Biological Nutrient Removal In Municipal Waste Water Treatment

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This civil engineering seminar topic gives an insight into Biological nutrient removal in municipal waste water treatment which is a much needed technology. Main problem is the rising concentration of nutrients. Nitrogen and phosphorus are the primary causes of eutrophication. Most recognizable manifestations are algal blooms. Symptoms are low dissolved oxygen, fish kills, murky water and depletion of flora and fauna.


Biological nutrients are organic materials. BNR is a process used to remove nitrogen and phosphorus using micro-organisms. BNR is comprised of two processes. They are 

biological nitrogen removal and biological phosphorus removal. 

1) Ammonia, nitrate, particulate organic nitrogen and soluble organic nitrogen.

2) Nitrification and denitrification.

3) Ammonia is oxidised to nitrite and nitrite is then oxidised to nitrate.

4) Reduction of nitrate to nitric oxide, nitrous oxide and nitrogen gas.

5) Soluble and particulate phosphorus.

6) The treatment process can be designed to promote the growth of PAO's. 

7) PAO's convert available organic matter to PHA's.

Treatment processes

1) Integrated Fixed Film Activated Sludge Process - 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.

2) Sequential Batch Reactor Process - Continuous flow system. Primarly for nitrogen removal. Flexible, inexpensive and efficient. Operational cost is high. Three phases involved in this are fill phase, react phase and settle phase.

3) 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.

4) Moving Bed Biofilm Reactor Process - 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.

5) Membrane Biological Reactor Process - 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.

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

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