Nitrogen removal and simultaneous nitrification and denitrification in a fluidized bed step-feed process

Development and Evaluation of Compact Aquaculture System for the Application of Zero Water-Exchange Inland Aquacultures

“…Occurrence of heterotrophic denitrification was possible because excessive solid accumulation on biofilters could create anaerobic zone required by denitrifying bacteria while organic carbon source was available from biological degradation of accumulated solids. Occurrence of simultaneous nitrification and denitrification was also reported elsewhere in biofilter systems treating aquaculture effluent as well as domestic and industrial nitrogenous wastewater [16][17][18][19]. …”

“…Filtration unit was another likely source of heterotrophic denitrification due to high solid accumulation on filtered media. The occurrence of simultaneous nitrification and heterotrophic denitrification in the compact aquaculture system was undesirable at the moment although it could lead to the complete nitrogen transformation to harmless compound (i.e., N2) and possible reduction in operational cost and equipment sizing [16,[18][19]. The reasons for that were related to the difficulty in predicting the onset of denitrification using the farmer existing equipment as well as higher cost of investment for sophisticated controlled equipment.…”

Preparation and characterization of antifouling graphene oxide/polyethersulfone ultrafiltration membrane: Application in MBR for dairy wastewater treatment

“…Therefore, the inner regions of the biological flocs probably did not receive oxygen and transformed to anoxic zones, thus providing favorable conditions for denitrification [49,50]. In such cases, nitrification occurs on the surface of the flocs, whereas denitrification occurs in the internal layers of the flocs due to a dissolved oxygen gradient, therefore simultaneous nitrification and denitrification (SND) take place in the reactor even during aeration [51,52]. Due to sludge concentration was high; part of the total nitrogen removal may be result from a higher nutrient uptake.…”

Effect of intermittent aeration cycle on nutrient removal and microbial community in a fluidized bed reactor-membrane bioreactor combo system

“…Nitrification is completed in two steps: ammonium (NH 4 ) oxidized into nitrite (NO 2 ) by ammonia-oxidizing bacteria (AOB), and NO 2 oxidized into nitrate (NO 3 ) by nitrite-oxidizing bacteria (NOB) (Ahmed, 2012). Although the stoichiometric showed the requirement of 2 mol of oxygen (75% for AOB and 25% for NOB) per mol of nitrogen to be nitrified (Ruiz et al, 2003), there has been several reports that also showed complete nitrification below 2.0 mg/L dissolved oxygen (DO) concentration (Bellucci et al, 2011;Wang et al, 2012). Current research efforts on intermittent aeration cycles (IAC) are leading to reduce the level of DO required for nitrification process.…”

“…Current research efforts on intermittent aeration cycles (IAC) are leading to reduce the level of DO required for nitrification process. During IAC (on/off), the main advantage has been reported the coexistence of nitrifier and denitrifier microbial communities that can perform simultaneous nitrification-denitrification (SND) activities in a single reactor (Third et al, 2003;Rong et al, 2007;Wang et al, 2012). This is due to DO level fluctuation which creates anoxic/oxic microenvironment during ''on'' and ''off'' operations (Huang and Ju, 2007;Guadie et al, 2013b).…”