Biological Nutrient Removal

transcript

Biological Nutrient Removal From

Municipal Wastewater

INTRODUCTION

Main problem - the rising concentration of nutrients

Primary causes of eutrophication - nitrogen and

phosphorus

Most recognizable manifestations - algal blooms.

Symptoms - low dissolved oxygen, fish kills, murky

water and depletion of flora and fauna

Biological Nutrient Removal ( BNR ) is a process used to

remove nitrogen and phosphorus using micro-organisms

BNR PROCESSES

BNR mainly consists of :

Biological Nitrogen Removal

Biological Phosphorous Removal

Effluent TN and TP Components

Biological Nitrogen Removal

Ammonia, nitrate, particulate organic nitrogen and

soluble organic nitrogen

Nitrification and denitrification

Ammonia is oxidised to nitrite and nitrite is then oxidised

to nitrate

Reduction of nitrate to nitric oxide, nitrous oxide and

nitrogen gas7

Biological Phosphorous Removal

Soluble and particulate phosphorous

The treatment process designed to promote the growth of

PAOs convert available organic matter to PHAs

Common Treatment Processes Integrated Fixed Film Activated Sludge (IFAS) Process

Sequential Batch Reactor ( SBR) Process

Oxidation Ditch Process

Membrane Biological Reactor (MBR) Process

Moving Bed Biofilm Reactor (MBBR) Process

Step Feed Process9

Integrated Fixed Film Activated

Sludge Process (IFAS)

Process combines fixed film technology with

conventional activated sludge

Filter media are added to an aeration basin to increase

the overall microbe population

Media can be fixed or floating

Fixed Systems

Floating Systems

Filter media provides surface area for the biological

growth to attach

Fine-mesh screens should be installed at the influent end

IFAS uses a secondary clarifier to settle sludge and

recirculate RAS

IFAS Continues..

15IFAS Process

Advantages

Higher capacity in same volume

Reseeding of suspended phase

Self-correcting system

IFAS Continues..

Sequential Batch Reactor Process

• Treat wastewater such as sewage or output from

anaerobic digesters or mechanical biological treatment

facilities in batches

• Consists of two or more identically equipped tanks

with a common inlet

There are five stages in the treatment process :

1) Fill

2) React

3) Settle

4) Decant

5) Idle

SBR Continues..

Advantages Flexible and easy to operate

Mixed-liquor solids cannot be washed out by hydraulic

surges

Equalization is provided

Quiescent settling provides low effluent TSS

5 to 8 mg/L TN is achievable concentration

SBR Continues..

Disadvantages More complex process design

Effluent quality depends upon reliable decanting facility

May need effluent equalization of batch discharge before

filtration and disinfection

SBR Continues..

Oxidation Ditches

Modified activated sludge

biological treatment

process that utilizes long

SRTs to remove

biodegradable organics

Treatment systems consist of a single or multi-channel

configuration within a ring, oval, or horseshoe-shaped

Horizontally or vertically mounted aerators provide

circulation, oxygen transfer, and aeration

May also be operated to achieve partial denitrification

Oxidation Ditch Continues…

Advantages More reliable owing to a constant water level and

continuous discharge

Long hydraulic retention time and complete mixing

Produces less sludge due to extended biological activity

Energy efficient operations result in reduced energy costs

Disadvantages Effluent suspended solids concentrations are relatively

high compared to other modifications of the activated

sludge process.

Requires a larger land area than other activated sludge

treatment options

Membrane Biological Reactor Process (MBR)

Combination of

microfiltration or

ultrafiltration with a

suspended growth

bioreactor

Biological reactor with

suspended biomass

Solids separation by

micro filtration

membranes with

nominal pore sizes

ranging from 0.1to

0.4µm

MBR Continues…

Common configurations are :

1) Internal or submerged

2) External or sidestream

MBR Continues…

External

Internal

Advantages Higher volumetric loading rates

Longer SRTs resulting in less sludge production

Operations at low DO

High quality effluent in terms of low turbidity, bacteria,

TSS and BOD

Less space required for wastewater treatment

MBR Continues…

Disadvantages High capital costs

Limited data on membrane life

Potential high cost of periodic membrane replacement

Need to control membrane fouling

MBR Continues…

Moving Bed Biofilm Reactor (MBBR)

Consists of an activated sludge aeration system

Uses polyethylene biofilm carriers operating in mixed

motion within an aerated wastewater treatment basin

Bacteria/activated sludge that grow on the internal surface

of the carriers break down the organic matter

Advantages Compact Design

Expandable

Single Pass Process

Load Responsive

Minimal Maintenance

MBBR Continues…

Step Feed Process

Continuous flow process

Influent flow is split to several feed locations

Contains alternating anoxic and aerobic stages

Advantages

Nitrogen concentrations less than 5 mg/L are possible

5 to 8 mg/L TN is achievable

Step Feed Process Continues…

Disadvantages More complex operation

Potential Nocardia growth problem

Requires dissolved oxygen control in each aeration zone

Step Feed Process Continues…

Comparison of BNR configurationsProcess Nitrogen Removal Phosphorus Removal

IFAS Good Moderate

SBR Moderate Inconsistent

Oxidation Ditch Excellent Good

MBR Excellent Moderate

MBBR Excellent Good

Step Feed Moderate None

REFERENCES

1. Margarida Marchetto, “Technologies Used in the Wastewater

Treatment for Nutrient Removal”, International Journal of

Waste Resources, 2013, Vol. 3, Issue 2

2. American Society of Civil Engineers (ASCE), Environmental

and Water Resources Institute (EWRI), Water Environment

Federation (WEF) “Biological nutrient Removal (BNR)

Operation in Wastewater Treatment Plants”, 2005, Manual of

Practice No. 29

3. Davood Nourmohammadi, Mir-Bager Esmaeeli, Hossein

Akbarian and Mohammad Ghasemian, “Nitrogen Removal in a

Full-Scale Domestic Wastewater Treatment Plant with

Activated Sludge and Trickling Filter”, Journal of

Environmental and Public Health, 2013, Vol. 5

4. Franklin. L. Burton, H David Stensel, “Wastewater

Engineering”, Tata McGraw – Hill Publishers, 2012, Edition 4

5. Santhosh Kumar Garg, “Sewage disposal and air pollution

engineering”, Khanna Publishers, 2012, Edition 24

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