Kind: captions
Language: en
okay
good morning everybody uh it's nice to
be here
and thanks for coming to the third
lesson from professor raj bhupathy
and this is the the series of
bio process engineering monday morning
lecture series in conjunction with
the 80th years of chemical engineering
education
in indonesia so
we thought further a delay i would
invite professor raj bhupathi
to present uh the uh
the pres the slides so we will
carry on uh from uh the
uh a bit of what we haven't done
the two weeks ago and then
the next uh will continue
with the
lecture today with the topic of
fundamentals of
anaerobic digestion
process right you can prevent your
slides
okay yeah i can all right thank you
i'm going to start with today's lecture
even though it's later to be anaerobic
digestion i didn't finish uh two weeks
ago where we talked about genetic
engineering so i'm gonna
finish that lecture and then i'm gonna
proceed to anaerobic digestion so
um we're gonna talk about synthetic
biology
so can anybody everybody can see my
slide yeah
see yes it's perfect okay good okay it's
clear
thank you all right okay so
um so we talked about genetic
engineering the now the hot topic is
synthetic biology where
you can synthesize the genes
and then you can put it what you can
custom make whatever genes you wanted to
make that can produce certain specific
enzyme or protein
you can put that in organism then that
can do that function for you so
so the definition of synthetic biology
is uh broadly refers to the use of
computer assisted biological engineering
to design
and construct new synthetic biological
parts
uh devices and system that do not exist
in nature
and the redesigning of existing
biological organisms so
basically you're putting that in the the
nucleotide you know a c
t g um synthesizing it
uh and then putting it into an organism
to express it so that's what synthetic
biology is okay
so synthetic biology inc incorporates
techniques on molecular biology
but it it's totally different from
recombinant dna technology
because it introduces synthetically
constructed part
um and it's not existed in nature
because even it's the same chemical
but these actg are synthesized in the
lab
so the construction of a new life form
with no natural
counterparts so that's why it's called
synthetic biology
um so if you look at the system um
biology where we study the organism
itself
and uh you know and then we look at the
function of the organisms
and then we do model and experiment and
do analysis that is
systems biology whatever is in nature
but we are studying them we are
understanding the genetic makeup of an
organisms and play with the
tools of genome and transcriptome
proteome
and then we you know play a model first
and do experiment and do analysis that
is called system biology
but synthetic biology is totally
different okay
so the the key aspect of synthetic
biology
is it differentiates from genetic
engineering and current biotechnology
approaches
here the application to the techniques
are normally used in engineering design
and development so we think about an
engine right
the system is like an engineer so what
how an engineer will proceed with
designing a system so
we are copying the same thing in
synthetic biology
so if you look at the engineering cycle
so if you want to make a product
first you get the specification of the
product and then you design the system
once you design it then you do modeling
so
after you model you implement and then
you do the testing and validation that's
the engineering cycle
so we are doing the exactly the same
thing in synthetic biology we are
doing specifications now putting these
nucleotides together and design
a new gene and that can do new
function and then we're testing it out
and then hopefully that will work out so
that is called synthetic biology
um so the approaches to this science is
you need to do dna synthesis you do dna
synthesis in the lab you just make this
nucleotide
um at the most basic level the synthetic
biology involves
synthesis of dna and then
that was uploaded return on a computer
okay so we
make the design in the computer and
printed out
from bottles of nucleic acid which is
atcg
all those nucleotides we talked about
last two weeks
and these dna stands are then inserted
into an organism through a variety of
genetic
engineering techniques so that is the
approach to synthetic biology
so we call these biobricks so biobricks
are standard dna sequence that code for
certain functions
and this sequence can be created to make
an organisms for example to glow
okay and and engineering the biobank
bio break into the organism should whole
organisms should glow
um so these um kind of um
practice will open up biobricks then the
researchers across the world can
construct
new genes and have new dna synthesis
it's totally
um you know made in the lab again it
doesn't exist in nature
so if you look at the the minimum cell
approach
uh the researchers most notably the
pioneer in this field is the
great inventor they're working to
produce organisms ourselves
that function with the minimum number of
genes to survive
okay so we can add that
dna sequence to the minimum genome or
cell
and produce variety of products like
biofuels or
medicine or vaccine or any other
synthetic product you want to make
okay so this is how it works so you do
in silicon design of genomes in the
computer you just work out the different
sequences
last week you learn about all those
bioinformatics and so
we can design a insilico genome and then
we synthesize the nucleotide
and we put those nucleotide into an
organisms which is assembly
in the intermediate um like e coli
and then you put the complete genome
into desirable organism like yeast
and then genome translation
transplantation into a suitable cell
and hopefully that will express the
function so this is basically
you're creating designing in the
computer first a nucleotide and
synthesizing a nucleotide
um in the lab and then put that
nucleotide into the organisms and make
sure that works
in the cell that you want to create so
now people in some other branches this
is called xenobiology xenobiology is
basically these scientists are
attempting to create
alternative genetic system such as a new
novel nucleic acid um you know creating
a suicide gene and bacteria
are mirror biology so if you instead of
putting the same
nucleotide you can create an alternate
alternator analog of the nucleotide okay
here is an example
you can create a nucleotide sequence
that can
kill the bacteria after it expresses the
protein
so when you put this vector carrying
suicide genes
and the organism going to express the
protein and make the product that you
want to
produce and then if you don't want the
bacteria to hang around the bacteria
going to
you know die and that's one of the
example of
synthetic biology another one is um
you can it's a mirror biology where you
can
um for example thiamin is a natural
nucleotide
um scientists have created a mirror
molecule
exactly equal to thymine is different in
structure which is phychlorous cell
and you can wherever thymine is in place
in e coli you can insert this nucleotide
it does the same function so um so here
is a
um example of um the exactly organisms
um putting replaced with time in
whatever timing they replace with five
chloro uracil
and this is called mirror biology okay
um so
now people are trying to make new
organisms that
never been existed in nature so you put
the nucleotide together and create cells
so this is like uh evolution at the
beginning howard
before life formed we have proto cells
um so researcher testing combination of
inanimate chemicals to create protocol
or synthetic life
without dna these protocells would be
likely
creating of life from the scratch okay
this is how
according to evolution the first
protocell was formed
we had all these chemical you know
evolved and then they are combined
together to make a protostar
so the fundamentals technique in
synthetic biology there are three key
technological enablers that can improve
this field
and those are computational modeling and
dna sequencing and dna synthesis so
first you do the modeling with
other nucleotide code and then put the
sequence in right place
and then you synthesize these sequences
and and
and those are in order that we
follow in synthetic biology so
computation modeling
is uh the synthetic biology approach
approaches the design of engineering
biological system through engineering
cycle as i showed you in one of the
slides
so you want to know what product you
want to make and look at all the
different genes already in there in
different system then how
best you can improve the natural genes
and by creating synthetic genes so and
then modeling that design to predict
system performance and you fabricate
this new genome okay and that is
important component of the synthetic
biology
so synthetic value therefore similar to
system value is the same
nucleotide sequence code and when you
put those genes it's going to express it
and going to produce a protein
but you are you are kind of um doing
that
by creating this genome okay so it's a
heavily computer model
model based um science
so the reading of sequencing your dna is
this next feature so you need to have a
dna sequencing
uh so as i said before in the last three
weeks you guys learned the
dna compress of these four nucleotide
base um
rd9 always combines with timing go on
and combines with the
cytosine so the entire content of dna
for a particular organism is called
genome this contain complete instruction
for construct
constructing any type of protein cell
tissues
argon etc so anything you want to create
you can synthesize
so once the genome has been sequenced
the next step is to rewrite or
synthesize
all parts of the genome then there are a
number of cases where the genome of an
argument has been entirely synthesized
so i'm going to give you a couple of
examples
and so this is how in nature um dna
synthesis happen you need to have all
these um
enzymes and you have to unwind the dna
and create a data dna
by putting the nucleotide so this is how
a cell works you need to have all this
enzyme um so using the same
system synthetically in 2002
um in the state university of new york
and stony brook
dr cello and his co-workers created a
poliovirus genome
the poliovirus um genome is already
published and so people know exactly
what
kind of gene genes make this polio virus
so they first produce the synthetically
synthesized poliovirus in the lab
so they mimicked creating the genome in
the lab and
created this virus okay and then in 2003
a bacteriophage with only 5
386 base pairs small base amount of base
pair
are assembled um uh by dr uh
craig venter in fragmenter institute so
these are the whole viruses created in
the lab
these viruses never existed in nature
before so that is an example of
synthetic biology okay
so with this kind of tweaking and
and you know putting the new dna created
in the lab you can do any kinds of
things like for example you can
create a lot of product you can design
and build a lot of engineering
biological system that can process
information
and for example people are now making
furnacing which is a essential building
block for a wide range of chemical
products
such as the detergents cosmetics
perfumes and a lot of
industrial lubricant and transportation
fields so
people already are making this kind of
product
using synthetic biology through
synthesizing new dna putting it in east
and east is expressing these genes that
they created
another successful synthetic biology
product is the malarial drug
the artemisin people engineered the
yeast and put
artemisinic acid production gene which
is
totally synthesized in the lab and this
is a
successfully commercially produced drug
through synthetic biology research
and then people are re-engineered um
salmonella typhimerium protein
um in the lab and then they put um
in the goat and the goat milk uh
produces a
powerful spider cell protein you can use
this
goat milk protein extracted and
make a lightweight bulletproof vest
okay so this is also successfully
commercialized and then if you look at
the energy sector
synthetic biology has been um people
been working on it
for example you can algae naturally
produces oil
but through synthetic biology you can
use tools and re-engineer
algae to produce oil that are chemically
similar
or identical to the oil that are used in
transportation
energy infrastructure like biodiesel
and similar consistency
the algae can produce by tweaking their
genes um so synthetic bile is also
working on natural natural product
substitutes um
there are um like the rubber uh one of
the main
ingredients is isoprene right the
building block for making
a rubber so now you can make isoprene
encoding genes and put them in e coli
and e coli can
express this protein can you can get
this isoprene
um through e coli cell so this is also
demonstrated successfully through
synthetic biology
and these are some other commercially
produced synthetic biology products like
vanilla you know and um
palm oil uh also now people can make
synthetically uh using synthetic genes
these are successfully produced um in
the lab
um so the release of synthetic microbes
threaten biological diversity so there
should be regulation
so i don't want to intentionally or
unintentionally release these organisms
and kind of create problem to
natural system so that is a big
regulatory issues that
people are um you know now in discussion
and worried about
what we are creating in the lab
shouldn't escape into the
into the nature um so
another one is people are working on
cleaning up environment
uh using synthetic biology so
a lot of labs in the us are doing
research in this field now
okay nothing is successfully
demonstrated yet but people are working
on
putting some synthetic genes in
different organisms
as i said before regulation in synthetic
biology is um
as a keto um you know is a big topic in
the us
so what is the risk and you need to
evaluate the risk and
when when you create this kind of
organisms
um so you need to establish shape
safeguard
and and and make sure it's nothing no
harm is done
to nature um
so that um an example of what is
synthetic biology
um um i can
you know move on to next topic or if you
have any question i can
take few minutes what do you think
renee what do you want me to do let me
go to the next topic
if there is one question so i can yeah
sure
yeah and uh any questions maybe
yes yes uh good morning professor
good morning yeah i'm really uh maturity
i
see is uh you modified from the e coli
and salmonella isn't it
yeah yeah you i mean you synthesize and
you put in
express this in in these organisms which
is what commercially people are using
yeah and yeast also being used yeah
uh is it because of e coli and
salmonella is
a more durable to the nature of
something
in that particular product a particular
product like in salmonella they're
looking at the spider
silk and um so that's the organism
ideal to express it so i'm i'm not sure
why they choose that i'm i'm thinking
the expression because the regular
regulatory mechanism of turning gene and
on and off that mechanism is maybe
suitable for that particular
sequence they put in there yeah i see
thank you thank you
all right okay thank you
that you can carry for the next segment
okay
now we're going to switch to the topic
of
today which is basically
anaerobic digestion um
i'm going to put the screen hopefully
you can see can you see this screen
back yet i'm gonna share the screen
again
now you can see it okay yeah it's
perfect
okay all right so the topic of the day
is the fundamentals of anaerobic
digestion
so if you look at anaerobic digestion
which is
a part of wastewater treatment process
so
it's a biological treatment process that
take care of
solids um in the wastewater so i'm going
to talk about
wastewater system in in general then i'm
going to go into anaerobic digestion
okay so if you look at all the
wastewater that we produce
in the world 90 of the wastewater does
not receive
any treatment at all so only maximum 10
if you look at all the sewage treatment
plant in the world
five to ten percent of the wastewater we
generate undergoes some kind of
treatment so
most of the wastewater they generate go
right into the natural
water body so which is kind of sad but
that is a reality okay
so anaerobic digestion is part of this
wastewater treatment
process so the concept of
aerobic treatment is um
the carbon and nitrogen fossils we put
out in the wastewater
is taken up by the microorganisms uh
mostly aerobic bacteria so they need
oxygen so we need to provide
oxygen for this reaction to
go through complete fruition so we need
to
this is a limiting step in aerobic
process i mean provide oxygen in
activated sludge
and the microorganisms multiply and use
this carbon we put in the wastewater as
a carbon source
as a result you produce a lot of co2
and then you produce biomass which is
more bacteria
multiply and then water so that's uh
basically
um what's going on in wastewater
treatment in under
aerobic conditions okay so
very quickly a few terms you need to
know i know some of you might have
already learned but
i don't know the audience i'm gonna just
quickly go through these terms so
when you talk about wastewater we talk
about uh body
cod solids so very quickly what is dod
is called biological oxygen demand
biochemical oxygen demand
is basically the amount of dissolved
oxygen needed by
aerobic bacteria to break down organic
carbon
in given volume of water at certain
temperature over specific period of time
so is basically what we are measuring is
the biologically
degradable organic carbon in the water
that's what peod term
refers to and the next one is cbod
which is called chemical oxygen demand
it is basically the measurement of
chemically
oxidizable organic carbon in water
so this includes both biodegradable and
non-biodegradable carbon so
um when you can measure cod by taking
total sample
that include carbon coming from
microorganisms
re can filter the sample and take
only soluble cod so you don't account
for carbon from biomass
okay so that's why it's called total cod
or soluble cod
okay
and then in the wastewater system we
also
talk about how much total solids in the
wastewater how much suspended solids
from a dissolved solid
so those are various uh parameters we
look at
how much particles are floating in the
water and when you
how much of them are suspended if you
can filter through
how much are dissolved it's like ions in
the water okay
and then reactor is basically a vessel
or a container where you put all this
wastewater and
allow bacteria to react and that is
called biological reactor
and then organic loading is basically
the amount of carbon
that we load into the system how much
code per day how much code per
you know hour depends on your reactor
so if you look at the biological
treatment system the
wastewater treatment should have
three unit process which is primary
secondary and tertiary treatment
primary is a physical process and
basically you screen
take out any solids by screening
and and then also sedimentation allow
the wastewater to settle and any solid
that can
settle you take it out so that is
primary it's a physical process
secondary treatment is where
the microorganism come into play this is
where we remove
the carbon nitrogen in the wastewater
and
mostly it's activated sludge and
trickling filter and other
biological reactor used in secondary so
this is where a lot of
activity takes place with microorganisms
and tertiary treatment is
a usually chemical process is a
disinfection process most of the cases
okay so some of the process criteria in
the wastewater system
is what is the loading rate as i said
before how much carbon you're putting
into the system
per hour per day uh what is the flow
rate how much
waste water is going into the reactor
again this could be per liter
per cubic meter or per
gallon per day or per hour um hydraulic
retention time
is refers to as the time the wastewater
spends
inside the reactor how long you're
keeping the waste water inside the
reactor
and solid retention time is how long the
sludge or
solid is retained in this case
the bacteria biomass can stay inside the
reactor you want to keep
your srt as long as possible and
keep your hrt shorter you want to treat
the wastewater fast
you want to keep the good bacteria in
your system a long period of time so
that is basically
the engineering design of these systems
and then we do process analysis looking
at how much
carbon going in how much carbon coming
out and what is a percent removal and
all that stuff
and then we go through mass balance and
so again looking at every
carbon nitrogen phosphorus and
microorganisms they do mass methods
so if you look at the function of
wastewater treatment
and they have to remove solids remove
carbon
remove nitrogen remove pathogenic
organisms moderately reduce them
and nowadays we worry about medical
residue like organic carbon
personal cap products and we are
throwing a lot of new stuff
nano particles all that stuff they are
worried about
and heavy metals so the most of the time
the older
wastewater system this is what's
supposed to take out these are
new and emerging problems now they have
to worry about
so as i said before these are the three
unit processor which is physical
biological chemical
i'm going to quickly go through um in
each other unit
okay so physical as i said we're
removing
um the debris and solid particles so we
use screen
we use sedimentation tank we do
floatation device
we use membrane filtration and all that
stuff
um used in a physical unit process
and the chemical unit process is
basically tertiary
and most of the time it disinfection and
sometimes we use
precipitation and absorption depending
on the design of the system
so disinfection mostly we use
chlorination uv light
ozone and all kinds of disinfection to
reduce the pathogen
in the wastewater so this is overall
schema wastewater
system we have primary treatment
secondary treatment
tertiary physical biological chemical
and then this is wastewater going
through then every time we have
sedimentation
tank we have primary solids we have
secondary solids
and those solids are taken care of by
the
anaerobic carbon cycle so here we use
the anaerobic digester
to take care of these solids in the
wastewater
and so the most of the talk today is
going to be
the fundamentals of this anaerobic
digestive process
so this is schematically showing how the
primary secondary tertiary
stage look like in wastewater treatment
system
and that's the actual municipal severe
treatment plan that has all these
unit processes put in place okay
and so if you look at it so we have the
solids taken care of by this anaerobic
digester once it is digested you need to
take care of the
solids that come out of the digester
that is treated so that goes through
um sludge drying bed and then you
dispose them
these solids separately so one of the a
product
uh main product of the anaerobic
digester is this meth and gas
and so we could benefit from this
process of getting energy
back into the plant
and this is variety of disinfection
system
again i went through chlorination and
all that stuff and that's how a uv light
system look like
banks of uv light instead of using
chlorination you can use uv light
and once the system goes through all
this process
primary secondary tertiary and this is
what
at the end of the process you will
supposed to have
removed in a good system suspended solid
you have
more than 90 percent bod remove more
than 90
phosphorus more than 90 percent nitrogen
around 70 percent
and this pathogens like e coli it can
remove
three to five harder logarithmic order
with disinfection
so this is how a successful
base water treatment plant looked like
when you have all these three unit
processes
work normally and work correctly
so let's look at anaerobic digester all
the solids they
have it in the sedimentation tank they
all go into the anaerobic digester so
it's basically a vessel or a reactor
and to have solids um sufficient time we
keep them
and allow the anaerobic bacteria
especially the methanogenic bacteria to
carry out
terminal oxidation step of carbon
so most of the time these are the three
major principle process going on in
anaerobic digester first is a hydrolysis
reaction
then acidogenesis and methanogenesis
in hydrolysis all the complex organics
are converted to simple
monomer and then the simple monomer are
converted to
short chain fatty acid like acetic acid
and then this fatty acid is converted by
methanogen to
methane gas and carbon dioxide so if you
look at the methane
the bio we call that biogas is which
contains 55 to 65
methane and 35 to 45 percent co2 and it
has
other gas like nitrogen ammonia hydrogen
sulfide hydrogen
if you're 100 methane you should have
994 btu per
cubic feet that's the energy density of
your methane
and these are the steps i just um showed
you you have hydrolysis
fermentation acetogenesis methanogenesis
so you have the complex
organic matter like carbohydrate protein
and fat are
hydrolyzed to simple sugar amino acid
fatty acids
and then we have these are converted to
volatile fatty acids
um and and then we have acidogenesis
convert any lung chain fatty acid to
acetic acid and hydrogen and co2 there
are two kinds of bacteria
one is taking um methanogen
then hydrogenotrophic methanogen so
these
um methanogens convert hydrogen silver
to methane
co2 and acetic acid the methane sure to
your final product
from your all the complex carbon in your
solids
are converted to these methane gas and
carbon dioxide
in the anaerobic digester so this is our
system look like what
what is the input what is the output
what's the gaseous output so you have
organic carbon organic nitrogen
phosphorus
sulfur nitrogen sulfate phosphate in the
solids
go into this anaerobic digester and it
is operated
anaerobically without oxygen allow the
anaerobic bacteria to react
with this waste and you produce variety
of gas
mostly methane and then the the liquid
which called digestate
the liquid that comes out sludge
contains
um this component which is good for
fertilizer um and then solids output
periodically to take the solids out of
the system
that's how a reactor look like it's a
big tank with a mixing device
and once the system works it's a simple
cstr anaerobic configuration reactor
and the biogas accumulates with the
floating drum going up and down
depending on the volume of gas produced
and this is a little more sophisticated
anaerobic
system with upflow anaerobic sludge
blanket reactor
where we create a sludge blanket with
granules or microorganism with a sludge
pad
and it works more efficiently than cstr
and then you have another system you
simply kind of put the solids in a big
lagoon and cover them with a
plastic cover it can collect your
methane gas so these are
a different configuration of anaerobic
digester
okay and this is schematically
showing what's happening so it operated
anaerobically it has a mixing device
and then you can digest the sludge comes
out
and sometimes if you you lose
microorganism you can recycle
some of those sludge back into the
system so you have bacteria going back
into the
anaerobic digester so you
the excess biomass is dispersal as a
cost because the solid that come out
you have to dispose off so that has
added cost to the wastewater treatment
plant
so you you produce a lot of um solids
after you go through the anaerobic
process you have to separate liquid and
solid
and and then you de-water them and dry
most of the time in drying bed using
solar sun
system and then you can use them as soil
lamender
amendment or fertilizer sometimes you
can use as a field
it has like a button you can make a
break out of it and you can make fuel
to put it back in the furnace to burn um
so
and this dispersal cars if you don't
have these system in place
and they have to contract out people to
take it out or they charge
the wastewater plant to take out the
solids
so that's a a very quick overview of
what is anaerobic digester now i'm going
to go a little more details i'm going to
talk about some
and give some problems try to solve some
problems
how to design a system a little more
detail okay
so historically a little bit history
behind this anaerobic treatment system
and mostly it evolved to reduce high
solid waste example of human waste
animal manure and agriculture waste
and so if you look at it in 1881 it's
called moro's automatic scavenger was
designed
in septic tank was designed in 1895 in
england
then in half tank was developed by carl
impact in 1905
in germany so it's been this technology
been around for a long time
so during the 70s and 80s oil embargo
this
become very popular in u.s because of
common policy um so in the u.s we have
lots and lots of anaerobic digester put
in
all over the country and then when the
oil price
become cheaper then it and this
you know this this it lost its value and
then
all these energy digests are you know
gone are not
functioning properly people didn't take
care of it and now it's coming back
because of sustainability sustainable
program
this energy has started getting popular
again
so let's look at how much solids um go
into the
digester so if you if you look at
typical sewage plant
sewage system the solids that come in
and go through this primary screening
um and sedimentation you after 100
you take out 35 through this process
then you get 65 percent of solids come
in um
into the system and then from that 65
percent of solids it goes through the uh
aerobic process and 30 is
oxidized and converted to sludge
and the 35 percent solids is pumped into
the
anaerobic digester and then whatever is
um go through the aerobic process which
is
we call secondary solids that is 25
percent
so the solids we put in anaerobic
digester is typically
60 35 is primary
25 percent is secondary solids before
aerobic treatment after aerobic
treatment all the solids go
into the anaerobic digester
so as i said before it's a high solid
system
um to take care of animal manure
biological sludge knife soil
and that's that mainly it is designed
for
um most of the time it is a cstr which
is continuous to tank reactor
in which your hrt is roughly equal to
srt
so your hrdness is almost the same
and designed based on volatile saudi
solids loading rate
anaerobic treatment a wastewater
requires basically long
srt to achieve better treatment
efficiency because anaerobes grow
slowly so you need to design a system so
the system should have the srt hrt
ratios
a ratio of 10 to one so you have high
srt to keep the slow growing bacteria
remain inside your reactor for a long
period of time so you don't want to lose
these methanogens because they
double very very slowly compared to e
coli you take a long time to multiply
how do you do that so i'm going to go
through um some scenarios and
and see how to do this
so let's uh redefine anaerobic system
it's a biological process carried out in
the absence of
oxygen for the stabilization of organic
material by conversion to ch4 which is
methane
and inorganic end products such as co2
and ammonia
so you get organic material nutrient
come from the solids
go through anaerobic microbial process
you get methane
you get co2 you get ammonia you get
biomass these are the anaerobic bacteria
accumulating in the system
this can go in two routes you can go
through
fermentation process which is no
electron acceptor at all
or where whatever electron acceptor that
comes with the solid
the bacteria are going to go through
using those electron acceptor and
and carry out anaerobic respiration such
as
sulfate reducing night reducing iron
reducing process where
those um sulfate and nitrate are used as
electron acceptors so
bacteria have choice they can use um
when there is no electron accepted
fermentation when the electron acceptor
go through anaerobic respiration
so in anaerobic fermentation as i said
there is no external electron acceptor
so the electrons are put into the
organic carbon itself so you have the
organic carbon converted to pyruvate
actually i get
2 atp out of that and so all the
electrons that is still in the carbon
are put back into the organic carbon
itself so you produce
a fermentation product like ethanol
fatty acids so you still have a lot of
carbon
in it in the fermentation process so you
still have other organisms to come and
you know continue to react with the
product and
and take it to terminal oxidation stuff
in the anaerobic respiration process as
i said these are various electron
acceptors
available in the anaerobic digester so
the electron acceptor
converts these
electron acceptor to reduce them to so
for example sulfate hydrogen sulfide
and carbon dioxide to methane and
nitrate to nitrogen gas
carbon is taken up and converted to
pyruvate
whenever electron is released and the
electron
is accepted by the electron acceptor
okay so this is anaerobic respiration
process
so we can so mostly it's very efficient
more energy bacteria get from
aerobic process then nitro reducing
condition then sulphur reducing
condition then
carbon dioxide which is methanogenic
condition
so what is the advantage of anaerobic
process
we have a lot of advantages serious
advantage less energy requirement
because
no aeration is needed so if you look at
aerobic process
the limitation is oxygen you have to
pump a lot of oxygen into the wastewater
so
here you save a lot of money right by
doing anaerobic system
and energy generation in the form of
methane you get this
methane gas in your system so again
there is how much energy you can produce
from
one kilogram of cod you can produce 1.16
kilowatt hour of energy
and then he produced less biomass so you
don't have to have a lot of solid
generated compared to aerobic process so
um here is less sludge produced compared
to aerobic process
so here is an example if under aerobic
process when you have one kilogram of
body
50 of that go into co2 and h2o 50
go into new biomass so here you are
accumulating biosolids more organisms
produce
whereas under anaerobic process one
kilogram of cod
90 goes to gas external oxidation of
carbon
only 10 percent is used to make new
bacteria so less solid accumulation
compared to aerobic process that's a
huge advantage in a large plant
you know so otherwise you're producing a
lot of solids
other advantage the anaerobic process um
use less um nutrient and
input nitrogen and posture requirement
and
an application of higher organic loading
rate you can
use the loading rate really high
compared to aerobic process and space
saving is really huge higher loading
rate require smaller reactor compared to
aerobic system
steer by you can save a lot of design
costs and
reactor cost operation cost
and then ability to transform several
hazardous chemicals so
anaerobic system can take um all these
hazardous compounds in the waste like
trichloroethylene trichloroethane
chloroform any other hazardous chemical
anaerobic bacteria
has the advantage of metabolizing
compared to aerobic bacteria
but it also has some limitations so
let's talk about some other limitations
the one major one is a long startup time
because as i said anaerobes grow slowly
so the initial start-up time is
longer compared to aerobic bacteria and
it has long recovery time if there is a
system failure
to reboot the system it's going to take
long recovery time because the organism
again start
multiplying slowly and then specific
nutrients
it sometimes requires trace elements you
need to put some
these trace elements like ion nickel and
cobalt
for optimum growth of anaerobic bacteria
and this system is more susceptible to
environmental conditions so
if you have sudden change in temperature
ph it's gonna kill off the
methanogen so those are some of the um
disadvantages of anaerobic system uh
let's look at as few more disadvantage
and if you have sulfate in your waste
water
the sulphate is going to take up
the carbon so your methane output going
to be less
because the organic carbon is now
completed competing by two organisms
methanogen and sulfur-reducing bacteria
as a result your methane production
going to be less
okay depending on what kind of
wastewater you have um everyone quality
of treated wastewater
um you know if you compare to other
system is not
um it is still good but the
microorganism because of the maintenance
and anaerobic system
may not be able to degrade organic
matter to the
you know maximum possible limit uh
compared to aerobic system
for ultimate final disposal so it still
has to go through land application all
that
process and then we have treatment of
high uh protein and nitrogen containing
wastewater
um there is still some problem that
nitrogen is not completely metabolized
even though we have this um process
anamox is now
um uh coming up on online
uh people are trying to take care of
nitrogen-rich wastewater
and these are some of the disadvantage
of anaerobic process
so let's compare aerobic and anaerobic
system
okay organic loading rate you can put a
lot of
um high loading into the system in
anaerobic system anywhere from 10 to 40
kilogram cod per cubic meter and
aerobic system maximum we put one and a
half kilograms eod per cubic meter
in activated sludge and biomass yield as
i said the yield is low so less solid
accumulating
okay you have high biomass yield almost
50 percent of your carbon
goes to biomass and specific substrate
utilization rate there's a high rate of
substitution rate in
anaerobic system and compared to low
rate
utilization and startup time um
anaerobic process take longer um
time for one to two months whereas
aerobic process
is advantageous startup time is less
um in solid retention time anaerobic uh
longer asset is essential you don't want
to lose the
good methanogens out of the reactor in
aerobic system
um solid return time is uh four to ten
ten days maximum in an activated sludge
process
and in terms of microbiology anaerobic
process involved multiple steps
uh as i said we go through hydrolysis
acidogenesis methanogenesis
so you need to maintain diversity of
microorganism to carry out the final
step of methane
and co2 so aerobic process mainly
uh you know one or two species
phenomenon
um except for a nutrient mold process if
you want a specific nutrient
more you need more organisms so here you
have if you look at the sewage treatment
they look for
zooglear amateurized is a perfect
organism
to carry out carbon removal
environmental factors here you need to
have highly
the organisms are highly susceptible to
temperature ph fluctuation in anaerobic
um in the aerobic is more robust
compared to environmental conditions
okay so those are some comparison
between anaerobes and arrows
and let's look at how much methane gas
can be generated through
complete anaerobic degradation of one
kilogram of cod
at standard temperature and pressure stp
so if you calculate you're going to
calculate the shift equivalent of
methane
so if you look at the methane oxygen and
the product you get
so 16 gram methane is equal to 64 gram
oxygen so 16 gram of methane is 64 gram
of
um cod so one gram of methane
equals to 4 gram of cod okay
so here we're going to convert methane
mass to equivalent volume right so
based on the ideal gas law one mole of
any gas at stp
occupies the volume of 22.4 liter
right so one mole of methane equals to
22.4
liter of methane so 16 gram
of um methane equals to 22.4
liter of methane if you can calculate
that 22.4 divided by 16 you get
1.4 liter of methane okay
and if you look at the methane
generation rate per unit of cod
if you put all that calculation i put in
place
uh one kilogram cod equal to
0.35 cubic meter of methane so if you
have one chlorine i'm sorry go into
anaerobic digester
at complete degradation process you
should be producing
0.35 cubic meter methane at stp
okay
so let's look at all this because you
need a diversity of microorganisms and a
lot of reaction
takes place so here is what you're
putting in the anaerobic it's a very
complex
carbon go into the system here protein
carbohydrate
and lipids and all that going into the
system
and so first thing you go through
hydrolysis you're producing
from protein to amino acid carbohydrate
sugar liquid to fatty acid and alcohol
and then second step is the acetogenesis
where the amino acids and sugars
are converted to acetate and then it
also produces long chain fatty acid like
propionic acid butyric acid
and these are all through hydrolytic
bacteria because
number one reaction is hydrolysis and
then number two is acetogenesis we are
producing the long chain fatty acid to
acetate
and also carb um co2 and
hydrogen and then we have homo acidogen
which
converts this co2 hydrogen to acetate
and then we have two kinds of
methanogens the acidotrophic methanogen
and hydrogenotrophic methanogen the
ratio is 72 percent is acidogenic
isotropic methanogen and anaerobic
system 28
is hydrogenotrophic methanogen and these
two kinds of methanogen
convert of this product into methane and
carbon dioxide
so if you look at the hydrolysis and
acidogenesis
um on methanogenesis you need to have
diversity of organisms so we're going to
go through
all the number one two three four five
all these different
group of organisms now we're gonna talk
about what are those bacteria involved
in the system
so let's look at process microbiology
the
anaerobic degradation of complex organic
matter is carried out by
series of bacteria and archaea
methanogens are archaea
and so we're going to talk about one by
one the reaction one which is hydrolysis
is carried out by fermentative bacteria
and this group of bacteria is
responsible for the first stage of
anaerobic digestion
right taking complex polymer into
monomer
equivalent to monomer of each each
material the anaerobic belong to the
family of streptococcia
enterobacteriaceae and bacteria is
clostridium
beauty vibrio these are the organisms
dominating
the hydrolytic process
and hydrogen producing acidogenic
bacteria
this group of bacteria um take this long
chain fatty acid and convert them to
acetic acid carbon dioxide and hydrogen
um
and alcohol also converted and these are
synthropic association of
acidogenic organism with methanogenic
hydrogen consuming bacteria help to
lower the
um hydrogen partial pressure because you
need you need to maintain
um hydrogen in the system at low
otherwise
you have propionic acid going to
accumulate
which can would sever your system okay
so it's all these organisms
work together in tandem
then look at the third group these are
called homo acidogens
uh homo city giants um basically take
the hydrogen
um bacterial hydrogen silver to users
those are clostridium
acidobacterium odi are these the major
ones in homosexual genetic bacteria in
the anaerobic digester
and they use the c wooden hydrogen
and convert them to acetic acid right
and this actually
is again taken by methanogens
then we have the last group is
methanogenic bacteria these are archaea
if you compare the bacteria and archaea
the aqia
they have no peptidoglycan and it's a
distinct
ribosome and it's totally different than
real bacteria
and so here are two kinds um the
two kinds that metabolize acetate are
methanosi and methanosana
and um this organism will
take care of the acetate in your system
convert them to methane and co2
so if you look at this uh the the
um ks value um between these two
organisms so you can see methanocity and
methanosina
which which does the bulk of the work
and that take out
almost 72 percent of the carbon into
into methane and co2
so what are the essential conditions
that you need for anaerobic
treatment that work efficiently you need
to avoid obviously
oxygen and make sure there's no toxicity
going in your influence
that can upset your bacteria you have to
maintain the ph between 6.2 and
x6.8 and 7.2 i'm going to talk about the
environmental factor in a minute uh you
got to maintain sufficient alkalinity
in your system um you need to have low
volatile fatty acid
um you don't want to accumulate
propionic acid in your system
uh temperature around miso lake range
for mesophyllic digestion
and then you need to have enough
nitrogen phosphorus you need to have
this
carbon nitrogen ratio carbon phosphorus
ratio
which is usually this is what for every
350 parts
cod seven parts nitrogen one part for
phosphorus for highly loaded system and
for the lightly loaded system it's a
thousand to seven to one
all right and you also need trace
elements um
for methanogens to work properly and
then you have the
sid hrt ratio um should be more than
one so
some some of the wastewater that is
successfully treated this
using anaerobic digester are these are
the wastewater alcohol production
brewery winery wastewater
sugar processing starch and resizing
waste from textile industry
um food processing waste bakery plant
pulp and paper mold dietary product
diary wastewater slaughterhouse
wastewater
and petrochemical wastewater are
successfully used
using anaerobic digestion process
and so environmental factor as i said
these
organisms are susceptible to
environmental factors so you need to
make sure that
the organisms uh you maintain if it is
misophoric digester
maintained in the range you very
thermophilic you can maintain
thermophilic range
so these are the three ranges uh you can
sacrophiles mesophyll thermophiles and
they have this temperature range the
bacteria like to grow on
and the rule of thumb the rate of
reaction
doubles for every 10 degree
temperature rise up to the optimum range
of
each group and then it's going to
decline when it
go beyond the optimum range so so for
every
um reaction double for every 10 degree
increase in temperature
so ph is an another environmental factor
so
ideally he won't have 7.8 to 8.2
because he had the acetogens they like
to grow between 5.5 and 6.5
and then he had the methanogens they
they like to have a little bit
alkaline condition so the ideal uh ph
condition
is um i mean methanogen like to grow
7.8.2 the ideal is 6.8 to 7.4
um so low ph reduce the activity of
methanogen
causing accumulation of your fatty acids
and hydrogen in your system
you don't have high hydrogen partial
pressure
at high partial pressure hydrogen you
have this propionic acid degrading
bacteria
will be inhibited so you have
accumulation of propionic acid and
and the whole system will shut down we
call that um
sour the digested in a garden sour are
stuck
and the remedial measure is you need to
you know
add carbonated bicarbonate
to maintain the buffering of the system
to
keep your ph around 6.8 to 7.4
so ph dependence on the methyl gene so
um
so relative activity of mesenogens and
ph this is the range ideally you want to
keep
very close to a neutral ph
so the in the vase itself we have a
natural buffering up to certain extent
we have a lot of ammonia come in the
wastewater
and the ammonia is converted to ammonium
carbonate so that could be a natural
buffer
and we have some salt sodium salt in
your system
and that sodium salt coming out of
sodium carbonate which is also a natural
buffer
giving an alkalinity in the system um
and also sulfate if you have some
sulfate you produce some
carbonate in your system so when the ph
starts to drop
the volatile fatty acid will accumulate
the alkalinity present within the system
try to neutralize your ph to certain
extent
so it won't go any further but if the
alkalinity
is not enough to buffer your ph then
we need to add external addition of
you know ph corrections
so then nutrient requirement you need
have
the trace metals um all microbial
processes including
anaerobes required nitrogen phosphorus
sulfate which are the macro
elements needed and then the trace
elements are these coenzymes
cobalt nickel molybdenum selenium these
are required for certain enzymes to
function properly so we need to
add them in a micro quantity trace
quantity
and the nutrients and trace requirements
for anaerobic process are much
lower as only four to ten percent of the
civil is removed is converted to biomass
because most of them are
converted to gas so so that's your
carbon nitrogen phosphorus ratio for
high loaded system and for a likely
loaded system
is um you know less nitrogen possible
requirement
so i'm going to show what is the
difference between high
and low in the next slide and then we're
going to take care of any toxicity that
coming into the system make sure that
um you know you don't put anything to
upset uh such as heavy metals
halogenated compound cyanides and it's
gonna
you know kill your good bacteria um
so sometimes halogenated compounds are
okay but
at high concentration it's going to be a
problem
so here's a what is a low anaerobic
reactor towards the high anaerobic
reactors so the low rate systems are the
anaerobic pond
septic tank in your house imhof tank
and standard rate of anaerobic digester
the high rate system are this biological
reactor that used in various
industrial waste water anaerobic contact
process
anaerobic filter afflues anaerobic
sludge blanket reactor fluid as reactor
hybrid reactor when you combine any of
this system you create a hybrid reactor
and then sequencing batch reactors so in
the low
rate anaerobic reactors your loading
rate is low
one to two kilogram of co2 per cubic
meter
whereas in the high rate you can
increase your loading rate to
five to twenty kilograms cod so it takes
up a lot of
carbon uh and handle them very
efficiently it can remove maximum up to
90 percent of the carbon
in this high rate system
so let's talk about few of these system
and the anaerobic contact process
which is basically designed as an
activated sludge process
um but it is um uh without oxygen okay
uh so the the completely mixed reactor
in a settling tank and the biomass is
recycled back so
you're not losing your biomass and so
the anaerobic contact process is able to
maintain high concentration of biomass
in the reactor and thus
a high solid retention tim