcalculated
NN22OO emissionemission fractionfraction forfor thisthis
pilotpilot digesterdigester isis 00..006006
percent,percent, resultingresulting lowerlower thanthan
thethe rangerange proposedproposed byby
ChandranChandran ((20112011)) forfor ASPsASPs
whenwhen normalizednormalized toto influentinfluent
TKNTKN (from(from 00..0101%% toto 11..88%%))..
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. 7. Experimental results. Experimental results. Pilot plant.
Nitrous oxide emissions in wastewater treatment plants: biological processes, methods for
sampling and measurement, decision support systems for planning and management.
A link between the N2O emissions
and ammonia loads incoming in the
digester through the excess sludge
was found, by means performing
analysis of the sludge
characteristics during the testing
days.
As shown in figure, an increasing As shown in figure, an increasing
of emissions was observed when of emissions was observed when
ammonia decreased, proving the ammonia decreased, proving the
dependence of Ndependence of N22O emissions O emissions
from nitrification processesfrom nitrification processes
DODO concentrationsconcentrations inin thethe pilotpilot tanktank
werewere notnot constantconstant becausebecause ofof
lackinglacking ofof aa DODO controller,controller, andand
nitratesnitrates werewere accumulatedaccumulated inin thethe
liquidliquid phasephase contributingcontributing probablyprobably
toto NN22OO emissionsemissions..
EVALUATE THE N2O EMISSIONS FROM AN AEROBIC DIGESTOR ON LAB SCALE
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Experimental results: pilot plant
International Seminar - University of Palermo 20 May 2016
Donatella Caniani 11
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
7. Future developmentsFULL – SCALE AEROBIC DIGESTER with submerged aerators
NO – AERATED TANKS (i.e. secondary settler)
MethodMethod forfor samplingsampling andand measurementsmeasurements
MethodMethod forfor samplingsampling andand measurementsmeasurements
Innovative wastewater treatment technologies
for energy saving and environmental protection
May 20, 2016 - Palermo
[email protected]@unibas.it