Biological Treatment Of Waste Water

Shaswati SahaCSIR-JRFWWT Division

Biological treatment process

AerobicAnaerobic

SuspendedFixed FilmHybrid

ContinuousBatch

Completely mixedPlug-flow

Biological reactors

Suspended Fixed Film

Completely mixed Plug flow

Continuous Batch

CSTRASP

SBR

Baffled Reactors

(Plug flow)

• Granular-UASB

• Biofilm-FFB, PBR, RBC

• Immobilized-Enz

• Membrane bioreactors

Activated sludge

Trickling filter Fixed bed biological filter. Filter bed - uniform rocks

gravels, crushed PVC bottle( 1-3 m deep).

Wastewater is ‘trickled’ or sprayed over the filter by rotating sprinkler.

Wastewater flows downward and causes a layer of biofilm to grow.

A perforated slab -the effluent and excess sludge to be collected supports the bottom of the filter.

Maintenance • Should be washed

periodically to prevent clogging.

• High hydraulic loading rate can be used to wash the filter

AdvantagesOperated at various organic and

hydraulic loading rate.

DisadvantagesHigh operation and maintenance cost.Need expert design and construction.Odor and insects.

Fluidized Bed Reactor(Fluidized Bed Biofilm Reactor)

Combination of attached growth and suspended growth.

Reactor is cylindrical with perforated distribution plates and conical entry sections.

Biological slime film is developed and maintained on a solid support medium.

Support media-maintained in suspension by upward flow of influent.

Fabricated media developed to support biomass growth within porous internal structure .

Types of Fluidized Bed Reactor (FBR)1. Captor• Biomass is grown inside polyester foam

pads

• Pads can be periodically removed and biomass can be squeezed

• Simple sparger is used 2. Oxitron:Sand particles overflow/clean recycled.High purity oxygen is used.

Advantages Low biomass sludge production. High biomass concentration. High strength waste water treatment. Low Sludge transport and disposal. High exposed liquid/biofilm surface

area. Low operation cost.

Application Aerobic FBR used for nitrate removal in

petroleum industry , coke plant , explosive factory, nuclear plant.

Anoxic FBR used for de-nitrification .

Inverse Fluidized Bed Biofilm Reactor

Reactor bed is consisting of biofilm attached to low density polypropylene particles

It expands downwards during fluidization

Allows the control of biomass loading and provides the high oxygen concentration in the reacting liquid media .

Fluidization can be conducted by an upward co-current flow of gas and liquid through bed.

Advantages

Large specific support

surface area

Fast biofilm formation

Effective and simple

control of biofilm

thickness

Expanded bed reactor

It consists of cylindrical structure packed with inert support particle to about 10% of its volume.

Sand ,Gravel, PVC ,Resin are used as support medium

The biofilm grows attached to the particle. The particles are expanded by upward velocity

of the liquid. Upward velocity is increased by recirculation of

the effluent.

Advantages

High COD removal Velocity to maintain delicate attached

biofilm Separation, Retardation and Bio-

coagulation of fine suspended solids Achievement of high conc. Biomass

ApplicationIt is efficient in treating very low concentration of sewage (150-600 mg / L COD) in low hydraulic retention time (30-60 min)

Rotating biological contractor

Used to consume organic matter (BOD) from wastewater.

Disks - covered with a biofilm(2-4 m diameter).

As rotates the biofilm is exposed to the wastewater only part of the time.

The rotation (1-2 rpm)

Advantages High

loading rate

Nitrification/

denitrification

Low o& M cost

Durable constructi

on

Odorless

Packed bed/ Column Reactor

Treated effluent

Gas

Media bed

Raw waste water

Treated effluent recycled

Advantage Easy construction/Easy O & M/Organisms do not form slime on packing.

Application Column packed with anthracite ,coal particle are used for de nitrification of uranium recovery waste water.

Contact digestor

.

Raw waste water

Recycled sludge Stabilized sludge

Gas

Settling tank

Advantages Not affected by suspended solids High COD removal Long sludge retention timeApplicationWastes from sugar processing, distilleries, farm slurries are treated by contact digestor.

Upflow Anerobic Sludge Blacket Reactor

Granular sludge bed.

Fluidized Zone.

Gas-solid separator

Features

Disadvantages

Low pathogen removal.

Low nutrient removal

Need post treatment of effluent.

Thank you