Biological Treatment of Wastewater

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BIOLOGICAL TREATMENT

G. N. MAHESHIKA

09

TH

JUNE, 2O15

WASTEWATER ENGINEERING

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OBJECTIVES

• Coagulation and removal of organic and inorganic

non-settleable colloidal particles

• Stabilization of dissolved organic matter

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CLASSIFICATIONS

1. Processes according to operational conditions• Aerobic process

• Anaerobic process

•Facultative process

• Anoxic process

2. Processes according to microbial maintenance in

the system• Suspended growth process

• Attached growth process

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Biological Wastewater Treatment

Suspended Growth

Aerobic

Activatedsludge process

Extendedaeration system

Aeratedlagoons

Wastestabilizationponds

Anaerobic

Complete mixanaerobicreactor

Contactanaerobicreactor

Attached Growth

Aerobic

Tricklingfilters

Bio-towers

Rotating

biologicalcontactors

Submergedfilters

Anaerobic

Packed bed up-flow and down-

flow reactors

Extended reactor

Fluidized bedreactor

Up-flow

anaerobic sludge

blanket reactor

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ASSIGNMENT

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PRINCIPLE OF AEROBIC BIOLOGICAL TREATMENT

•

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•

PRINCIPLE OF ANAEROBIC BIOLOGICAL TREATMENT

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AEROBIC VS. ANAEROBIC PROCESSES

•Molecular O2 as TEA

• Wide spectrum of OM

can be oxidized

• More stable end products

• High growth rates of

microorganisms

• More biological sludge

• For large quantities of

diluted wastewater

•SO4

2-

, CO2, organiccompounds as TEA

• End products are odorous

• Slow process

• Low sludge production

• For concentrated wastes

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100

60

30

10

100

20

60

20

Efficiency: 90% 80%

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FACTORS FOR IMPROVED EFFICIENCY

•

Availability of many MO• Better contact between MO and organic matter

• Favorable environmental conditions

(Temperature, pH, nutrient requirement, retentiontime…)

• Availability of oxygen for aerobic treatment process

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BIO-KINETIC COEFFICIENTS/ GROWTH CONSTANTS

Understanding the kinetics of,

• Microbial growth rate

• Substrate utilization rate

• Limiting substrate or nutrients

• Endogenous decay or death rate of MO

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The growth curve of MO

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Ex: Specific growth rate, µ

Yield coefficient, Y

Maximum substrate utilization rate, K

Net specific growth rate,r’

g

Hydraulic retention time (HRT), θ

Cell retention time (SRT), θc

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• Biomass concentration in the reactor, X

• Substrate concentration, S

• Rate of growth, rg

• Maximum specific growth rate of biomass, µmax

• Half velocity constant, Ks

• Substrate utilization rate, rsu

• Endogenous decay coefficient, Kd

• Rate of endogenous decay of biomass, rd

•

Observed yield coefficient, Yobs

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KINETICS TO BIOLOGICAL TREATMENT

• Prediction of effluent biomass and substrate

concentrations

• Prediction of bio-kinetic coefficients

• Kinetics to activated sludge biological treatment

process

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Cont.

• Biological nitrification

• Biological denitrification

• Biological mechanism of phosphorous removal