Michael Stenstrom | University of California, Los Angeles (original) (raw)

Papers by Michael Stenstrom

Water Environment Research, 2000

This paper presented the valuable observations that when reclaimed water is microfiltered, the di... more This paper presented the valuable observations that when reclaimed water is microfiltered, the disinfection requirements of the California Wastewater Reclamation Criteria, known as Title 22, may be met with a considerably lower UV dose than the 1400 J/m recommended by the National Water Research Institute and the California Department of Health Services. Because power consumption is the largest component of the cost of UV disinfection systems, a significant reduction in the dose that a system needs to deliver may significantly improve the economics of disinfection. The authors have done the research community a service by reporting measurements that provide a preliminary indication of the reduction that may be possible when microfiltration precedes disinfection and thereby removes many microorganisms and particles that could shelter pathogens from irradiation. (Incidentally, this suggests that microfiltered water would also be easier to disinfect by other methods, including chlorination.) However, there is apparent near constancy in the observed inactivation factor at differing calculated doses in the first lamp bank of the test apparatus and a weak dependence of observed inactivation on calculated dose in the second bank, differing from the expected first-order kinetics. The authors attribute these differences to a departure from ideal hydraulic conditions in the reactor and attempt to quantify this departure by fitting the results from the second bank to a model consisting of a series of continuously stirred tank reactors (CSTRs). Because the best fit occurs for a series of seven CSTRs, they conclude that the second bank results show considerable backmixing, contrary to the conclusion of a tracer hydraulic study (Darby et al., 1993) that indicated that flow in this type of unit, a Trojan UV2000 (Trojan Technologies, Inc., London, Ontario, Canada), is a close approximation to ideal plug flow. Moreover, the authors state, without elaboration, that the way to improve the hydraulic design is to take care with “lamp configuration and distribution within the wetted area.” All of this prompts the following comments and questions. Have any specific suggestions been formulated for changing the lamp configuration and distribution within the wetted area? Are the authors familiar with the work of Blatchley and his colleagues at Purdue, as reported in a refereed journal paper (Blatchley et al., 1995, and Iranpour and Straub, 1997)? It seems that Figures 3 and 4 in this paper are particularly relevant for understanding the hydraulics in this kind of UV disinfector because these figures show that a flow with directly observed backmixing is smoothed into plug flow by passing through an array of UV lamps and that a boundary layer was present near the bottom of the channel. Also, have the authors considered the possible role of boundary layers, as described in basic fluid mechanics texts (Currie, 1974), in causing departures from ideal plug flow? The CSTRs of the authors’ model are merely mathematical fictions, providing an intuitively grasped justification for the formulas used in the model. On the other hand, boundary layers are well known to exist physically and to play an important role in many fluid systems. Have the authors had access to the report by Anderson and Tchobanoglous (1995) on a thorough hydraulic study carried out in Orange County, California, on a UV2000 system that was not perfectly level? The close approximation to plug flow observed in the Orange County study may be a counterexample to the authors’ hypothesis that the postulated backmixing may have resulted from imperfect leveling of the unit. Also, Anderson and Tchobanoglous mention that the ratio of lamp array length to lamp diameter in this system is large enough to induce a close approximation to plug flow, which is consistent with the observations by Blatchley et al. (1995). These considerations are discussed at greater length in Iranpour et al. (1998), which also explains why the hydraulics in the horizontal array in the large disinfection channel used by Blatchley et al. are similar to those in the smaller UV2000. Comparison of the authors’ original report (Jolis and Hirano, 1993) with the published paper shows that the dose estimation method was presented more clearly in the report. The authors stated there that the calculation by the single point source summation method was actually carried out by Trojan Technologies, resulting in the following formula used by the authors:

This report was printed on recycled paper. www.usc.edu/dept/geography/ESPE The Center for Sustain... more This report was printed on recycled paper. www.usc.edu/dept/geography/ESPE The Center for Sustainable Cities engages in multidisciplinary research and education on the environmental, social and economic sustainability challenges facing metropolitan regions, and contributes to the development of public policy that improves the natural and human environment of cities.

Proceedings of the Water Environment Federation, 2007

Abstract: The lack of proper wastewater treatment results in production of CO 2 and CH 4 without ... more Abstract: The lack of proper wastewater treatment results in production of CO 2 and CH 4 without the opportunity for carbon sequestration and energy recovery, with deleterious effects for global warming. Without extending wastewater treatment to all urban areas ...

Proceedings of the Water Environment Federation, 2017

World Environmental and Water Resources Congress 2020, 2020

A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (... more A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (138-mgd) high purity oxygen activated sludge plant. The plant failed this and a subsequent process water test and the failure required the development of a procedure to determine oxygen transfer capacity of the plant. The American Society of Civil Engineer's clean water oxygen transfer standard was used in conjunction with process modeling and pilot-scale alpha factor testing. Clean water test results and a dynamic process model which predicts head-space gas purity are presented.

Davis of the UCLA Water Quality Laboratory helped with pilot plant construction and data collecti... more Davis of the UCLA Water Quality Laboratory helped with pilot plant construction and data collection during parts of the study .

Environmental Pollution, 2020

Breaking of biochar during compaction of amended soil used in roadside biofilters or landfill cov... more Breaking of biochar during compaction of amended soil used in roadside biofilters or landfill cover can affect infiltration, clog amended soil, and change its pollutant removal capacity. It is unknown how the initial biochar size affects the biochar breaking, clogging potential, and contaminant removal capacity of biochar-amended soil. We compacted a mixture of coarse sand and biochar with sizes smaller than, similar to or larger than the sand and applied stormwater contaminated with E. coli in columns packed with the compacted sand-biochar mixture. Coating biochar with a dye and analyzing the dye concentration in the broken biochar particles eluted from the columns, we proved that biochar predominantly breaks under compaction by disintegration or splitting, not abrasion, and increases in biochar size decrease the likelihood of biochar breaking. We attribute this result to the effective dissipation of compaction energy through a greater number of contact points between a large biochar particle and the adjacent particles. Most of the broken biochar particles deposited in the pores, resulting in an exponential decrease in hydraulic conductivity of amended sand with an increase in suspended sediment loading. The clogging rate was higher in the columns with smaller biochar. The columns with small biochar also exhibited high E. coli removal capacity, partly because of an increase in straining by the smaller pore size created by the deposition of fine biochar particles created during compaction. These results are useful in selecting appropriate biochar size for its application in soils and roadside biofilters for water treatment.

Proceedings of the Water Environment Federation, 2013

Wastewater aeration is a highly complex and dynamic process for which site-specific analysis and ... more Wastewater aeration is a highly complex and dynamic process for which site-specific analysis and control are needed. Off-gas testing is a method that can determine the aeration process requirements and conditions in real-time, so that appropriate operational changes and control strategies can be implemented. For this research project, off-gas analyzers were installed at five wastewater treatment plants in Southern California to continuously measure standard oxygen transfer efficiency (SOTE) and off-gas flux and perform a subsequent energy analysis. The results were as expected and show that there is an inverse relationship between SOTE and offgas flux that follows a distinct diurnal pattern. The energy analysis showed that the energy usage during peak demand is amplified due to compounding factors of increased COD and volumetric wastewater load. Utilizing off-gas monitoring to determine process requirements and performance, many energy saving strategies (e.g. blower type, variable frequency drives, control strategies) that can lower peak and overall energy demand are feasible and can be implemented in a energy rebate program.

Applied Biochemistry and Biotechnology, 1995

... CJ RIVARD, *'1 J. B . RODRIGUEZ, 2 NJ NAGLE, 1 JR SELF, 2 BD KAY, 1 PN SOLTANPOUR, 2 AND... more ... CJ RIVARD, *'1 J. B . RODRIGUEZ, 2 NJ NAGLE, 1 JR SELF, 2 BD KAY, 1 PN SOLTANPOUR, 2 AND RA NIEVES ~ ... The authors thank Bert Yungen and Ian Boatwood of Pan Pacific Fisheries, Inc., for facilitating the procurement of tuna-processing wastes (sludge). ...

Water Environment Research, Sep 1, 2004

Journal of Water Pollution Control Federation, 1989

A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (... more A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (138-mgd) high purity oxygen activated sludge plant. The plant failed this and a subsequent process water test and the failure required the development of a procedure to determine oxygen transfer capacity of the plant. The American Society of Civil Engineer's clean water oxygen transfer standard was used in conjunction with process modeling and pilot-scale alpha factor testing. Clean water test results and a dynamic process model which predicts head-space gas purity are presented.

Water Environment Research, Sep 1, 2011

IWA Publishing eBooks, May 15, 2023

Chapter 9 Aeration and Mixing in the textbook Biological Wastewater Treatment: Principles, Modell... more Chapter 9 Aeration and Mixing in the textbook Biological Wastewater Treatment: Principles, Modelling and Design (Chen et al., 2020) introduces the fundamental quantities related to oxygen transfer and aeration, their dynamics in relation to the biological process dynamics, the equipment required to provide aeration, and the relation between mixing and aeration. Here we also present the energy implications of aeration and mixing. This chapter applies all of this content through examples, questions and exercises. 9.2 LEARNING OBJECTIVES After the successful completion of this chapter, the reader will be able to: • Describe the equipment for aeration and mixing and its functioning. • Size the equipment based on average and peak process conditions. • Specify the number of aeration diffusers necessary to meet the oxygen requirement of a biological process. • Quantify the mixing effectiveness in a suspended-growth process. 9.3 EXAMPLES Example 9.3.1 Aeration system design A wastewater treatment plant requires an average mass of oxygen per day RO2 = 8,640 kgO2/d. The aeration tanks are 5 m deep and the diffusers are to be installed 30 cm above the floor. The diffusers utilize 9 inch

IWA Publishing eBooks, 2018

Journal of Cleaner Production, Feb 1, 2022

Tratamiento biológico de aguas residuales: principios, modelación y diseño, 2018, ISBN 9781780409245, págs. 273-305, 2018

Water Research, 2020

The entire vascular tree of 58 lower extremities with high-grade critical limb ischemia (CLI) was... more The entire vascular tree of 58 lower extremities with high-grade critical limb ischemia (CLI) was assessed with three-station time resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography (T-MRA) and correlated with digital subtraction angiography (DSA) examinations and TransAtlantic Inter-Society Consensus II (TASC II) guidelines. Kappa (κ) statistics were utilized to evaluate the agreement of stenosis scores (5-point scale; 0 normal to 4 occlusion) based on T-MRA and DSA. With DSA as the standard, significant stenosis instances (stenosis score ≥2) among vascular segments were compared. The κ-statistics of image quality (4-point scale; 1 nondiagnostic to 4 excellent) of T-MRA and TASC II classification assessed by a radiologist and a vascular surgeon were also evaluated. Among 870 vascular segments, excellent agreement was observed between T-MRA and DSA (mean κ = 0.883) in revealing stenosis (mean stenosis score, 2.1 ± 1.3 versus 2.0 ± 1.3). T-MRA harbored overall high sensitivity (99.5%), specificity (93.6%), positive predictive value (95.4%), negative predictive value (99.6%), and accuracy (97.7%) in depicting significant stenosis. Excellent interobserver agreement (mean κ = 0.818) of superb image quality (mean score = 3.5-3.6) of T-MRA and outstanding agreement of TASC II classification of aortoiliac and femoral-popliteal lesions (κ = 0.912-0.917) between two raters further verified the clinical feasibility of T-MRA for treatment planning. * * Surgical findings was regarded as gold standard while there were discordance between T-MRA and DSA (4 DP and 2PL were not opacified on DSA but seemed patent on MRA with subsequent surgical confirmation of patency). * Stenosis scores (T-MRA versus DSA) were assessed with kappa statistics.

Water Environment Research, 2000

This paper presented the valuable observations that when reclaimed water is microfiltered, the di... more This paper presented the valuable observations that when reclaimed water is microfiltered, the disinfection requirements of the California Wastewater Reclamation Criteria, known as Title 22, may be met with a considerably lower UV dose than the 1400 J/m recommended by the National Water Research Institute and the California Department of Health Services. Because power consumption is the largest component of the cost of UV disinfection systems, a significant reduction in the dose that a system needs to deliver may significantly improve the economics of disinfection. The authors have done the research community a service by reporting measurements that provide a preliminary indication of the reduction that may be possible when microfiltration precedes disinfection and thereby removes many microorganisms and particles that could shelter pathogens from irradiation. (Incidentally, this suggests that microfiltered water would also be easier to disinfect by other methods, including chlorination.) However, there is apparent near constancy in the observed inactivation factor at differing calculated doses in the first lamp bank of the test apparatus and a weak dependence of observed inactivation on calculated dose in the second bank, differing from the expected first-order kinetics. The authors attribute these differences to a departure from ideal hydraulic conditions in the reactor and attempt to quantify this departure by fitting the results from the second bank to a model consisting of a series of continuously stirred tank reactors (CSTRs). Because the best fit occurs for a series of seven CSTRs, they conclude that the second bank results show considerable backmixing, contrary to the conclusion of a tracer hydraulic study (Darby et al., 1993) that indicated that flow in this type of unit, a Trojan UV2000 (Trojan Technologies, Inc., London, Ontario, Canada), is a close approximation to ideal plug flow. Moreover, the authors state, without elaboration, that the way to improve the hydraulic design is to take care with “lamp configuration and distribution within the wetted area.” All of this prompts the following comments and questions. Have any specific suggestions been formulated for changing the lamp configuration and distribution within the wetted area? Are the authors familiar with the work of Blatchley and his colleagues at Purdue, as reported in a refereed journal paper (Blatchley et al., 1995, and Iranpour and Straub, 1997)? It seems that Figures 3 and 4 in this paper are particularly relevant for understanding the hydraulics in this kind of UV disinfector because these figures show that a flow with directly observed backmixing is smoothed into plug flow by passing through an array of UV lamps and that a boundary layer was present near the bottom of the channel. Also, have the authors considered the possible role of boundary layers, as described in basic fluid mechanics texts (Currie, 1974), in causing departures from ideal plug flow? The CSTRs of the authors’ model are merely mathematical fictions, providing an intuitively grasped justification for the formulas used in the model. On the other hand, boundary layers are well known to exist physically and to play an important role in many fluid systems. Have the authors had access to the report by Anderson and Tchobanoglous (1995) on a thorough hydraulic study carried out in Orange County, California, on a UV2000 system that was not perfectly level? The close approximation to plug flow observed in the Orange County study may be a counterexample to the authors’ hypothesis that the postulated backmixing may have resulted from imperfect leveling of the unit. Also, Anderson and Tchobanoglous mention that the ratio of lamp array length to lamp diameter in this system is large enough to induce a close approximation to plug flow, which is consistent with the observations by Blatchley et al. (1995). These considerations are discussed at greater length in Iranpour et al. (1998), which also explains why the hydraulics in the horizontal array in the large disinfection channel used by Blatchley et al. are similar to those in the smaller UV2000. Comparison of the authors’ original report (Jolis and Hirano, 1993) with the published paper shows that the dose estimation method was presented more clearly in the report. The authors stated there that the calculation by the single point source summation method was actually carried out by Trojan Technologies, resulting in the following formula used by the authors:

This report was printed on recycled paper. www.usc.edu/dept/geography/ESPE The Center for Sustain... more This report was printed on recycled paper. www.usc.edu/dept/geography/ESPE The Center for Sustainable Cities engages in multidisciplinary research and education on the environmental, social and economic sustainability challenges facing metropolitan regions, and contributes to the development of public policy that improves the natural and human environment of cities.

Proceedings of the Water Environment Federation, 2007

Abstract: The lack of proper wastewater treatment results in production of CO 2 and CH 4 without ... more Abstract: The lack of proper wastewater treatment results in production of CO 2 and CH 4 without the opportunity for carbon sequestration and energy recovery, with deleterious effects for global warming. Without extending wastewater treatment to all urban areas ...

Proceedings of the Water Environment Federation, 2017

World Environmental and Water Resources Congress 2020, 2020

A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (... more A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (138-mgd) high purity oxygen activated sludge plant. The plant failed this and a subsequent process water test and the failure required the development of a procedure to determine oxygen transfer capacity of the plant. The American Society of Civil Engineer's clean water oxygen transfer standard was used in conjunction with process modeling and pilot-scale alpha factor testing. Clean water test results and a dynamic process model which predicts head-space gas purity are presented.

Davis of the UCLA Water Quality Laboratory helped with pilot plant construction and data collecti... more Davis of the UCLA Water Quality Laboratory helped with pilot plant construction and data collection during parts of the study .

Environmental Pollution, 2020

Breaking of biochar during compaction of amended soil used in roadside biofilters or landfill cov... more Breaking of biochar during compaction of amended soil used in roadside biofilters or landfill cover can affect infiltration, clog amended soil, and change its pollutant removal capacity. It is unknown how the initial biochar size affects the biochar breaking, clogging potential, and contaminant removal capacity of biochar-amended soil. We compacted a mixture of coarse sand and biochar with sizes smaller than, similar to or larger than the sand and applied stormwater contaminated with E. coli in columns packed with the compacted sand-biochar mixture. Coating biochar with a dye and analyzing the dye concentration in the broken biochar particles eluted from the columns, we proved that biochar predominantly breaks under compaction by disintegration or splitting, not abrasion, and increases in biochar size decrease the likelihood of biochar breaking. We attribute this result to the effective dissipation of compaction energy through a greater number of contact points between a large biochar particle and the adjacent particles. Most of the broken biochar particles deposited in the pores, resulting in an exponential decrease in hydraulic conductivity of amended sand with an increase in suspended sediment loading. The clogging rate was higher in the columns with smaller biochar. The columns with small biochar also exhibited high E. coli removal capacity, partly because of an increase in straining by the smaller pore size created by the deposition of fine biochar particles created during compaction. These results are useful in selecting appropriate biochar size for its application in soils and roadside biofilters for water treatment.

Proceedings of the Water Environment Federation, 2013

Wastewater aeration is a highly complex and dynamic process for which site-specific analysis and ... more Wastewater aeration is a highly complex and dynamic process for which site-specific analysis and control are needed. Off-gas testing is a method that can determine the aeration process requirements and conditions in real-time, so that appropriate operational changes and control strategies can be implemented. For this research project, off-gas analyzers were installed at five wastewater treatment plants in Southern California to continuously measure standard oxygen transfer efficiency (SOTE) and off-gas flux and perform a subsequent energy analysis. The results were as expected and show that there is an inverse relationship between SOTE and offgas flux that follows a distinct diurnal pattern. The energy analysis showed that the energy usage during peak demand is amplified due to compounding factors of increased COD and volumetric wastewater load. Utilizing off-gas monitoring to determine process requirements and performance, many energy saving strategies (e.g. blower type, variable frequency drives, control strategies) that can lower peak and overall energy demand are feasible and can be implemented in a energy rebate program.

Applied Biochemistry and Biotechnology, 1995

... CJ RIVARD, *'1 J. B . RODRIGUEZ, 2 NJ NAGLE, 1 JR SELF, 2 BD KAY, 1 PN SOLTANPOUR, 2 AND... more ... CJ RIVARD, *'1 J. B . RODRIGUEZ, 2 NJ NAGLE, 1 JR SELF, 2 BD KAY, 1 PN SOLTANPOUR, 2 AND RA NIEVES ~ ... The authors thank Bert Yungen and Ian Boatwood of Pan Pacific Fisheries, Inc., for facilitating the procurement of tuna-processing wastes (sludge). ...

Water Environment Research, Sep 1, 2004

Journal of Water Pollution Control Federation, 1989

A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (... more A process-water, oxygen transfer compliance test was performed in November, 1983 on a 6.0-m 3/S (138-mgd) high purity oxygen activated sludge plant. The plant failed this and a subsequent process water test and the failure required the development of a procedure to determine oxygen transfer capacity of the plant. The American Society of Civil Engineer's clean water oxygen transfer standard was used in conjunction with process modeling and pilot-scale alpha factor testing. Clean water test results and a dynamic process model which predicts head-space gas purity are presented.

Water Environment Research, Sep 1, 2011

IWA Publishing eBooks, May 15, 2023

Chapter 9 Aeration and Mixing in the textbook Biological Wastewater Treatment: Principles, Modell... more Chapter 9 Aeration and Mixing in the textbook Biological Wastewater Treatment: Principles, Modelling and Design (Chen et al., 2020) introduces the fundamental quantities related to oxygen transfer and aeration, their dynamics in relation to the biological process dynamics, the equipment required to provide aeration, and the relation between mixing and aeration. Here we also present the energy implications of aeration and mixing. This chapter applies all of this content through examples, questions and exercises. 9.2 LEARNING OBJECTIVES After the successful completion of this chapter, the reader will be able to: • Describe the equipment for aeration and mixing and its functioning. • Size the equipment based on average and peak process conditions. • Specify the number of aeration diffusers necessary to meet the oxygen requirement of a biological process. • Quantify the mixing effectiveness in a suspended-growth process. 9.3 EXAMPLES Example 9.3.1 Aeration system design A wastewater treatment plant requires an average mass of oxygen per day RO2 = 8,640 kgO2/d. The aeration tanks are 5 m deep and the diffusers are to be installed 30 cm above the floor. The diffusers utilize 9 inch

IWA Publishing eBooks, 2018

Journal of Cleaner Production, Feb 1, 2022

Tratamiento biológico de aguas residuales: principios, modelación y diseño, 2018, ISBN 9781780409245, págs. 273-305, 2018

Water Research, 2020

The entire vascular tree of 58 lower extremities with high-grade critical limb ischemia (CLI) was... more The entire vascular tree of 58 lower extremities with high-grade critical limb ischemia (CLI) was assessed with three-station time resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography (T-MRA) and correlated with digital subtraction angiography (DSA) examinations and TransAtlantic Inter-Society Consensus II (TASC II) guidelines. Kappa (κ) statistics were utilized to evaluate the agreement of stenosis scores (5-point scale; 0 normal to 4 occlusion) based on T-MRA and DSA. With DSA as the standard, significant stenosis instances (stenosis score ≥2) among vascular segments were compared. The κ-statistics of image quality (4-point scale; 1 nondiagnostic to 4 excellent) of T-MRA and TASC II classification assessed by a radiologist and a vascular surgeon were also evaluated. Among 870 vascular segments, excellent agreement was observed between T-MRA and DSA (mean κ = 0.883) in revealing stenosis (mean stenosis score, 2.1 ± 1.3 versus 2.0 ± 1.3). T-MRA harbored overall high sensitivity (99.5%), specificity (93.6%), positive predictive value (95.4%), negative predictive value (99.6%), and accuracy (97.7%) in depicting significant stenosis. Excellent interobserver agreement (mean κ = 0.818) of superb image quality (mean score = 3.5-3.6) of T-MRA and outstanding agreement of TASC II classification of aortoiliac and femoral-popliteal lesions (κ = 0.912-0.917) between two raters further verified the clinical feasibility of T-MRA for treatment planning. * * Surgical findings was regarded as gold standard while there were discordance between T-MRA and DSA (4 DP and 2PL were not opacified on DSA but seemed patent on MRA with subsequent surgical confirmation of patency). * Stenosis scores (T-MRA versus DSA) were assessed with kappa statistics.