Abg- Biological Processes Ajmer

8/4/2019 Abg- Biological Processes Ajmer

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Biological Processes forBiological Processes for

wastewater treatmentwastewater treatment

A.B. GuptaA.B. GuptaPCE, MNIT jaipurPCE, MNIT jaipur


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OUTLINE OF PRESENTATIONOUTLINE OF PRESENTATION

An overview of biological wastewaterAn overview of biological wastewatertreatment.treatment.

Important aspects in microbial metabolism.Important aspects in microbial metabolism.Principal organisms responsible forPrincipal organisms responsible forwastewater treatment.wastewater treatment.

key factors governing biological growth andkey factors governing biological growth andwaste treatment kinetics.waste treatment kinetics.


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Application of fundamentals andApplication of fundamentals andkinetics of biological process.kinetics of biological process.

Different options for suspended growthDifferent options for suspended growth

and fixed film systems, their applicationand fixed film systems, their applicationand limitationsand limitations


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BIOLOGICAL PRINCIPLES OFBIOLOGICAL PRINCIPLES OFWASTE WATER TREATMENTWASTE WATER TREATMENT

Biological TP: a method of contact betweenmicrobes and substrate. Suitabletemperature, pH, nutrients etc. arerequired for microbial growth. Such agrowth results into the removal ofsubstrate.


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Objective of biological treatmentObjective of biological treatment::

Coagulate and remove the non-settle ableCoagulate and remove the non-settle ablecolloidal solids .colloidal solids .

Stabilize the organic matter.Stabilize the organic matter.

Reduce the organic matter.Reduce the organic matter. Remove the nutrients.Remove the nutrients.

In short, stabilize organic matter: convert organic

matter to nonbiodegradable form so that it doesnot exert oxygen demand.


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MicrobesMicrobes

Virtually every environmental niche

Extremes of pH and salinity

Extremes of temperature and pressure

Without air (Anaerobic)

Growth on many chemical substrates

Attached to surfaces in biofilms

Geothermal vents and subterraneandeposits


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MICROBIAL METABOLISM

General nutritional requirements -:General nutritional requirements -:

CARBON SUBSTRATE (org. or inorg.)

ELECTRON DONOR

ENERGY SOURCE Need for molecular oxygen.Need for molecular oxygen.

Basic elements required-C,O ,N,H, P,S

Inorganic elements: K,Mg,Ca,Fe,Na,Cl


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Role of microbesRole of microbes

-

SINGLESINGLEBACTERIUMBACTERIUM

2.0 m

ORGANICORGANICPOLLUTANTPOLLUTANT

AND NUTRIENTSAND NUTRIENTS

(C,P,N,O,Fe,S)(C,P,N,O,Fe,S)

GROWTH - CELL DIVISIONGROWTH - CELL DIVISION

INCREASE IN BIOMASSINCREASE IN BIOMASS(assimilation)(assimilation)

COCO22

evolvedevolved

(dissimilation)(dissimilation)

OO22

consumptionconsumption

Controlled release of energyControlled release of energy

Slow Burning!Slow Burning!


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Basic growthBasic growth


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Types of microbesTypes of microbes

Depending on the energy and carbon source AUTOTROPHS: microbes requiring inorganic carbonaceous

compounds. HETEROTROPHS: microbes requiring organic

compounds . PHOTOTROPHS: microbes consuming light as energy

source . CHEMOTROPHS: microbes obtaining energy from oxidation of

org. or inorg. Compounds. ORGANOTROPHS: organic compounds as source of electron.

LITHOTROPHS: inorganic compounds as source of electron. E.g. nitrifying bacteria is an example ofchemolitho-

autotrophs.


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CLASSIFICATION OF

MICROORGANISMS

PHOTOAUTOTROPHIC

CHEMOAUTOTROPHIC

AUTOTROPHIC HETEROTROPIC

CHEMOHETEROTROPHIC

PHOTOHETEROTROPHIC

CO2

Organic carbon

INORGANIC ORGANIC

OXIDATION REDUCTION REACTION


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MicrobesMicrobes

By relationship to oxygen obligate aerobes: need oxygen, use it as

terminal electron acceptor

obligate anaerobes: cannot grow in thepresence of oxygen

facultative anaerobes: under certain

conditions can grow in the absence of oxygen


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EnergeticsEnergetics


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Central MetabolismCentral Metabolism Basically the working in a microbial cell is more or less

like a tower by which energy generation through avarious combination of substrates is detected.

EMP (Glycolysis and TCA /Krebs Cycle).

C6

2C3(2ATP,2 NADH,2 pyruvate)

(2NADH &2CO2) 2C2 TCA 4CO2, 6NADH

,2ATP & 2FADH2


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Net EnergyNet Energy

Most of the usable energy is being converted to-:

1. 10 Molecules of NADH (two from glycolysis, twofrom the transition stage, and six from the Krebs

cycle)2. 2 molecules of FADH23. 4 Molecules of ATP (net gain is only of 2ATPs)


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Important organisms in w/wImportant organisms in w/wtreatmenttreatment

Bacteria Fungi

Nemotodes


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Algae


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Protozoa Rotifers, ciliates,crustaceans

Stentor Celops

Paramecium


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BASIC REQUIREMENTS FORBASIC REQUIREMENTS FOREFFECTIVE DESIGN OF TPEFFECTIVE DESIGN OF TP

Environmental conditions that affect microbialgrowth.

1. pH 2. Temp 3. Nutrients4. Subs conc. & composition

5. D.O. 6. Contact / extent of mixing


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Method of contact between microbesand substrate.

Quantification of growth and substrateremoval

Method of separation of microbes and

substrate after desired substrateremoval is achieved


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Bacterial Growth curve in terms ofBacterial Growth curve in terms ofNumbersNumbers

Log

Growth curve

Lag

phase

Stationary phaseStationary phase

Death

phase

TIME

LOGLOG

NUMBERNUMBEROFOF

CELLSCELLS


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BACTERIA MULTIPLICATION:BACTERIA MULTIPLICATION:

dx/dS = Y REPRODUCED BY BINARY FISSION

GROWTH RATE:dx/dt = x - Kdt

x = microbial cell massS= Substrate, t = time

Y= Growth Yield coefficientK

d= decay rate

= specific growth rate coefficient


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GROWTH LIMITINGGROWTH LIMITING

NUTRIENTNUTRIENT

MONOD EQUATION:

= m S/(ks +S)

where:=specific growth rate coff.

m =maximum growth rate coeff.

s =conc. of limiting nutrient.ks =half saturation coeff.


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dS/dt = k X S/(ks +S)

K= maximum specific substrate utilizationrate


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EFFECT OF TEMPERATURE:EFFECT OF TEMPERATURE:

Influences metabolic activities of microbes

Effect of temperature on reaction rate of a

biological process:Kt = K20(t-20)

Kt = reaction rate at (t) degree Celsius

K20=reaction rate at (20)degree Celsius

= temperature activity coefficientt = temperature in degree Celsius


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Limiting nutrient cons. ,,ss

Specific

growth

rate,

Maximum rate

m

ks

m/2m/2

Effects of a

limitingnutrients

on the

specific

growth rate


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Kinetic design approach

Mass balance of MO at dX/dt=0 i.e.,steady state growth

Mass balance of substrate at dS/dt =0 i.e.,

steady state substrate removal Above equations are required to be

performed over the reactor and

separator system, m,K, ks,kd etc. are obtained experimentally before designing.


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Activated Sludge Process is thesuspended-growth biological treatmentprocess, based on providing intimate contact

between the sewage and activated sludge.The Activated Sludge is the sludge

obtained by settling sewage in presence of

abundant O2 so as to enrich with aerobicmicro-organisms.

Activated Sludge Process

R


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screensGrit

chamber

Primary

Settlingtank

aeration chlorination

Raw water

Secondary

Settlingtank

Effluentto disposal

Reareation

Activated SludgePump

ActivatedSludge return

SludgeThickener

SludgeDigestion To Sludge Drying

Flow Diagram of ASP


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A,T,

Va, X,Se

SecondarySecondary

ClarifierClarifier

Q, So

Q(1+R)

X, Se

(Q-Qw),

Xe, Se

Qw, Xr, SeRQ, Xr, Se

ACTIVATED SLUDGE KINETIC MODEL


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Microorganism and Substrate Mass Balance

Rate of accumulation = Biomass in + Biomassof biomass in system growth - biomass out

(dX/dt)V = QXo + V [rg- kdX ] QXrg = mXS /(Ks+S)

(dX/dt)V = QXo + V[mXS/(Ks+S) - kdX ] - QX

rg = Growth rate of biomass

Kd= Endogenous decaycoefficient.


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Mean Cell Retention Time

The time for which the cells remain inthe system. It is given as-

c = Mass of solids Mass of solidsin system leaving system/day

c = VX/(QwXw+ QeXe)


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Substrate Balance Equation

(dS/dt)V = QSo QS V[ mXS/ Y(Ks+S)]

For Steady State

Y=Decimal fraction of Food mass

converted to biomass

dS/dt = Zero(So S) = [mXS/Y(Ks+S)]


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X = m(So - S)/K(1+kd)

X = Y(So - S)/(1+kd)

Effluent concentration

Effluent substrate concentration

S = Ks(1+kd)/(Yk - kd)-1


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MICROBIOLOGICALMICROBIOLOGICALPROBLEMS, THEIR CAUSESPROBLEMS, THEIR CAUSES

& CONTROL IN ASP& CONTROL IN ASP


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INTRODUCTIONINTRODUCTION

The real "heart" of the activated sludge system isthe development and maintenance of a mixedmicrobial culture (activated sludge) that treatswastewater and which can be managed.

The best approach to troubleshooting theactivated sludge process is based onmicroscopic examination and oxygen uptake rate(OUR) testing to determine the basic cause ofthe problem or upset and whether it ismicrobiological in nature.


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MICROBIOLOGY PROBLEMS AND THEIRMICROBIOLOGY PROBLEMS AND THEIR

CAUSESCAUSES

Bulking sludge

Rising sludge

Foaming Poor floc formation, pin floc and dispersedgrowth.

Toxicity


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BULKING SLUDGEBULKING SLUDGE It is a stage in which an over abundance of filamentous organisms is

present in the mixed liquor in the activated sludge.

Types of sludge bulking

Zoogloea bulking- Zoogloea occur at high F/M conditions and whenspecific organic acids and alcohols are high in amount due to septicityor low oxygen conditions.

Viscous bulking it is the result of excessive extracellular polymersubstances by biomass, causing poor compaction and settling ofbiomass in secondary clarifiers, increased effluent BOD and poorsludge dewaterability.


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Filamentous bulking over growth offilaments effect both the zone settlingvelocity and sludge compaction.

RISING SLUDGERISING SLUDGE


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RISING SLUDGERISING SLUDGE

Sludge rise occurs when bacteria common in theactivated sludge floc respire using nitrate inplace of free oxygen when it is lacking andrelease nitrogen gas as a by-product. This gas is

only slightly soluble in water and small nitrogengas bubbles form in the activated sludge andcause sludge blanket flotation in the final clarifier.

FOAMINGFOAMING


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FOAMINGFOAMING

Nocardia andmicrothrix parcivellaare two mainfilamentous

organisms causefoaming.


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DESCRIPTION AND CAUSES OFDESCRIPTION AND CAUSES OF

ACTIVATED SLUDGE FOAMSACTIVATED SLUDGE FOAMSFoam Description Cause(s)

thin, white to grey foam low cell residence time or "young" sludge(startup foam)

hite, frothy, billowing foam once common due to nonbiodegradabledetergents (now uncommon)

pumice-like, grey foam (ashing) excessive fines recycle from other processes (e.g. anaerobic digesters)

thick sludge blanket on the final clarifier(s) denitrification

thick, pasty or slimy, greyish foam(industrial systems only)

nutrient-deficient foam; foam consistsof polysaccharide material releasedfrom the floc

thick, brown, stable foam enriched infilaments

filament-induced foaming, caused byNocardia, Microthrix or type 1863


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POOR FLOC FORMATION, PIN FLOC ANDPOOR FLOC FORMATION, PIN FLOC ANDDISPERSED GROWTHDISPERSED GROWTH

Floc-forming species share the characteristic of the formation of anextracellular polysaccharide ("slime") layer, also termed a glycocalyx.

Floc-forming species may grow in a dispersed and non-settleable form ifthe growth rate is too fast. This condition, termed dispersed growth,occurs often in industrial waste treatment, generally due to high organic

loading (high food to microorganism ratio (F/M) conditions). No flocs develop and biomass settling does not occur, resulting in a very

turbid effluent.

Small, weak flocs can be formed that are easily sheared and subject tohydraulic surge flotation in the final clarifier. These small flocs, termed

pin floc, consist only of floc-forming bacteria without a filamentbackbone, usually


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TOXICITYTOXICITY The washing of cement or lime trucks to a manhole, dumping of

congealed diesel fuel to the sewer system, and overload of smallsystems with septage (which contains a high amount of organicacids and sulfides which can be toxic).

Sulfide toxicity to activated sludge is more common than currently

recognized. Sulfide may originate from outside the activatedsludge system, from septic influent wastewater or from septagedisposal, or it may originate "in-house", from anaerobic digesterflows or from aeration basins or primary or final clarifiers withsludge build-up and anaerobic conditions.

Hydrogen sulfide toxicity is highly pH dependent, due to the H2S

form being the toxic agent and not HS-.

CONTROL METHODS FOR BULKING ANDCONTROL METHODS FOR BULKING AND


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CONTROL METHODS FOR BULKING ANDCONTROL METHODS FOR BULKING ANDFOAMINGFOAMING

Sludge Juggling

Polymer and Coagulant Addition

Chlorination

Low Dissolved Oxygen Problems Low F/M Problems and Selectors

Nutrient Deficiency

Foaming Control


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Conventional plug flow:- Settled water andrecycled activated sludge enter the headend of the aeration tank and are mixed bydiffused air or mechanical aeration. During

the aeration period adsorption, flocculationand oxidation of organic matter occurs.

Modifications of ASP

Modified aeration:- It is similar to conven--tional plug flow except that shorteraeration time and higher F/M ratio areused.


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Tapered aeration:- Varying aeration rates

are applied over the tank length dependingon the oxygen demand. Greater amounts ofair are supplied to the head end of the

aeration tank, and the amount diminish asthe mixed liquor approaches the effluentend.


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SecondarySecondary

clarifierclarifierEffluentEffluent

SLUDGE RETURNSLUDGE RETURNSLUDGESLUDGE

WASTEWASTE

ReactorReactor

CompressedCompressed

airair

PrimaryPrimary

effluenteffluent

Tapered aerationTapered aeration


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Step feed aeration

Generally three or more parallel channelsare used. The settled waste water isintroduced at several point in the aerationtank to equalize the F/M ratio, thus lowering

peak oxygen demand.


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SecondarySecondary



WASTEWASTE

ReactorReactor

CompressedCompressed

airair

PrimaryPrimary

effluenteffluent STEP FEED AREATIONSTEP FEED AREATION


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It operate in the endogenous respirationphase of the growth curve, which requiresa low organic loading and long aeration

time.

Extended aeration :-


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SecondarySecondary



WASTEWASTE

ReactorReactor

PrimaryPrimary

effluenteffluent

Extended AerationExtended Aeration


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Deep shaft processDeep shaft process

It is a Process having a mechanism of great depthaeration (depth of 40 to 150 m as an aeration tank) and it ispracticed where land is in short supply.

It can treat the waste water at higher rate.

It is also known as a space efficient and energy efficientbiological process.

D h ftDeep shaft


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Deep shaftDeep shaft

It is a high intensity aerobic liquid effluent treatment process,having a single vertical shaft.

Vertical shaft is divided in up-flow and down-flow sectionsknown as the riser and down comer.

The effluent circulates rapidly in the shaft driven by the injectionof compressed air which provides a differential density in theriser and down comer.

The resultant turbulent flow provides intense mixing of gas,liquid and biomass.


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Description:Description:

The liquor typically takes between 2 to 6 minutes tocirculate once around the shaft and head tank and onaverage it circulates 20 to 40 times before discharge.

The low ratio of the feed to the re-circulation flowmeans that the feed is rapidly diluted and mixed withthe entire mass of activated sludge in the system.

Typically shaft, is between one and eight metres in

diameter and surmounting the shaft is gasdisengagement head tank.


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Deep Shaft Advanced BiologicalDeep Shaft Advanced Biological


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Deep Shaft Advanced BiologicalDeep Shaft Advanced Biological

Treatment Process:Treatment Process:

High intensity aerobic liquid effluent treatmentprocess with oxygen transfer rate typically 10

times higher than conventional process.

Well suited for treatment of high strengthswastes with low operating and capital cost

P f d Ch i iP f d Ch t i ti


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Performance and Characteristics:Performance and Characteristics:(Examples for paper-manufacturing)(Examples for paper-manufacturing)

BOD removal rate: >90% (215mg/l -> 10mg/l)

COD removal rate: >80% (260mg/l -> 37mg/l)

BOD volumetric load: 3.7kg/(m3 d)

Retention time: 1hour

Operational advantages of DeepOperational advantages of Deep


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Operational advantages of DeepOperational advantages of Deep

Shaft:Shaft:

Oxygen rate transfer is 10 times higher than for conventionalprocesses.

Full automation possible with minimal instrumentation.

Resistance to changes in flow rates, BOD loadings and toxinsresults in robust and reliable performance.

Capable of treating a wider range of liquor strengths (typically 1 -30 kg BOD/m3 day compared with 0.4 -1.3 for conventional plants).

Can operate at higher MLSS concentration (3-10 g/l compared to2-5 g/l) for conventional plants.


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Design sludge loading (kg BOD per day/kg of MLSS)is higher, (0.7 to 3.5 compared with 0.1 to 0.5), and

this reduces reactor size.

Limited growth of filamentous organisms meansimproved sludge settling and smaller clarifiers.

Less sludge produced per kg BOD removed.

No moving parts with low maintenance costs.

Overall cost effective high performance.

G l d t f D Sh ftGeneral advantages of Deep Shaft:


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General advantages of Deep Shaft:General advantages of Deep Shaft:

Proven and reliable technology with more than 80 plants in

operation.

Low capital and operating costs.

Low land area requirements.

Mechanical simplicity.

High energy efficiency i.e. 1-4Kg BOD/kwhr.

Environmental friendly.


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Primary treatment not required.

High BOD removal rates.

High oxygen intensity (up to 2.5 Kg/M^3/hr compared to 0.1to 0.3 for conventional processes).

High efficiency of oxygen utilization.

Process reamains unaffected by change in temperature.


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Applications:Applications:

Pulp paper paper-product manufacturing industry

Food industry

Chemical industry

Sewage industry


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LAGOONSLAGOONS


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LAGOONSLAGOONS


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LAGOONSLAGOONS

Lagoons are deep waste stabilization ponds -likebodies of water or basins designed to receive,hold, and treat wastewater for a predeterminedperiod of time by artificial means of aeration.

In the lagoon, wastewater is treated through acombination of physical, biological, and chemicalprocesses.


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TYPES OF LAGOONSTYPES OF LAGOONSTYPES OF LAGOONSTYPES OF LAGOONS

According to the microbial activity in the aeratedlagoons-

Aerobic aerated lagoons.Facultative aerated lagoons.

AEROBIC AERATEDAEROBIC AERATEDAEROBIC AERATEDAEROBIC AERATED


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AEROBIC AERATEDAEROBIC AERATED

LAGOONSLAGOONS

AEROBIC AERATEDAEROBIC AERATED

LAGOONSLAGOONS

Dissolved oxygen is present throughout much ofthe depth of aerobic lagoons.

They tend to be much shallower than other

lagoons. They are better suited for warm, sunny climates,

where they are less likely to freeze.

HRT = 3 TO 60 days.

FACULTATIVE AERATEDFACULTATIVE AERATEDFACULTATIVE AERATEDFACULTATIVE AERATED


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FACULTATIVE AERATEDFACULTATIVE AERATED

LAGOONSLAGOONS

FACULTATIVE AERATEDFACULTATIVE AERATED

LAGOONSLAGOONS

Three types of zones are presentAerobic Zone.

Anaerobic Zone.

Facultative Zone. HRT is higher than aerobic lagoons because time

requires for the solids to settle and for many

pathogens viruses to either die off or settle out.

Wind


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CO2

Anaerob

i

cZone

Aerobic

Anaerob

i

cZone

Faculta

tive

Zone

O2

alga

e

(CO2, NO2, PO4, SO4)

Aerobic

Bacteria

Biomass

Biomass

Anaerobic

Bacteria

Sludge Blanket

Organic acids &

Compounds of C, N, P, S

Im ermeable linin

Sunligh

t


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Two Three or Four Lagoons AreTwo Three or Four Lagoons AreTwo Three or Four Lagoons AreTwo Three or Four Lagoons Are


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Two, Three, or Four Lagoons AreTwo, Three, or Four Lagoons Are

Better Than OneBetter Than One

Two, Three, or Four Lagoons AreTwo, Three, or Four Lagoons Are

Better Than OneBetter Than One

Each lagoon cell has a different function to perform, and adifferent kind of lagoon design may be used for each cell.

In SeriesIn SeriesWhen lagoons operate inWhen lagoons operate in

series, more of the solidseries, more of the solid

material in the wastewater,material in the wastewater,

such as algae, has ansuch as algae, has anopportunity to settle outopportunity to settle out

before the effluent isbefore the effluent is

disposed of.disposed of.

In ParallelIn ParallelThis system design isThis system design is

particularly useful inparticularly useful in

cold climates or wherecold climates or where

lagoons are coveredlagoons are coveredwith ice for parts of thewith ice for parts of the

yearyear


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ApplicabilityApplicabilityApplicabilityApplicability

Type of Lagoon ApplicationAerobic Lagoon Municipal and industrial wastewaters of

low to medium strength.

Facultative Lagoon Treated raw, screened, or primarysettled municipal wastewater andbiodegradable industrial wastewaters.

O i A d M i


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Operation And MaintenanceOperation And Maintenance

For Facultative Lagoons

Most facultative lagoons are designed to operate by gravity flow.

The system is not maintenance intensive and power costs are

minimal because pumps and other electrically operated devicesmay not be required.

Earthen structures used as impoundments must be inspected

for rodent damage.

O ti A d M i t


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Operation And MaintenanceOperation And MaintenanceOperation And MaintenanceOperation And Maintenance

For Aerobic Lagoons

Any earthen structures used as impoundments must be periodically

inspected. If left unchecked, rodent damage can cause severe

weakening of lagoon embankments.

In submerged diffused aeration, the routine application of HCl gas

in the system is used to dissolve accumulated material on the

diffuser units

The use of submerged perforated tubing for diffused aeration

requires maintenance and cleaning on a routine basis to maintain

design aeration rates

Li it ti


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LimitationsLimitationsFor Aerated Lagoons

Aerated lagoons may experience ice formation on the water

surface during cold weather periods

Reduced rates of biological activity also occur during cold

weatherFormation of ice on Floating Aerators.

For facultative

LagoonsThe inability of the process to meet a 30 mg/L limit for TSS

due to the presence of algae in the effluent.

Odors may be a problem in the spring and fall during periods of

excessive algal blooms and unfavorable weather conditions


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Attached-CultureAttached-Culture

SystemsSystemsTrickling FilterTrickling Filter

Rotating Biological ContactorsRotating Biological Contactors

Bio-TowersBio-Towers


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Trickling FilterTrickling Filter

Biofilm or bacterial film or biomass isgrown or developed on solid medium.Such as rocks, stone pieces, syntheticmedium etc. This media is randomlypacked in reactor. Wastewater is

applied on the top through a rotatingarm and it trickles down of the bottom.In its travel to the bottom of TF,wastewater is brought into the centreof biofilm attached to the medium. Theprocess may be depicted as shownbelow.

How does it work?How does it work?


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How does it work?How does it work?

1. O2 and Nutrients (BOD etc ) are transferredto the fixed film by diffusion

2. Energy of oxidation helps build the microbialfilm through synthesis

Continue..How does itContinue..How does it


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3. Bacteria metabolise contents of the fixed film.4. Biofilm grows or get thickened.

5. As its thickness increases, inner layer becomesanaerobic.

work?work?

Continue..How does itContinue..How does it


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6. Outer bio layer remains aerobic.7. With more thickening of biological layer, cells in inner layer die

and their lyses can generate acidic conditions.

work?work?


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8. The bio film gets slough off and is beingcarried away by the wastewater.

9. In SST, biofilm material is separated.

Continue..How does it work?


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Sludge in TF = 100 day (long cendogeous

decay, low X, more stablised Sludge) Actual Biomass is difficult to analyse

Overall yield coefficient is 60 80% of AST

Process

High rate TF produce more Sludge

Sludge in Trickling Filter:


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Natural draft : Temperature difference in air &

wastewater

If wastewater temp. < Ambient temp. : downward

flow of air ,

If Wastewater Temp. > Ambient Temp. : Upward Flow

of Air.

nder drains & collecting systems should be

designed to flow no more than half to allow force

air passing

Air Supply in TF:


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Hydraulics of Trickling Filter:

Rotating arm: - 2 rpm

Peripheral Speed: 0.5 3.7 m/min (two arm

system)

Arm length : 4.5 70m

Ports : 95mm in dia.

15cm above media.

Flow velocity in arms > 0.3 0.6 m/s to

A li i f T i kli Fil


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Application of Trickling Filter

Onsite TreatmentHouse Hold


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Classification of filtersClassification of filters

Low-rate filtersLow-rate filtersIntermediate-rate filtersIntermediate-rate filters

High-rate filtersHigh-rate filtersSuper rate filtersSuper rate filters


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Parameter Low Rate Filter

(LRF)

Intermediate Rate

Filter (IRF)

High rate Filter

(HRF)

H--- Hydraulic

loading m3/m2 -d

1 4 4 10 10 40

Uol. loading

kg/m3 d

0.08 0.32 0.28 0.48 0.32 1.0

Depth, m 1.5 3.0 1.25 2.5 1.0 2.0

Recirculation

Ratio

0 0 1 1 3

Power

Requirements

kw/103 m3

2 4 2 8 6 10

Each area ------- the does at least at 5 min intervals.


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Low-rate filters

A constant hydraulic loading is maintained bysuction-level controlled pumps or dosing siphon.

Dosing tanks are small having 2 min detention

time.In low-rate filters the top 2 to 4 ft of the

filter medium will have appreciable

biological slime.

Low-rate filters provide good BOD removal buthighly nitrified effluent.

Odors are a common problem with low- rate filter

in warm weather.


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Intermediate-rate and high -rate filter

In these filters recirculation of the filter effluentpermits higher organic loadings.

PRIMARY

CLARIFIER

FILTER CLARIFIERInfluent

Recycle

Effluent

PRIMERY

CLARIFIER FILTER CLREFIERInfluent

Effluent

Recycle

Single-stage filters with various recirculation

IN

Recycle Recycle


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P.C. I-STAGE F. II-STAGE F. C.

IN.EFF.

P.C. I-STAGE F. II-STAGE F. C.C.

N.I EFF.

Recycle Recycle

P.C. I-STAGE F. II-STAGE F. C.IN. EFF.

Recycle Recycle

Trickling-filters flow sheets with various recirculation patterns

Two- stage filters

Intermediate Rate and High Rate Filters

Recirculation of filter effluent around the filter results in


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Recirculation of filter effluent around the filter results in

the return of viable organisms.

This method of operation improves treatment efficiency

Recirculation also helps to prevent ponding in the filter

and reduce the nuisance from odors and flies.

Super-rate filtersThese filters have various types of synthetic and

wood packing media.

Application high strength wastes and roughing units.

High surface area per unit volume synthetic media filter

Used to achieve the nitrification of treatment effluent at

extremely loading rates.


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Rotating Biological ContactorsRotating Biological Contactors

Rotating biological contactors, commonlyreferred to as RBC's, are less prevalent

than trickling filters. However, RBC'sproduce a high quality effluent and wastewater operators should be familiar with

them.


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Nomenclature:Nomenclature:


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Nomenclature:Nomenclature:

RBCRBC


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.RBC.RBC

When do we use what:When do we use what:


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When do we use what:When do we use what:


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Process operation:Process operation:


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Process operation:Process operation:

Pretreatment : To prevent accumulation of solids & settling in

trough.

To protect RBC from shock/ toxic loads Flow equalisation : Low retention time in RBC is offset by high

conc. of biomass

Staging :

2-4 stages BOD removal 6 or more Nitrification


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Hydraulics :

Minimum head loss No recycle / recirculation method

Flow distribution Not very critical, mixing due to rotation is very

effective Enclosures:

Useful against rain/ snow

Limit heat loss Limit direct exposure to sunlight and hence

growth of algae limits

Protect the disk from deterioration due to UV

Advantages of RBCAdvantages of RBC


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Advantages of RBCAdvantages of RBC

Low food to micro-organism ratio resulting in higherefficiency of organic matter removal

Low hydraulic retention periods minimizing tank volume and capital costs

Low head loss and lower power requirement Inherent simplicity and low operational and

maintenance cost Ability to resist shock loads

Ability to lend itself to modular fabrication to suitrequired effluent quality


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The RBC is a fixed media filter in which themicroorganisms are housed on a series of largediscs. These discs are supported on a singleshaft which is slowly rotated through thewastewater by an air or electric driven motor.The RBC is covered by a removable fibreglasshousing which has access portals at each end.


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The discs are covered with a thick coatingof slime. This slime is the microorganisms,both aerobic and anaerobic, which treat

the wastewater. RBC's act much like atrickling filter in that the contactors performwell at removing BOD.

RBCRBC


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..RBC..RBC

Radius of discs varies from 1.5 to 2.00 mtr. Thickness of plate or disc is 10 mm to 30 mm.

Spacing is generally 2-3 cm to prevent bridging

between growth on two adjacent plates. Rpm of shaft is kept as 4 to 6 rmp.

Major draw back of this system is shaft failure, dueto torque caused due to 60 % dry and almost40% area submersed in in the waste water.

Abg- Biological Processes Ajmer

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