Proceedings of the Water Environment Federation, 2000
Simultaneous biological nutrient removal (SBNR) is the occurrence of significant biological nutri... more Simultaneous biological nutrient removal (SBNR) is the occurrence of significant biological nutrient removal in biological wastewater treatment systems where defined anaerobic and anoxic zones do not exist. There is growing evidence that significant SBNR can occur in many systems, ...
The accuracy of a biofilm reactor model depends on the extent to which physical system conditions... more The accuracy of a biofilm reactor model depends on the extent to which physical system conditions (particularly bulk-liquid hydrodynamics and their influence on biofilm dynamics) deviate from the ideal conditions upon which the model is based. It follows that an improved capacity to model a biofilm reactor does not necessarily rely on an improved biofilm model, but does rely on an improved mathematical description of the biofilm reactor and its components. Existing biofilm reactor models typically include a one-dimensional biofilm model, a process (biokinetic and stoichiometric) model, and a continuous flow stirred tank reactor (CFSTR) mass balance that [when organizing CFSTRs in series] creates a pseudo two-dimensional (2-D) model of bulk-liquid hydrodynamics approaching plug flow. In such a biofilm reactor model, the user-defined biofilm area is specified for each CFSTR; thereby, X carrier does not exit the boundaries of the CFSTR to which they are assigned or exchange boundaries with other CFSTRs in the series. The error introduced by this pseudo 2-D biofilm reactor modeling approach may adversely affect model results and limit model-user capacity to accurately calibrate a model. This paper presents a new sub-model that describes the migration of X carrier and associated biofilms, and evaluates the impact that X carrier migration and axial dispersion has on simulated system performance. Relevance of the new biofilm reactor model to engineering situations is discussed by applying it to known biofilm reactor types and operational conditions.
ABSTRACT The phosphorus removal capabilities of the Virginia Initiative Plant (VIP) process, a hi... more ABSTRACT The phosphorus removal capabilities of the Virginia Initiative Plant (VIP) process, a high-rate biological nutrient removal (BNR) process, are presented and compared to the high-rate A2/0 and the low-rate University of Capetown (UCT) processes. The results indicate superior phosphorus removal capability for the VIP process compared to the A2/0 and UCT processes. In general, VIP process phosphorus removal was maximized by operation at the lowest possible total process mean cell residence time (MCRT) and with an aerobic hydraulic residence time (HRT) not exceeding 4 hours. A total process MCRT of 5 days provided acceptable nitrogen removal and excellent phosphorus removal for wastewater temperatures of 20°C or above, while a total process MCRT of 20 days would be required at a temperature of 12°C. Operation of the VIP process at an aerobic HRT greater than 4 hours apparently resulted in oxidation of stored organic matter that adversely affected phosphorus uptake kinetics. Data analysis suggested that the VIP process could have been operated at an anaerobic HRT as short as 20 minutes. Superior phosphorus removal performance was observed for the VIP process compared to the A2/0 process when the BOD5/TPO4 ratio of the wastewater was significantly less than 20.
Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phospho... more Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phosphorus in excess of that required for biomass synthesis in a biological wastewater treatment system without defined anaerobic or anoxic zones. Evidence is growing that significant SBNR can occur in many systems, including the aerobic zone of systems already configured for biological nutrient removal. Although SBNR systems offer several potential advantages, they cannot be fully realized until the mechanisms responsible for SBNR are better understood. Consequently, a research program was initiated with the basic hypothesis that three mechanisms might be responsible for SBNR: the reactor macroenvironment, the floc microenvironment, and novel microorganisms. Previously, the nutrient removal capabilities of seven full‐scale, staged, closed‐loop bioreactors known as Orbal oxidation ditches were evaluated. Chemical analysis and microbiological observations suggested that SBNR occurred in these systems. Three of these plants were further examined in this research to evaluate the importance of novel microorganisms, especially for nitrogen removal. A screening tool was developed to determine the relative significance of the activities of microorganisms capable of autotrophic denitrification and heterotrophic nitrification‐aerobic denitrification in biological nutrient removal systems. The results indicated that novel microorganisms were not substantial contributors to SBNR in the plants studied. Phosphorus metabolism (anaerobic release, aerobic uptake) was also tested in one of the plants. Activity within the mixed liquor that was consistent with current theories for phosphorus‐accumulating organisms (PAOs) was observed. Along with other observations, this suggests the presence of PAOs in the facilities studied.
to the short batch test period provided (<12 hrs) which would not allow a population shift and fu... more to the short batch test period provided (<12 hrs) which would not allow a population shift and further justified with the electron microscopy results. The results also indicate that glycogen serves not only as source of reducing power for PHA production but also serves as an alternative energy source when the poly-P pool of the PAOs is depleted. Slow generation of ATP via glycolytic pathway at 5 o C cannot satisfy energy requirements of EBPR cells to complete several cell functions including acetate uptake and PHA storage. However, the glycolytic pathway is efficiently operable at warm temperatures (>20 o C). The reduced performance of enhanced EBPR facilities operated at warm temperature may not be a result of GAO proliferation; instead it may be related the efficient use of the glycolytic pathway by PAOs which results in more glycogen storage and less P uptake, thereby reducing the phosphorus removal performance of the facility.
ABSTRACT Modelling concepts: HFO precipitation, aging, P adsorption Validation with experiments i... more ABSTRACT Modelling concepts: HFO precipitation, aging, P adsorption Validation with experiments in tap water (Szabo et al., 2008) Influence of mixing Influence of HFO aging and time Low P effluent requirement chemical dosing Objective: Ensuring compliant effluent phosphorus concentrations, saving chemicals and limiting chemical sludge production Method: development of a model able to optimize multi-point dosage optimize temporal dosage predict interaction of bio-P and chemP predict alkalinity loss Background: Iron dosage leads to rapid hydrous ferric oxide (HFO, close to 2-line ferrihydrite) precipitation. Phosphorus is removed mainly by: adsorption of phosphate onto HFO co-precipitation of phosphate into HFO flocs (Smith et al., 2008)
One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofil... more One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofilm reactor design. Limitations using mechanistic biofilm models for engineering design do not rely on improved biofilm models, but rely on improved biofilm reactor models. This is important when considering that biofilm reactors containing submerged, free-moving biofilm carriers are the most widely applied biofilm system(s) for municipal wastewater treatment. This paper presents a new biofilm reactor model that considers the impact of submerged free-moving biofilm carrier (Xcarrier) movement on system performance. The model accounts for a hydrodynamic condition characterized as plug flow with back mixing (to model axial dispersion). The relevance of this new biofilm reactor model to engineering situations is evaluated by applying it to relevant scenarios and comparing model results.
Based on the International Water Association's (London) Activated Sludge Model No. 2 (ASM2), ... more Based on the International Water Association's (London) Activated Sludge Model No. 2 (ASM2), biochemistry rate expressions for general heterotrophs and phosphorus‐accumulating organisms (PAOs) were introduced to a previously developed, three‐dimensional computational fluid dynamics (CFD) activated sludge model that characterized the mixing pattern within the outer channel of a full‐scale, closed‐loop bioreactor. Using acetate as the sole carbon and energy source, CFD simulations for general heterotrophs or PAOs individually agreed well with those of ASM2 for a chemostat with the same operating conditions. Competition between and selection of heterotrophs and PAOs was verified using conventional completely mixed and tanks‐in‐series models. Then, competition was studied in the CFD model. These results demonstrated that PAOs and heterotrophs can theoretically coexist in a single bioreactor when the oxygen input is appropriate to allow sufficient low‐dissolved‐oxygen zones to develop.
Proceedings of the Water Environment Federation, 2008
1 Department of Chemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 2 Depar... more 1 Department of Chemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 2 Department of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 3 University of Technology and Economics, 1111 Budapest, ...
Proceedings of the Water Environment Federation, 2013
A dynamic physico-chemical model for chemical phosphorus removal in wastewater is presented as a ... more A dynamic physico-chemical model for chemical phosphorus removal in wastewater is presented as a tool to optimize chemical dosing simultaneously while ensuring compliant effluent phosphorus concentration. This new model predicts the kinetic and stoichiometric variable processes of precipitation of hydrous ferric oxides (HFO), phosphates adsorption and co-precipitation. It is combined with chemical equilibrium and physical precipitation reactions in order to model observed bulk dynamics in terms of pH. The model is calibrated and validated based on previous studies and experimental data from Smith et al. (2008) and Szabo et al. (2008) as a first step for full-plant implementation. The simulation results show that the structure of the model describes adequately the mechanisms of adsorption and co-precipitation of phosphate species onto HFO and that the model is robust under various experimental conditions.
Proceedings of the Water Environment Federation, 2007
Beginning in the early 1980's, the waters of Western Long Island Sound showed significant degrada... more Beginning in the early 1980's, the waters of Western Long Island Sound showed significant degradation and low dissolved oxygen (hypoxia) caused primarily by nitrogen enrichment from runoff, atmospheric deposition, and sewage plant discharges. Located on the Western reach of long Island Sound near New York City, the Stamford, CT, Water Pollution Control Authority (WPCA) was the first municipality in CT to begin experimenting with nitrogen removal in the early 1990s and conducted a study funded by the U.S. Environmental Protection Agency (EPA) to demonstrate new nitrogen removal technology. This project was followed in the late 90's by plant improvements to further enhance nitrogen removal (50 to 60% nitrogen removal). The Stamford WPCA recently completed and commissioned a $105M nitrogen upgrade and expansion to 90,840 m 3 /day (24 mgd). About $50M was associated with nitrogen removal processes. Designed to achieve nitrogen removal on the order of 80 to 90% to levels of 4 mg/L Total nitrogen (TN) or less, the upgraded plant has been operating in the high level nitrogen removal mode since the spring of 2006. Treatment consists of preliminary and primary treatment followed by suspended growth biological nitrogen removal (BNR) with biological reactors using pre-and post-anoxic zones (methanol fed to post-anoxic zone), ultraviolet (UV) disinfection, and discharge to the Sound. Solids handling includes thickening of primary and WAS, dewatering and landfilling. Construction of a sludge dryer is ongoing and is expected to be completed in late 2007. Unique treatment challenges for this project included cold water (12 o C), a history of severe foaming, and high levels of refractory nitrogen. Operating at 68,200 m 3 /day (18 mgd), the plant began achieving very low effluent TN (3-4 mg/L) in May of 2006 when final construction and equipment related issues were resolved and methanol addition to the secondary anoxic zone was begun. Although the plant achieves complete nitrification and nitrate removal to less than 1.0 mg/L, effluent refractory organic nitrogen has been high relative to other municipal POTWs (organic nitrogen of 3.8 mg/L in May, with a soluble component of 2.0 mg/L). Nocardia-foam control measures have performed successfully. Ammonia and nitrate analyzers are being added to further optimize performance. The sale of nitrogen credits can offset nearly half of plant operating costs.
American Society of Civil Engineers eBooks, Jun 30, 2004
This paper provides an overview of the impact of global wanning concerns on wastewater treatment ... more This paper provides an overview of the impact of global wanning concerns on wastewater treatment plant design and operation. The issues surrounding global wanning concerns are discussed, along with the linkage between global warming and greenhouse gas emissions. US greenhouse gas emission inventories are reviewed, along with the role of wastewater treatment plants in reducing such emissions. It is found that process related emissions from wastewater treatment plants are less than 1% of total greenhouse gas emissions. Limited flexibility exists to reduce process-related emissions. One of the principal options is to minimize CH 4 emissions at the expense of CO 2 emissions by stabilizing biodegradable organic matter aerobically rather than anaerobically, or by capturing and combusting any CH 4 produced. The global warming potential of CH 4 is 21 times higher than that of CO 2 . Principal options for reducing greenhouse gas emissions involve selection of biosolids reuse options and energy consumption measures. Landfilling of waste biosolids should be avoided as this leads to CH 4 emissions. Agricultural reuse can reduce greenhouse gas emissions if land management practices increase soil organic carbon content and/or if crops are grown that can be used to produce renewable fuels (such as ethanol). Greenhouse gas emissions can also be reduced by energy conservation measures that reduce the use of fossil fuels, or the consumption of energy produced from them. Greenhouse gas emissions may be considered during the evaluation of alternatives for upgrading wastewater treatment plants, or as part of an overall emissions inventory.
Proceedings of the Water Environment Federation, 2000
Abstract: The phenomenon of nitrogen and phosphorus removal in aerated biological reactors where ... more Abstract: The phenomenon of nitrogen and phosphorus removal in aerated biological reactors where no formal anoxic or anaerobic zones are present is referred to as simultaneous biological nutrient removal (SBNR). One possible mechanism for SBNR is ...
A demonstrated approach to design the, socalled, medium-bubble air diffusion oxygen transfer syst... more A demonstrated approach to design the, socalled, medium-bubble air diffusion oxygen transfer system for moving bed biofilm reactor (MBBR) and integrated fixed film activated sludge (IFAS) processes is described. Operational fullscale biological water resource recovery systems treating municipal sewage, designed using this methodology, provide reliable service. Further improvement is possible, however, as knowledge gaps are filled and results in more rationally-based system designs. Pilot-scale testing demonstrates significant enhancement of oxygen transfer capacity from the presence of media. Establishment of the relationship in full-scale systems between diffuser submergence, aeration rate, and biofilm carrier fill fraction will enhance MBBR and IFAS aerobic process design, cost, and performance. Limited testing of full-scale systems prevents computation of alpha values and can be addressed by further full-scale testing under actual operating conditions. Control of MBBR and IFAS aerobic zone oxygen transfer systems can be optimized by recognizing that varying residual dissolved oxygen concentrations are needed, depending on operating conditions. Further application of oxygen transfer control approaches used in activated sludge systems, such as ammonia-based oxygen transfer system control, further improves MBBR and IFAS system energy efficiency. Water Environ. Res., 90, 615 (2018).
Proceedings of the Water Environment Federation, 2000
Simultaneous biological nutrient removal (SBNR) is the occurrence of significant biological nutri... more Simultaneous biological nutrient removal (SBNR) is the occurrence of significant biological nutrient removal in biological wastewater treatment systems where defined anaerobic and anoxic zones do not exist. There is growing evidence that significant SBNR can occur in many systems, ...
The accuracy of a biofilm reactor model depends on the extent to which physical system conditions... more The accuracy of a biofilm reactor model depends on the extent to which physical system conditions (particularly bulk-liquid hydrodynamics and their influence on biofilm dynamics) deviate from the ideal conditions upon which the model is based. It follows that an improved capacity to model a biofilm reactor does not necessarily rely on an improved biofilm model, but does rely on an improved mathematical description of the biofilm reactor and its components. Existing biofilm reactor models typically include a one-dimensional biofilm model, a process (biokinetic and stoichiometric) model, and a continuous flow stirred tank reactor (CFSTR) mass balance that [when organizing CFSTRs in series] creates a pseudo two-dimensional (2-D) model of bulk-liquid hydrodynamics approaching plug flow. In such a biofilm reactor model, the user-defined biofilm area is specified for each CFSTR; thereby, X carrier does not exit the boundaries of the CFSTR to which they are assigned or exchange boundaries with other CFSTRs in the series. The error introduced by this pseudo 2-D biofilm reactor modeling approach may adversely affect model results and limit model-user capacity to accurately calibrate a model. This paper presents a new sub-model that describes the migration of X carrier and associated biofilms, and evaluates the impact that X carrier migration and axial dispersion has on simulated system performance. Relevance of the new biofilm reactor model to engineering situations is discussed by applying it to known biofilm reactor types and operational conditions.
ABSTRACT The phosphorus removal capabilities of the Virginia Initiative Plant (VIP) process, a hi... more ABSTRACT The phosphorus removal capabilities of the Virginia Initiative Plant (VIP) process, a high-rate biological nutrient removal (BNR) process, are presented and compared to the high-rate A2/0 and the low-rate University of Capetown (UCT) processes. The results indicate superior phosphorus removal capability for the VIP process compared to the A2/0 and UCT processes. In general, VIP process phosphorus removal was maximized by operation at the lowest possible total process mean cell residence time (MCRT) and with an aerobic hydraulic residence time (HRT) not exceeding 4 hours. A total process MCRT of 5 days provided acceptable nitrogen removal and excellent phosphorus removal for wastewater temperatures of 20°C or above, while a total process MCRT of 20 days would be required at a temperature of 12°C. Operation of the VIP process at an aerobic HRT greater than 4 hours apparently resulted in oxidation of stored organic matter that adversely affected phosphorus uptake kinetics. Data analysis suggested that the VIP process could have been operated at an anaerobic HRT as short as 20 minutes. Superior phosphorus removal performance was observed for the VIP process compared to the A2/0 process when the BOD5/TPO4 ratio of the wastewater was significantly less than 20.
Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phospho... more Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phosphorus in excess of that required for biomass synthesis in a biological wastewater treatment system without defined anaerobic or anoxic zones. Evidence is growing that significant SBNR can occur in many systems, including the aerobic zone of systems already configured for biological nutrient removal. Although SBNR systems offer several potential advantages, they cannot be fully realized until the mechanisms responsible for SBNR are better understood. Consequently, a research program was initiated with the basic hypothesis that three mechanisms might be responsible for SBNR: the reactor macroenvironment, the floc microenvironment, and novel microorganisms. Previously, the nutrient removal capabilities of seven full‐scale, staged, closed‐loop bioreactors known as Orbal oxidation ditches were evaluated. Chemical analysis and microbiological observations suggested that SBNR occurred in these systems. Three of these plants were further examined in this research to evaluate the importance of novel microorganisms, especially for nitrogen removal. A screening tool was developed to determine the relative significance of the activities of microorganisms capable of autotrophic denitrification and heterotrophic nitrification‐aerobic denitrification in biological nutrient removal systems. The results indicated that novel microorganisms were not substantial contributors to SBNR in the plants studied. Phosphorus metabolism (anaerobic release, aerobic uptake) was also tested in one of the plants. Activity within the mixed liquor that was consistent with current theories for phosphorus‐accumulating organisms (PAOs) was observed. Along with other observations, this suggests the presence of PAOs in the facilities studied.
to the short batch test period provided (<12 hrs) which would not allow a population shift and fu... more to the short batch test period provided (<12 hrs) which would not allow a population shift and further justified with the electron microscopy results. The results also indicate that glycogen serves not only as source of reducing power for PHA production but also serves as an alternative energy source when the poly-P pool of the PAOs is depleted. Slow generation of ATP via glycolytic pathway at 5 o C cannot satisfy energy requirements of EBPR cells to complete several cell functions including acetate uptake and PHA storage. However, the glycolytic pathway is efficiently operable at warm temperatures (>20 o C). The reduced performance of enhanced EBPR facilities operated at warm temperature may not be a result of GAO proliferation; instead it may be related the efficient use of the glycolytic pathway by PAOs which results in more glycogen storage and less P uptake, thereby reducing the phosphorus removal performance of the facility.
ABSTRACT Modelling concepts: HFO precipitation, aging, P adsorption Validation with experiments i... more ABSTRACT Modelling concepts: HFO precipitation, aging, P adsorption Validation with experiments in tap water (Szabo et al., 2008) Influence of mixing Influence of HFO aging and time Low P effluent requirement chemical dosing Objective: Ensuring compliant effluent phosphorus concentrations, saving chemicals and limiting chemical sludge production Method: development of a model able to optimize multi-point dosage optimize temporal dosage predict interaction of bio-P and chemP predict alkalinity loss Background: Iron dosage leads to rapid hydrous ferric oxide (HFO, close to 2-line ferrihydrite) precipitation. Phosphorus is removed mainly by: adsorption of phosphate onto HFO co-precipitation of phosphate into HFO flocs (Smith et al., 2008)
One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofil... more One-dimensional (1-D) biofilm models have been demonstrated reliable for specific types of biofilm reactor design. Limitations using mechanistic biofilm models for engineering design do not rely on improved biofilm models, but rely on improved biofilm reactor models. This is important when considering that biofilm reactors containing submerged, free-moving biofilm carriers are the most widely applied biofilm system(s) for municipal wastewater treatment. This paper presents a new biofilm reactor model that considers the impact of submerged free-moving biofilm carrier (Xcarrier) movement on system performance. The model accounts for a hydrodynamic condition characterized as plug flow with back mixing (to model axial dispersion). The relevance of this new biofilm reactor model to engineering situations is evaluated by applying it to relevant scenarios and comparing model results.
Based on the International Water Association's (London) Activated Sludge Model No. 2 (ASM2), ... more Based on the International Water Association's (London) Activated Sludge Model No. 2 (ASM2), biochemistry rate expressions for general heterotrophs and phosphorus‐accumulating organisms (PAOs) were introduced to a previously developed, three‐dimensional computational fluid dynamics (CFD) activated sludge model that characterized the mixing pattern within the outer channel of a full‐scale, closed‐loop bioreactor. Using acetate as the sole carbon and energy source, CFD simulations for general heterotrophs or PAOs individually agreed well with those of ASM2 for a chemostat with the same operating conditions. Competition between and selection of heterotrophs and PAOs was verified using conventional completely mixed and tanks‐in‐series models. Then, competition was studied in the CFD model. These results demonstrated that PAOs and heterotrophs can theoretically coexist in a single bioreactor when the oxygen input is appropriate to allow sufficient low‐dissolved‐oxygen zones to develop.
Proceedings of the Water Environment Federation, 2008
1 Department of Chemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 2 Depar... more 1 Department of Chemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 2 Department of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 3 University of Technology and Economics, 1111 Budapest, ...
Proceedings of the Water Environment Federation, 2013
A dynamic physico-chemical model for chemical phosphorus removal in wastewater is presented as a ... more A dynamic physico-chemical model for chemical phosphorus removal in wastewater is presented as a tool to optimize chemical dosing simultaneously while ensuring compliant effluent phosphorus concentration. This new model predicts the kinetic and stoichiometric variable processes of precipitation of hydrous ferric oxides (HFO), phosphates adsorption and co-precipitation. It is combined with chemical equilibrium and physical precipitation reactions in order to model observed bulk dynamics in terms of pH. The model is calibrated and validated based on previous studies and experimental data from Smith et al. (2008) and Szabo et al. (2008) as a first step for full-plant implementation. The simulation results show that the structure of the model describes adequately the mechanisms of adsorption and co-precipitation of phosphate species onto HFO and that the model is robust under various experimental conditions.
Proceedings of the Water Environment Federation, 2007
Beginning in the early 1980's, the waters of Western Long Island Sound showed significant degrada... more Beginning in the early 1980's, the waters of Western Long Island Sound showed significant degradation and low dissolved oxygen (hypoxia) caused primarily by nitrogen enrichment from runoff, atmospheric deposition, and sewage plant discharges. Located on the Western reach of long Island Sound near New York City, the Stamford, CT, Water Pollution Control Authority (WPCA) was the first municipality in CT to begin experimenting with nitrogen removal in the early 1990s and conducted a study funded by the U.S. Environmental Protection Agency (EPA) to demonstrate new nitrogen removal technology. This project was followed in the late 90's by plant improvements to further enhance nitrogen removal (50 to 60% nitrogen removal). The Stamford WPCA recently completed and commissioned a $105M nitrogen upgrade and expansion to 90,840 m 3 /day (24 mgd). About $50M was associated with nitrogen removal processes. Designed to achieve nitrogen removal on the order of 80 to 90% to levels of 4 mg/L Total nitrogen (TN) or less, the upgraded plant has been operating in the high level nitrogen removal mode since the spring of 2006. Treatment consists of preliminary and primary treatment followed by suspended growth biological nitrogen removal (BNR) with biological reactors using pre-and post-anoxic zones (methanol fed to post-anoxic zone), ultraviolet (UV) disinfection, and discharge to the Sound. Solids handling includes thickening of primary and WAS, dewatering and landfilling. Construction of a sludge dryer is ongoing and is expected to be completed in late 2007. Unique treatment challenges for this project included cold water (12 o C), a history of severe foaming, and high levels of refractory nitrogen. Operating at 68,200 m 3 /day (18 mgd), the plant began achieving very low effluent TN (3-4 mg/L) in May of 2006 when final construction and equipment related issues were resolved and methanol addition to the secondary anoxic zone was begun. Although the plant achieves complete nitrification and nitrate removal to less than 1.0 mg/L, effluent refractory organic nitrogen has been high relative to other municipal POTWs (organic nitrogen of 3.8 mg/L in May, with a soluble component of 2.0 mg/L). Nocardia-foam control measures have performed successfully. Ammonia and nitrate analyzers are being added to further optimize performance. The sale of nitrogen credits can offset nearly half of plant operating costs.
American Society of Civil Engineers eBooks, Jun 30, 2004
This paper provides an overview of the impact of global wanning concerns on wastewater treatment ... more This paper provides an overview of the impact of global wanning concerns on wastewater treatment plant design and operation. The issues surrounding global wanning concerns are discussed, along with the linkage between global warming and greenhouse gas emissions. US greenhouse gas emission inventories are reviewed, along with the role of wastewater treatment plants in reducing such emissions. It is found that process related emissions from wastewater treatment plants are less than 1% of total greenhouse gas emissions. Limited flexibility exists to reduce process-related emissions. One of the principal options is to minimize CH 4 emissions at the expense of CO 2 emissions by stabilizing biodegradable organic matter aerobically rather than anaerobically, or by capturing and combusting any CH 4 produced. The global warming potential of CH 4 is 21 times higher than that of CO 2 . Principal options for reducing greenhouse gas emissions involve selection of biosolids reuse options and energy consumption measures. Landfilling of waste biosolids should be avoided as this leads to CH 4 emissions. Agricultural reuse can reduce greenhouse gas emissions if land management practices increase soil organic carbon content and/or if crops are grown that can be used to produce renewable fuels (such as ethanol). Greenhouse gas emissions can also be reduced by energy conservation measures that reduce the use of fossil fuels, or the consumption of energy produced from them. Greenhouse gas emissions may be considered during the evaluation of alternatives for upgrading wastewater treatment plants, or as part of an overall emissions inventory.
Proceedings of the Water Environment Federation, 2000
Abstract: The phenomenon of nitrogen and phosphorus removal in aerated biological reactors where ... more Abstract: The phenomenon of nitrogen and phosphorus removal in aerated biological reactors where no formal anoxic or anaerobic zones are present is referred to as simultaneous biological nutrient removal (SBNR). One possible mechanism for SBNR is ...
A demonstrated approach to design the, socalled, medium-bubble air diffusion oxygen transfer syst... more A demonstrated approach to design the, socalled, medium-bubble air diffusion oxygen transfer system for moving bed biofilm reactor (MBBR) and integrated fixed film activated sludge (IFAS) processes is described. Operational fullscale biological water resource recovery systems treating municipal sewage, designed using this methodology, provide reliable service. Further improvement is possible, however, as knowledge gaps are filled and results in more rationally-based system designs. Pilot-scale testing demonstrates significant enhancement of oxygen transfer capacity from the presence of media. Establishment of the relationship in full-scale systems between diffuser submergence, aeration rate, and biofilm carrier fill fraction will enhance MBBR and IFAS aerobic process design, cost, and performance. Limited testing of full-scale systems prevents computation of alpha values and can be addressed by further full-scale testing under actual operating conditions. Control of MBBR and IFAS aerobic zone oxygen transfer systems can be optimized by recognizing that varying residual dissolved oxygen concentrations are needed, depending on operating conditions. Further application of oxygen transfer control approaches used in activated sludge systems, such as ammonia-based oxygen transfer system control, further improves MBBR and IFAS system energy efficiency. Water Environ. Res., 90, 615 (2018).
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