ert 417/4 waste treatment in bioprocess industry sem 1 (2009/2010) ‘biological treatment’ by;...
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ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
‘Biological Treatment’
By; Mrs Hafiza Binti Shukor
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
OBJECTIVES OF BIOLOGICAL TREATMENT To transform (eg. Oxidize) dissolved
and particulate biodegradable constituents into acceptable end products
Capture and incorporate suspended and nonsettleable colloidal solids into a biological floc or biofilm
Transform or remove nutrients such as nitrogen and phosphorus.
Remove specific trace organic constituents and compounds.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
ROLE OF MICROORGANISMS IN WW TREATMENT
To remove dissolved and particulate carbonaceous BOD and the stabilization of organic matter found in ww.
microorganisms are used to;oxidize (convert) the dissolved and
particulate carbonaceous organic matter into simple end products and additional biomass.
Remove N2 and P in ww treatment process Oxidizing NH3 (nitrification) to nitrite and
nitrateReduce the oxidized nitrogen to gaseous
nitrogen. Biomass (S.G > H2O) can be removed from the
treated liquid by gravity settling.
OgHfCOnewcellsedPOcNHbOismmicroorgana 223
432 )()(
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
TYPES OF BIOLOGICAL PROCESS FOR WW TREATMENT
A)Suspended Growth ProcessB) Attached Growth Process
A) Suspended Growth ProcessBiological treatment processes in which
microorganism responsible for the conversion of the organic matter or other constituent to gases or cell tissue.
The microorganism responsible for treatment are maintained in liquid suspension by appropriate mixing methods.
Operated with a +ve DO conc but applications exist where suspended growth anaerobic reactors are used such as for high organic conc industrial ww and organic sludges.
Most common suspended growth process used is activated sludge process and aerated lagoon
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
influenteffluent
sludgeReturn activated sludge
air
Plug flow aeration tank clarifier
influenteffluent
sludgeReturn activated sludge
Complete-mixaeration tank
clarifier
Plug Flow Activated Sludge Process
Complete-Mix Activated Sludge Process
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
activated sludge: microbial aggregates (flocs) in the aeration tank.
Flocs stay in suspension with mixing by aeration.
Recycle of the activated sludge is crucial to maintaining a high concentration of cells.
Activated sludge?
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Barrack
Grit Chamb
er
Secondary
clarifier
Disinfection
Aeration
Tanks
Primary Clarifier
screenings grit sludge Waste sludge (optional)
effluent
sludge
Return activated sludgeWaste sludge
(optional)
Activated Sludge Process
influent
Barrack
Settling Pond Disinfectio
n
Aerated
Lagoon
screenings Waste sludge (optional)
effluent
sludge
Aerated Lagoon
influent
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
B) Attach Growth ProcessThe microorganisms responsible for the conversion of organic material or nutrients are attached to an inert packing material.The organic material and nutrients are removed from the wastewater flowing past the attached growth also known as biofilm.Packing materials used include;
Rock Gravel Sand Wide range of plastic Other synthetic materials.
Can be operated as aerobic as aerobic or anaerobic processes.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Attach Growth Process (continue….)
The packaging can be submerged completely in liquid or not submerged with air or gas space above the biofilm liquid layer.The most common aerobic attach growth process used is trickling filter and rotating biological contactors
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Trickling Filter Process
Rotating Biological Contactors
Barrack
Grit Chamb
er
Secondary
clarifier
Disinfection
Trickling
Filters
Primary Clarifier
screenings grit sludgeWaste sludge
(optional)
effluent
sludge
recycle
influent
Barrack
Grit Chamb
er
Secondary
clarifier
Disinfection
RBS units
Primary Clarifier
screenings grit sludge
effluent
sludge
influent
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Trickling Filter with Rock Packing
Tower Trickling Filter with Plastic Packing
influenteffluent
sludgeRecycle (optional)
Trickling Filter with Rock Packing
clarifier
influenteffluent
sludgeRecycle (optional)
Trickling Filter with Plastic Packing
clarifier
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
CLASSIFICATION OF MICROORGANISM
AUTOTROPHIC HETEROTHROPHIC CHEMOHETROTHROPHIC
PhotoautotrophicEnergy source – lightCarbon source – CO2
Photoheterotropic Energy source – onorganic redox reactionCarbon source – CO2
Aerobicoxygen as final electron acceptor
Chemoautotrophic Energy source – inorganic redox reactionCarbon source – CO2
ChemoheterotropicEnergy source – lightCarbon source – organic
AnaerobicNO3
- , SO42-, and CO2 as
electron acceptorNOTE;Autotrophic- organism that derive cell carbon from CO2
Heterothrophic – organism use organic carbon for formation new biomass
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
MICROORGANISM IN WW
Bacteria: major componentFungi: low pH, toxicity, N
deficient wasteProtozoa: gazing on bacteriaRotifers: multicellular
organism (help to floc formation)
Algae: supply oxygen to ww.Organic/ inorganic particle
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Aerobic heterotrophic bacteria are main “activated”organisms.
→Microbial community is highly diverse and competative.
Floc formation is really key –individual bacteria do not settle fast enough to be captured in the settling tank. Cells not in flocs are washed out.
The suspended flocs particles are called “activated”.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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BACTERIAL GROWTH & BIOMASS YIELD
BIOMASS GROWTHMostly organic materialsAn increase of biomass can be measured by VSS, particulate COD or TSSOther parameter to indicate biomass growth are DNA, protein content and ATP.VSS used as an apparent indicator of biomass production (measure of reactor solid in general)BIOMASS YIELD
)(__
__,_
consumedutilizedsubstrateg
producedbiomassgYYieldBiomass
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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RATE OF UTILIZATION OF SOLUBLE SUBSTRATE
SK
kXSr
s
su Rate of substrate
conc change due to
utilization (g/m3.day)
Max specific substrate utilization rate,
g substrate/g microb .day
Biomass (microorganism) conc, g/m3Growth-limiting substrate conc in solution, g/m3
Half velocity constant (substrate concat one-half the max specific substrate utilization rate, g/m3)
Substrate= the term used to denote the organic matter or nutrients that are converted during biological treatment or that may be limiting in biological treatment. Eg. Carbonaceous organic matter is ww is referred as the substrate that is converted during biological treatment.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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Sub
stra
te u
tiliz
ati
on r
ate
, -r
suSubstrate concentration, mg bsCOD/L
ks
max
Rate of change of substrate utilization vs biodegradable soluble COD conc based on saturation type model.From figure, max
substrate utilization rate occurs at high substrate conc.
In practice, biological treatment systems are designed to produce an effluent with extremely low substrate value.
When the substrate is being used at its max rate, the bacteria are also growing at their max rate.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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The max specific growth rate of bacteria is related to the max specific substrate utilization rate as follow;
kYm
max specific bacterial growth
rate, g new cells/g cells.day
max specific substrate
utilization rate, g/g.day
True yield coefficient, g/g
SK
kXSr
s
su SKY
XSr
s
m
su
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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RATE OF BIOMASS GROWTH WITH SOLUBLE SUBSTRATE
Relation between the rate growth & rate of substrate utilization is applicable in both batch and continuous culture systems.
xkYrr
xkxrdt
dxr
dsug
dg
g
Endogenous decay;
Net biomass production rate
Endogenous decay coefficient, gVSS/gVSS.day
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
-
d
s
su
sug
sug
m
s
g
s
mg
s
mg
g
kSk
ykSx
kdx
x
yr
dt
dx
x
concbiomassxbydevidex
kdx
x
yr
x
r
kdxyrr
ykwherekdx
Sk
kXSyr
kdxSk
XS
y
yr
kdxSk
XSr
kdxxdt
dxr
1
.)..(.......................
,..............
Net Biomass Growth;
System boundry
influenteffluent
sludge
Return activated sludge
Complete-mixaeration tank
clarifierQ, So, Xo (Q-Qw), S, Xe
Qw, S, Xw
Qr, S, XR
S, X,V
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
In the aeration tank, contact time is provided for mixing and aerating influent ww with the microbial suspension, generally referred to as the mixed liquor suspended solids (MLSS) or mixed liquor volatile suspended solids (MLVSS)
SUSPENDED GROWTH PROCESSSchematic of activated sludge unit
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Biomass Mass Balance
-Rate of accumulation of microorganism within the system boundary
Rate of flow microorganism into the system boundary
Rate of flow accumulation of microorganism out of the system boundary
Net growth of microorganism within the system boundary
= +
VrXQXQQQXVdt
dxgRwewo
.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
-
VrXQXQQQXVdt
dxgRwewo
.
dt
dx
VQ
oXwQ
eXRX
gr
Where,= rate of change of biomass concentration in reactor measured as gVSS/m3.day= reactor volume (aeration tank)m3= influent flowrate, m3/day
=concentration fo biomass in influent, gVSS/m3= waste sludge flowrate, m3/day= concentration of biomass in effluent, gVSS/m3
= concentration of biomass in return line from clarifier, gVSS/m3= net rate of biomass production, gVSS/m3.day
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Assumption;Xo = 0 (neglected) Steady state condition prevail (dx/dt)=0
VrXQXQQQXVdt
dxgRwewo
.
VrXQXQQgRwew
XkYrrdsug
VXkYrXQXQQ
dsuRwew
Where,
d
su
Rwewk
X
YrVXXQXQQ /
÷VX
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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d
su
Rwewk
X
YrVXXQXQQ /
Rwew
XQXQQ
VXSRT
Inverse above equation
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
- Rwew
XQXQQ
VXSRT
Sludge Retention Time (SRT)
Important designOperating parameter for activated sludge processIs average time the activated sludge solid are in the systemIs determine by dividing the mass of solid in the aeration tank by the solids removed daily via the effluent and by washing for process control
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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Substrate Mass BalanceIs a mass balance for substrate utilization in an AERATION TANK
Accumulation
Inflow Outflow
Generation
= +
VrQSQSVdt
dSsuo
.
Influent soluble substrate concentration, g/m3
Outflow soluble substrate concentration, g/m3
Assumption,At steady state, dS/dt=0
VrQSQSVdt
dSsuo
.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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d
s
d
s
d
s
s
o
s
o
suo
kSRTYkSK
S
kSRTSK
YkS
kSK
YkS
SRT
Hence
Sk
kXS
Q
VSS
Q
V
Sk
kXSSS
VrSSQ
11
1
1
,
SRTk
SSYSRTx
kSRTYk
kXSS
kSRTYkQ
VkXSS
Sk
S
Q
VkXSS
d
o
do
do
s
o
1
1
11
The reactor biomass conc is a function of SRT
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
-Rw
XQ
VXSRT
If no return sludge flow where all sludge produce present in the effluent clarifier tank…….the SRT equation become;
System boundry
influenteffluent
sludge
Complete-mixaeration tank
clarifierQ, So, Xo (Q-Qw), S, Xe
Qw, S, Xw
S, X,V
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
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Solid Production
Solid production from biological reactor represent the mass of material must be removed each day to maintain the process.Solid production in terms of TS,VSS and biomass.SRT provide expression to calculate total sludge produce daily from activated sludge process.
SRT
VXP T
VSSTX
Total solid waste daily (gVSS/d)
Total MLVSS conc in aeration tank, gVSS/m3
Volume of reactor (m3)
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
-
SRT
VXP
TX
Biomass waste daily (gVSS/d)
Niomass conc, gVSS/m3
Volume of reactor (m3)
To find amount of biomass wastes perday (Px), the biomass concentration, X can be used in place of XT in equation before;
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Mixed Liquor Solid Concentration
Total MLVSS in aeration tank
Biomass conc
nbVSS conc, xi
=+
iTXXX
Comprise of;nbVSS in influentnbVSS in wastenbVSS produce from cell debris duty to decay ratio
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Designed based on loading (the amount of organic matter added relative to the microorganisms available)
Commonly called the food-to-microorganisms ratio, F/M
F measured as BOD. M measured as volatile suspended solids concentration (VSS)
F/M is the amount of BOD/day per amount of MLVSS in the aeration tank
Design of Activated Sludge
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Food to Microorganism (F/M) Ratio
Defines as BOD @ COD applied perunit volume of mixed liquor
X
S
VX
QS
biomassmicrobialtotal
ratesubstrateappliedtotal
M
F oo
__
___
Where;F/M = food to biomass ratio (g BOD or COD/g VSS.day)Q=influent ww flowrate, m3/daySo=influent BOD @ COD conc, g/m3V=aeration tank volume ,m3.X=mixed liquor biomass conc in the aeration tank , g/m3 =hudraulic retention time of aeration tank, V/Q,day
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
Sludge Volume Index (SVI)
where V is volume of settled sludge after 30 min
Sludge settleability is determinedby sludge volume index (SVI)
SVI (ml/g) = ___________
MLSS
V x 1000
Final settling tank
sludge 1-L
mL
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
EXAMPLE ; ACTIVATED SLUDGE PROCESSAn activated sludge plant is set at SRT value of
10day. The reactor volume is 20 000m3 and MLSS conc is 400g/m3. Determine;a)The sludge production rate.b)The sludge washing flowrate when washing from reactor.c)The sludge washing flowrate when washing from recycle line. The concentration of suspended solid in recycle line is 10 000 g/m3. The solid loss in secondry rectifier is neglegible.
ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2009/2010)
THE END