title: The temperature response of nitrate removal in denitrification beds

authors: Carter, Anna Marie

subjects: nitrate removal

abstract: The addition of reactive nitrogen (Nᵣ) to agricultural systems has helped crop production match human population growth. However, the addition of Nᵣ comes at a cost to environment in the form of ozone destruction, habitat degradation and biodiversity loss. Denitrification beds represent an effective method for the removal of Nᵣ from a range of wastewaters and groundwater with high nitrate (NO₃¯) concentrations. Beds are lined containers filled with a carbon (C) source to enhance denitrification: the conversion of NO₃¯ to unreactive dinitrogen (N₂). 

In general, the rate of NO₃¯ removal in denitrification beds increases with increasing temperature. However, the temperature response of NO₃¯ removal in beds is poorly constrained as other controlling factors (e.g. NO₃¯ concentration and C source availability) can obscure the effect of temperature. The objective of this study was to measure the rates of NO₃¯ removal in three denitrification beds as temperature changed seasonally. The beds were located in the North Island of New Zealand and were loaded with NO₃¯ from wastewater from a hydroponic glasshouse (Karaka), domestic effluent from a campground (Motutere) and wastewater and domestic effluent from a research station (Newstead). Water samples were collected from wells installed along the length of each bed every month and were analysed for NO₃¯ concentration by ion chromatography. Rates of NO₃¯ removal were calculated using the change in NO₃¯ concentration and the flow rate. The temperatures of the beds were also measured at each sampling. 

Nitrate concentrations declined along the length of each denitrification bed and rates of NO₃¯ removal were calculated to average 3.6, 4.3 and 1.7 g N m¯³ day¯¹ for Karaka, Motutere and Newstead, respectively. The rates of removal increased with increasing temperature at Karaka and Motutere and the Q₁₀ values (the factor by which the rate of removal increased for a 10 °C increase in temperature) were calculated as 4.1 and 2.2 for Karaka and Motutere, respectively. The rates of NO₃¯ removal and Q₁₀ values were similar to those reported in previous studies of denitrification beds both in New Zealand and overseas. However, the rate of NO₃¯ removal at Karaka was less than the rate of removal of 7.6 g N m¯³ day¯¹ previously measured at Karaka in a study 5 years ago. Similarly, the temperature response at Karaka was higher than the Q₁₀ of 2 reported in this previous study at Karaka. The decrease in removal and increase in Q₁₀ may have been due to a decline in C source quality. 

There was no evidence of an increase in the rate of NO₃¯ removal with temperature at Newstead, with a Q₁₀ calculated as 1.0. The denitrification bed had been recently installed and was in a start-up phase. It was likely that the pretreatment system, in particular the nitrifying component responsible for converting ammonium (NH4+) in the effluent to NO₃¯, was not functioning effectively which resulted in low NO₃¯ concentrations entering the bed at Newstead. Nitrate was depleted within the beds at Motutere and Newstead which indicated that the rates of removal were NO₃¯ limited and that the temperature response may not have been adequately measured. 

This study confirmed that the rate of NO₃¯ removal increased with increasing temperature in the denitrification beds at Karaka and Motutere. The temperature response of NO₃¯ removal was similar to the response reported in previous studies of denitrification beds. However, additional research is required to further constrain the range of Q₁₀ values from which future denitrification beds can be designed to optimise NO₃¯ removal. Whether Q₁₀ values increase as wood chips age and C quality decreases also requires further investigation.

text: The temperature response of nitrate removal in denitrification beds The addition of reactive nitrogen (Nᵣ) to agricultural systems has helped crop production match human population growth. However, the addition of Nᵣ comes at a cost to environment in the form of ozone destruction, habitat degradation and biodiversity loss. Denitrification beds represent an effective method for the removal of Nᵣ from a range of wastewaters and groundwater with high nitrate (NO₃¯) concentrations. Beds are lined containers filled with a carbon (C) source to enhance denitrification: the conversion of NO₃¯ to unreactive dinitrogen (N₂). 

In general, the rate of NO₃¯ removal in denitrification beds increases with increasing temperature. However, the temperature response of NO₃¯ removal in beds is poorly constrained as other controlling factors (e.g. NO₃¯ concentration and C source availability) can obscure the effect of temperature. The objective of this study was to measure the rates of NO₃¯ removal in three denitrification beds as temperature changed seasonally. The beds were located in the North Island of New Zealand and were loaded with NO₃¯ from wastewater from a hydroponic glasshouse (Karaka), domestic effluent from a campground (Motutere) and wastewater and domestic effluent from a research station (Newstead). Water samples were collected from wells installed along the length of each bed every month and were analysed for NO₃¯ concentration by ion chromatography. Rates of NO₃¯ removal were calculated using the change in NO₃¯ concentration and the flow rate. The temperatures of the beds were also measured at each sampling. 

Nitrate concentrations declined along the length of each denitrification bed and rates of NO₃¯ removal were calculated to average 3.6, 4.3 and 1.7 g N m¯³ day¯¹ for Karaka, Motutere and Newstead, respectively. The rates of removal increased with increasing temperature at Karaka and Motutere and the Q₁₀ values (the factor by which the rate of removal increased for a 10 °C increase in temperature) were calculated as 4.1 and 2.2 for Karaka and Motutere, respectively. The rates of NO₃¯ removal and Q₁₀ values were similar to those reported in previous studies of denitrification beds both in New Zealand and overseas. However, the rate of NO₃¯ removal at Karaka was less than the rate of removal of 7.6 g N m¯³ day¯¹ previously measured at Karaka in a study 5 years ago. Similarly, the temperature response at Karaka was higher than the Q₁₀ of 2 reported in this previous study at Karaka. The decrease in removal and increase in Q₁₀ may have been due to a decline in C source quality. 

There was no evidence of an increase in the rate of NO₃¯ removal with temperature at Newstead, with a Q₁₀ calculated as 1.0. The denitrification bed had been recently installed and was in a start-up phase. It was likely that the pretreatment system, in particular the nitrifying component responsible for converting ammonium (NH4+) in the effluent to NO₃¯, was not functioning effectively which resulted in low NO₃¯ concentrations entering the bed at Newstead. Nitrate was depleted within the beds at Motutere and Newstead which indicated that the rates of removal were NO₃¯ limited and that the temperature response may not have been adequately measured. 

This study confirmed that the rate of NO₃¯ removal increased with increasing temperature in the denitrification beds at Karaka and Motutere. The temperature response of NO₃¯ removal was similar to the response reported in previous studies of denitrification beds. However, additional research is required to further constrain the range of Q₁₀ values from which future denitrification beds can be designed to optimise NO₃¯ removal. Whether Q₁₀ values increase as wood chips age and C quality decreases also requires further investigation.

year: 2014

title: Global Diversity of Desert Hypolithic Cyanobacteria

authors: Lacap-Bugler, Donnabella C.

subjects: Science & Technology

abstract: Global patterns in diversity were estimated for cyanobacteria-dominated hypolithic communities that colonize ventral surfaces of quartz stones and are common in desert environments. A total of 64 hypolithic communities were recovered from deserts on every continent plus a tropical moisture sufficient location. Community diversity was estimated using a combined t-RFLP fingerprinting and high throughput sequencing approach. The t-RFLP analysis revealed desert communities were different from the single non-desert location. A striking pattern also emerged where Antarctic desert communities were clearly distinct from all other deserts. Some overlap in community similarity occurred for hot, cold and tundra deserts. A further observation was that the producer-consumer ratio displayed a significant negative correlation with growing season, such that shorter growing seasons supported communities with greater abundance of producers, and this pattern was independent of macroclimate. High-throughput sequencing of 16S rRNA and nifH genes from four representative samples validated the t-RFLP study and revealed patterns of taxonomic and putative diazotrophic diversity for desert communities from the Taklimakan Desert, Tibetan Plateau, Canadian Arctic and Antarctic. All communities were dominated by cyanobacteria and among these 21 taxa were potentially endemic to any given desert location. Some others occurred in all but the most extreme hot and polar deserts suggesting they were relatively less well adapted to environmental stress. The t-RFLP and sequencing data revealed the two most abundant cyanobacterial taxa were Phormidium in Antarctic and Tibetan deserts and Chroococcidiopsis in hot and cold deserts. The Arctic tundra displayed a more heterogenous cyanobacterial assemblage and this was attributed to the maritime-influenced sampling location. The most abundant heterotrophic taxa were ubiquitous among samples and belonged to the Acidobacteria, Actinobacteria, Bacteroidetes, and Proteobacteria. Sequencing using nitrogenase gene-specific primers revealed all putative diazotrophs were Proteobacteria of the orders Burkholderiales, Rhizobiales, and Rhodospirillales. We envisage cyanobacterial carbon input to the system is accompanied by nitrogen fixation largely from non-cyanobacterial taxa. Overall the results indicate desert hypoliths worldwide are dominated by cyanobacteria and that growing season is a useful predictor of their abundance. Differences in cyanobacterial taxa encountered may reflect their adaptation to different moisture availability regimes in polar and non-polar deserts.

text: Global Diversity of Desert Hypolithic Cyanobacteria Global patterns in diversity were estimated for cyanobacteria-dominated hypolithic communities that colonize ventral surfaces of quartz stones and are common in desert environments. A total of 64 hypolithic communities were recovered from deserts on every continent plus a tropical moisture sufficient location. Community diversity was estimated using a combined t-RFLP fingerprinting and high throughput sequencing approach. The t-RFLP analysis revealed desert communities were different from the single non-desert location. A striking pattern also emerged where Antarctic desert communities were clearly distinct from all other deserts. Some overlap in community similarity occurred for hot, cold and tundra deserts. A further observation was that the producer-consumer ratio displayed a significant negative correlation with growing season, such that shorter growing seasons supported communities with greater abundance of producers, and this pattern was independent of macroclimate. High-throughput sequencing of 16S rRNA and nifH genes from four representative samples validated the t-RFLP study and revealed patterns of taxonomic and putative diazotrophic diversity for desert communities from the Taklimakan Desert, Tibetan Plateau, Canadian Arctic and Antarctic. All communities were dominated by cyanobacteria and among these 21 taxa were potentially endemic to any given desert location. Some others occurred in all but the most extreme hot and polar deserts suggesting they were relatively less well adapted to environmental stress. The t-RFLP and sequencing data revealed the two most abundant cyanobacterial taxa were Phormidium in Antarctic and Tibetan deserts and Chroococcidiopsis in hot and cold deserts. The Arctic tundra displayed a more heterogenous cyanobacterial assemblage and this was attributed to the maritime-influenced sampling location. The most abundant heterotrophic taxa were ubiquitous among samples and belonged to the Acidobacteria, Actinobacteria, Bacteroidetes, and Proteobacteria. Sequencing using nitrogenase gene-specific primers revealed all putative diazotrophs were Proteobacteria of the orders Burkholderiales, Rhizobiales, and Rhodospirillales. We envisage cyanobacterial carbon input to the system is accompanied by nitrogen fixation largely from non-cyanobacterial taxa. Overall the results indicate desert hypoliths worldwide are dominated by cyanobacteria and that growing season is a useful predictor of their abundance. Differences in cyanobacterial taxa encountered may reflect their adaptation to different moisture availability regimes in polar and non-polar deserts.

year: 2017

title: Environmental performance outcomes and indicators for indigenous peoples: Review of literature

authors: Kennedy, Nathan

subjects: New Zealand

abstract: The literature review in this report was the starting point for developing a Māori research strand (2003-2009) within the Planning Under Co-operative Mandates (PUCM) research programme (1995-2009). An early task of the PUCM Māori team was to review the international literature on environmental outcomes and indicators for indigenous peoples. This was in order to gain an understanding of what had been written on the subject and to become familiar with approaches taken by others that might provide lessons for the development of our proposed kaupapa Māori outcomes and indicators framework and methodology, which was aimed at local government performance in Aotearoa/New Zealand. This current report is not intended to provide an exhaustive catalogue of writings on environmental performance outcomes and indicators for indigenous peoples, including Māori. Rather, some of the more obvious and important writings are noted as a ready reference for others interested in this topic. Before detailing the approach we took in carrying out the review, the key terms, outcomes and indicators, are defined.

text: Environmental performance outcomes and indicators for indigenous peoples: Review of literature The literature review in this report was the starting point for developing a Māori research strand (2003-2009) within the Planning Under Co-operative Mandates (PUCM) research programme (1995-2009). An early task of the PUCM Māori team was to review the international literature on environmental outcomes and indicators for indigenous peoples. This was in order to gain an understanding of what had been written on the subject and to become familiar with approaches taken by others that might provide lessons for the development of our proposed kaupapa Māori outcomes and indicators framework and methodology, which was aimed at local government performance in Aotearoa/New Zealand. This current report is not intended to provide an exhaustive catalogue of writings on environmental performance outcomes and indicators for indigenous peoples, including Māori. Rather, some of the more obvious and important writings are noted as a ready reference for others interested in this topic. Before detailing the approach we took in carrying out the review, the key terms, outcomes and indicators, are defined.

year: 2009-07-31