Transcript Power Point - Assiut University

Industrial wastewater treatment to
Polyhydroxyalkanoates as biodegradable polymers
Prof. Dr. Adel Mohamed Kamal El-Dean
[email protected]
Assiut University
1
‫{ وجعلنا من الماء كل شيء حي }‬
‫سورة األنبياء‬
‫‪We made from water every living thing‬‬
‫‪2‬‬
Water and its important:
In view of the increasing demand for water and in the
light of water problems, which may be faced Egypt in
the near future, the all types of waste water should be
recycled and reuse. Sugar and paper mills consume
huge amounts of water, which should recycled and
reused.
Major problems in the handling of water:
•use of high quality drinking water for all applications
• expensive sewer systems with a restricted live time
• dilution and only elimination of nutrients
• no recovery of resources (nutrients, energy, …)
• enormous production of excess sludge
3
Industrial wastewater in the sugar and paper mills
contain many of dissolved organic matter, which is
difficult to remove by water treatment, especially those
which containing sugars.
This water is an ideal environment for the growth of
micro-organisms. These microorganisms feed on
organic material and water soluble sugars making it
consume dissolved oxygen in the water. This leads to a
higher level of Biological oxygen demand (BOD) in this
waste water in addition to, these microbes may be
pathogenic and /or toxinogenic sources. In mostly the
water of these factories are disposal to the Nile River or
into the sea .
4
When BOD Levels are high, dissolved oxygen (DO)
levels decrease because the oxygen that is available in
the water is being consumed by the microorganisms .
Since less dissolved oxygen is available in the water,
fish and other aquatic organisms may not survive.
The main purposes of wastewater treatment systems
are to remove organic pollutants, but it would be very
attractive if there were a way to recover the organic
pollutants as valuable organic materials. One of the
possible ways to recover organic pollutants in
wastewater
is
to
convert
them
into
polyhydroxyalkanoates
(PHAs),
which
are
biodegradable plastics.
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Role of polymer in our life:
Today, polymers have become a necessary part of
contemporary life pertaining to their durability and
resistance to degradation [1].
Worldwide production of petroleum based synthetic
polymer was approximately 270.0 million tons in
2007]2] and these synthetic polymers are found to be
recalcitrant to microbial degradation [3].
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Nowadays, we live in the „Plastic Age“…
250 million ton
(only fossil
100 million ton
resources)
1.5 million ton
(total)
(total)
60 years ago
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20 years ago
2010
Importance
• 2003- North
America only
– 107 billion pounds of
synthetic plastics
produced from
petroleum
– Take >50 years to
degrade
– Improper disposal and
failure to recycle 
overflowing landfills
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Quantities of Utilized Plastic Materials in
Different Global Regions
250 Mtons / a World production & consumption of
Plastic Materials
9
TODAY: Polymers Predominately Deriving from
Petro-Industry
•Disadvantages of fossil base
polymer
•Highly Resistant Polymeric
Materials
•No natural degradation
•Insufficient performance of
recycling systems
•High risk connected to the
thermal conversion of plastic by
inceneration.
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What the material which can be used
instead of plastic?
The answer is polyhydroxyalkanoates.
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Polyhydroxyalkanoastes
Polyhydroxyalkanoastes (PHAs) are naturallyoccurring polymers produced by bacteria.
They are produced within the bacterial cell and
can be extracted and processed adhesives,
films, and polymer performance additives. As
a family of polymers, PHAs have functional
properties sufficient to replace a significant
portion of the 300 billion pounds of petroleumbased plastics used worldwide today.
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Polyhydroxyalkanoate (PHAs)
•Polyesters accumulated by wide rage of bacteria
• Intercellular carbon and energy storage
compounds
• Produced under condition of limiting nutritional
elements such as N, P, S, Mg, etc
•Properties depending on monomers and chain
length: thermoplastic – elastomeric
•PHA industrially produced by Metabolix
(Cambrige, MA) using a pure culture of
Ralstonia eutropha
•Biologically degradable
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Polyhydroxyalkanoate (PHAs) History
News of the commercial exploitation of PHB
started in 1963 when Chemistry and Engineering
News published an article concerning the
development of a thermoplastic biopolymer
material which was grown by fermentation. The
article described how the polymer was extracted
from bacterial cells where PHB grew in the form of
sub-micron granules. A treatment of the dry
bacteria with acetone was followed by a
chloroform extraction which provided a polymer
yield of 70–80% or more based on the dry weight of
the bacteria [4].
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Polyhydroxyalkanoates (PHAs)
Structures:
R
O
O CH (CH2)n C
100-30000
n=1
n=1
n=1
n=1
n=1
n=1
n=2
n=3
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R = hydrogen
methyl
ethyl
propyl
pentyl
nonyl
R = hydrogen
R = hydrogen
poly(-3-hydroxypropionate
poly(-3-hydroxybutyrate
poly(-3-hydroxyvalerate
poly(-3-hydroxyhexanoate
poly(-3-hydroxyoctanoate
poly(-3-hydroxydodecanoate
poly(-4-hydroxybutyrate
poly(-5-hydroxybutyrate
Polyhydroxyalkanoates (PHAs): Produced under
conditions of:
Low limiting nutrients (P, S, N, O)
Excess carbon
2 different types:
Short-chain-length
3-5 Carbons
Medium-chain-length
6-14 Carbons
~250 different bacteria have been found to produce some
form of PHAs
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Polyhydroxybutyrate (PHB)
• Example of shortchain-length PHA
• Produced in activated
sludge
• Found in Alcaligenes
eutrophus
• Accumulated
intracellularly as
granules (>80% cell
dry weight)
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Lee et al., 1996
Bioplastic Production Using Mixed Microbial Cultures
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PHA Biosynthesis
Ojumu et al., 2004
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Applications
Field
Industry
Application
Products, films, paper laminates & sheets,
bags and containers
– Automobiles
Medical
Sutures, ligament replacements, controlled drug
release mechanisms, arterial grafts…
Household Disposable razors, utensils, diapers, feminine
hygiene products, containers…
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Main disadvantage of biodegradable materials,
•Too high production costs
•Synthetic plastics ~ 1€/kg
•Polylactic acid ~ 3-4 €/kg
•Starch compounds ~ 2-4 €/kg
•Polyhydroxyalkanoates ~ 3.5-5€/kg
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Option to lower PHA production costs using mixing
cultures:
Pure Culture fermentation
• Expensive raw materials
• High investment and operational costs
• High yields of PHA production (80%PHA/cell dry
weight)
Mixed Cultures (e.g. activated sludge)
• Cheap substrates-waste materials
• Low operational costs
• Lower yield of PHA production (60%PHA/cell dry
weight)
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Industrial wastewaters for PHA production
•
•
•
•
•
•
•
•
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Food waste
Olive and palm oil mills
effluents
Sugar-cane molasses
Diary effluent
Paper mill effluents
Fruit and tomato
cannery effluents
Brewery effluent
Municipal wastewaters
Acidogenic
fermentation
PHA
production
Methane versus PHA Production
• Yield of methane: 0.350 m3/kg COD
• Methane selling price: 0.2 € /m3
0.07€/kg COD
•Yield of PHA: 0.40 kg PHB/kg COD
•PHB selling price: 5 €/kg
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2 €/kg COD
Production of polyhydroxyalkanoates (PHAs) in
activated sludge treating wastewater using mixed
cultures
represents
an
economical
and
environmental promising alternative to pure culture
fermentation.
A process for production of PHA from a paper mill
and sugar factories wastewater was examined at
many research laboratories .
Pulp and paper mills generate varieties of pollutants
depending upon the type of the pulping process
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The wood pulping and production of the paper products
generate a considerable amount of pollutants
characterized by biochemical oxygen demand (BOD),
chemical oxygen demand (COD), suspended solids (SS),
toxicity, and color when untreated or poorly treated
effluents are discharged to receiving water.
The high water usage, between 20,000 and 60,000
gallons per ton of product, results in large amounts of
wastewater generation [5].
The effluents from the industry cause slime growth,
thermal impacts, scum formation, color problems, and
loss of aesthetic beauty in the environment. They also
increase the amount of toxic substances in the water,
causing death to the zooplankton and fish, as well as
profoundly affecting the terrestrial ecosystem [6].
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Carbon Cycle of Bioplastics
CO2
Photosynthesis H2O
Biodegradation
Recycle
Plants
Plastic Products
Carbohydrates
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Fermentation
PHA Polymer
The attempt to develop more cost effective processes
for PHA production include the use of mixed cultures
based processes and low cost substrates based on
agro-industrial wastes and by-products.
Selection of a stable culture with a high PHA storage
capacity is of major importance for the effectiveness of
the process.
Examples of using byproducts in production of PHAs
From sugar cane molasses:
In this example, the use of sugar cane molasses (a byproduct of the sugar refinery industry with a very high
sugar content and low cost) was investigated for the
production of bioplastics by mixed microbial cultures.
Two-stage process were developed for PHA production by
mixed cultures from sugar cane molasses, comprising:
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1. continuous molasses acidogenic fermentation,
2. Selection of a PHA-accumulating culture and batch
PHA accumulation using the enriched culture and the
fermented molasses thus produced. Different strategies
were investigated for culture selection on a fermented
molasses feed in either a sequencing batch reactor or a
continuous ADF system, in order to understand the
impact of reactor configuration and operating mode on
the “Feast and Famine” process. The cultures thus
selected were compared in terms of microbial
population composition and PHA storage capacity.
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The molasses acidogenic fermentation was carried out in
a continuous reactor under anaerobic conditions
(T=30ºC; HRT=10h and OLR = 1 g/l.h of sugars).
In a first moment, the CSTR was operated at different pH
values ranging from 5 to 7 (in order to assess the effect
of different VFA profiles in the fermented molasses on
PHA production).
A pH of 6 was then selected to operate the reactor to
produce the effluent used in all remaining experiments.
The reactor effluent was clarified by ultrafiltration and the
clarified fermented molasses were used as a feedstock
for culture selection and PHA batch accumulation after
pH adjustment.
Culture selection was carried out in both anaerobic SBR
subjected to feast and famine conditions and anaerobic
continuous ADF system composed of two reactors and a
settler.
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The SBR 12 hour cycles consisted of four discrete periods:
fill (12.5 min); aerobiosis (feast and famine) (11 h); settling
(38.5 min) and draw (9 min). Both systems – SBR and
continuous – were operated under similar conditions of
organic loading rate (60 – 120 Cmmol VFA/l.d), carbon to
nitrogen ratio (C/N/P of 100/8/1), hydraulic (HRT of 1d) and
sludge retention times (SRT of 10d).
Moreover, similar feast to famine ratios were used in both
systems, since the hydraulic retention times of the two
continuous ADF reactors were designed to match the
lengths of the feast and famine phases of the SBR cycle.
Preliminary PHA accumulation tests were carried out
feeding the clarified fermented molasses produced at
different pH to a PHA-accumulating culture selected using
acetate as the carbon source (the selection process was
described [7]).
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In order to compare the accumulation efficiencies of the
cultures selected using the two different reactor systems,
PHA accumulation tests were carried out in a batch reactor
inoculated with sludge from either one of the two culture
enrichment systems (SBR or continuous ADF system) and
fed with clarified fermented molasses produced in the
anaerobic reactor (operated at pH 6).
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Sequencing
Batch
Reactor
Cane molasses
Anerobic
CSTR
Fermented
molasses
Clarified
Fermented
molasses
Biomass
Acidogenic fermentation
PHA production process from
sugar molasses by mixed
cultures using a Sequencing
Batch Reactor.
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Batch
reactor
SBR
Clarified
fermented
molasses
Feast
reactor
Famine
reactor
Batch
reactor
PHA production
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Qiong Wu et al reported that a strain of Bacillus sp.
coded JMa5 was isolated from molasses contaminated
soil. The strain was able to grow at a temperature as
high as 45◦C and in 250 g/l molasses although the
optimal growth temperature was 35–37◦C. Cell density
reached 30 g/l 8 h after inoculation in a batch culture
with an initial concentration of 210 g/l molasses. Under
fed-batch conditions, the cells grew to a dry weight of 70
g/l after 30 h of fermentation. The strain accumulated
25–35%, (w/w) polyhydroxybutyrate (PHB) during
fermentation. PHB accumulation was a growth
associated process [8].
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From starchy wastewater:
Polyhydroxyalkanoate (PHA) was produced from a
starchy wastewater in a two-step process of microbial
acidogenesis and acid polymerization. The starchy
organic waste was first digested in a thermophilic
upflow anaerobic sludge blanket (UASB) reactor to
form acetic (60–80%), propionic (10–30%) and butyric
(5–40%) acids. The total volatile fatty acids reached
4000 mg/L at a chemical oxygen demand (COD)
loading rate of 25–35 g/L day1.
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A carbon balance indicates that up to 43% of the organic
carbon in the starchy waste went to the organic acids and
the rest to biogas, volatile suspended solids and residual
sludge accumulated in the reactor. The acid composition
profile was affected by COD loading rate: a medium rate
around 9 g l1 day1 gave a high propionic acid content
(29% wt) and a high rate around 26 g l1 day1 led to a high
butyric acid content (34% wt). The acids in the effluent
solution after microfiltration were utilized and
polymerized into PHA by bacterium Alcaligenes
eutrophus in a second reactor. Fifty grams of PHA was
produced from 100 g total organic carbon (TOC) utilized,
a yield of 28% based on TOC, which is comparable with
55 g PHA per 100 g TOC of pure butyric and propionic
acids used.
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PHA formation from individual acids was further
investigated in a semi-batch reactor with three acid
feeding rates. With a limited nitrogen source (80–100 mg
NH3 per liter), the active biomass of A. eutrophus, not
including the accumulated PHA in cells, was maintained at
a constant level (8–9 g l1) while PHA content in the cell
mass increased continuously in 45 h; 48% PHA with
butyric acid and 53% PHA with propionic acid,
respectively. Polyhydroxybutyrate was formed from
butyric acid and poly(hydroxybutyrate-hydroxyvalerate)
formed from propionic acid with 38% hydroxyvalerate [9].
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Recovery of PHAs from Cells
PHA producing microorganisms stained with Sudan black
or Nile blue
Cells separated out by centrifugation or filtration
PHA is recovered using solvents (chloroform) to break
cell wall & extract polymer
Purification of polymer
Nighat Naheed et al reported that three types of organic
waste contaminated soils were selected for the isolation
of polyhydroxyalkanoates producing bacteria that is,
molasses, oil/ghee and sewerage. A total of 54 bacterial
strains were isolated and screened for the PHA
production [10].
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References:
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Srivastava; , J Polym Environ (2012) 20:446–453
2. Lazarevic D, Aoustin E, Buclet N, Brandt N (2010) Plastic
waste management in the context of a European recycling
society: comparing results and uncertainties in a life cycle
perspective. Resour Conserv Recycling 55:246–259
3. Flechter A (1993) Plastics from Bacteria and for Bacteria:
PHA as matural, biodegradable polyesters. Springer, New
York, pp 77–93.
4. R. H. Marchessault; Cellulose (2009) 16:357–359
5. Nemerow N. L., Dasgupta A. Industrial and hazardous
waste management, New York: Van Nostrand Reinhold; 1991.
6. D. Pokhrel, T. Viraraghavan; Science of the Total
Environment 333 (2004) 37– 58
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7. Serafim, L.S., Lemos, P.C., Oliveira, R. and Reis, M.A.M.
(2004). Optimization of polyhydroxybutyrate production by
mixed cultures submitted to aerobic dynamic feeding
conditions. Biotechnol. Bioeng. 87(2), 145-160.
8. Qiong Wu, Honghua Huang, Guohong Hu, Jinchun
Chen, KP Ho & Guo-Qiang Chen; Antonie van
Leeuwenhoek 80: 111–118, 2001.
9. Jian Yu; Journal of Biotechnology 86 (2001) 105–112
10. Nighat Naheed, Nazia Jamil, Shahida Hasnain and
Ghulam Abbas; African Journal of Biotechnology Vol.
11(16), pp. 3321-3332,
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Polyhdroxyalkanoate as
biopdegridable polymers
Biodegradable thermoplastics from renewable resources
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Thank you
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