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Temporal Sodium Flux In A Woodlot Soil Irrigated With Secondary Treated Effluent: The Implications For Sustainable Irrigation And Soil ManagementLucas, Steven Andrew January 2007 (has links)
This study reports results obtained and the approach taken in investigating the temporal sodium flux in a woodlot soil receiving secondary treated effluent at Branxton, NSW. Previous research has shown woodlot soils receiving secondary treated effluent undergo an increase in exchangeable sodium percentage (ESP) over time. Increased soil ESP influences micro-aggregate/soil pore stability and, particularly when subject to irrigation waters of specific low-electrolyte concentrations, results in decreased soil permeability and a subsequent need to reduce effluent application rates. Therefore, in irrigated woodlot soils it has been necessary to implement strategies to remove excess sodium from the root zone to maintain optimum permeability of the receiving soil, that is, maintaining the cation balance (as soil ESP) to promote optimum soil pore size. To maintain optimum permeability, an understanding is needed of temporal variations in the accumulation/leaching (flux) of sodium within a soil under secondary treated effluent irrigated conditions. The ability to define the sodium flux depends on the frequency of soil sampling and the ability to interpret the net loss/gain in soil sodium in relation to the applied hydraulic load over time. Past research has measured changes in soil ESP on an annual basis, or longer, making it impossible to interpret temporal sodium flux within a given year. The rate of change of soil ESP has ramifications for optimum permeability within an effluent irrigated woodlot. With respect to increasing/decreasing soil ESP, a major response of the clay particles within micro-aggregates is the deformation of conducting soil pores and reduced hydraulic conductivities. In addition, clay dispersion is governed by the soil ESP and electrolyte concentration of the infiltrating waters at the time, where dispersed clay particles may block conducting soil pores and further reduce hydraulic conductivity. Therefore, investigating the temporal sodium flux in conjunction with the temporal variation in electrolyte concentration of infiltrating waters will give greater insight into the response of effluent irrigated soils to sodium-rich waters over time. Three research aims were formed to investigate temporal sodium flux. These include: 1. To investigate trends in the dominant water balance components for a woodlot soil receiving secondary treated effluent (STE); 2. To examine temporal and spatial variation in both the water balance components and measured soil properties, particularly the sodium flux; and 3. To investigate the implications of the sodium flux on the loss of soil structure and drainage over time (dispersion events), particularly in relation to temporal changes in soil ESP and effluent SAR. Monitoring programs for water balance components and soil parameters covered the period January 2002 – October 2003. Every two months, soil samples were taken at designated sites and at different depths (10, 20, 40, 60, and 80 cm). These samples were analysed for exchangeable cations (Ca2+, Mg2+, Na+ and K+), from which the ESP values were derived. Also, this appears to be the first time that soil sampling at this frequency, which enables the temporal sodium flux to be determined, has been carried out. Column leaching experiments were also performed over the study period to illustrate the response of the woodlot soil, in terms of micro-aggregate stability, to hydraulic loads of varying SAR. Column leaching experiments also confirmed the rate of solute movement through the soil profile and the woodlot soil’s ability to bind/exchange sodium under different hydraulic loads and electrolyte concentrations. Soil extraction plate methods were used to determine wilting point and field capacity for these soils. The Sodium Adsorption Ratio (SAR), which is the solutional equivalent to soil ESP, was used to define the electrolyte concentration of the applied effluent and rainfall to the woodlot. The net loss/gain of exchangeable sodium at different depths and times was determined and compared with changes in water balance components and the measured volumetric soil water over time. The soil water surplus/deficit was recorded at a daily time-step and a cumulative approach was used to determine the long-term soil water surplus/deficit. In addition, variations in groundwater levels were monitored to observe if surplus irrigation events were reflected in temporal trends. As a result of determining the temporal variation in soil ESP, effluent and rainfall SAR, daily soil water deficit/surplus (short-term), cumulative soil water deficit/surplus (long-term) and volumetric soil moisture, temporal trends are presented. The sodium flux was then investigated by interpreting trends in the monitored data with respect to the dominant water balance components. All parameters were then used to model the potential dispersive behaviour of the receiving soil over time and depth, in relation to the volume and electrolyte concentration of the effluent and rainfall applied over time. The implications for soil structure and permeability depend on variations in soil ESP and effluent SAR. Results from this research show that soil ESP varied by as much as 24% over a four-month period and is shown to be a function of the sodium loading (from STE) and soil water surplus/deficit. On each sampling occasion, soil ESP generally increased with depth at all irrigated sites. Soil ESP at non-irrigated sites was much lower than irrigated sites, although the variability in soil ESP was much greater. Variations in SAR of the waters received by the woodlot soil (effluent and rainfall) over the study period ranged from 0.5 to 5.9. It is shown that the SAR range, coupled with variations in soil ESP, has ramifications for maintaining long-term soil structure. Soil structure at different sites within a woodlot will respond differently according to the soil ESP/effluent SAR relationship. The dispersive potential of soil at a given ESP receiving irrigation waters of known SAR was assessed in light of the relationship between soil ESP and effluent SAR. This showed the dynamic response of effluent irrigated soils to the long-term temporal variation in electrolyte concentration of rainfall/effluent. The relationship between soil ESP and effluent SAR is graphically presented as a continuum, which in turn can be used as a management tool for assessing the potential for dispersion of clay particles in a soil of known ESP and irrigated with waters of known SAR. By identifying trends in the temporal sodium flux, the optimum permeability of the receiving soil can be assessed in relation to the electrolyte concentration of the applied waters and the soil exchangeable sodium percentage (ESP). Secondary treated effluent application rates can then be corrected to prevent “dispersive” irrigation events over the long term and/or management strategies applied to remove excess sodium from the soil profile. The significance of the research is that a better understanding of the temporal dynamics of sodium in the soil profile will allow improved management of effluent irrigated woodlots, with the aim of making the practice sustainable with respect to controlling accumulating soil sodium and maintaining soil structure for future landuse. / PhD Doctorate
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Uso de água residuária com diferentes sistemas de irrigação no desenvolvimento e na qualidade microbiológica do meloeiroPeres, Milene Rodrigues [UNESP] 22 June 2004 (has links) (PDF)
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peres_mr_me_botfca.pdf: 447911 bytes, checksum: 06235bd11b664da7bc2fbecfde5fcbb1 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / O aumento da população mundial, aliado à atividade humana e ao fenômeno da urbanização, torna necessário uma disposição eficiente e ambientalmente segura das águas residuárias (esgotos). Deve-se ressaltar que os resíduos orgânicos presentes nestas águas são fontes riquíssimas de matéria orgânica e nutrientes minerais, elementos necessários à produção das culturas. O uso de esgotos tratados, principalmente de origem doméstica na irrigação de culturas, tem sido praticado em muitos países há muitos séculos. Nos países em desenvolvimento ou em processo de industrialização acelerada existe atualmente uma grande necessidade do desenvolvimento de métodos para atender à crescente demanda de água, particularmente para irrigação, e de proteger os mananciais existentes contra a poluição. Conforme esta demanda cresce, o tratamento e uso de águas residuárias vai se tornando mais importante. Em quase todos os países do Oriente Médio grandes projetos de reuso foram e continuam a ser implantados para atender a irrigação e reservar os limitados mananciais existentes para o abastecimento de água potável. Há um enorme potencial de reuso de águas residuárias na agricultura, entretanto, este uso requer estudos que orientem sua aplicação. É fundamental que se inicie o desenvolvimento de padrões e códigos de uso, visando uma atividade sustentada, ecologicamente compatível e isenta de riscos à saúde pública dos grupos de risco envolvidos. Esta dissertação teve como objetivo avaliar o uso do esgoto doméstico tratado na irrigação de melão. Foram testadas duas formas de aplicação da água de irrigação: esgoto doméstico tratado e uma fonte de água limpa, com três sistemas de irrigação (gotejamento superficial, gotejamento enterrado e sulco). Foram avaliados o desempenho agronômico e o grau de contaminação do produto agrícola... / The increase of the world population, ally to the human activity and the phenomenon of the urbanization, turns necessary an efficient disposition of wastewater (sewers). It should be emphasized that the present organic residues in wastewaters are rich sources of organic matter and nutrients minerals, necessary elements to the production of the crops. The use of treated sewers, mainly of domestic origin in the irrigation of crops, it has been practiced in many countries from many centuries. In the developing countries exists a great need of the development of methods to assist to crescent demand of water, particularly for irrigation, and of protecting the existent springs against the pollution. As this demand grows, the treatment and use of wastewater goes if turning more important. In almost all of the countries of Middle East projects have been implanted to assist the irrigation and to reserve the limited existent springs for the drinkable water supply. There is an enormous potential of wastewater use in the agriculture, however, this use requests studies to guide its application. It is fundamental that it begins the development of patterns and use codes, seeking a sustained activity, ecologically compatible and it exempts from risks to the public health of the risk groups involved. This dissertation had as objective evaluate the use of domestic wastewater in the melon irrigation. Two water qualities were evaluated: domestic wastewater and a source of clean water, with three irrigation systems (surface drip, subsurface drip and furrow). They were appraised the agronomic acting and the degree of contamination of the agricultural product, for each combination of quality of the water and adopted overhead irrigation. The results showed us that the irrigation systems didn't differ considering the melon yield. The use of wastewater didn't bring benefits for the increase of the productivity... (Complete abstract click electronic access below)
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Effect of chemical oxygen demand on the ability of some cover crops to prevent mineral accumulation in a sandy vineyard soil irrigated with augmented winery wastewaterOchse, Charles Henry January 2015 (has links)
Thesis (MTech (Agriculture))--Cape Peninsula University of Technology. / During the past years government regulations concerning winery effluent became stricter to protect the environment. Wineries are continually improving wastewater management and finding appropriate ways to reduce cellar effluent. Due to water scarcity in South Africa, it could be a huge advantage if winery effluent could be used as irrigation water for vineyards. If the industry can re-use the untreated wastewater, it will not only save a huge amount of irrigation water, but it will also be able to get rid of the vast amount of cellar effluent.
Grape production plays a major role in agriculture worldwide. The world production of grapes worldwide in 2013 was 751 MgL. South Africa is the 9th biggest wine producer in the world with 10 X 10HL of wine.
In the earlier years of wine production in South Africa, the small volumes of winery wastewater did not have a negative impact on the environment but with the increased volumes over the last years, the possibility of contamination of the soil and the environment has increased. Government decided to regulate the irrigation of cellar effluent with the National Water Act of 1998 as approved by the Department of Water Affairs (DWAF).
There are different ways to get rid of cellar effluent. One successful way is by constructed wetlands where plants are used to break down minerals which could be detrimental to the environment. This is a successful way to get rid of cellar effluent but could take up to six weeks before the mineral contents can be broken down by the plants. Another way is to use bio-reactors to break down the contents of the cellar effluent, but this is expensive.
Wastewater consists of important nutrients needed for plant growth such as macro-nutrients like N, P, K and micro-nutrients like Fe, Zn, Mn and Cu and a substantial amount of organic matter. If cellar water, just like domestic wastewater is used for irrigation the farmer can save water when he uses less fertiliser, because of the high nutrient content in the cellar effluent.
If cover crops such as oats (Avena sativa L. cv. Pallinup) in winter and pearl millet (Pennisetum glaucum (L.) R. Br.) in summer can be used to remove excess cations, as well as unwanted chemicals such as toxic metals from the soil, it may result in effluent water with a higher chemical oxygen demand (COD) level than the current legal limitations that can be used to irrigate the vineyard. The aim of this project was, therefore, to determine the ability of oat and pearl millet cover crop to remove excess minerals from the soil irrigated with augmented water at different COD levels, without a negative effect on growth and yield of the vineyard or wine quality. Field trials were carried out in a Cabernet Sauvignon/99 Richter vineyard established on a sandy soil at the Goudini Cellar near Rawsonville.
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Uso de água residuária com diferentes sistemas de irrigação no desenvolvimento e na qualidade microbiológica do meloeiro /Peres, Milene Rodrigues, 1977- January 2004 (has links)
Orientador: João Carlos Cury Saad / Banca: Raimundo Leite Cruz / Banca: Jarbas Honório de Miranda / Resumo: O aumento da população mundial, aliado à atividade humana e ao fenômeno da urbanização, torna necessário uma disposição eficiente e ambientalmente segura das águas residuárias (esgotos). Deve-se ressaltar que os resíduos orgânicos presentes nestas águas são fontes riquíssimas de matéria orgânica e nutrientes minerais, elementos necessários à produção das culturas. O uso de esgotos tratados, principalmente de origem doméstica na irrigação de culturas, tem sido praticado em muitos países há muitos séculos. Nos países em desenvolvimento ou em processo de industrialização acelerada existe atualmente uma grande necessidade do desenvolvimento de métodos para atender à crescente demanda de água, particularmente para irrigação, e de proteger os mananciais existentes contra a poluição. Conforme esta demanda cresce, o tratamento e uso de águas residuárias vai se tornando mais importante. Em quase todos os países do Oriente Médio grandes projetos de reuso foram e continuam a ser implantados para atender a irrigação e reservar os limitados mananciais existentes para o abastecimento de água potável. Há um enorme potencial de reuso de águas residuárias na agricultura, entretanto, este uso requer estudos que orientem sua aplicação. É fundamental que se inicie o desenvolvimento de padrões e códigos de uso, visando uma atividade sustentada, ecologicamente compatível e isenta de riscos à saúde pública dos grupos de risco envolvidos. Esta dissertação teve como objetivo avaliar o uso do esgoto doméstico tratado na irrigação de melão. Foram testadas duas formas de aplicação da água de irrigação: esgoto doméstico tratado e uma fonte de água limpa, com três sistemas de irrigação (gotejamento superficial, gotejamento enterrado e sulco). Foram avaliados o desempenho agronômico e o grau de contaminação do produto agrícola... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The increase of the world population, ally to the human activity and the phenomenon of the urbanization, turns necessary an efficient disposition of wastewater (sewers). It should be emphasized that the present organic residues in wastewaters are rich sources of organic matter and nutrients minerals, necessary elements to the production of the crops. The use of treated sewers, mainly of domestic origin in the irrigation of crops, it has been practiced in many countries from many centuries. In the developing countries exists a great need of the development of methods to assist to crescent demand of water, particularly for irrigation, and of protecting the existent springs against the pollution. As this demand grows, the treatment and use of wastewater goes if turning more important. In almost all of the countries of Middle East projects have been implanted to assist the irrigation and to reserve the limited existent springs for the drinkable water supply. There is an enormous potential of wastewater use in the agriculture, however, this use requests studies to guide its application. It is fundamental that it begins the development of patterns and use codes, seeking a sustained activity, ecologically compatible and it exempts from risks to the public health of the risk groups involved. This dissertation had as objective evaluate the use of domestic wastewater in the melon irrigation. Two water qualities were evaluated: domestic wastewater and a source of clean water, with three irrigation systems (surface drip, subsurface drip and furrow). They were appraised the agronomic acting and the degree of contamination of the agricultural product, for each combination of quality of the water and adopted overhead irrigation. The results showed us that the irrigation systems didn't differ considering the melon yield. The use of wastewater didn't bring benefits for the increase of the productivity... (Complete abstract click electronic access below) / Mestre
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Avaliação da qualidade microbiológica e produção de alface americana (Lactuca sativa L.) sob diferentes sistemas de irrigação, utilizando águas residuáriasAzevedo, Leonardo Pretto de [UNESP] 22 June 2004 (has links) (PDF)
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azevedo_lp_me_botfca.pdf: 665165 bytes, checksum: 451d83c7c677e62bbaf23503d1d6324a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / A crescente expansão demográfica, o aumento da demanda por água potável, a elevação dos índices de poluição, o manejo inadequado de solos e florestas, e a contaminação de rios e lençóis freáticos têm causado sérios problemas ambientais, indisponibilizando grande porcentagem da água doce existente para utilização direta. Estima-se que apenas metade da população da América Latina seja beneficiada com redes de coleta de esgoto e que 90% deste volume coletado esteja sendo despejado em algum corpo de água superficial sem tratamento prévio. Como alternativa para este problema, grande quantidade de águas residuárias tem sido utilizada na agricultura, tornando imprescindível o desenvolvimento de novas tecnologias e métodos de aplicação segura destes efluentes na irrigação de produtos para consumo humano. Visando a necessidade de desenvolver técnicas seguras de aplicação de águas residuárias na agricultura, buscou-se no presente trabalho comparar parâmetros de produção, qualidade microbiológica e acúmulo de nitrato na cultura da alface americana, submetida à irrigação com água potável e com efluente de tratamento de esgoto doméstico, nos sistemas de irrigação por gotejo (superficial e enterrado), sulcos e microaspersão. A alface foi cultivada a campo, na Fazenda Experimental Lageado, da Faculdade de Ciências Agronômicas, localizada no município de Botucatu. As irrigações foram realizadas a cada 48 horas, durante os últimos trinta dias da cultura, repondo a lâmina evapotranspirada neste período. Verificou-se neste trabalho que os maiores valores de produção foram obtidos na irrigação por gotejo superficial, com águas residuárias. Quando comparada a influência do tipo de água utilizada em cada sistema, os valores de produção obtidos também foram maiores para a irrigação com águas residuárias no gotejo superficial, gotejo enterrado... . / The demographic expansion, the demand increase by potable water, the increase on pollution rates, the unsuitable soil and forests management, and the contamination of rivers and subsurface water have caused serious environment problems, and it became unavailable a high percentage of water for direct use. Only 49% of Latin American population has a sewer net; from this number, it was estimated that 90% hasn't been treated before being thrown away in a surface water source, causing more problems. A high quantity of wastewater has been used in agriculture as an alternative to this problem, what attracts the attention to the need of more researches about the development of a new technology and secure methods to apply effluents on irrigated crops to human consume. Counting on the possibility of develop secure techniques to apply wastewater in agriculture, this work had the aim of comparing American lettuce production, microbiological quality and nitrate level, using irrigation with potable water and domestic sewer treatment effluent, under drip (surface and subsurface), furrow and sprinklers irrigation systems. Lettuce was planted in a field, on Lageado Experimental Farm, Agronomical Sciences College, São Paulo State University, in Botucatu / SP, Brazil. The irrigations were carried out each 48 hours, during the last thirty days of the crop, adding the water rates lost in this period. It was verified in this work that higher production values were obtained with wastewater applied with surface drip irrigation. When comparing the influence of the kind of water used in each system, the production values also were higher on wastewater irrigation with drip irrigation (surface and subsurface) and furrows. On microbiological quality, only the lettuce irrigated by subsurface drip irrigation and furrows showed safe contamination values to fecal coliform and Salmonella, according to... (Complete abstract, click electronic address below).
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Avaliação da qualidade microbiológica e produção de alface americana (Lactuca sativa L.) sob diferentes sistemas de irrigação, utilizando águas residuárias /Azevedo, Leonardo Pretto de, 1978- January 2004 (has links)
Orientador: João Carlos Cury Saad / Banca: Hélio Grassi Filho / Banca: Sergio Nascimento Duarte / Resumo: A crescente expansão demográfica, o aumento da demanda por água potável, a elevação dos índices de poluição, o manejo inadequado de solos e florestas, e a contaminação de rios e lençóis freáticos têm causado sérios problemas ambientais, indisponibilizando grande porcentagem da água doce existente para utilização direta. Estima-se que apenas metade da população da América Latina seja beneficiada com redes de coleta de esgoto e que 90% deste volume coletado esteja sendo despejado em algum corpo de água superficial sem tratamento prévio. Como alternativa para este problema, grande quantidade de águas residuárias tem sido utilizada na agricultura, tornando imprescindível o desenvolvimento de novas tecnologias e métodos de aplicação segura destes efluentes na irrigação de produtos para consumo humano. Visando a necessidade de desenvolver técnicas seguras de aplicação de águas residuárias na agricultura, buscou-se no presente trabalho comparar parâmetros de produção, qualidade microbiológica e acúmulo de nitrato na cultura da alface americana, submetida à irrigação com água potável e com efluente de tratamento de esgoto doméstico, nos sistemas de irrigação por gotejo (superficial e enterrado), sulcos e microaspersão. A alface foi cultivada a campo, na Fazenda Experimental Lageado, da Faculdade de Ciências Agronômicas, localizada no município de Botucatu. As irrigações foram realizadas a cada 48 horas, durante os últimos trinta dias da cultura, repondo a lâmina evapotranspirada neste período. Verificou-se neste trabalho que os maiores valores de produção foram obtidos na irrigação por gotejo superficial, com águas residuárias. Quando comparada a influência do tipo de água utilizada em cada sistema, os valores de produção obtidos também foram maiores para a irrigação com águas residuárias no gotejo superficial, gotejo enterrado... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The demographic expansion, the demand increase by potable water, the increase on pollution rates, the unsuitable soil and forests management, and the contamination of rivers and subsurface water have caused serious environment problems, and it became unavailable a high percentage of water for direct use. Only 49% of Latin American population has a sewer net; from this number, it was estimated that 90% hasn't been treated before being thrown away in a surface water source, causing more problems. A high quantity of wastewater has been used in agriculture as an alternative to this problem, what attracts the attention to the need of more researches about the development of a new technology and secure methods to apply effluents on irrigated crops to human consume. Counting on the possibility of develop secure techniques to apply wastewater in agriculture, this work had the aim of comparing American lettuce production, microbiological quality and nitrate level, using irrigation with potable water and domestic sewer treatment effluent, under drip (surface and subsurface), furrow and sprinklers irrigation systems. Lettuce was planted in a field, on Lageado Experimental Farm, Agronomical Sciences College, São Paulo State University, in Botucatu / SP, Brazil. The irrigations were carried out each 48 hours, during the last thirty days of the crop, adding the water rates lost in this period. It was verified in this work that higher production values were obtained with wastewater applied with surface drip irrigation. When comparing the influence of the kind of water used in each system, the production values also were higher on wastewater irrigation with drip irrigation (surface and subsurface) and furrows. On microbiological quality, only the lettuce irrigated by subsurface drip irrigation and furrows showed safe contamination values to fecal coliform and Salmonella, according to... (Complete abstract, click electronic address below). / Mestre
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The fate and effects of sewage-derived pharmaceuticals in soilGielen, Gertruda Jacqueline Hariette Petronella January 2007 (has links)
The behaviour and impact of pharmaceuticals in the environment are still poorly understood. Pharmaceuticals are widely used and continually released into the environment causing increasing concerns about their impact on the environment beyond the intended human or veterinary use. Prescribed pharmaceuticals, typically, enter the environment either through excretion after human use or disposal of surplus medication. Sewage treatment plants do not completely remove pharmaceuticals and their metabolites and these have been detected in sewage treatment plant effluent and receiving waters. Land application of treated sewage effluent is widely practiced in New Zealand as an alternative to surface water discharge. Methods were developed to determine selected pharmaceuticals in environmental matrices such as sewage effluent, sewage solids, soil, and soil water. From these, pharmaceutical removal efficiencies were determined for three common sewage treatment processes; activated sludge, composting and land application of sewage effluent. The impacts of some common pharmaceuticals on soil microbial communities, together with the effect of prolonged exposure to sewage effluent on these communities were examined. Additionally, toxicity of sewage effluent, and toxicity mechanisms of specific pharmaceuticals were investigated using luminescent micro-organisms and lettuce seedlings. Pharmaceuticals were successfully detected in sewage effluent, sewage solids, compost, soil and soil water. The sewage treatment processes investigated, including land application, were able to remove or reduce pharmaceutical concentrations in sewage. In case of land application, volcanic soils were more efficient than sandy soils in pharmaceutical removal while irrigation rate and level of sewage pre-treatment also showed some effect on removal efficiency. Pharmaceuticals were not acutely toxic at environmental levels currently detected. Exposure of microbial communities to unnaturally high levels of pharmaceuticals did demonstrate that most pharmaceuticals were potentially able to induce stress in the microbial community although microbes were able to metabolise some of these pharmaceuticals. Twelve years of effluent irrigation resulted in microbial adaptation to aspirin, acetaminophen and tetracycline, indicating that these pharmaceuticals had an effect on microbial community. Presently, land application of treated sewage waste may be a suitable treatment for additional pharmaceutical removal provided that land application schemes are designed appropriately, and pharmaceutical accumulation in the soil is occasionally monitored. It would be prudent to recognise the potential risk that could be caused by chronic exposure to pharmaceuticals such that continued vigilance may lead to future indications of chronic effects at an early stage.
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The fate and effects of sewage-derived pharmaceuticals in soilGielen, Gertruda Jacqueline Hariette Petronella January 2007 (has links)
The behaviour and impact of pharmaceuticals in the environment are still poorly understood. Pharmaceuticals are widely used and continually released into the environment causing increasing concerns about their impact on the environment beyond the intended human or veterinary use. Prescribed pharmaceuticals, typically, enter the environment either through excretion after human use or disposal of surplus medication. Sewage treatment plants do not completely remove pharmaceuticals and their metabolites and these have been detected in sewage treatment plant effluent and receiving waters. Land application of treated sewage effluent is widely practiced in New Zealand as an alternative to surface water discharge. Methods were developed to determine selected pharmaceuticals in environmental matrices such as sewage effluent, sewage solids, soil, and soil water. From these, pharmaceutical removal efficiencies were determined for three common sewage treatment processes; activated sludge, composting and land application of sewage effluent. The impacts of some common pharmaceuticals on soil microbial communities, together with the effect of prolonged exposure to sewage effluent on these communities were examined. Additionally, toxicity of sewage effluent, and toxicity mechanisms of specific pharmaceuticals were investigated using luminescent micro-organisms and lettuce seedlings. Pharmaceuticals were successfully detected in sewage effluent, sewage solids, compost, soil and soil water. The sewage treatment processes investigated, including land application, were able to remove or reduce pharmaceutical concentrations in sewage. In case of land application, volcanic soils were more efficient than sandy soils in pharmaceutical removal while irrigation rate and level of sewage pre-treatment also showed some effect on removal efficiency. Pharmaceuticals were not acutely toxic at environmental levels currently detected. Exposure of microbial communities to unnaturally high levels of pharmaceuticals did demonstrate that most pharmaceuticals were potentially able to induce stress in the microbial community although microbes were able to metabolise some of these pharmaceuticals. Twelve years of effluent irrigation resulted in microbial adaptation to aspirin, acetaminophen and tetracycline, indicating that these pharmaceuticals had an effect on microbial community. Presently, land application of treated sewage waste may be a suitable treatment for additional pharmaceutical removal provided that land application schemes are designed appropriately, and pharmaceutical accumulation in the soil is occasionally monitored. It would be prudent to recognise the potential risk that could be caused by chronic exposure to pharmaceuticals such that continued vigilance may lead to future indications of chronic effects at an early stage.
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