Nitrogen Removal
High levels of nitrogen in water resources create hazard to human health and the environment. In many watersheds nitrogen from wastewater contributes 40 to 80 percent of total nitrogen loads (Lombardo, 2007). When Designing wastewater treatment system, nitrogen removal is the main concern. There are different methods used to remove nitrogen in the wastewater. Nitrogen in the ammonia form is toxic to certain aquatic organism (USEPA, 2002). According to USEPA (2002), Organic and inorganic forms of nitrogen may cause eutrophicaion (i.e., high productivity of algae) problems in nitrogen-limited freshwater lakes and in estuarine and coastal water.
Content Table
Removal Processes
Ammonium is one of the most commonly encountered nitrogenous pollutants in wastewater (Bodalo et. al., 2005). Loss to the (surface) water gives rise to acidification and eutrophication. Biological removal requires biological nitrification (generally to nitrate). In the case of total nitrogen removal the nitrate must be converted to (di)nitrogen gas. There are several biological processes that can be used if nitrogen removal is required.It can also be removed from wastewater by ion exchange.
Nitrification-Denitrification
The Nitrification-Denitrification process is the most common process for the removal of ammonium from wastewater. Ammonium is first oxidized biologically to nitrate in an aerobic process:
NH4+ + 2O2 --> NO3- + 2H+ + H2O
The process is autotrophic (uses CO2 as carbon source for biomass) and therefore has a low yield and slow growth rate. The produced nitrate is reduced to dinitrogen gas in denitrification. The process takes place anoxically and is coupled to the oxidation of organic material or sulfide:
NO3- + COD --> N2 + CO2 + biomass
If COD or sulfide is sufficiently available in the wastewater, it will be used in this reaction. In COD-deficient wastewaters however it is added externally (e.g. in the form of methanol, glycerol etc).
The running cost of the nitrification-denitrification are mainly associated with aeration (for nitrification), excess sludge prodction and the COD required for denitrification and are specified in Table xxx
| cost factor | nitrification | denitrification | ||
|---|---|---|---|---|
| aeration | 4.57 g-O2/g-N | - | ||
| COD | - | |||
| sludge production | 0.1 gX/gN | |||
Nitritation-Denitritation
Nitrogen removal from wastewater with high nitrogen concentration and low COD/N ratio via nitrite is advantageous (Jenicek et. al., 2004). The combination of nitritation-denitritation is highly beneficial for the domestic wastewater treatment in terms of lower carbon requirements, reduced oxygen demand and less biomass production (Zeng et. al., 2010).
Nitritation-Anammox
It is common to find effluents characterized by low C/N ratios which are usually difficult to be treated by means of conventional nitrification-denitrification processes. For those cases the use of the combined partial nitrification-anammox processes is an option. Both processes can be performed in two units sequentially operated (Van Dongen et al., 2001) in such a way that in the first unit the partial nitrification to nitrite of half of the ammonia contained in the wastewater takes place. This generated media is then fed to a second unit where the anammox process occurs. Another option consists of the use of a single aerobic unit where the biomass grows as a biofilm to perform simultaneously both processes. In the external layers of the biofilm the partial nitrification takes place while the anammox process is carried out in the inner anoxic zones of the biofilm (Sliekers et al. 2002). Both processes are normally operated at temperatures around 30 ºC. When the treated wastewater is characterized by low C/N ratios and low temperatures the use of these combined processes at low temperature is recommended. Recent research indicated that the anammox process can be succesfully operated at temperatures in the range of 20 ºC to treat effluents from anaerobic digesters (Vázquez-Padín et al., 2009).
- Industrial Wastewater Treatment
- Nutrient Recovery Proceedings
- Mechanism and Design of Sequencing Batch Reactors for Nutrient Removal
- Sequencing Batch Reactor
- Wastewater Ultraviolet Disinfection 1
- Wastewater Ultraviolet Disinfection 2
- Wastewater Disinfection
- Reduction Sludge Production in Wastewater treatment Plants
- Sludge
- Sludge Reduction: Technologies Integrated in the Sludge Handling Units
- Sludge Reduction: Technologies Integrated in the Waste Handling Units
- Research Needs in Leachate Treatment for Remediation of Aquatic Environment
- Activated Sludge Process
References
Bodalo A., Gomez, J.L., Gomez, E., Leon, G. and M. Tejera. 2005. Ammonium Removal from Aqueous Solutions by Reverse Osmosis Using Cellulose Acetate Membranes. Elsevier. 184 (2005) 149-155.
Jenicek P., Svehla, P., Zabranska, J., and Dohanyos, M. 2004. Factors Affecting Nitrogen Removal by Nitritation/Denitritation. Water Science Technology. 49(5-6):73-9.
Lombardo, P. 2007. Nitrogen Removal: Centralized versus Decentralized Passive Treatment. Government Engineering.
United States Environmental Protection Agency. 2002. Onsite Wastewater Treatment Systems Technology Fact Sheet 9. http://www.deq.state.va.us/export/sites/default/wastewater/documents/EnhancedNutrientremoval.pdf
Sliekers, O., Derwort, N., Campos-Gomez, J. L., Strous, M., Kuenen, J. G. & Jetten, M. S. M. (2002). Completely autotrophic nitrogen removal over nitrite in a single reactor. Water Research 36, 2475 – 2482.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
van Dongen, U., Jetten, M.S.M., van Loosdrecht, M.C.M. (2001). The SHARON®-Anammox® process for treatment of ammonium rich wastewater. Water Science and Technology 44(1), 153-160.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Vázquez-Padín J., Fernádez I., Figueroa M., Mosquera-Corral A., Campos J.L., Méndez R. (2009). Applications of Anammox based processes to treat anaerobic digester supernatant at room temperature. Bioresource Technology 100, 2988–2994.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Zeng W., Zhang, Y, Li L., Peng Y., and S. Wang. 2010. Simultanieous Nitritation and Denitritation of Domestic Wastewater Without Addition of External Carbon Sources at Limited Aeration and Normal Temperatures. Desalination Publication. 21 (2010) 210-219.
Links
Nitrogen Removal from Wastewater (The Water Planet Company).
Nitrogen Removal Module (New York Department of Environmental Conservation).
Nitrogen Removal in Wastewater Stabilization Lagoons (Joe Middlebrooks et.al., 6th National Drinking Water and Wastewater Technology Transfer Workshop).
More Reading
Henze,M, Harremoës,P., Jansen, J.la Cour and E. Arvin : Biological Wastewater treatment - Biological and chemical processes.3.ed. Springer 2002
Onsite Wastewater Treatment System Manual. (U.S. Environmental Protection Agency)
