Biological Nutrient Removal (BNR) is a process used for nitrogen and phosphorus removal from wastewater before it is discharged into surface or ground water.To control eutrophication in receiving water bodies, biological nutrient removal (BNR) of nitrogen and phosphorus has been widely used in wastewater treatment practice, both for the upgrade of existing wastewater treatment facilities and the design of new facilities.

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2. INTRODUCTION
• Biological Nutrient Removal (BNR) is a process used for nitrogen and
phosphorus removal from wastewater before it is discharged into surface or
ground water.
• To control eutrophication in receiving water bodies, biological nutrient
removal (BNR) of nitrogen and phosphorus has been widely used in
wastewater treatment practice, both for the upgrade of existing wastewater
treatment facilities and the design of new facilities.

3. Eutrophication
Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically
compounds containing nitrogen, phosphorus, or both.

4. Causes and Effects
• In municipal wastewater treatment plant discharge causes cultural eutrophication
(nutrient enrichment due to human activities) in surface waters.
• Summer algal blooms are a familiar example of this eutrophication, and can
present problems for ecosystems and people alike: low dissolved oxygen, fish kills,
murky water, and depletion of desirable flora and fauna.

5. Challenges
• Conventional biological processes designed to meet secondary treatment
effluent standards typically do not remove total nitrogen (TN) and total
phosphorus (TP) to the extent needed to protect receiving waters.
• Wastewater treatment facilities are increasingly being required to implement
processes that reduce effluent nutrient concentrations to safe levels.

6. BNR Processes
BNR is comprised of two processes:
• Biological Nitrogen Removal
• Biological Phosphorus Removal

8. 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 gas.

9. Biological Phosphorus Removal
• Soluble and particulate phosphorus.
• The treatment process can be designed to promote the growth of PAOs.
• PAOs convert available organic matter to PHAs.
• PAOs - Polyphosphate-accumulating organisms - are a group of bacteria that,
under certain conditions, facilitate the removal of large amounts of
phosphorus from wastewater in a process,
• PHAs - Polyhydroxyalkanoates- are linear polyesters produced in nature by
bacterial fermentation of sugar or lipids.

10. Treatment Processes
• Integrated fixed film activated sludge process
• Sequential batch reactor process
• Step feed process
• Moving bed biofilm reactor process
• Membrane biological reactor process
• Oxidation ditch process

11. Integrated Fixed FilmActivated Sludge Process(IFAS)
• Combines fixed film technology with conventional activated sludge.
• Immerse a solid support media into an aeration basin.
• Media can be fixed or floating.
• Textile mesh material, floating sponges or plastic media.
• Provides surface area for biological growth to attach.
• Creates additional biomass.
• Provides additional biological activity.
• Increases solids settling.
• Increases waste water treatment facilities.

14. Sequential Batch Reactor Process(SBR)
• Continuous flow system.
• Primarily for nitrogen removal.
• Flexible, inexpensive and efficient.
• Operational cost is high.
• Three phases
Fill phase
React phase
Settle phase
SBR Operating Principle

15. Step Feed Process
• Continuous flow process.
• Influent flow is split to several feed locations.
• Recycle sludge stream is sent to the beginning.
• Higher solids retention time is achieved providing enhanced treatment.
• Phosphorus removal is limited.

16. Moving Bed Biofilm Reactor Process(MBBR)
• Direct derivative of fixed film activated sludge process.
• Hdpe carrier elements are used.
• Provide sites for bacteria attachment.
• Allows higher concentration of active biomass.
• More treatment capacity.
• Phosphorus removal requires additional stages.

17. Membrane Biological Reactor Process(MBR)
• Consists of separate aeration tanks and membrane filtration tanks.
• The membrane elements separate solids from the treated effluent.
• Excess solids are wasted directly from the aeration tanks.
• Membranes vary from hollow tube filters to flat panels.
• Require several cleaning cycles.

18. Oxidation Ditch Process
• Oxidation ditch is a large circular basin with aerators.
• Removes organic matter and pollutants
• Adsorption, oxidation and decomposition.
• Ensures stable, continuous D.O measurement.
• Reduces operating costs.
• Eliminates the need for manual cleaning.

19. BNR Process Modelling
• Practical implementation of BNR technology.
• Widely and successfully used.
• To improve understanding of the BNR processes.
• To optimize design and operation of the BNR processes.
• A computer programme simulator is required.
• To implement all unit process models and link them.
• To set up aWWTP with particular flow scheme, influent characteristics and
operation conditions.
• To represent the biological transformations.
• The model needs to be calibrated and validated before it is used.

20. Requirements to set up aWWTP process model

21. Conclusion
• BNR is an established technology.
• Implementation and operation is a challenge.
• Complex and high cost.
• Requires trained design engineers and operators.
• BNR process modelling is a useful tool for design and operation ofWWTPs.

22. References
• http://water.me.vccs.edu/courses/ENV295/lesson18_2b.htm
• http://www.headworksinternational.com/biological-wastewater-
treatment/bnr.aspx
• http://www.headworksinternational.com/biological-wastewater-
treatment/mbbr.aspx
• http://ascelibrary.org/doi/abs/10.1061/(ASCE)EE.1943-7870.0000462
• http://water.me.vccs.edu/concepts/oxidation.html

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