Proceedings of the Water Environment Federation, 2009
Solutions for sludge treatment and disposal produced at waste water treatment plants have to be r... more Solutions for sludge treatment and disposal produced at waste water treatment plants have to be reliable at any time and therefore need a legally, organisationally and technically sound background. The legal background normally is created at a national or even supranational (EU) level. The technical and organisational solutions can be manifold depending on the specific local situation at a treatment plant. This paper deals with the development of indicators for sludge treatment and disposal that enable the decision makers at a national level to assess sludge disposal options in regard to economic and ecological relevance. Special emphasis is given to the use of sludge in agriculture as it follows the ideas of recycling of valuable nutrients from waste water to agriculture. This investigation shows the different relevance of sludge disposal for the treatment plant operators and for agriculture in terms of economy and reliability. For treatment plants, sludge disposal represents a very important cost factor, much less for the “consumers” of waste water services. For agriculture, sludge is of low economic relevance while for a farmer using sludge as P-fertiliser it can be high. The most relevant ecological aspect of sludge disposal is with the P-content of sludge, which has a high relevance in regional material cycle while it is low for nitrogen, the value of organic matter in the sludge has only local/regional relevance. The method developed can be applied for other countries. The results for Austria (an EU member state) are calculated and discussed in detail.
ABSTRACT Concern over New Zealand's environmental quality and the long-term impacts of ag... more ABSTRACT Concern over New Zealand's environmental quality and the long-term impacts of agricultural sector activities on water quality is increasing. Lake and river water quality is declining as a result of past and current land use practices and national and regional initiatives are being developed to halt and reverse the declines. Plantation forestry is a low impact land use by comparison to other agricultural sectors, requiring less nutrient input in terms of fertiliser and causing less environmental impact on ground and surface water from nutrient leaching. A nutrient balance model has been developed to predict nutrient fluxes within plantation systems, over one or more rotations. The model is a simple mass balance model; it predicts nutrient uptake by a crop and partitions nutrients into the various pools within the soil/plant system. The model predicts when there will be surpluses or deficits in the system and consequently when there is an increased risk of nutrient transfer or a need for fertiliser application. Running different scenarios demonstrates the effect of vegetation management, harvesting intensity, or change in productivity due to climate change on the pools of nitrogen during a rotation, and the effects of multiple rotations on soil phosphorus pools. Using the model to develop various scenarios will enable the development of multiple land use scenarios, with a focus on minimising the nutrient 'footprint' or impact for a specific catchment or region. Predictions of nutrient fluxes can contribute to the development of nutrient trading models, where the value of plantation forestry as a low nutrient footprint land use may be recognised as an additional economic benefit above the value of the tree crop.
Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood densi... more Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood density) is often assumed constant by the elastic similarity model, and in determination of critical buckling height (H(crit)), few studies have tested this assumption within species. Here this assumption is tested for Pinus radiata growing across an environmental gradient, and theory is combined with data to develop a model of Young's modulus. Analyses use an extensive series of environmental plots covering the range of climatic and edaphic conditions over which P. radiata is grown in New Zealand. Reduced major axis regression was used to determine scaling exponents between log-log plots of H(crit) vs. groundline diameter (D), and E/rho vs. D. Path analysis was used to identify significant direct and indirect (through stem slenderness) edaphic and climatic influences on E. Density-specific stiffness exhibited 3-fold variation. As E/rho scaled positively with D, the exponent of 0.95 betwe...
Variation in traits within a plant species contributes to differences in soil physicochemistry an... more Variation in traits within a plant species contributes to differences in soil physicochemistry and rhizosphere microbial communities. However, how intraspecific variation in plant responses to nitrogen (N) shapes these communities remains unclear. We studied whether plant responses to organic and inorganic N forms vary among genotypes, and if these responses were associated with variation in root-associated communities. We investigated how the root microbiomes of two Pinus radiata D. Don genotypes were altered by two years of N-fertilisation in field conditions. We characterised rhizosphere bacterial and fungal communities, as well as root-associated fungal communities, of trees receiving yearly additions of NH4NO3 or L-arginine, and control trees. We also measured plant traits and rhizosphere soil physicochemical properties. Two main findings emerged: (i) N form and tree genotype affected soil physicochemical properties as well as plant measures, and these responses were associated...
Afforestation of grassland has been globally identified as being an important means for creating ... more Afforestation of grassland has been globally identified as being an important means for creating a sink for atmospheric carbon (C). However, the impact of afforestation on soil C is still poorly understood, due to the paucity of well designed long-term experiments and the lack of investigation into the response of different soil C fractions to afforestation. In addition, little is known about the origins of soil C and soil organic matter (SOM) stability after afforestation. In a retrospective study, we measured C mass in the soil light and heavy fractions in the first 10 years after afforestation of grassland with Eucalyptus nitens, Pinus radiata and Cupressus macrocarpa. The results suggest that C mass in the soil heavy fraction remained stable, but the C mass in the light fraction decreased at year 5 under three species. Soil δ13C analysis showed that the decrease in the light fraction may be due to reduced C inputs from grassland species litter and low inputs from the still young...
Large quantities of biosolids (sewage sludge), which are produced from municipal wastewater treat... more Large quantities of biosolids (sewage sludge), which are produced from municipal wastewater treatment, are ever-increasing because of the commissioning of new treatment plants and continuous upgrades of the existing facilities. Significant efforts have been made recently to develop new technologies to manage biosolids and make useful products from them. In this paper, we provide a review of the technologies in biosolids management. At present, the most common beneficial use of biosolids is agricultural land application because of inherent fertiliser values found in biosolids. Expansion of land application, however, may be limited in the future because of more stringent regulatory requirements and public concern about food chain contamination in some countries. Perceived as a green energy source, the combustion of biosolids has received renewed interest. Anaerobic digestion is generally a more effective method than incineration for energy recovery, and digested biosolids are suitable...
Proceedings of the Water Environment Federation, 2009
Solutions for sludge treatment and disposal produced at waste water treatment plants have to be r... more Solutions for sludge treatment and disposal produced at waste water treatment plants have to be reliable at any time and therefore need a legally, organisationally and technically sound background. The legal background normally is created at a national or even supranational (EU) level. The technical and organisational solutions can be manifold depending on the specific local situation at a treatment plant. This paper deals with the development of indicators for sludge treatment and disposal that enable the decision makers at a national level to assess sludge disposal options in regard to economic and ecological relevance. Special emphasis is given to the use of sludge in agriculture as it follows the ideas of recycling of valuable nutrients from waste water to agriculture. This investigation shows the different relevance of sludge disposal for the treatment plant operators and for agriculture in terms of economy and reliability. For treatment plants, sludge disposal represents a very important cost factor, much less for the “consumers” of waste water services. For agriculture, sludge is of low economic relevance while for a farmer using sludge as P-fertiliser it can be high. The most relevant ecological aspect of sludge disposal is with the P-content of sludge, which has a high relevance in regional material cycle while it is low for nitrogen, the value of organic matter in the sludge has only local/regional relevance. The method developed can be applied for other countries. The results for Austria (an EU member state) are calculated and discussed in detail.
ABSTRACT Concern over New Zealand's environmental quality and the long-term impacts of ag... more ABSTRACT Concern over New Zealand's environmental quality and the long-term impacts of agricultural sector activities on water quality is increasing. Lake and river water quality is declining as a result of past and current land use practices and national and regional initiatives are being developed to halt and reverse the declines. Plantation forestry is a low impact land use by comparison to other agricultural sectors, requiring less nutrient input in terms of fertiliser and causing less environmental impact on ground and surface water from nutrient leaching. A nutrient balance model has been developed to predict nutrient fluxes within plantation systems, over one or more rotations. The model is a simple mass balance model; it predicts nutrient uptake by a crop and partitions nutrients into the various pools within the soil/plant system. The model predicts when there will be surpluses or deficits in the system and consequently when there is an increased risk of nutrient transfer or a need for fertiliser application. Running different scenarios demonstrates the effect of vegetation management, harvesting intensity, or change in productivity due to climate change on the pools of nitrogen during a rotation, and the effects of multiple rotations on soil phosphorus pools. Using the model to develop various scenarios will enable the development of multiple land use scenarios, with a focus on minimising the nutrient 'footprint' or impact for a specific catchment or region. Predictions of nutrient fluxes can contribute to the development of nutrient trading models, where the value of plantation forestry as a low nutrient footprint land use may be recognised as an additional economic benefit above the value of the tree crop.
Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood densi... more Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood density) is often assumed constant by the elastic similarity model, and in determination of critical buckling height (H(crit)), few studies have tested this assumption within species. Here this assumption is tested for Pinus radiata growing across an environmental gradient, and theory is combined with data to develop a model of Young's modulus. Analyses use an extensive series of environmental plots covering the range of climatic and edaphic conditions over which P. radiata is grown in New Zealand. Reduced major axis regression was used to determine scaling exponents between log-log plots of H(crit) vs. groundline diameter (D), and E/rho vs. D. Path analysis was used to identify significant direct and indirect (through stem slenderness) edaphic and climatic influences on E. Density-specific stiffness exhibited 3-fold variation. As E/rho scaled positively with D, the exponent of 0.95 betwe...
Variation in traits within a plant species contributes to differences in soil physicochemistry an... more Variation in traits within a plant species contributes to differences in soil physicochemistry and rhizosphere microbial communities. However, how intraspecific variation in plant responses to nitrogen (N) shapes these communities remains unclear. We studied whether plant responses to organic and inorganic N forms vary among genotypes, and if these responses were associated with variation in root-associated communities. We investigated how the root microbiomes of two Pinus radiata D. Don genotypes were altered by two years of N-fertilisation in field conditions. We characterised rhizosphere bacterial and fungal communities, as well as root-associated fungal communities, of trees receiving yearly additions of NH4NO3 or L-arginine, and control trees. We also measured plant traits and rhizosphere soil physicochemical properties. Two main findings emerged: (i) N form and tree genotype affected soil physicochemical properties as well as plant measures, and these responses were associated...
Afforestation of grassland has been globally identified as being an important means for creating ... more Afforestation of grassland has been globally identified as being an important means for creating a sink for atmospheric carbon (C). However, the impact of afforestation on soil C is still poorly understood, due to the paucity of well designed long-term experiments and the lack of investigation into the response of different soil C fractions to afforestation. In addition, little is known about the origins of soil C and soil organic matter (SOM) stability after afforestation. In a retrospective study, we measured C mass in the soil light and heavy fractions in the first 10 years after afforestation of grassland with Eucalyptus nitens, Pinus radiata and Cupressus macrocarpa. The results suggest that C mass in the soil heavy fraction remained stable, but the C mass in the light fraction decreased at year 5 under three species. Soil δ13C analysis showed that the decrease in the light fraction may be due to reduced C inputs from grassland species litter and low inputs from the still young...
Large quantities of biosolids (sewage sludge), which are produced from municipal wastewater treat... more Large quantities of biosolids (sewage sludge), which are produced from municipal wastewater treatment, are ever-increasing because of the commissioning of new treatment plants and continuous upgrades of the existing facilities. Significant efforts have been made recently to develop new technologies to manage biosolids and make useful products from them. In this paper, we provide a review of the technologies in biosolids management. At present, the most common beneficial use of biosolids is agricultural land application because of inherent fertiliser values found in biosolids. Expansion of land application, however, may be limited in the future because of more stringent regulatory requirements and public concern about food chain contamination in some countries. Perceived as a green energy source, the combustion of biosolids has received renewed interest. Anaerobic digestion is generally a more effective method than incineration for energy recovery, and digested biosolids are suitable...
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