title: Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds

authors: Warneke, Sören

subjects: denitrification

abstract: Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO₃⁻) from point source discharges into non-reactive dinitrogen (N₂) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO₃⁻ removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m³) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO₃⁻enriched water (14.38 mg N L⁻¹and 17.15 mg N L⁻¹). After 2.5 years of incubation measurements were made of NO₃⁻–N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO₃⁻, nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N₂O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO₃⁻–N removal. Nitrate–N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m⁻³ d⁻¹ (maize cobs), and were predominantly limited by C availability and temperature (Q₁₀ = 1.2) when NO₃⁻–N outlet concentrations remained above 1 mg L⁻¹. The NO₃⁻–N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N2O emission in warmer environments. Maize cob substrate had the highest NO₃⁻–N removal rate, but adverse effects include TOC release, dissolved N₂O release and substantial carbon consumption by non-denitrifiers. Woodchips removed less than half of NO₃⁻ removed by maize cobs, but provided ideal conditions for denitrifying bacteria, and adverse effects were not observed. Therefore we recommend the combination of maize cobs and woodchips to enhance NO₃⁻ removal while minimizing adverse effects in denitrification beds.

text: Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO₃⁻) from point source discharges into non-reactive dinitrogen (N₂) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO₃⁻ removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m³) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO₃⁻enriched water (14.38 mg N L⁻¹and 17.15 mg N L⁻¹). After 2.5 years of incubation measurements were made of NO₃⁻–N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO₃⁻, nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N₂O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO₃⁻–N removal. Nitrate–N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m⁻³ d⁻¹ (maize cobs), and were predominantly limited by C availability and temperature (Q₁₀ = 1.2) when NO₃⁻–N outlet concentrations remained above 1 mg L⁻¹. The NO₃⁻–N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N2O emission in warmer environments. Maize cob substrate had the highest NO₃⁻–N removal rate, but adverse effects include TOC release, dissolved N₂O release and substantial carbon consumption by non-denitrifiers. Woodchips removed less than half of NO₃⁻ removed by maize cobs, but provided ideal conditions for denitrifying bacteria, and adverse effects were not observed. Therefore we recommend the combination of maize cobs and woodchips to enhance NO₃⁻ removal while minimizing adverse effects in denitrification beds.

year: 2011

title: Comprehensive income: The perceived usefulness of total recognised revenues and expenses in New Zealand

authors: Beale, Robert

abstract: Since 1995, the financial reports of New Zealand entities have been legally required to disclose a measure of comprehensive income known as Total Recognised Revenues and Expenses (TRRE). Financial analysts and members of the Institute of Chartered Accountants of New Zealand were surveyed between 1994 and 1996 to investigate their views on whether TRRE is useful for financial analysis, making economic decisions, and whether it is a useful addition to the financial reports. The findings provided a reasonable level of support for the view that TRRE is useful for financial analysis, such as assessing return on investment. However, there were strong reservations over whether it is useful to use TRRE as a basis for determining remuneration packages for top management, or for predicting cash flows. Overall, there was strong support for the view that TRRE provides information that assists with making economic decisions, and that it is a useful addition to the financial reports.

text: Comprehensive income: The perceived usefulness of total recognised revenues and expenses in New Zealand Since 1995, the financial reports of New Zealand entities have been legally required to disclose a measure of comprehensive income known as Total Recognised Revenues and Expenses (TRRE). Financial analysts and members of the Institute of Chartered Accountants of New Zealand were surveyed between 1994 and 1996 to investigate their views on whether TRRE is useful for financial analysis, making economic decisions, and whether it is a useful addition to the financial reports. The findings provided a reasonable level of support for the view that TRRE is useful for financial analysis, such as assessing return on investment. However, there were strong reservations over whether it is useful to use TRRE as a basis for determining remuneration packages for top management, or for predicting cash flows. Overall, there was strong support for the view that TRRE provides information that assists with making economic decisions, and that it is a useful addition to the financial reports.

year: 1999

title: The Marist missionaries' first encounters with inhabitants of the Pacific

authors: William, Jennings

subjects: missionaries

abstract: Missionaries of the French-based Society of Mary (Marists) arrived in the Pacific in the late 1830s. Reports by European travellers and missionaries had told the first Marists to expect Pacific peoples who were either cannibals or noble savages. Their encounter with recently-converted Mangarevans in the Gambier Islands led them to believe that idyllic Christian societies could be created in the South Pacific. This belief influenced the first Marists' descriptions of Pacific peoples, notably New Zealand Maori. The Marists consequently emphasised the noble savage trope and downplayed cannibalism. They also displayed a relatively tolerant attitude towards indigenous practices.

text: The Marist missionaries' first encounters with inhabitants of the Pacific Missionaries of the French-based Society of Mary (Marists) arrived in the Pacific in the late 1830s. Reports by European travellers and missionaries had told the first Marists to expect Pacific peoples who were either cannibals or noble savages. Their encounter with recently-converted Mangarevans in the Gambier Islands led them to believe that idyllic Christian societies could be created in the South Pacific. This belief influenced the first Marists' descriptions of Pacific peoples, notably New Zealand Maori. The Marists consequently emphasised the noble savage trope and downplayed cannibalism. They also displayed a relatively tolerant attitude towards indigenous practices.

year: 2013