Journal American Water Works Association, Oct 1, 2020
Having recently published an article in AWWA Water Science, Tarrah Henrie answered a few question... more Having recently published an article in AWWA Water Science, Tarrah Henrie answered a few questions from its editor-in-chief Kenneth L. Mercer about the research.
The best available technologies for hexavalent chromium [Cr(VI)] treatment can be cost prohibitiv... more The best available technologies for hexavalent chromium [Cr(VI)] treatment can be cost prohibitive and operationally complex. Direct stannous [Sn(II)] chloride application to reduce Cr(VI) to trivalent chromium is an alternative treatment approach that could substantially decrease treatment costs. A full-scale demonstration was conducted at the Coachella Valley Water District to investigate the ability of Sn(II) to reduce Cr(VI) in a chlorinated groundwater system. An average Sn(II) dose of 0.5 mg-Sn/L, which corresponds to~7.3 times the stoichiometric dose ratio for Cr(VI) reduction, was able to maintain Cr(VI) at <10 μg/L throughout the distribution system over a 30-day period. Tin (Sn) and chromium (Cr) concentrations decreased with increasing distance from stannous feed locations, suggesting accumulation in the distribution system. Distribution system pipescale analysis after the demonstration found the presence of Sn and Cr in pipe scales; however, minimal Sn and Cr release was observed during main flushing at the end of the demonstration.
Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being c... more Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench-and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs. When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous-and ferrousbased reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 mg/L chromium breakthrough with 7 resins varied by as much as a factor of 2 and correlated (R 2 ¼ 0.84) with resin total exchange capacities. Spent brine reuse, segmented regeneration (an optimized brine reuse method), ferrous reduction, and nanofiltration of spent brine were estimated to decrease O&M costs by 30, 70, 63, and 61%, respectively. Selection of high performing resins was the most simple way to decrease O&M costs (up to 70% savings). The sum of nitrate and sulfate raw water equivalent concentrations was found to be the principal water quality parameter that influenced the performance of 4 resins in 7 different groundwaters because nitrate and sulfate concentrations were orders of magnitude greater than chromium concentrations. Resins with higher chromium capacities eluted more co-contaminants including arsenic, selenium, uranium, and vanadium because they likely had higher co-contaminant capacities. Co-contaminant elution was found to be complex because associations can form between regenerant and co-eluting anions. Sodium chloride was the most efficient regenerant, though other regenerants provided benefits such as enhanced uranium elution most likely by complexing with uranium to inhibit its precipitation. Nitrate peaking was found to be limited even when reusing untreated and nanofiltration treated spent brine.
Corrosion of piping and solder can be a primary source of lead contamination in drinking water. T... more Corrosion of piping and solder can be a primary source of lead contamination in drinking water. To minimize the problem, water utilities implement a variety of corrosion control treatments, including pH and alkalinity adjustment, corrosion inhibitors, and other approaches.
Affordability is critical in drinking water treatment selection, requiring consideration of both ... more Affordability is critical in drinking water treatment selection, requiring consideration of both capital and operations and maintenance (O&M) costs. With ongoing O&M costs as a potential limiting factor in the economic sustainability of treatment, recent work in California explores a new approach using consolidated management of multiple water systems to reduce O&M costs. In the context of drinking water treatment for nitrate removal, affordability of treatment with and without consolidated management was investigated for three small systems in the Central Valley. Findings from initial cost estimates suggest that consolidated management of nitrate treatment has the potential to be more affordable than the conventional approach; estimated total annualized costs were reduced by as much as 44%, primarily as a result of anticipated O&M savings on disposal and labor costs. This assessment also highlights the practical application of various affordability metrics, including consideration of socioeconomic indicators, cost of living, nondiscretionary expenditures, affordability ratios, and affordability thresholds.
Having recently published an article in AWWA Water Science, Natalie Hull answered a few questions... more Having recently published an article in AWWA Water Science, Natalie Hull answered a few questions from its editor-in-chief Kenneth L. Mercer about the research.
Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being c... more Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench- and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs. When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous- and ferrous-based reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 μg/L chromium breakthrough with 7 resins varied by as much as a...
Journal American Water Works Association, Oct 1, 2020
Having recently published an article in AWWA Water Science, Tarrah Henrie answered a few question... more Having recently published an article in AWWA Water Science, Tarrah Henrie answered a few questions from its editor-in-chief Kenneth L. Mercer about the research.
The best available technologies for hexavalent chromium [Cr(VI)] treatment can be cost prohibitiv... more The best available technologies for hexavalent chromium [Cr(VI)] treatment can be cost prohibitive and operationally complex. Direct stannous [Sn(II)] chloride application to reduce Cr(VI) to trivalent chromium is an alternative treatment approach that could substantially decrease treatment costs. A full-scale demonstration was conducted at the Coachella Valley Water District to investigate the ability of Sn(II) to reduce Cr(VI) in a chlorinated groundwater system. An average Sn(II) dose of 0.5 mg-Sn/L, which corresponds to~7.3 times the stoichiometric dose ratio for Cr(VI) reduction, was able to maintain Cr(VI) at <10 μg/L throughout the distribution system over a 30-day period. Tin (Sn) and chromium (Cr) concentrations decreased with increasing distance from stannous feed locations, suggesting accumulation in the distribution system. Distribution system pipescale analysis after the demonstration found the presence of Sn and Cr in pipe scales; however, minimal Sn and Cr release was observed during main flushing at the end of the demonstration.
Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being c... more Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench-and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs. When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous-and ferrousbased reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 mg/L chromium breakthrough with 7 resins varied by as much as a factor of 2 and correlated (R 2 ¼ 0.84) with resin total exchange capacities. Spent brine reuse, segmented regeneration (an optimized brine reuse method), ferrous reduction, and nanofiltration of spent brine were estimated to decrease O&M costs by 30, 70, 63, and 61%, respectively. Selection of high performing resins was the most simple way to decrease O&M costs (up to 70% savings). The sum of nitrate and sulfate raw water equivalent concentrations was found to be the principal water quality parameter that influenced the performance of 4 resins in 7 different groundwaters because nitrate and sulfate concentrations were orders of magnitude greater than chromium concentrations. Resins with higher chromium capacities eluted more co-contaminants including arsenic, selenium, uranium, and vanadium because they likely had higher co-contaminant capacities. Co-contaminant elution was found to be complex because associations can form between regenerant and co-eluting anions. Sodium chloride was the most efficient regenerant, though other regenerants provided benefits such as enhanced uranium elution most likely by complexing with uranium to inhibit its precipitation. Nitrate peaking was found to be limited even when reusing untreated and nanofiltration treated spent brine.
Corrosion of piping and solder can be a primary source of lead contamination in drinking water. T... more Corrosion of piping and solder can be a primary source of lead contamination in drinking water. To minimize the problem, water utilities implement a variety of corrosion control treatments, including pH and alkalinity adjustment, corrosion inhibitors, and other approaches.
Affordability is critical in drinking water treatment selection, requiring consideration of both ... more Affordability is critical in drinking water treatment selection, requiring consideration of both capital and operations and maintenance (O&M) costs. With ongoing O&M costs as a potential limiting factor in the economic sustainability of treatment, recent work in California explores a new approach using consolidated management of multiple water systems to reduce O&M costs. In the context of drinking water treatment for nitrate removal, affordability of treatment with and without consolidated management was investigated for three small systems in the Central Valley. Findings from initial cost estimates suggest that consolidated management of nitrate treatment has the potential to be more affordable than the conventional approach; estimated total annualized costs were reduced by as much as 44%, primarily as a result of anticipated O&M savings on disposal and labor costs. This assessment also highlights the practical application of various affordability metrics, including consideration of socioeconomic indicators, cost of living, nondiscretionary expenditures, affordability ratios, and affordability thresholds.
Having recently published an article in AWWA Water Science, Natalie Hull answered a few questions... more Having recently published an article in AWWA Water Science, Natalie Hull answered a few questions from its editor-in-chief Kenneth L. Mercer about the research.
Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being c... more Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench- and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs. When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous- and ferrous-based reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 μg/L chromium breakthrough with 7 resins varied by as much as a...
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