title: Microbial Processes and Nitrate removal in Denitrification Beds

authors: Warneke, Sören

subjects: denitrification

abstract: Abstract The anthropogenic abundance of reactive nitrogen (N) forms has increased in the last few decades, increasing food production, but also resulting in increased eutrophication, algae blooms, loss of biodiversity, and greenhouse gas (GHG) emissions, in aquatic and terrestrial ecosystems. Denitrification beds are one approach to return this reactive N back to the atmosphere. These beds are large containers filled with a carbon (C) substrate, often wood byproducts. This substrate acts as a C and energy source for denitrifiers to reduce nitrate (NO₃⁻) from point source discharges into non-reactive dinitrogen (N₂) gas. This study investigated the biological mechanisms, controlling factors and adverse effects of NO₃⁻ removal in a woodchip denitrification bed (176 m x 5 m x 1.5 m) treating glasshouse effluent, and in barrels (0.2 m³) testing alternative carbon substrates for use in denitrification beds (pine and eucalyptus woodchips, sawdust, green waste, maize cobs and wheat straw). Furthermore, different techniques for measuring denitrification rates were compared and an approach for determining reliable NO₃⁻ removal rates in denitrification beds was developed. 
The NO₃⁻-N removal rates of the large denitrification bed averaged 7.6 g N m⁻³ bed volume d⁻¹ and increased with increasing temperature (Q₁₀ = 2.1). Microbial denitrification was the main NO₃⁻ removal mechanism in the denitrification bed and was always limited by C, rather than by NO₃⁻ availability. Dissimilatory nitrate reduction to ammonium (DNRA) and anammox were likely minor processes due to low ammonia (NH₄⁺) and nitrite (NO₂⁻) concentrations throughout the bed. Sulfate (SO₄²⁻) reduction, and methanogenesis, could not compete with NO₃⁻ reduction for C due to continuously high NO₃⁻ concentrations in the bed (>37 mg N L⁻¹). Aerobic processes dominated in the first few meters of the bed and close to the surface, but dissolved oxygen (DO) concentrations decreased rapidly along the bed from the inlet and remained low throughout most of the bed. There were some adverse effects observed in the denitrification bed associated with NO₃⁻ removal. About 4.3% of NO₃⁻-N removed from the bed was released as nitrous oxide (N₂O), but methane (CH₄) emissions from the surface of the bed were very low. A total of 35.4 kg d⁻¹ of carbon dioxide (CO₂) was released from the bed, but was not considered to contribute to a net increase in CO₂ concentrations of the atmosphere as the substrate (woodchips) used in the bed would likely decayed to CO₂ if used for other purposes. A net dissolved organic carbon (DOC) loss from the outlet was not detected. Longevity of the C substrate of the denitrification bed to support denitrification was about 39 years as calculated from the total C losses (CO₂ emissions and release of dissolved CO₂ and DOC from the bed). In a barrel study of different carbon substrates, NO₃⁻ removal was predominantly limited by C availability and temperature (Q₁₀ = 1.2) when NO₃⁻-N concentrations were above 1 mg L⁻¹. All C substrates showed high numbers of denitrification genes (nitrite reductase, nirS and nirK; nitrous oxide reductase, nosZ), providing further support that microbial denitrification was responsible for NO₃⁻ removal. Substrates incubated at 27.1 °C had greater ratio of nir/nosZ genes than substrates incubated at 16.8 °C, which was possibly a partial explanation for higher N₂O production in the warmer barrels. Wheat straw released 10% of NO₃⁻-N removed as dissolved N₂O, while all other carbon substrates released on average about 1.4% of the removed NO₃⁻-N as dissolved N₂O. Methane production occurred when NO₃⁻ concentrations were below 2 mg L-1 in the barrels. Maize cobs removed about 2.5 times more NO₃⁻ than woodchips, but released total organic carbon (TOC) in the outflow and a substantial portion of C was likely consumed by non-denitrifiers. Woodchips had low adverse effects and provided ideal conditions for denitrifiers determined by the relatively high ratio of denitrification gene copies/16S rRNA copies compared to the other C substrates examined. 
Investigating different approaches to determine denitrification rates revealed that both the acetylene inhibition method and the copy number of nitrite reductase genes (nirS, nirK) were useful for comparative estimations of NO₃⁻ removal rates between different carbon substrates and temperatures. However, neither approach could be used to quantify actual rates of denitrification. The acetylene inhibition method overestimated the actual NO₃⁻ removal rate by five fold. An in situ push-pull test using enriched ¹⁵NO₃⁻ was useful for determining denitrification rates at one specific point in a denitrification bed but would require multiple testing sites to obtain an average rate of NO₃⁻ removal for the bed. Comparing the ratio of the slopes of natural abundance ¹⁵N-N₂ and ¹⁵N- NO₃⁻ along the length of the bed determined the portion of NO₃⁻ removed by microbial denitrification, but not the denitrification rate. Measurements of dissolved N₂ concentration along the length of the bed were a useful approach to determine denitrification rates. This last approach was rapid and produced relatively accurate rates of NO₃⁻ removal compared to the other approaches conducted in this study. In summary, denitrification beds are an efficient approach for removing NO₃⁻ from point source discharges, but the beds do produce some N₂O. Woodchips could be combined with maize cobs to enhance NO₃⁻ removal rates while keeping adverse effects low in denitrification beds. Measurement of N₂ concentrations along the length and water flow of the bed was the most appropriate approach to determine denitrification rates of denitrifying bioreactors, and may also be useful in other ecosystems with high NO₃⁻ concentration and even flow.

text: Microbial Processes and Nitrate removal in Denitrification Beds Abstract The anthropogenic abundance of reactive nitrogen (N) forms has increased in the last few decades, increasing food production, but also resulting in increased eutrophication, algae blooms, loss of biodiversity, and greenhouse gas (GHG) emissions, in aquatic and terrestrial ecosystems. Denitrification beds are one approach to return this reactive N back to the atmosphere. These beds are large containers filled with a carbon (C) substrate, often wood byproducts. This substrate acts as a C and energy source for denitrifiers to reduce nitrate (NO₃⁻) from point source discharges into non-reactive dinitrogen (N₂) gas. This study investigated the biological mechanisms, controlling factors and adverse effects of NO₃⁻ removal in a woodchip denitrification bed (176 m x 5 m x 1.5 m) treating glasshouse effluent, and in barrels (0.2 m³) testing alternative carbon substrates for use in denitrification beds (pine and eucalyptus woodchips, sawdust, green waste, maize cobs and wheat straw). Furthermore, different techniques for measuring denitrification rates were compared and an approach for determining reliable NO₃⁻ removal rates in denitrification beds was developed. 
The NO₃⁻-N removal rates of the large denitrification bed averaged 7.6 g N m⁻³ bed volume d⁻¹ and increased with increasing temperature (Q₁₀ = 2.1). Microbial denitrification was the main NO₃⁻ removal mechanism in the denitrification bed and was always limited by C, rather than by NO₃⁻ availability. Dissimilatory nitrate reduction to ammonium (DNRA) and anammox were likely minor processes due to low ammonia (NH₄⁺) and nitrite (NO₂⁻) concentrations throughout the bed. Sulfate (SO₄²⁻) reduction, and methanogenesis, could not compete with NO₃⁻ reduction for C due to continuously high NO₃⁻ concentrations in the bed (>37 mg N L⁻¹). Aerobic processes dominated in the first few meters of the bed and close to the surface, but dissolved oxygen (DO) concentrations decreased rapidly along the bed from the inlet and remained low throughout most of the bed. There were some adverse effects observed in the denitrification bed associated with NO₃⁻ removal. About 4.3% of NO₃⁻-N removed from the bed was released as nitrous oxide (N₂O), but methane (CH₄) emissions from the surface of the bed were very low. A total of 35.4 kg d⁻¹ of carbon dioxide (CO₂) was released from the bed, but was not considered to contribute to a net increase in CO₂ concentrations of the atmosphere as the substrate (woodchips) used in the bed would likely decayed to CO₂ if used for other purposes. A net dissolved organic carbon (DOC) loss from the outlet was not detected. Longevity of the C substrate of the denitrification bed to support denitrification was about 39 years as calculated from the total C losses (CO₂ emissions and release of dissolved CO₂ and DOC from the bed). In a barrel study of different carbon substrates, NO₃⁻ removal was predominantly limited by C availability and temperature (Q₁₀ = 1.2) when NO₃⁻-N concentrations were above 1 mg L⁻¹. All C substrates showed high numbers of denitrification genes (nitrite reductase, nirS and nirK; nitrous oxide reductase, nosZ), providing further support that microbial denitrification was responsible for NO₃⁻ removal. Substrates incubated at 27.1 °C had greater ratio of nir/nosZ genes than substrates incubated at 16.8 °C, which was possibly a partial explanation for higher N₂O production in the warmer barrels. Wheat straw released 10% of NO₃⁻-N removed as dissolved N₂O, while all other carbon substrates released on average about 1.4% of the removed NO₃⁻-N as dissolved N₂O. Methane production occurred when NO₃⁻ concentrations were below 2 mg L-1 in the barrels. Maize cobs removed about 2.5 times more NO₃⁻ than woodchips, but released total organic carbon (TOC) in the outflow and a substantial portion of C was likely consumed by non-denitrifiers. Woodchips had low adverse effects and provided ideal conditions for denitrifiers determined by the relatively high ratio of denitrification gene copies/16S rRNA copies compared to the other C substrates examined. 
Investigating different approaches to determine denitrification rates revealed that both the acetylene inhibition method and the copy number of nitrite reductase genes (nirS, nirK) were useful for comparative estimations of NO₃⁻ removal rates between different carbon substrates and temperatures. However, neither approach could be used to quantify actual rates of denitrification. The acetylene inhibition method overestimated the actual NO₃⁻ removal rate by five fold. An in situ push-pull test using enriched ¹⁵NO₃⁻ was useful for determining denitrification rates at one specific point in a denitrification bed but would require multiple testing sites to obtain an average rate of NO₃⁻ removal for the bed. Comparing the ratio of the slopes of natural abundance ¹⁵N-N₂ and ¹⁵N- NO₃⁻ along the length of the bed determined the portion of NO₃⁻ removed by microbial denitrification, but not the denitrification rate. Measurements of dissolved N₂ concentration along the length of the bed were a useful approach to determine denitrification rates. This last approach was rapid and produced relatively accurate rates of NO₃⁻ removal compared to the other approaches conducted in this study. In summary, denitrification beds are an efficient approach for removing NO₃⁻ from point source discharges, but the beds do produce some N₂O. Woodchips could be combined with maize cobs to enhance NO₃⁻ removal rates while keeping adverse effects low in denitrification beds. Measurement of N₂ concentrations along the length and water flow of the bed was the most appropriate approach to determine denitrification rates of denitrifying bioreactors, and may also be useful in other ecosystems with high NO₃⁻ concentration and even flow.

year: 2011

title: An Analysis of the Concept of 'Sustainability' in Mining Agreements in Papua New Guinea: The case of Hidden Valley/Hamata Mine

authors: Esonu, Bernard

subjects: Papua New Guinea

abstract: This thesis examined the way in which notions of economic, social and environmental sustainability were addressed in mining agreements in Papua New Guinea (PNG), through a case study of the Hidden Valley/Hamata mine. The thesis offered a discussion of indigenous and western perspectives on economic, social and environmental perspectives and practices. It then developed a model of sustainable development drawn from the scholarly literature and applied it to the case study.

The thesis explored the extent to which principles of sustainable development were incorporated into the mining agreement, as well as in negotiations amongst key actors. The study analysed key documents relating to sustainable development in PNG, including relevant national legislation and the memorandum of agreement negotiated amongst the principal actors in the Hidden Valley/Hamata mine. In addition, interviews and focus groups with the main participants in the Hidden Valley/Hamata case were also analysed. The analysis revealed significant deficiencies in the understandings of issues around sustainable development among all actors, which affected the negotiations of the mining agreement. The dominant concern for all actors, reflected in the analysis of documents and interviews, was economic. Furthermore, indigenous perspectives on sustainability were not given a hearing in the negotiations.

The study demonstrated that the major power differences between government and the mining company, on the one hand, and the landowners, on the other hand, prevented meaningful participation of the affected villagers in the negotiation process. The contradictory role of the state as both the regulator of the mining company and its partner in the mining development, along with a lack of awareness about issues of sustainable development, adds to the difficulty of implementing the provisions of the Environment Act.  The thesis concludes by developing an analytical framework for negotiating sustainable development in mining agreements through incorporating indigenous and western perspectives and practices of economic, social and environmental sustainability in development projects.

The significance of this research is that it addresses a gap in the literature on sustainable development with specific reference to mining in PNG. It offers insights into the negotiation process of mining agreements and offers a framework for negotiating sustainable development in practice in the future.

text: An Analysis of the Concept of 'Sustainability' in Mining Agreements in Papua New Guinea: The case of Hidden Valley/Hamata Mine This thesis examined the way in which notions of economic, social and environmental sustainability were addressed in mining agreements in Papua New Guinea (PNG), through a case study of the Hidden Valley/Hamata mine. The thesis offered a discussion of indigenous and western perspectives on economic, social and environmental perspectives and practices. It then developed a model of sustainable development drawn from the scholarly literature and applied it to the case study.

The thesis explored the extent to which principles of sustainable development were incorporated into the mining agreement, as well as in negotiations amongst key actors. The study analysed key documents relating to sustainable development in PNG, including relevant national legislation and the memorandum of agreement negotiated amongst the principal actors in the Hidden Valley/Hamata mine. In addition, interviews and focus groups with the main participants in the Hidden Valley/Hamata case were also analysed. The analysis revealed significant deficiencies in the understandings of issues around sustainable development among all actors, which affected the negotiations of the mining agreement. The dominant concern for all actors, reflected in the analysis of documents and interviews, was economic. Furthermore, indigenous perspectives on sustainability were not given a hearing in the negotiations.

The study demonstrated that the major power differences between government and the mining company, on the one hand, and the landowners, on the other hand, prevented meaningful participation of the affected villagers in the negotiation process. The contradictory role of the state as both the regulator of the mining company and its partner in the mining development, along with a lack of awareness about issues of sustainable development, adds to the difficulty of implementing the provisions of the Environment Act.  The thesis concludes by developing an analytical framework for negotiating sustainable development in mining agreements through incorporating indigenous and western perspectives and practices of economic, social and environmental sustainability in development projects.

The significance of this research is that it addresses a gap in the literature on sustainable development with specific reference to mining in PNG. It offers insights into the negotiation process of mining agreements and offers a framework for negotiating sustainable development in practice in the future.

year: 2009

title: Ngā tai e rere nei i waho o Mauao

authors: Ngahuia, Dixon

subjects: Waiata Māori

abstract: "I te ao o ngā tūpuna he maha ngā kaupapa o taua wā i mau ki rō waiata, e whakaata mai ana i ngā kōrero-ā-iwi, ngā taukumekume i waenganui Māori, Pākehā, i waenganui hoki i ngā Māori anō. Nā wai hoki ka puta mai ngā herenga ki waenganui i tēnā iwi, i tēnā hapū, ka whakahoahoa tēnā iwi ki tēnā, te mutunga mai ka whānau ake ngā rōpū hou hei wānanga i ngā kaupapa i manawapātia. I pērā anō hoki ngā iwi o Tauranga Moana, ka huri atu ki tēnei iwi, ki tēnā hei huarahi tautoko āwhina mai i aua kaupapa nei. Ko ngā pupurihanga o ēnei taonga tuku iho e whakaahua mai ana i ngā kaupapa i waenganui i te ao Māori i aua wā, mō te iwi, mō te tangata kotahi rānei. Mā ēnei hoki kitea atu ai tā rātou titiro ki te ao i aua wā. 

He whiringa kōrero tēnei pepa mō tētehi waiata a Ngāi-TeRangi e whakamōhio ake ana i tētehi taukumekume i waenganui i a rāua ko Ngāti Kahungunu. Ka kitea i roto i ngā kōrero ka puta ngā huarahi whakapā atu ai ki tēnā iwi, hapū i waenganui, i waho atu rānei o Ngāi-TeRangi hei āwhina mai i te pupuri mana. Arā anō hoki te whakanui i ēnei momo waiata, ōna mana me te mātauranga Māori e pupū ake ana i konei. 

The waiata of our tūpuna Māori (Māori ancestors) capture in verse many issues and topics that were of significance at the time they were composed. They provide us with snapshots of iwi histories, including accounts of battles between Māori and Pākehā and between Māori and Māori. They tell us of alliances formed and reformed between tribes and hapū and of the reasons for these alliances. We see how the alignment and realignment of kin loyalties related to the issues of the day. Tauranga Moana iwi were not immune to such activities: tribal loyalties were chameleon-like, many alliances being pursued in relation to common interests. The ‘oral mapping’ of these local narratives that we find in waiata provides an illustration of topics relevant to individuals and to iwi: personal and collective statements about the ‘order’ of their day. They provide us with an insight into our ancestors’ ‘ways of seeing the world’. Above all, they are fundamental to the illustration and preservation of Māori knowledge. 
 
This paper presents an analysis of a Ngāi-TeRangi waiata tangi (lament) which relates to activities linking the iwi in a political stance against Ngāti Kahungunu. What is demonstrated is the intricate network of iwi and hapū involvement, within and without Ngāi-TeRangi, in the quest for honour. What is also demonstrated is the importance of waiata as significant literary achievements, as oral treasures."

text: Ngā tai e rere nei i waho o Mauao "I te ao o ngā tūpuna he maha ngā kaupapa o taua wā i mau ki rō waiata, e whakaata mai ana i ngā kōrero-ā-iwi, ngā taukumekume i waenganui Māori, Pākehā, i waenganui hoki i ngā Māori anō. Nā wai hoki ka puta mai ngā herenga ki waenganui i tēnā iwi, i tēnā hapū, ka whakahoahoa tēnā iwi ki tēnā, te mutunga mai ka whānau ake ngā rōpū hou hei wānanga i ngā kaupapa i manawapātia. I pērā anō hoki ngā iwi o Tauranga Moana, ka huri atu ki tēnei iwi, ki tēnā hei huarahi tautoko āwhina mai i aua kaupapa nei. Ko ngā pupurihanga o ēnei taonga tuku iho e whakaahua mai ana i ngā kaupapa i waenganui i te ao Māori i aua wā, mō te iwi, mō te tangata kotahi rānei. Mā ēnei hoki kitea atu ai tā rātou titiro ki te ao i aua wā. 

He whiringa kōrero tēnei pepa mō tētehi waiata a Ngāi-TeRangi e whakamōhio ake ana i tētehi taukumekume i waenganui i a rāua ko Ngāti Kahungunu. Ka kitea i roto i ngā kōrero ka puta ngā huarahi whakapā atu ai ki tēnā iwi, hapū i waenganui, i waho atu rānei o Ngāi-TeRangi hei āwhina mai i te pupuri mana. Arā anō hoki te whakanui i ēnei momo waiata, ōna mana me te mātauranga Māori e pupū ake ana i konei. 

The waiata of our tūpuna Māori (Māori ancestors) capture in verse many issues and topics that were of significance at the time they were composed. They provide us with snapshots of iwi histories, including accounts of battles between Māori and Pākehā and between Māori and Māori. They tell us of alliances formed and reformed between tribes and hapū and of the reasons for these alliances. We see how the alignment and realignment of kin loyalties related to the issues of the day. Tauranga Moana iwi were not immune to such activities: tribal loyalties were chameleon-like, many alliances being pursued in relation to common interests. The ‘oral mapping’ of these local narratives that we find in waiata provides an illustration of topics relevant to individuals and to iwi: personal and collective statements about the ‘order’ of their day. They provide us with an insight into our ancestors’ ‘ways of seeing the world’. Above all, they are fundamental to the illustration and preservation of Māori knowledge. 
 
This paper presents an analysis of a Ngāi-TeRangi waiata tangi (lament) which relates to activities linking the iwi in a political stance against Ngāti Kahungunu. What is demonstrated is the intricate network of iwi and hapū involvement, within and without Ngāi-TeRangi, in the quest for honour. What is also demonstrated is the importance of waiata as significant literary achievements, as oral treasures."

year: 2002-09