SLIDE 1 Improvement of VFA production from food waste using biological pretreatments
Y . K. CHEAH1; C. VIDAL-ANTICH1; J. DOSTA1,2; J. MATA- ÁLVAREZ1,2
1 Departament d’Enginyeria Química i Química Analítica. Universitat
de Barcelona
2 Water Research Institute. Universitat de Barcelona
jdosta@ub.edu
SLIDE 2
Introduction
FOOD WASTE TREATMENT (OR CO- TREATMENT) IN THE BIOREFINERY CONTEXT
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SLIDE 3 METHANOGENESIS
CH4 + CO2 ACIDOGENIC FERMENTATION
HYDROL YSI S ACIDOGENE SIS & ACETOGEN ESIS
3
Introduction
ype of substrate and co-substrates fed
parameters
VFA Concentration VFA Composition Ratio CODVFA/CODSOLUBLE
REGULATION OF
INTERMEDIATE PRODUCTS (propionic acid, butyric acid, …)
ACETIC ACID H2, CO2
Fatty acids, alcohols Aminoacids, Simple sugars LIPIDS CARBOHYDRA TES PROTEINS
e d c b a
P N O H C
3 4 4
PO P NH N
SLIDE 4
Introduction
BIOLOGICAL PRE- TREATMENTS
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Hydrolysis is usually the limiting step of acidogenic fermentation. BIOLOGICAL PRETREATMENTS are getting more attention to improve acidogenic fermentation. since they do not require reagent addition and do not require high energy demands to be applied. In this study, 2 biological pretreatments were studied to improve hydrolysis and VFA production: 1) ADDITION OF MATURE COMPOST
Mature compost contains a variety of hydrolytic bacteria , by adding it into acidogenic fermenter, they will enhance solubilisation and hence, increase the rate of hydrolysis for VFA production.
2) ADDITION OF WASTE ACTIVATED SLUDGE PRETREATED AT 55ºC
T reating WAS at 55 ºC, the microorganisms release extracellular polymeric substances (EPS) that are contained in their own metabolic system resulting in autohydrolysis (Carvajal et al., 2013; Arias et al., 2018).
SLIDE 5
Materials and methods
EXPERIMENTAL DEVICES FOR ACIDOGENIC FERMENTATION Batch test assays Semi-continuous lab-scale reactors (5L)
Operating at 35°C and 3.5/5d of HRT, pH6/7, with and without compost addition
ANAL YTICAL METHODS
Standard Methods for the Examination of Water and Wastewater (APHA, 2012)
Efgect of mature compost or pretreated WAS addition
SUBSTRATE AND INOCULUM
SUBSTRATES INOCULUM FOOD WASTE (University Canteen) WASTE ACTIVATED SLUDGE (municipal WWTP) MATURE COMPOST (MBT plant treating OFMSW and Parks and gardens waste) Effmuent from acidogenic fermenters treating FW initially inoculated with anaerobic digetate (mesophilic conditions) of sewage sludge
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SLIDE 6 Results and discussion
Features: T = 35ºC HRT 3.5 days VS: 4.1-6.1 %w/w Acetic acid and butyric acid concentrations were predominant at pH 6.0 although FW was randomly collected from a University canteen
REFERENCE ACIDOGENIC FERMENTER TREATING FW
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 5 10 15 20 25 30 35 OLR at HRT 3.5d O L R (g V S /(L .d )
2500 5000 7500 10000 12500
Heptanoi c Caproic Isocaproi c V aleric Isovaleric Butyric Isobutyri c
V F A c o n c e n t r a t i o n ( m g V F A / L ) 0 % compost, pH 6, HRT 3.5d
pH control
Difgeren t collecti
periods 6
SLIDE 7 Results and discussion
BATCH FERMENTATION ASSAYS OF FW ADDING MATURE COMPOST
Experiment carried out in duplicate. Ratio inoculum/Fresh FW : 1:1 (VS basis)
Compost added (% ST) 0 % 2.5 % 3.5 % 4.5 % VFA Improvement (%) at pH 6 (10d)
12.9% 9.7% FW (% VS in the mixture) 50 % 44 % 41 % 39 %
1 2 3 4 5 6 7 10 0% 20% 40% 60% 80% 100% Heptanoic Hexanoic Isocaproic Valeric Isovaleric Butyric Isobutyric Propionic Acetic Time (days) P e r c e n t a g e o f V F A ( % C O D )
10 days , 2.5% mature compost pH 6
pH 6 pH 7
10 days , 2.5% mature compost, pH 7
VFA Improvement (%) at pH 7
1.6%
2 3 4 6 7 10 0% 20% 40% 60% 80% 100% Heptanoic Hexanoic Isocaproic Valeric Isovaleric Butyric Isobutyric Propionic Acetic Time (days) P e r c e n t a g e o f V F A ( % C O D )
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SLIDE 8 Results and discussion
BATCH FERMENTATION ASSAYS OF FW ADDING MATURE COMPOST
Mature compost Higher solubilisation and ammonium release Mature compost Higher butyric acid production Mature compost Similar distribution
Mature compost Higher ammonium release 8
SLIDE 9 Results and discussion
SEMI-CONTINUOUS OPERATION ACIDOGENIC FERMENTER pH 6
A Reference B 2.5% compost C 1.5% compost A Reference B 2.5% compost C 3.5% compost A,C Ref. B 2.5% compo st A,B,C Ref.
Similar VFA production using 2.5% and 3.5 w/w compost Slightly lower VFA production when using 1.5% instead of 2.5 w/w compost
11-19% higher (%VS
29-51% higher (% VS infm. 3.8-3.9%)
VFA production enhancement using 2.5% w/w
impact at lower OLR
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SLIDE 10 Results and discussion
SEMI-CONTINUOUS OPERATION ACIDOGENIC FERMENTER pH 6
be boosted up in the beginning and maintained its dominance during the experiment, with compost doses between 1.5-3.5%w/w at pH 6.
proportion when compost is added (from up to 12.2% (COD basis) in the reference reactor to up to 23.5%)
expressed in terms of sCOD and NH4
+-N
release was detected in the fermenters working with mature compost addition.
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SLIDE 11
Results and discussion
SEMI-CONTINUOUS OPERATION ACIDOGENIC FERMENTER pH 6 and 7
A : No change B: 0% compost, pH 7, TRH 5 d C : No change A: No change B: No change C: HRT to 5 d A Ref. B: 2.5 % compost pH 6 C: 2.5 % compost pH 7
High VFA production enhancement using 2.5% w/w compost at pH 7
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SLIDE 12 Results and discussion
SEMI-CONTINUOUS OPERATION ACIDOGENIC FERMENTER
addition of 2.5% mature compost, an improvement
VFA concentration (on COD basis) were recorded with respect to the reference reactor.
propionic (from 1.6 to 7.7%), valeric (from 0.8 to 5.6%) acids production was
compared to
REACTOR A - REFERENCE REACTOR B REACTOR C
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SLIDE 13 Results and discussion
SOLUBILISATION ASSAYS WITH PRETREATED WAS AT 55ºC
- A growth of VS solubisation from 3% to 26% at 9h was
- bserved.
- 4h 30 min were enough time of WAS autohydrolysis with
25% of solubilisation. Experiment carried out in duplicate with bottles of 1L of working volume. Every 60-90 min, the T sS and VsS are analysed to determine the solubilisation (SsV/SV) of WAS
60 120 180 240 300 360 420 480 540 0% 5% 10% 15% 20% 25% 30%
WAS Solubilisation at 55 ºC
Time (min) S ( VSs/VS %)
150 min 240 min 90 min
35ºC Pretreated WAS (55ºC at 4h)
+
Food Waste
Food Waste Hydrolysis and VFA production enhancement
No enhanced VS solubilizati
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SLIDE 14 Results and discussion
PRETREATED WAS (55ºC AT 2.5 H) + FOOD WASTE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2000 4000 6000 8000 10000 12000 14000 16000 18000 FW Wp W
Time (d) C O D V F A c o n c e n t r a t i o n ( m g C O D - L - 1 ) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2000 4000 6000 8000 10000 12000 14000 16000 18000 20%FW+80%WAS 20%FW+80%WAS_Theoric 50%FW+50%WAS 50%FW+50%WAS_Theoric Time (d) C O D V F A c o n c e n t r a t io n ( m g C O D - L - 1 )
Discontinuous assays:
- Food Waste (FW)
- Pre-treated WAS (Wp)
- WAS (W)
- 20% FW + 80 % pre-treated WAS (in VS content)
- 50 % FW + 50 % pre-treated WAS (in VS content)
- 80 % FW + 20 % pre-treated WAS (in VS content)
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SLIDE 15 Results and discussion 50 % FW + 50 % pre-treated WAS (in V content)
(pH: 3.9 -> 3.7)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA (% C O D )
Food Waste (FW)
PRETREATED WAS (55ºC AT 2.5 H) + FOOD WASTE
Pre-treated WAS (Wp)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA (% C O D )
(pH: 6.5 -> 7.8)
80 % FW + 20 % pre-treated WAS (in VS content)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA (% C O D )
(pH: 3.9 -> 4.6)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA ( % C O D )
(pH: 5.5 -> 5.9)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA (% C O D )
(pH: 5.8 -> 7.8)
WAS (W)
1 4 5 6 7 8 9 12 13 14 0% 20% 40% 60% 80% 100%
Time (d) V FA (% C O D )
(pH: 6.4 -> 7.9)
20% FW + 80 % pre-treated WAS (in VS content)
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SLIDE 16
Conclusions
CONCLUSIONS
The addition of 2.5% w/w of mature compost to a semi-continuous acidogenic fermenter treating FW at mesophilic conditions (35ºC), pH 6 and HRT of 3.5 days led to an improvement of the VFA yield up to 51.2 % (on VFA basis) The mature compost dosage at pH 6 resulted in a higher percentage of butyric acid on COD basis in the fermentation broth, increasing from up to 12.2 % (0% compost addition) to up to 23.5 % (2.5% compost addition). When pH was changed from pH 6 to pH 7, VFA production was boosted and a higher production of propionic and valeric acids was recorded with respect to the reactor working at pH 6. Regarding WAS pretreatment, solubilisation of WAS at 55ºC from 3% to 25% took place in 4h. Synergies in VFA production when mixing pretreated WAS at 55ºC during 2.5h and FW were observed for mixtures containing up to 50% VS of FW. No synergies were observed when mixing WAS at 55ºC during 1.5 and 4 h.
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SLIDE 17 Improvement of VFA production from food waste using biological pretreatments
Y . K. CHEAH1; C. VIDAL-ANTICH1; J. DOSTA1,2; J. MATA- ÁLVAREZ1,2
1 Departament d’Enginyeria Química i Química Analítica. Universitat
de Barcelona
2 Water Research Institute. Universitat de Barcelona
jdosta@ub.edu
