Vfa Recovery Process

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Venice 2012

Fourth International Symposium

On Energy From Biomass And Waste

San Servolo,

Venice (Italy)12-15 November 2012

Use of complex effluent streams as a potential source of

Volatile Fatty acids (VFA)

Dr. Myrto-Panagiota Zacharof

Swansea University, Wales

United Kingdom

Dr. Robert William Lovitt

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Introduction

Low Carbon Research Institute

(LCRI) Project H2 Wales

Swansea University Group is

involved in Liquid/Solid Separations

from Complex Effluent Sources

Development of a number of process

to recover useable materials in solidor liquid form and chemical

intermediates from waste sources.

CWATER

Swansea University Group

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Volatile Fatty Acids (VFA)

VFA are fatty acids with a carbon chain of six or fewer carbons

,straight chain and branched.

Also known as carboxylic acids due to the carboxylic group they have.

Also named low molecular weight (LMW) organic acids due to theirsmall molar mass.

They are of great industrial importance applied in the field of food and

beverages and in the pharmaceutical and chemical fabrication field.

They play a central role in the metabolism of carbon in the environment

especially in acidogenic fermentations

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Industrial and Commercial

Application of VFA

Formicacid

Antibacterial

agent

Rubber

processing

Tanning

Pharmaceutica

lmanufacturing

Pesticides

Acetic acid Vinyl acetate

monomer(polymers,

adhensives, dyes)

Food additive

Solvent

Vinegar

Ester production

Chemicals

Lactic acid

Anti acne agents

Moisturizers

Skin lightning agents

Food-Beverageadditive

Chemical

Monomer forbiodegradablepolymers

Buffering agent

Butyric acid

Esters used foodindustry as aromaadditive

Food additive,flavoring

Pharmaceuticals

Animal feedsupplement

Fishing baitadditive

Propionicacid

Animal andHuman food

additive

Chemicalintermediate

Solvent

Flavouringagent

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Commercial Value of VFA

Carboxylic

Acids

Chemical formula Market size(tonnes/ year)

Price per tonne

(USD, $)

Formic HCOOH 30.000 800-1200

Acetic CH3COOH 3.500.000 400-800

Propionic CH3CH2COOH 180.000 1500-1650

Butyric CH3(CH2) 2COOH 30.000 2000-2500

Caproic CH3(CH2) 4COOH 25.000 2250-2500

Lactic CH3CHOHCOOH 120.000 1000-1800

Table 1: Commercial Value of Industrially Important VFA

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Biological Synthesis of VFA Products

Fermentation, of carbohydrates,

in other words, the breakdown andre-assembly of biochemicals underthe presence of a microorganisms,in anaerobic growth conditions

Several waste and non wastematerials can used as substrate, solid and liquid waste sludge

deriving from agricultural or foodsources

other complex effluent streamssuch as municipal or industrialwastewater. Fig 1:Schematic diagram of fermentation

process

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Industrial Fermentation Process

Fig 1:Schematic diagram of industrial fermentation process

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Anaerobic Digestion, a source of

VFA?

Anaerobic digestion (AD), oracidogenic fermentation,

Traditional treatment, it can beperformed on various solid orliquid substrates, such as silage ormanure leading to the production of

biogas, methane CO2 used inenergy generation.

Acidogenesis represents one of thestages towards methanogenesis.VFA are the main solublecompounds generated

VFA could represent a sources ofvaluable carbon materials forchemicals products provided theycan be recovered economically. Source: SCHUER(2008)

Fig 3:Schematic diagram of AD process

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Advantages and Commercial Benefits of VFA

Recovery

Obvious commercial benefits include

The reduced demand on municipal treatment plants as reduced carbon isextracted so reducing costs and energy requirements of oxidation and therelease of CO2

The extraction of reduced carbon (as VFA) for reuse and substitution ofacetate and other VFAsderived from petrochemicals so reducing relianceon fossil carbon for chemicals of favourable nutrients

Chemical based industry becomes uncoupled of fossil carbon and itsincreasing cost

Valorisation of waste carbon

Fixation of carbon as chemicals rather that their release as CO2 Reduceseconomical and enviromental impact of waste treatment.

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Composition of Complex Effluent Streams

Parameter Range Mean Standard Deviation (2)

pH 6.2-7.1 6.5 0.3

TS (Total Solids) (g L-1) 4.520-12.350 5.600 312

VS ( Volatile solids)( g L-1) 3.616-10.490 4.3680 278

VSS (Volatile Suspended solids)( g

L-1)

3.220-9.750 3.960 235

TOC (Total organic carbon)( g L-1

) 1.130-3.110 1.820 254

VFA (Volatile fatty acids)

(g L-1)

2-12 5 0.5

(Ammonia-Nitrogen)( g L-1) 14-47 19 4

Carbohydrate (%) 31.2-38.7 34 0.5

Protein (g L-1) 25.1-28.2 26 1.2

Lipids (g L-1) 7.6-11.7 9 0.9

Fibber (g L-1) 20.3-30.7 25 1.5

Table 4: Physicochemical composition of coagulated sludge (Kim, Simiya, Shin, Kim & Kim, 2005)PERSONAL DRAFT COPY


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Downstream Processing Methods for VFA RecoverySeparation methods Description Advantages Disadvantages

Precipitation Calcium salts are added in the

medium , to neutralize the acids.

The resulting calcium

carboxylate solutions, can beconcentrated by evaporation, then

crystallized and separated of the

mother liquor

Higher product yields, low

capital costs, products of high

purities

Generating solid wastes as

sulfuric acid is used to release

carboxylic acids from the

calcium carboxylates.

Distillation Ammonia is used to neutralize

the acids reacting to form

ammonia carboxylate, which is

then mixed with alcohol to form

esters , to be separated by

distillation

Highly pure products, byproducts

can be used as fertilizer

High energy and capital costs

related to distillation that is used

to separate the alcohol from

carboxylic acids after the formed

esters are hydrolyzed.

Adsorption Ion exchange resins used to

exchange to adsorb carboxylate

ions of the feeds

Easily operable High resin costs, High energy

demand due to resin

regeneration, low adsorption

capacities, separation is not

highly selective

Electrodialysis Negatively charged carboxylate

ions move through an anion

exchange membrane towards the

anode in the electrodialyzerthrough electric current

Carboxylate is concentrated in

aqueous solution , does not

require acid treatment to adjust

pH

The products have high

impurities , further purification

might be required , difficulties in

scaling up , high energy demand

Solvent Extraction Organic acids use to extract

carboxylic acids from the stream

Higher product yields, suitable

for carboxylate salt production,

lower costs

The feed needs to be acidified foe

efficient extraction , extractants

needs to be regenerated by

distillation or back extraction.

Membrane Separations Use of membrane filters of

various pore sizes to treat the

mixed effluents for solids

removal and fractionate thedesired substances for recovery

High product yields, suitable for

a wide range of applications,

economic , easy to scale up

Membrane fouling , clogging

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Membrane Separation

Now well established in the

food and pharma industries

More recently industrial waste

streams , municipal , domestic

and industrial wastewater.

A complete range of membrane

filtration technologies. Microfiltration (MF)

Ultrafiltration (UF)

Nanofiltration (NF)

Reverse Osmosis (RO)

Employed to clarify,

concentrate, desalt and

fractionate, components from

waste such as whey and other

substances. Fig 5:Separation efficiency of membraneprocessesPERSONAL DRAFT COPY


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Membrane Separation Advantages

Several beneficial features lay in membrane processing, including the

ability to recover the acids and concentrate them

Has been applied to many simple (well defined) waste systems

Reuse or more economical disposal of waste

Low pressure operation

Simple scale-up using commercial modules Ease of in-situ separation of VFA.

The process has shown treatment feasibility for several types of aqueous

waste streams. The main problem that develops is membrane fouling which

needs to be avoided and may requires frequent cleaning of the membrane tomanage the process effectively.

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Membrane Separation of Organic acids

Nanofiltration Of all pressure-driven membrane

processes, nanofiltration is thebest candidate process to deal

with the problem as neither

reverse osmosis or ultrafilration

can separate salts from relatively

small organic molecules.

Nanofiltration may have another

advantage of exploiting Donnan

charges exclusion as most

nanofiltration membranes possessfixed charges

Fig.6.: Nanofiltration efficiency

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Membrane Separation of Organic acids

Nanofiltration The surface of the NF membrane

is easy disrupted so care has to

taken in the pre-treatment of the

system to create a robust

separation process

Investigating of these systems now

underway, i.e.

Membrane selection,

separation and optimisation studies

of model solutions,

Filtration pre-treatment studies ofAD sludge using MF

MBR design for in situ VFA

recovery from acidogenic reactors .

Fig.7.:Sterlitech HP4750 stirred cell unit

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Aknowledgments

Dr. Robert William Lovitt

Mr. Michael Gerardo

Dr. Paul Williams

Dr. Darren Oatley

[email protected]

Questions

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mailto:[email protected]:[email protected]:[email protected]

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