biological nutrient removal
TRANSCRIPT
Biological Nutrient Removal From
Municipal Wastewater
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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
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Biological Nutrient Removal ( BNR ) is a process used to
remove nitrogen and phosphorus using micro-organisms
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BNR PROCESSES
BNR mainly consists of :
Biological Nitrogen Removal
Biological Phosphorous Removal
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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
PAOs convert available organic matter to PHAs
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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
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Fixed Systems
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Floating Systems
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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
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IFAS Continues..
15IFAS Process
Advantages
Higher capacity in same volume
Reseeding of suspended phase
Self-correcting system
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IFAS Continues..
Sequential Batch Reactor Process
(SBR)
• 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
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There are five stages in the treatment process :
1) Fill
2) React
3) Settle
4) Decant
5) Idle
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SBR Continues..
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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
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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
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SBR Continues..
Oxidation Ditches
Modified activated sludge
biological treatment
process that utilizes long
SRTs to remove
biodegradable organics
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Treatment systems consist of a single or multi-channel
configuration within a ring, oval, or horseshoe-shaped
basin
Horizontally or vertically mounted aerators provide
circulation, oxygen transfer, and aeration
May also be operated to achieve partial denitrification
Oxidation Ditch Continues…
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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
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Oxidation Ditch Continues…
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
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Oxidation Ditch Continues…
Membrane Biological Reactor Process (MBR)
Combination of
microfiltration or
ultrafiltration with a
suspended growth
bioreactor
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Biological reactor with
suspended biomass
Solids separation by
micro filtration
membranes with
nominal pore sizes
ranging from 0.1to
0.4µm
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MBR Continues…
Common configurations are :
1) Internal or submerged
2) External or sidestream
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MBR Continues…
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External
Internal
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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
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MBR Continues…
Disadvantages High capital costs
Limited data on membrane life
Potential high cost of periodic membrane replacement
Need to control membrane fouling
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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
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Advantages Compact Design
Expandable
Single Pass Process
Load Responsive
Minimal Maintenance
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MBBR Continues…
Step Feed Process
Continuous flow process
Influent flow is split to several feed locations
Contains alternating anoxic and aerobic stages
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Advantages
Nitrogen concentrations less than 5 mg/L are possible
5 to 8 mg/L TN is achievable
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Step Feed Process Continues…
Disadvantages More complex operation
Potential Nocardia growth problem
Requires dissolved oxygen control in each aeration zone
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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
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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
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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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Any Questions ????
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Thank You
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