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Nitrous oxide is a greenhouse gas with a global warming potential 310 times that of the contribution of CO2. It is now recognized that the potential exists for N20 emission to be significant from some biological nutrient removal (BNR) processes. The control of N20 off-gas must therefore be considered when operating a BNR system. The main objectives of this research were to investigate the mechanisms involved in the production and reduction of nitrous oxide in biological wastewater treatment systems, and to use N20 off-gas as a real-time control parameter to assess ammonia oxidation in a simultaneous nitrification, denitrification and phosphorus removal (SNDPR) system. Strategies to diminish the emission of nitrous oxide from the treatment process were also studied. The data support the conclusion that a hybrid system, including suspended sludge and biofilm in the same reactor of a sequencing batch reactor (SBR) was a more effective system than a conventional suspended growth system, in terms of overall effluent quality, SND efficiency and lower emission of N20. In the hybrid system, nitrification occurred mostly in the suspended sludge; the biofilm played the major role in denitrification. It was also determined that N20 off-gas from the hybrid system was mainly a result of heterotrophic denitrification, rather than nitrification. N20 reduction rates were found to be higher with the existence of an external carbon source and the absence of DO. It was also observed that N20 reduction rates were higher for acetate, than for lactose, in the presence and absence of DO. Denitrification using stored carbon resulted in the production of more N20 off-gas than denitrification using an external carbon source. The largest production of N20 off-gas occurred when the internal carbon source was PHA during aerobic conditions. Based on the results of the investigation into the factors affecting N20 emissions, operating strategies for N20 off-gas control were suggested. These strate.
The discharge of point- and non-point source pollutants into surface waters resulting from industrial and/or municipal activities is a major focus of environmental regulation in the United States. As a result, the National Pollutant Discharge Elimination System (NPDES) permit program was established in 1972 in an effort to regulate discharges from industrial or municipal sources, including wastewater treatment plants (WWTP). To further protect Florida water quality, in 1978, State legislation enacted the Grizzle-Figg Act for Tampa Bay, which requires advanced wastewater treatment for any discharge into sensitive water bodies. A common use of wastewater effluent in the Tampa Bay area is for reclaimed water for irrigation. This leads to an estimated 90% reduction of total nitrogen (TN) load to the bay in comparison to direct discharge (TBEP, 2016). One type of wastewater treatment process that has been shown to have low aeration and chemical requirements is simultaneous nitrification denitrification (SND), which can be carried out in an oxidation ditch. SND is a biological process for nitrogen removal where nitrification and denitrification occur at the same time within the same reactor. An oxidation ditch is a race-track type reactor that promotes the occurrence biological conversion of reactive nitrogen to nitrogen gas (N2) and additionally can provide enhanced biological phosphorus removal (EBPR). Many theories exist as to the mechanisms that allow SND to occur, but the literature is inconclusive as to whether the presence of different zones within the floc, within the reactor itself, a combination of the two or unique microorganisms are responsible for SND. Advantages of SND include efficient (80-96%) nitrogen removal, with significant reductions in energy, chemical, equipment and spatial requirements.
Aerobic Granular Sludge has recently received growing attention by researchers and technology developers, worldwide. Laboratory studies and preliminary field tests led to the conclusion that granular activated sludge can be readily established and profitably used in activated sludge plants, provided 'correct' process conditions are chosen. But what makes process conditions 'correct'? And what makes granules different from activated sludge flocs? Answers to these question are offered in Aerobic Granular Sludge. Major topics covered in this book include: Reasons and mechanism of aerobic granule formation Structure of the microbial population of aerobic granules Role, composition and physical properties of EPS Diffuse limitation and microbial activity within granules Physio-chemical characteristics Operation and application of granule reactors Scale-up aspects of granular sludge reactors, and case studies Aerobic Granular Sludge provides up-to-date information about a rapidly emerging new technology of biological treatment.
The nitrogen cycle and nitrous oxide; Atmospheric chemical processes of the nitrogen, including nitrous oxide; Microbiology and genetics of denitrifiers; Physiology and biochemistry of denitrification; The status of nitric oxide and nitrous oxide as intermediates in denitrification; Denitrification in wastewater management; Nitrous oxide and nitrogen gas production in fertilizer loss; Terrestrial nitrification as a sopurce of atmospheric nitrous oxide; Dissimilatory nitrate reduction to ammonia; Nitrous oxide in the oceans.
Nitrification and denitrification are essential processes for the aquatic ecological system and vital for human health. While ammonia is applied for disinfection together with chlorine to produce chloramine, excessive ammonia may cause nitrification and bacteria growth in the water transmission pipeline. Since excessive discharge may cause eutrophication and deterioration of the aquatic system, nitrate is regulated for wastewater discharge in sensitive areas. Further, nitrate needs to be monitored and controlled in drinking water treatment to protect against methemoglobinemia in bottle-fed infants. Various conventional technologies exist, such as adsorption, ion exchange, photocatalytic oxidation, air stripping, biological nitrification and denitrification, and so on, to remove nitrogenous compounds from water. Since ammonia and nitrate are important constituents in fertilizers besides phosphorus (P) and potassium (K), nutrient recovery is drawing attention to maintaining the supply of reliable and sustainable fertilizers. This book provides a comprehensive overview of nitrification and denitrification.
This book contains the papers presented at a Nato Advanced Re search Workshop entitled "DENITRIFICATION IN THE N-CYCLE," held in Braunschweig (W-Germany) from 24 to 27 Mai 1983. All expenses were provided by the North Atlantic Treaty Organization. The scientific programme was in the first instance planned by some members of the Eco-Science Panel under the stimulating organization of Dr. Oscar Ravera and the final programme was prepared in co-operation between Ravera and myself. However, even during the meeting important con tributions were added. The meeting was hosted by the Microbiologi cal Dept. of F.A.L., which also took care of the organizatory as pects. Nitrate is constantly lost from both terrestial and aquatic ecosystems, causing rnixed feelings between ecologists and agricul turists. While bacteriologically very rnuch is known, the ecology of the processes is still poorly understood, nor can it be evaluated what it rneans as an econornic loss for farrners and world food produc tion. Therefore this NATO Advanced Workshop was established to per mit a lirnited nurnber of scientists active in this field to corne to gether for a short while to address the following objectives: 1) To exchange ideas between scientists (bacteriologists and ecologists) and agronornists. 2) To assess the state of the art. 3) To discuss the difficulties of experimentation in the field. 4) To define future research. In order to accornplish these objectives, the workshopwas organ ized in three parts with the following thernes: 1) Bacteriological aspects of dentrification
Most wastewater treatment plants in the United States must be upgraded to reduce nutrient discharges. These improvements are needed to meet upcoming permit requirements and to prevent negative environmental impacts like eutrophication of receiving water bodies. However, one of the potential side-effects of increased nitrogen removal in wastewater treatment processes is increased nitrous oxide (N2O) emissions from biological nitrification and denitrification. N2O is a greenhouse gas (GHG) approximately 300 times stronger than an equivalent amount of CO2; thus, it is imperative to (1) establish comprehensive methodologies to accurately quantify N2O emissions from full-scale treatment processes and (2) understand the relevant process parameters and microbiology involved in emissions from wastewater treatment. This serves to ultimately minimize emissions (and therefore the carbon footprint) of wastewater treatment plants (WWTPs). To address this, emissions from two wastewater treatment processes were quantified, and relevant process parameters and microbial emission pathways were investigated. While the two treatment systems differ in terms of scale and processes utilized, both are innovative wastewater treatment technologies designed for efficient use of space and nutrient removal. (1) At Brightwater Treatment Plant (Woodinville, WA), aqueous and gaseous N2O monitoring techniques were employed at a full-scale membrane bioreactor (MBR) for 5.5 months. To the knowledge of the investigators, this campaign was the most comprehensive study of a fully covered MBR to date. Emission estimates from both aqueous and gaseous analyzers were compared to determine their reliability, and the average emission factor (using data from both analyzers) was 0.58% of plant influent total Kjeldahl nitrogen (TKN) emitted as N2O-N. Emissions were positively correlated with influent pH, nitrification efficiency, and aeration basin/effluent NH4+and NO3−. They correlated negatively with primary effluent COD:N ratio and effluent pH, signifying that nitrification was likely the dominant N2O-production pathway. (2) A laboratory-scale, aerobic granular sludge (AGS) sequencing batch reactor (SBR) was operated for 11 months to measure N2O emissions with full phosphate removal and simultaneous nitrification-denitrification (SND). The reactor was operated at varying dissolved oxygen (DO) concentrations and with nitrite (NO2−) spikes to investigate the impact of these process parameters on emissions. Increased DO and NO2- concentrations were associated with increased emissions. N2O was minimized at a dissolved oxygen concentration of 1 mg O2 L−1, with an emission factor of 0.18% of oxidized NH3-N emitted as N2O-N. This emission factor is lower than many previously reported factors from AGS reactors. Molecular analyses revealed a population of microbes capable of shortcut nitrogen removal, which is advantageous for wastewater treatment because of decreased oxygen and carbon requirements.