Post on 02-Jun-2018
transcript
8/10/2019 Vfa Recovery Process
1/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
2/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
3/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
4/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
5/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
6/20
8/10/2019 Vfa Recovery Process
7/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
8/20
Industrial Fermentation Process
Fig 1:Schematic diagram of industrial fermentation process
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
9/20
8/10/2019 Vfa Recovery Process
10/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
11/20
8/10/2019 Vfa Recovery Process
12/20
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.
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
13/20
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
8/10/2019 Vfa Recovery Process
14/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
15/20
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
8/10/2019 Vfa Recovery Process
16/20
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.
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
17/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
18/20
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
PERSONAL DRAFT COPY
8/10/2019 Vfa Recovery Process
19/20
8/10/2019 Vfa Recovery Process
20/20
Aknowledgments
Dr. Robert William Lovitt
Mr. Michael Gerardo
Dr. Paul Williams
Dr. Darren Oatley
M.Zacharof@swansea.ac.uk
Questions
PERSONAL DRAFT COPY
mailto:M.Zacharof@swansea.ac.ukmailto:M.Zacharof@swansea.ac.ukmailto:M.Zacharof@swansea.ac.uk