title: Nitrate removal from three different effluents using large-scale denitrification beds

authors: Schipper, Louis A.

subjects: denitrification

abstract: Simple technologies that remove nitrate from effluents and other point discharges need to be developed to reduce pollution of receiving waters. Denitrification beds are lined containers filled with organic carbon (typically wood chip or coarse sawdust) and are a technology that is proving promising. Water containing NO₃⁻ (treated effluent or agricultural drainage) is passed through the bed and the wood chips act as an energy source for denitrifying bacteria that convert NO₃⁻ to N gases. There are few data on the efficiency of NO₃ removal in large-scale beds. We report here NO₃⁻ removal results from three large denitrification beds with volumes of 83, 294, and 1320 m³ treating dairy shed effluent, treated domestic effluent and glasshouse effluent, respectively. Nitrate was nearly completely removed from the dairy shed effluent (annual load of 31 kg N) and domestic effluent (annual load 365 kg N). In these beds, NO₃ removal, presumably by denitrification, was limited by NO₃⁻ concentration. However, the bed treating glasshouse effluent was overwhelmed by very high NO₃⁻ concentration (about 250 g N m⁻³) and high flow rates (about 150 m³ d⁻¹) but still reduced NO₃⁻ concentration to about 150 g N m⁻³. For this bed, long-term NO₃⁻  removal was between 5 and 10 g N m⁻³ of bed material when NO₃⁻  was non-limiting and was similar to rates reported for other smaller denitrification beds. As expected, organic N, ammonium and phosphorus were not removed from any of the effluents following passage through the beds. Our results suggest that denitrification beds are a relatively inexpensive system to construct and operate, and are suitable for final treatment of a range of NO₃⁻-laden effluents.

text: Nitrate removal from three different effluents using large-scale denitrification beds Simple technologies that remove nitrate from effluents and other point discharges need to be developed to reduce pollution of receiving waters. Denitrification beds are lined containers filled with organic carbon (typically wood chip or coarse sawdust) and are a technology that is proving promising. Water containing NO₃⁻ (treated effluent or agricultural drainage) is passed through the bed and the wood chips act as an energy source for denitrifying bacteria that convert NO₃⁻ to N gases. There are few data on the efficiency of NO₃ removal in large-scale beds. We report here NO₃⁻ removal results from three large denitrification beds with volumes of 83, 294, and 1320 m³ treating dairy shed effluent, treated domestic effluent and glasshouse effluent, respectively. Nitrate was nearly completely removed from the dairy shed effluent (annual load of 31 kg N) and domestic effluent (annual load 365 kg N). In these beds, NO₃ removal, presumably by denitrification, was limited by NO₃⁻ concentration. However, the bed treating glasshouse effluent was overwhelmed by very high NO₃⁻ concentration (about 250 g N m⁻³) and high flow rates (about 150 m³ d⁻¹) but still reduced NO₃⁻ concentration to about 150 g N m⁻³. For this bed, long-term NO₃⁻  removal was between 5 and 10 g N m⁻³ of bed material when NO₃⁻  was non-limiting and was similar to rates reported for other smaller denitrification beds. As expected, organic N, ammonium and phosphorus were not removed from any of the effluents following passage through the beds. Our results suggest that denitrification beds are a relatively inexpensive system to construct and operate, and are suitable for final treatment of a range of NO₃⁻-laden effluents.

year: 2010

title: Derivation of lake mixing and stratification indices from high-resolution lake buoy data

authors: Read, Jordan S.

subjects: lake analyser

abstract: Lake Analyzer is a numerical code coupled with supporting visualization tools for determining indices of mixing and stratification that are critical to the biogeochemical cycles of lakes and reservoirs. Stability indices, including Lake Number, Wedderburn Number, Schmidt Stability, and thermocline depth are calculated according to established literature definitions and returned to the user in a time series format. The program was created for the analysis of high-frequency data collected from instrumented lake buoys, in support of the emerging field of aquatic sensor network science. Available outputs for the Lake Analyzer program are: water temperature (error-checked and/or down-sampled), wind speed (error-checked and/or down-sampled), metalimnion extent (top and bottom), thermocline depth, friction velocity, Lake Number, Wedderburn Number, Schmidt Stability, mode-1 vertical seiche period, and Brunt-Väisälä buoyancy frequency. Secondary outputs for several of these indices delineate the parent thermocline depth (seasonal thermocline) from the shallower secondary or diurnal thermocline. Lake Analyzer provides a program suite and best practices for the comparison of mixing and stratification indices in lakes across gradients of climate, hydro-physiography, and time, and enables a more detailed understanding of the resulting biogeochemical transformations at different spatial and temporal scales.

text: Derivation of lake mixing and stratification indices from high-resolution lake buoy data Lake Analyzer is a numerical code coupled with supporting visualization tools for determining indices of mixing and stratification that are critical to the biogeochemical cycles of lakes and reservoirs. Stability indices, including Lake Number, Wedderburn Number, Schmidt Stability, and thermocline depth are calculated according to established literature definitions and returned to the user in a time series format. The program was created for the analysis of high-frequency data collected from instrumented lake buoys, in support of the emerging field of aquatic sensor network science. Available outputs for the Lake Analyzer program are: water temperature (error-checked and/or down-sampled), wind speed (error-checked and/or down-sampled), metalimnion extent (top and bottom), thermocline depth, friction velocity, Lake Number, Wedderburn Number, Schmidt Stability, mode-1 vertical seiche period, and Brunt-Väisälä buoyancy frequency. Secondary outputs for several of these indices delineate the parent thermocline depth (seasonal thermocline) from the shallower secondary or diurnal thermocline. Lake Analyzer provides a program suite and best practices for the comparison of mixing and stratification indices in lakes across gradients of climate, hydro-physiography, and time, and enables a more detailed understanding of the resulting biogeochemical transformations at different spatial and temporal scales.

year: 2011

title: Grounding our collective Talanoa, Enabling open conversations

authors: Fa'avae, David Taufui Mkiato

abstract: As co-editors in this special issue of the Waikato Journal of Education (WJE), we share our talanoa thoughts and open conversations from the University of Waikato in Kirikiriroa (Hamilton), a place and space that has a special relationship with Waikato-Tainui and the Kīngitanga. We acknowledge our ties with Māori as tangata moana (people of the ocean), noting the past as well as the existing vā connections between the Kīngitanga and other Pacific peoples and leaders, including the House of Tupou, the royal family of Tonga. We are also mindful of our responsibility to honour Te Tiriti and to the honouring of tangata whenua and their mana whenua. At the same time, we embrace the ancestral connections between Māori and Pacific people through shared common heritages (Te Punga Somerville, 2012), of voyaging, wayfinding, knowledge and ako by which they settled Moananuiākea (the Hawaiian term for the Pacific Ocean) in one of “the greatest feats in human history” (Hawaii State Legislature, 2021, n.p.). We hope this volume honours those relationships and our shared whakapapa, whanaungatanga, and kaupapa.

text: Grounding our collective Talanoa, Enabling open conversations As co-editors in this special issue of the Waikato Journal of Education (WJE), we share our talanoa thoughts and open conversations from the University of Waikato in Kirikiriroa (Hamilton), a place and space that has a special relationship with Waikato-Tainui and the Kīngitanga. We acknowledge our ties with Māori as tangata moana (people of the ocean), noting the past as well as the existing vā connections between the Kīngitanga and other Pacific peoples and leaders, including the House of Tupou, the royal family of Tonga. We are also mindful of our responsibility to honour Te Tiriti and to the honouring of tangata whenua and their mana whenua. At the same time, we embrace the ancestral connections between Māori and Pacific people through shared common heritages (Te Punga Somerville, 2012), of voyaging, wayfinding, knowledge and ako by which they settled Moananuiākea (the Hawaiian term for the Pacific Ocean) in one of “the greatest feats in human history” (Hawaii State Legislature, 2021, n.p.). We hope this volume honours those relationships and our shared whakapapa, whanaungatanga, and kaupapa.

year: 2021