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Author: Traven Aldin Wood
Publisher:
ISBN:
Category : Cyanobacteria
Languages : en
Pages : 151
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Book Description
Cyanobacteria present significant public health and engineering challenges due to their expansive growth and potential synthesis of microcystins in surface waters that are used as a drinking water source. Eutrophication of surface waters coupled with favorable climatic conditions can create ideal growth environments for these organisms to develop what is known as a cyanobacterial harmful algal bloom (cHAB). Development of methods to predict the presence and impact of microcystins in drinking water treatment systems is a complex process due to system uncertainties. This research developed two predictive models, first to estimate microcystin concentrations at a water treatment intake, second, to estimate the risks of finished water detections after treatment and resultant health effects to consumers. The first model uses qPCR data to adjust phycocyanin measurements to improve predictive linear regression relationships. Cyanobacterial 16S rRNA and mcy genes provide a quantitative means of measuring and detecting potentially toxic genera/speciess of a cHAB. Phycocyanin is a preferred predictive tool because it can be measured in real-time, but the drawback is that it cannot distinguish between toxic genera/speciess of a bloom. Therefore, it was hypothesized that genus specific ratios using qPCR data could be used to adjust phycocyanin measurements, making them more specific to the proportion of the bloom that is producing toxin. Data was obtained from a water treatment plant (WTP) intake at Tappan Lake, Ohio, a drinking water source for the Village of Cadiz. Using Pearson correlations and linear regressive analysis, it was found that adjusted phycocyanin, based on Planktothrix 16S and Planktothrix mcyE gene abundance ratios, exhibits improved correlation with microcystins. Furthermore, the analysis demonstrated the practicality of the adjustment in turning negative correlations between phycocyanin and microcystins to positive. More data from other water systems are needed to validate the findings of this study. The second model utilizes a stochastic method to model the risk of microcystin finished water detections after water treatment. Data needed for such a model include initial and finished water toxin detections, removal efficiencies of various treatment processes, and exposure data related to a consumer. Three different methods for modelling the health status of a bloom in order to determine the intra- to extracellular (E/I) ratio of initial toxin concentrations were explored. Then, water treatment characteristics specific to the 2014 Toledo Water Crisis (TWC) were modeled to obtain estimated finished water detections. Finally, health risks were estimated using a hazard quotient based on finished water detections and exposure scenarios. Risk estimates for children were greater than adults and present throughout the crisis. This model produced accurate predictive outputs that are consistent with conditions observed during the 2014 TWC. Furthermore, this model presents a novel method of assigning E/I ratios to initial microcystin concentrations, which is useful for assessing and predicting WTP resiliency amidst a changing bloom. Together, these models can serve as an innovative way of predicting microcystins from intake to tap.
Author: Traven Aldin Wood
Publisher:
ISBN:
Category : Cyanobacteria
Languages : en
Pages : 151
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Book Description
Cyanobacteria present significant public health and engineering challenges due to their expansive growth and potential synthesis of microcystins in surface waters that are used as a drinking water source. Eutrophication of surface waters coupled with favorable climatic conditions can create ideal growth environments for these organisms to develop what is known as a cyanobacterial harmful algal bloom (cHAB). Development of methods to predict the presence and impact of microcystins in drinking water treatment systems is a complex process due to system uncertainties. This research developed two predictive models, first to estimate microcystin concentrations at a water treatment intake, second, to estimate the risks of finished water detections after treatment and resultant health effects to consumers. The first model uses qPCR data to adjust phycocyanin measurements to improve predictive linear regression relationships. Cyanobacterial 16S rRNA and mcy genes provide a quantitative means of measuring and detecting potentially toxic genera/speciess of a cHAB. Phycocyanin is a preferred predictive tool because it can be measured in real-time, but the drawback is that it cannot distinguish between toxic genera/speciess of a bloom. Therefore, it was hypothesized that genus specific ratios using qPCR data could be used to adjust phycocyanin measurements, making them more specific to the proportion of the bloom that is producing toxin. Data was obtained from a water treatment plant (WTP) intake at Tappan Lake, Ohio, a drinking water source for the Village of Cadiz. Using Pearson correlations and linear regressive analysis, it was found that adjusted phycocyanin, based on Planktothrix 16S and Planktothrix mcyE gene abundance ratios, exhibits improved correlation with microcystins. Furthermore, the analysis demonstrated the practicality of the adjustment in turning negative correlations between phycocyanin and microcystins to positive. More data from other water systems are needed to validate the findings of this study. The second model utilizes a stochastic method to model the risk of microcystin finished water detections after water treatment. Data needed for such a model include initial and finished water toxin detections, removal efficiencies of various treatment processes, and exposure data related to a consumer. Three different methods for modelling the health status of a bloom in order to determine the intra- to extracellular (E/I) ratio of initial toxin concentrations were explored. Then, water treatment characteristics specific to the 2014 Toledo Water Crisis (TWC) were modeled to obtain estimated finished water detections. Finally, health risks were estimated using a hazard quotient based on finished water detections and exposure scenarios. Risk estimates for children were greater than adults and present throughout the crisis. This model produced accurate predictive outputs that are consistent with conditions observed during the 2014 TWC. Furthermore, this model presents a novel method of assigning E/I ratios to initial microcystin concentrations, which is useful for assessing and predicting WTP resiliency amidst a changing bloom. Together, these models can serve as an innovative way of predicting microcystins from intake to tap.
Author: Donna S. Francy
Publisher:
ISBN:
Category : Recreation areas
Languages : en
Pages : 0
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Author: Gemma Charlebois
Publisher:
ISBN:
Category : Cyanobacteria
Languages : en
Pages : 163
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Appropriate and effective drinking water treatment is critical to the protection of public health. Toxic cyanobacterial blooms are a globally increasing drinking water source quality-associated health risk as even very low (>1.5 parts per billion (ppb) or micrograms per litre ([mu]g/L)) concentrations of the cyanobacteria-produced toxin microcystin can be unsafe to drink. Increased pressures on freshwater supplies as well as climate change associated factors such as alternating periods of drought and intense storms and increasing water temperature cause more nutrient runoff into water supplies and create favourable conditions for the growth of cyanobacteria. Ozone is generally understood to effectively destroy many toxins during drinking water treatment. Its efficacy, however, can be adversely impacted by the presence of natural organic matter, often measured as dissolved organic carbon (DOC). The conditions that create favourable growth conditions for cyanobacteria, can also increase the concentrations of DOC in the source water of a drinking water treatment facility. The objectives of this research were to determine whether ozone is an effective cyanobacterial toxin elimination technology at the conditions studied; specifically in the presence of high DOC (~10 mg/L), to determine the efficacy of ozone in the destruction of intercellular (within cells) toxin vs. extracellular (within water matrix) toxin, and to determine the extent of cell destruction by ozone. Bench-scale experiments were conducted. Both extracted toxin and cyanobacterial cells were added to coagulated/flocculated/clarified water collected from the Mannheim Water Treatment Plant in Kitchener, Ontario. Microcystin concentrations were measured by the ELISA method and by liquid chromatography-mass spectroscopy-mass spectroscopy (LC-MS-MS). This investigation confirmed that ozone can destroy extracellular microcystin-LR to below 1.5 [mu]g/L (ppb) at ozone residuals above 0.3 mg O3/L when the aqueous DOC concentration was below 5 mg/L. The relationship between required ozone residual to achieve adequate extracellular toxin destruction and DOC concentration in the water matrix was quantitatively described. Notably, when Microcystis aeruginosa cells were present, an amount equivalent to less than 50% of the concentration of extracellular microcystin-LR was destroyed by ozone. This demonstrates that significant oxidative capacity is required to lyse the cells before ozone can destroy intercellular toxin. The novel contribution of this work is that this relationship was 1) demonstrated through using toxin in extracted and cellular forms and 2) maintained when all other critical operational factors (i.e., ozone residual, DOC concentration, water matrix) were the same. These results underscore the need to reassess operational requirements for ozonation for the treatment of cyanobacterial toxins when intact cells are present as opposed to extracellular toxin, which is used in most performance assessments. Notably, as the aqueous DOC concentration increased, the proportion of live cells present following ozonation (as measured by intercellular toxin concentrations) also increased. Therefore, not only does DOC decrease the efficacy of ozone to destroy toxin, it decreases the oxidative capacity to lyse cells; moreover, the rate is not directly proportional to the aqueous DOC concentration. As a result, increases in ozone residual concentration had a minimal effect on toxin destruction in these cases. In other words, the levels of toxin destruction that would have been expected based on comparable ozone residuals in absence of DOC (or when only low levels of DOC were present) were not achieved because of the significant oxidant/ozone demand of DOC when present at high aqueous (~10 mg/L) concentrations. Another important contribution of this work was the demonstration that not all cyanobacterial cells were destroyed following ozonation; thus, they were described as “Damaged and Potentially Viable (DAPV)” cells. These cells were present at ozone residuals less than 0.45 mg O3/L, logically suggesting that incomplete oxidative treatment occurs at lower ozone residual concentrations. Notably, these DAPV cells may have the potential to reproduce; given this and the common assessment of treatment performance using extracellular toxin, the efficacy and operational requirements of oxidative treatment of cyanobacterial cells by ozonation may need to re-evaluated for situations in which live cells are present. These observations also underscore the need to more fully assess the significance of DAPV cells.
Author: Federal-Provincial Subcommittee on Drinking Water (Canada)
Publisher:
ISBN:
Category : Cyanobacteria
Languages : en
Pages : 58
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Author:
Publisher:
ISBN:
Category : Drinking water
Languages : en
Pages : 214
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Author: H. Kenneth Hudnell
Publisher: Springer Science & Business Media
ISBN: 0387758658
Category : Medical
Languages : en
Pages : 955
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Book Description
With the ever-increasing incidence of harmful cyanobacterial algal blooms, this monograph has added urgency and will be essential reading for all sorts of researchers, from neuroscientists to cancer research specialists. The volume contains the proceedings of the 2005 International Symposium on Cyanobacterial Harmful Algal Blooms, and has been edited by H. Kenneth Hudnell, of the US Environmental Protection Agency. It contains much of the most recent research into the subject.
Author: Saloni Singh
Publisher:
ISBN:
Category : Cyanobacteria
Languages : en
Pages : 145
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Book Description
Cyanotoxins are a group of toxins produced by cyanobacteria that can be harmful to human health. Drinking water is a major pathway to exposure and therefore the presence of cyanobacteria and cyanotoxins in drinking water is a concern for drinking water utilities. Microcystins are a commonly occurring group of cyanotoxins in North America. Microcystin-LR is currently the only regulated cyanotoxin in Canada, with a maximum acceptable concentration of 1.5 [microgram]/L total microcystin-LR in treated drinking water. Cyanobacterial blooms have occurred in the Great Lakes, a major drinking water source in Ontario. Climate change and rising temperatures bring a greater risk of cyanobacteria occurrences. This makes cyanobacteria and cyanotoxins a growing concern for drinking water treatment plants in Ontario. Conventional drinking water treatment processes have the ability to remove microcystins. Removals vary based on plant configuration, operating conditions and water quality characteristics. Understanding how well individual treatment processes are performing can assist utilities in developing a response plan for the event of a cyanobacteria bloom. The aim of this research was to assess microcystin removal at three Ontario drinking water treatment plants under different treatment scenarios. Extracellular (dissolved) microcystin removal, as well as cyanobacterial cell removal (intracellular microcystin removal) were assessed. Cell lysis and the resulting increase in dissolved microcystin concentration are highly variable and difficult to predict; however information was provided on cell lysis and microcystin accumulation from the published literature. This study evaluated microcystin removal by drinking water treatment processes at three Ontario drinking water treatment plants: Woodward Avenue Water Treatment Plant (City of Hamilton), Elgin Area Water Treatment Plant (City of London), and DeCew Falls Water Treatment Plant (Niagara Region). This study did not involve any sampling. Data on microcystin removal were collected from existing studies and literature. Data on plant operations and water quality were collected from each treatment plant. This information was used to assess extracellular microcystin and cyanobacterial cell removal for each treatment process. The Hazen-Adams Cyanotoxin Tool for Oxidation Kinetics (CyanoTOX®) was used to predict extracellular microcystin removal with chlorination processes. The three water treatment plants assessed in this study utilize chlorination, coagulation, flocculation, sedimentation, and filtration. One plant also employs chloramination for secondary disinfection, another plant employs powdered activated carbon (PAC) seasonally, and two plants employ UV disinfection. Chloramine and UV disinfection are not effective in treating microcystins. Chlorination is a key mechanism for microcystin removal, but can cause cell lysis and toxin release. Because of this, chlorination can reduce the total microcystin concentration but may increase the extracellular microcystin concentration. Extracellular microcystin removal increases with increasing CT (product of the oxidant concentration and the contact time with water), decreasing pH, and increasing temperature. Treatment scenarios were developed based on CT, pH, and temperature, and evaluated using CyanoTOX®. Cell lysis and dissolved microcystin increase seen in the literature at similar CT values were summarized. PAC can remove extracellular microcystins through adsorption. Treatment scenarios for PAC were developed based on dose and contact time, and assessed using data from existing studies. Limited information on factors affecting cyanobacterial cell removal is available for coagulation, flocculation, sedimentation, and filtration processes. Therefore, a best-case, worst-case, and average scenario for cell removal were estimated based on the literature. Coagulation, flocculation, sedimentation and filtration processes are not effective in treating extracellular cyanotoxins. This research shows that a scenario-based approach may be used to predict microcystin removals. The results of this study may assist utilities in predicting the risk of microcystin breakthrough in treated water, making treatment decisions, and in developing a cyanotoxin management plan. Overall, under average conditions, the three drinking water treatment plants could expect high (>90%) intra- and extracellular microcystin removals. Chlorination is the primary treatment barrier for dissolved microcystin removal. Coagulation, flocculation, sedimentation and filtration are the primary treatment barrier for cell removal. Chlorination at the intakes may hinder cyanotoxin removal: cell lysis would result in fewer intact cells being removed by coagulation, flocculation, sedimentation and filtration, and the amount of microcystin released may be too much for the current chlorination processes to sufficiently remove. This study is limited by the availability of information available in the literature. In particular, little information was available on cell removal with coagulation, flocculation, sedimentation and filtration processes. For PAC processes, removals vary with different PACs and waters. For more accurate microcystin removal estimates, bench-scale or pilot-scale studies are warranted.
Author: Caroline Moore
Publisher:
ISBN: 9781369311723
Category :
Languages : en
Pages :
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Microcystins are toxic, ubiquitous environmental contaminants produced by blue-green algae and found in water, sediment and food. With over 80 structural variants, the most commonly tested variant, MC-LR, has been found worldwide and has been linked to acute, lethal hepatotoxicoses in humans and animals. Produced in response to increased water temperatures, high phosphate and nitrate run off, stagnant water and other environmental cues, microcystin contaminations are predicted to increase with rising global water temperatures. Microcystins are resistant to degradation via chemical treatment and boiling, and pose a threat to both drinking water facilities in industrialized countries as well as developing areas of the world where surface waters are typically untreated. While the acute hepatotoxic effects of microcystins have been intensively studied, their potential toxic effects on other organ systems are not well understood. Microcystins cross the blood brain barrier and enter neurons where they can cause oxidative stress, and cause loss of memory in mammalian models. Case reports of human microcystin exposure include signs of neurotoxicity, but to date the effects of microcystins on specific neuronal cell types have not been evaluated. The research presented here establishes a novel model system using Caenorhabditis elegans (C. elegans) to evaluate the in vivo effects of MC- LR and MC-LF on sensory neuron function and serine/threonine protein phosphatase (PP) activity and gene expression. Since inhibition of serine/threonine protein phosphatases is the primary mechanism of action of microcystin toxicity in mammals, these data support the use of C. elegans as a platform for comparative studies of microcystin variants across species. This thesis broadens our knowledge of microcystin toxicity to identify mechanisms in addition to PP1 and PP2A, the two most studied serine/threonine protein phosphatases in microcystin research, including catalytic and regulatory subunits of PP2B, PP4, and PP6. In this investigation of microcystin neurotoxicity, the serine/threonine protein phosphatase inhibition assay was used in three different applications. First, it was used to screen water and rumen samples in veterinary toxicosis cases to quickly diagnose the presence of PP1 inhibitors such as microcystins. Second, the ability of microcystins to directly target C. elegans serine/threonine protein phosphatases was evaluated using protein extract from C. elegans. Third, the assay was modified to analyze protein phosphatase activity after C. elegans were exposed to MC-LF and MC-LR in vivo. The serine/threonine protein phosphatase inhibition assays and C. elegans model presented in this thesis can be applied to better understand the mechanisms of microcystin toxicity and to screen environmental samples for microcystin contamination using sensitive endpoints, both of which will improve public health risk assessments of these important waterborne contaminants.
Author: Haihong Song
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Microcystins, potent toxins produced by cyanobacteria, occur widely in aquatic systems across the world, and are a known environmental and public health hazard. Therefore, it is important to understand their fate in aquatic systems. As an important component of aquatic systems, sediments play multiple roles in the distribution and natural attenuation of microcystins. However, systematic studies identifying the effects of environmental variables on the variability of microcystins in lake sediments are lacking, and the contribution of sediments to the removal of these toxins in the water body are not yet clear. Hence, this research aimed to: (a) investigate the variability of microcystins in lake sediments; and (b) identify the relative contribution of the biodegradation and adsorption ability of sediments to the removal of microcystins from the water. As research into microcystins in lake sediments has been hindered by the lack of an effective analysis method, a further aim of this study was to develop a method to quantify these toxins in sediment samples using supercritical carbon dioxide. The first part of this research involved a field study, analysing microcystin concentrations in lake sediments and their correlation with environmental variables. Microcystins were detected in all sediment samples, even at one of the sampling sites with negligible cyanobacterial biomass present in the water. The concentration of these toxins in lake sediments had a weak, but significant correlation with intracellular microcystins, total microcystins and cyanobacterial biomass in the water. Furthermore, their variability of in lake sediments could be explained by a combination of total microcystins in the water, cyanobacterial biomass in the water, pH and temperature. In the second part of this research, changes in the concentration of microcystin-LR (MCLR) in the water in the presence of sediments were quantified in a laboratory experiment. The results of this experiment showed that each time MCLR was added to sterile lake water in the presence of sediments, MCLR concentration decreased significantly following an exponential decay curve, with no observed lag phase. Comparison between different treatment conditions implied that the adsorption and biodegradation ability of sediments caused the MCLR removal and that biodegradation was the dominant mechanism. The final part of this research investigated the use of supercritical carbon dioxide in quantifying microcystins in sediment samples. A protocol was developed which included the optimisation of extraction conditions using supercritical carbon dioxide. This protocol was use to quantify microcystin concentrations in natural field samples. The results showed that for sediment samples with added MCLR, the conventional method recovered more spiked MCLR but fewer microcystin variants. In contrast, supercritical carbon dioxide with water as modifier extracted a higher amount of total microcystins. Overall, this research highlights the wide occurrence of microcystins in the sediments of the studied lake, and the biodegradation ability of sediments to remove microcystins quantitatively from the water. This study suggests that researchers and water management authorities should include sediments when assessing the potential hazards and fate of microcystins in aquatic systems.
Author: Kimberly K. Zulliger
Publisher:
ISBN:
Category :
Languages : en
Pages : 224
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