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Apr 15, 2023 174 likes •303 views

Session XXIV Recovery of materials from wastewater & sludge Sludge management Downstream processing for Polyhydroxyalkanoates from mixed microbial cultures: Study of microbial activity inhibition, polymer recovery and characterizations

SLIDE 1

Downstream processing for Polyhydroxyalkanoates from mixed microbial cultures: Study of microbial activity inhibition, polymer recovery and characterizations

1Department of Chemistry University of Rome La Sapienza

laura.lorini@uniroma1.it

Session XXIV Recovery of materials from wastewater & sludge – Sludge management

1L. Lorini, 1F

. Valentino, 1G. Bifolchi, 1A. Martinelli, 1M. Majone

SLIDE 2

Polyhydroxyalkanoates (PHA)

Biodegradable

commodity film

Packaging interlayer film
Specialty durables (such

as electronics)

Slow C-release system

for groundwater remediation

(Kunansudari, Exp Polym Let 2010)

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Product related Pro’s Family of copolymers with tunable composition Main constituent of several bioplastics

non biodegradabl e, mechanical recycling biodegradab le, recycling with organic waste Bio-based feedstock Biodegradabilit y Biopolym ers starch blends, PLA, PHA Bio-PE (PP/PVS), biobased PET PE, PP, PS, PVC, PET ecc. PBAT, PBS, PCL Oil-based plastics Bio-based feedstock and biodegradability

SLIDE 3

PHA production from MMC and organic waste

Stage III: PHA production Stage II (SBR): biomass selection/ enrichment (ADF) Acidogenic Fermentation Sludge from wastewater treatment plant VFA VFA MMC Activated sludge PHA-rich biomass Solid fraction Liquid fraction Anaerobic Digestion Energy Nutrients PHA extraction

Biodegradab le bioplastics

PHA processing Organic fraction of municipal solid waste (OFMSW)

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SLIDE 4

Pilot platform

Wastewater Treatment Plant in Treviso (North-East

f Italy)

SLIDE 5

Aim of the study

Optimization of a stabilization method

 Infmuence of pH ➔ H2SO4; NaOH  Oxidation➔ NaClO  Excess of substrates  Thermal treatments➔ oven dried at 70°C (with or

without shock at 170°C) Innovative extraction and recovery methods

 Non-chlorinated solvent: ethyl acetate

Characterization of extracted polymer:

 GC-FID ➔ purity, recovery yield and monomeric

composition

 Capillary viscosimetry ➔ molecular weight  DSC ➔ thermal properties

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SLIDE 6

Selection of PHA-producing biomass (SBR)

Operative cycle (12 h)

Feeding= 10 min Reaction 1= 140 min Withdrawal= 3 min Nitrogen feeding= 5 min Reaction 2= 562 min

V = 1L Organic load rate (OLR) 4.25 gCOD/L d VFA (85% Acetic acid; 15% Propionic acid) T= 25°C

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SLIDE 7

PHA accumulation step

Batch reactor V= 0.5L
6h test
Multispike strategy (85% Acetic acid;

15% Propionic acid)

Selection (SBR) PHA storing biomass Accumulati

(Batch) PHA-rich biomass

1 2 3 4 5 6 7 500 1000 1500 2000 2500

PHA content

t (h) PHA mgCOD/L

VF A

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Stabilization tests

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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

End of batch test Centrifuged 170°C+70°C 70°C

P H A t / P H A e n d o f a c c u m u l a t i o n

0,5 1 1,5 2 2,5 3

0% 2000% 4000% 6000% 8000% 10000% 12000%

time (h)

PHA t /PHAend of accumulation Two kinds of thermal treatment

SLIDE 9

Extraction and characterization

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Purity (PHA %w/w) 95.3 % (CHCl3); 85.2 % (NaClO) Recovery yield (%w/w) 83.2 % (CHCl3); 87.4 % (NaClO) 5 different batches (Pilot scale Batches 11, 15, 19, 22, 24) and 1 batch (Lab scale) thermally stabilized Soxhlet extraction with CHCl3 Oxidation with NaClO

B. 11
B. 15
B. 19
B. 22
B. 24 Lab scale

50000 100000 150000 200000 CHCl3 NaClO Mv (KDa)

SLIDE 10

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Batch 11 thermally stabilized Extraction in a pressurized steel reactor with Ethyl acetate (100 and 125°C) for 1h Residues extracted with CHCl3

Non-chlorinated solvent extraction

SLIDE 11

Conclusions and future prospectives

Thermal treatment applicable at pilot scale
NaClO gave results comparable to traditional chloroform

extraction

Ethyl acetate selectively extracts shorter chains
Evaluation of the efgects of thermal treatment on the

polymer, in comparison with an acidifjcation method applied at pilot scale

Optimization of Ethyl acetate extraction and use of other

non-chlorinated solvents

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SLIDE 12