Selected Products for Advanced Nutrient Removal
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Advanced Nutrient Removal
Many Western municipalities are now required to remove nutrients in their wastewater treatment plants. Nitrogen compounds are the primary EPA and state focus, regulating the concentration of ammonia, or total TKN in the final effluent. A few Western agencies are also required to remove phosphorus, and many believe that phosphorus removal will soon be required in their renewed NPDES permit.
Biological oxidation of ammonia by nitrification can be accomplished in activated sludge plants by using longer sludge ages in conventional plug flow aeration basins, in SBR’s, in MBR’s, in single oxidation ditches, and oxidation ditches operated in series. This can be accomplished with simultaneous nitrification and denitrification in the aerated basin to conserve energy and recover alkalinity, or enhanced further by denitrification in anoxic selector zones. Fixed film media can also be used to grow and retain nitrifying bacteria on conventional plastic media nitrification trickling biofilter, by adding plastic media in the aerated AS basin (IFAS), or in a submerged aerated tank after secondary clarification(MBBR). Biological denitrification reduces the nitrates and nitrites produced by nitrification, reducing effluent TKN by forming nitrogen gas released to the atmosphere.
Phosphorus removal can be accomplished with chemical precipitation, but more cost effectively with various forms of biological phosphorus removal included in the nitrogen removing BNR process. A newer viable “green” product development directly removes phosphorus from clarified liquor, recovering and packaging the product as fertilizer for sustained commercial sale.
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MBBR - Moving Bed Bioreactor
The Moving Bed Biofilm Reactor (MBBR) process is based on attached growth biofilm principles of biological wastewater treatment. The core of the process is the biofilm carrier elements or media. While the biofilm is fixed to the media, the media is thoroughly mixed within a reactor and retained in the reactor.
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Denitrification Systems can remove nitrate-nitrogen (NO3-N) and suspended solids (SS) in a single treatment step. Fixed-film biological denitrification processes can also serve as a deep bed filtration system capable of removing suspended solids to virtually any final effluent requirement. Most systems integrate well with other plant treatment processes to provide superior total nitrogen (TN) and phosphorous removal. Denitrication is used as the final treatment step in the total nitrogen removal process to help each facility meet stringent TN discharge limits of 3 mg/l.