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Incorporation of membranes in water and wastewater treatment plants is becoming increasingly popular, especially when high quality end-product is needed. This chapter provides an overview of the efficiencies of low- and high-pressure membranes used for the removal of intracellular (microfiltration and ultrafiltration) and extracellular (nanofiltration and reverse osmosis) cyanotoxins, respectively. The removal of taste and odor compounds with high pressure membranes is also discussed. Details on the application of commercially available membranes are provided in terms of removal of cyanobacterial metabolites and membrane performance (including fouling). Based on the cited literature, it becomes apparent that the rejection percentage of a solute by high-pressure membranes is affected by various properties of the membrane, including its molecular weight cut-off, desalting degree, porosity, morphology, and hydrophobicity as well as the charge and hydrophobicity of the solute and matrix. Finally, the results from an integrated study combining coagulation, activated carbon adsorption, and membrane filtration for the removal of cyanobacteria and cyanotoxins are discussed.

BackgroundExcess loads of nutrients finding their way into waterbodies can cause rapid and excessive growth of phytoplankton species and lead to the formation of cyanobacterial harmful algal blooms (cyano-HABs). Toxic cyanobacteria produce a broad range of bioactive metabolites, some of which are known as cyanotoxins. These metabolites can negatively impact the ecosystem, and human and animal health, thus their presence needs to be closely monitored and mitigated. This study aimed to monitor St. George Lake (Athalassa National Forest Park, Cyprus) for its water quality characteristics, and initiate a new methodology to control the bloom that occurred in the lake during summer 2019, by comparing hydrogen peroxide treatment with novel metallic peroxide granules as source of hydrogen peroxide.ResultsLake monitoring showed that pH, salinity, total dissolved solids and conductivity varied throughout the year, and nutrients concentration was high, indicating a eutrophic lake. The cyanobacteriumMerismopediasp. bloomed in the lake between June and September 2019, comprising up to 99% of the phytoplankton biovolume. The presence of microcystin synthase encoding gene (mcyB, mcyE) was documented, however microcystins were not detected by tandem mass spectroscopy. Treatment with liquid hydrogen peroxide in concentrations 1 to 5 mg L−1had no effect on the phycocyanin fluorescence (Ft) and quantum yield of PSII (Fv/Fm) indicating an ineffective treatment for the denseMerismopediabloom (1 million cells mL−1 ± 20%). Metallic peroxide granules tested for their H2O2releasing capacity in St. George Lake water, showing that CaO2released higher H2O2concentration and therefore have better mitigation efficiency than MgO2granules.ConclusionThe present study highlights the importance of monitoring several water parameters to conclude on the different actions to be taken to limit eutrophication in the catchment area. The findings demonstrated that testing for the presence of genes involved in cyanotoxin production may not be sufficient to follow cyanotoxins in the water, therefore it should be accompanied with analytical confirmation. Treatment experiments indicated that slow release of H2O2from peroxide granules may be an alternative to liquid hydrogen peroxide when applied in appropriate doses, but further investigation is needed before it is applied at the field.Graphic Abstract

Photocatalytic oxidation for the degradation of cyanobacteria (aka blue–green algae) and cyanotoxins has been extensively studied since its first application by Robertson and Lawton in 1997. Along with testing treatability of various cyanobacteria and cyanotoxins, significant advances in materials engineering have been made. Improvements on the properties of titanium dioxide and other inorganic photocatalysts include bandgap narrowing, adsorption-mediated decomposition, electron–hole recombination prevention, photocatalyst immobilization, reactor design innovation, light emitting diode usage, and/or oxidant injection, resulting in more green, sustainable, and scalable photocatalytic oxidation processes. Herein, we report not only synthesis methods, materials properties and performance, and features of photocatalysts but also transformation products, and toxicity evaluation of treatments. Studies have delivered significant scientific findings and described promising features such as visible light activation, floating photocatalytic reactors, photocatalytic membranes, and multiple functionality for insitu remediation under solar radiation, ultimately. At last, scale-up potential of the materials and reactors and future research needs are discussed.

The authors acknowledge COST Action ES 1105 "CYANOCOST Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management" and COST Action Global Change Biology ES 1201 NETLAKE -Networking Lake Observatories in Europe" for contributing to this study through networking and knowledge sharing with European experts in the field. We acknowledge the members of the Global Lake Ecological Observatory Network (GLEON) for their collaborative spirit and enthusiasm that inspired the grassroots effort of the EMLS. E.M. was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis. We thank Pieter Slot for assisting with the pigment analysis. We thank Dr. Ian Jones for valuable feedback on an earlier version of the manuscript. We thank the Leibniz Institute of Freshwater Ecology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart, and the Leibniz Association for financial support. H.P. was supported by the US National Science Foundation (1840715, 1831096). A.C.'s work was funded by the Spanish Agencia Estatal de Investigacion and EU funds through the project CLIMAWET (CGL2015-69557-R). The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland. We are grateful to Kristiina Vuorio from the Freshwater Centre of the Finnish Environment institute for her help in organizing, collecting and analysing samples by the University of Jyvaskyla and to Gerald Dorflinger from the Water Development Department of Cyprus for his assistance with the sampling in Cyprus and for granting the CUT team permission to use WDD's equipment. Finally, we would like to thank the numerous other assistants that helped realizing each local survey. Open access funding provided by Universite de Geneve., To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature., European Cooperation in Science and Technology (COST) ES 1105 ES 1201, Swiss State Secretariat for Education, Research and Innovation, University of Geneva, Leibniz Association, National Science Foundation (NSF) 1840715 1831096, Spanish Agencia Estatal de Investigacion, European Commission CGL2015-69557-R, Department of Agriculture, Environment and Rural Affairs, Northern Ireland

Biological and advanced chemical treatment of cyanotoxins and other cyanobacteria-related contaminants such as taste and odor compounds, results in the formation of myriad transformation products (TPs) prior to their mineralization to simpler compounds such as H2O and CO2. This chapter gives an overview of the TPs formed for the major groups of cyanotoxins, with both biological and chemical treatment processes. In addition, it provides detailed explanations on the mechanistic steps followed that lead up to the formation of stable TPs for each oxidant used. It becomes apparent that besides the oxidizing ability of each oxidant, TP formation can be affected by the experimental conditions used, including oxidant and catalyst dose, solution pH, and presence of scavengers. Finally, the toxic potential of TPs is discussed.

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains. © 2018 by the authors. Licensee MDPI, Basel, Switzerland., The authors acknowledge COST Action ES 1105 “CYANOCOST—Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE—Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from the University of Geneva. We thank Clare Ahnlund, Ena Suarez and Irene Gallego for helping out with the Swiss survey. We thank Wendy Beekman and Els J. Faassen for the nutrient and toxin analysis.

This study investigated the coupling of sulfate radical generating oxidants, (persulfate, PS and peroxymonosulfate, PMS) with TiO2 photocatalysis for the degradation of microcystin-LR (MC-LR). Treatment efficiency was evaluated by estimating the electrical energy per order (EEO). Oxidant addition at 4 mg/L reduced the energy requirements of the treatment by 60% and 12% for PMS and PS, respectively compared with conventional photocatalysis. Quenching studies indicated that both sulfate and hydroxyl radicals contributed towards the degradation of MC-LR for both oxidants, while Electron Paramagnetic Resonance (EPR) studies confirmed that the oxidants prolonged that lifetime of both radicals (concentration maxima shifted from 10 to 20 min), allowing for bulk diffusion and enhancing cyanotoxin removal. Structural identification of transformation products (TPs) formed during all treatments, indicated that early stage degradation of MC-LR occurred mainly on the aromatic ring and conjugated carbon double bonds of the ADDA amino acid. In addition, simultaneous hydroxyl substitution of the aromatic ring and the conjugated double carbon bonds of ADDA (m/z = 1027.5) are reported for the first time. Oxidant addition also increased the rates of formation/degradation of TPs and affected the overall toxicity of the treated samples. The detoxification and degradation order of the treatments was UVA/TiO2/PMS > UVA/TiO2/PS>> UVA/TiO2.

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment., The authors acknowledge COST Action ES 1105 “CYANOCOST – Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE – Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis and the University of Wageningen for covering the costs of this analysis from the personal funding of dr. Miquel Lürling. We thank Pieter Slot for assisting with the pigment analysis and the University of Amsterdam for covering the costs of the analysis through funding from the group of Prof. Jef Huisman and dr. Petra Visser (IBED). We would like to thank the Environmental Data Initiative for covering the cost of archiving the EMLS dataset. We would like to thank the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dept. of Experimental Limnology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart; and the Leibniz Association for financial support. The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland.

Worldwide water shortage increase and water quality depletion from microbial and chemical compounds, pose significant challenges for today's water treatment industry. Both the development of new advanced oxidation technologies, but also the enhancement of existing conventional technologies is of high interest. This study tested improvements to conventional ozonation that reduce the formation of the oxidation-by-product bromate, while maintaining the effectiveness for removal emerging contaminants (atrazine). MnO4−, ClO2−, ClO2, ClO−, CH3COOO−, HSO5− or S2O8−2 with NH4+ were tested as pre-treatments to ozonation of ground water. Each oxidant and NH4+ were added in a single stage or separately prior to ozonation. To the best of our knowledge, this is the first study that has tested all the above-mentioned oxidants for the same water matrix. Based on our results, the most promising pre-treatments were MnO4− − NH4+, ClO2− − NH4+ and ClO2 − NH4+. MnO4− − NH4+ was the only pre-treatment that did not inhibit atrazine removal. When compared with the previously proposed Cl2/NH4+ pre-treatment, MnO4− + NH4+ was found as effective for preventing BrO3− formation, while atrazine removal was higher. In addition, MnO4− + NH4+ can be added in a single stage (compared to the 2 stage addition of Cl2/NH4+) without causing the formation of potentially harmful chlorination-by-products.

Exposure to beta-N-methylamino-l-alanine (BMAA) might be linked to the incidence of amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. Analytical chemistry plays a crucial role in determining human BMAA exposure and the associated health risk, but the performance of various analytical methods currently employed is rarely compared. A CYANOCOST initiated workshop was organized aimed at training scientists in BMAA analysis, creating mutual understanding and paving the way towards interlaboratory comparison exercises. During this workshop, we tested different methods (extraction followed by derivatization and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis, or directly followed by LC-MS/MS analysis) for trueness and intermediate precision. We adapted three workup methods for the underivatized analysis of animal, brain and cyanobacterial samples. Based on recovery of the internal standard D(3)BMAA, the underivatized methods were accurate (mean recovery 80%) and precise (mean relative standard deviation 10%), except for the cyanobacterium Leptolyngbya. However, total BMAA concentrations in the positive controls (cycad seeds) showed higher variation (relative standard deviation 21%-32%), implying that D(3)BMAA was not a good indicator for the release of BMAA from bound forms. Significant losses occurred during workup for the derivatized method, resulting in low recovery (

This chapter discusses thoroughly the outcomes of the TiO2 photocatalytic degradation of organic contaminants of emerging concern, including manmade (insecticides, organochlorinated compounds, and antibiotics) and naturally occurring compounds (cyanotoxins and taste and odor compounds). Specifically, information is provided on the degradation of various organic contaminants in actual water samples, their corresponding reaction kinetics, the individual effects of water quality parameters (including pH, natural organic matter, and alkalinity) and nano-interfacial adsorption phenomena. Emphasis is given to the mechanisms of photocatalytic degradation of organic contaminants based on their structural differences and the corresponding transformation products formed.

Cyanobacteria blooms pose an environmental hazard because of the release of water soluble toxic compounds, called cyanotoxins. Microcystins (MCs), hepatotoxic cyclic peptide toxins, are the most widespread cyanotoxins with microcystin-LR (MC-LR) the most common and toxic variant. Health effects of MCs have resulted in the need of using efficient treatment methods for the removal of this class of toxins in water supplies. While physical treatment methods can remove MCs at full or some extent from contaminated water, their function is primary separation of the whole toxins as intact molecules and further processing is required. On the other hand, chemical oxidation processes are a promising alternative treatment option due to the potential of complete destruction of the MCs, transformation to less toxic by-products, and even complete mineralization. MCs reactivity towards different conventional oxidants is strongly affected by water quality parameters like pH, DOC and oxidant dose. Although there is a general trend for MCs oxidation (ozone > permanganate > chlorine >>> chlorine-based oxidants), the selection of the appropriate oxidant for toxin elimination during water treatment should be assessed for each particular source of water. Although advanced oxidation processes are generally more effective on MCs degradation than conventional oxidation processes, scale-up studies are needed before these methods are considered as economically-feasible and practical sustainable alternatives in water treatment facilities. In this review, recent literature concerning treatment of MCs in water by conventional and advanced oxidation processes are reviewed and discussed in terms of the degree of degradation, reaction kinetics, identity and toxicity of oxidation by-products and possible degradation pathways.

Degradation of the cyanotoxin microcystin-LR (m/z 995.5) using sulfate radical-based advanced oxidation technologies (AOTs) and identification of reaction intermediates formed during treatment were investigated in this study. To the best of our knowledge this is the first study on the degradation and identification of reaction intermediates for any cyanotoxin with SO(4)(•-). Tandem mass spectrometry designated the formation of nine (as m/z) reaction intermediates with four of them (m/z 1011.5, 1027.5, 1029.5, and 1045.5) having multiple peaks in the TIC chromatogram. New peaks that were not observed with hydroxyl radical formed during photocatalytic oxidation (PCO) have been detected such as m/z 1045.5. The initially formed intermediates involved the oxidation of the unsaturated bonds of MC-LR especially the diene bonds located on the chain of the Adda amino acid. Subsequent intermediates implicated the oxidative cleavage of small functional groups (i.e., -COOH), up to the complete removal of the Adda chain. The electrophilic character of SO(4)(•-) is proven by the multihydroxylation of the aromatic ring. Toward the end of treatment, simultaneous oxidation of the Adda chain and the cyclic structure occurred without the formation of linear products.

The presence of the harmful cyanobacterial toxins in water resources worldwide drives the development of an innovative and practical water treatment technology with great urgency. This study deals with two important aspects: the fabrication of mesoporous nitrogen-doped TiO2 (N-TiO2) photocatalysts and their environmental application for the destruction of microcystin-LR (MC-LR) under visible light. In a nanotechnological sol-gel synthesis method, a nitrogen-containing surfactant (dodecylammonium chloride) was introduced as a pore templating material for tailor-designing the structural properties of TiO2 and as a nitrogen dopant for its visible light response. The resulting N-TiO2 exhibited significantly enhanced structural properties including 2-8 nm mesoporous structure (porosity 44%) and high surface area of 150 m2/g. Red shift in light absorbance up to 468 nm, 0.9 eV lower binding energy of electrons in Ti 2p state, and reduced interplanar distance of crystal lattices proved nitrogen doping in the TiO2 lattice. Due to its narrow band gap at 2.65 eV, N-TiO2 efficiently degraded MC-LR under visible spectrum above 420 nm. Acidic condition (pH 3.5) was more favorable for the adsorption and photocatalytic degradation of MC-LR on N-TiO2 due to electrostatic attraction forces between negatively charged MC-LR and +6.5 mV charged N-TiO2. Even under UV light, MC-LR was decomposed 3-4 times faster using N-TiO2 than control TiO2. The degradation pathways and reaction intermediates of MC-LR were not directly related to the energy source for TiO2 activation (UV and visible) and nature of TiO2 (neat and nitrogen-doped). This study implies a strong possibility for the in situ photocatalytic remediation of contaminated water with cyanobacterial toxins and other toxic compounds using solar light, a sustainable source of energy.

This study compared the UVC/S2O8(2-) system with the more commonly used AOP in water industry, UVC/H2O2, and examined whether the first one can be an economically feasible alternative technology. Atrazine and 4 volatile compounds (methyl tert-butyl ether, cis-dichlorethen, 1,4-dioxane and 1,1,1-trichloroethane) were chosen as model contaminants because they exhibit different susceptibility to UVC photolysis and AOPs. A collimated beam apparatus was utilized for the majority of the experiments (controlled environment, without mass transfer phenomena), while selected experiments were performed in a flow-through reactor to simulate industrial applications. Initial experiments on the activation of oxidants with a LP lamp indicated that S2O8(2-) is photolysed about 2.3 times faster than H2O2 and that the applied treatment times were not sufficient to utilize the majority of the oxidant. The effect of oxidants' concentrations were tested with atrazine alone and in the micropollutants' mixture and it was decided to use 11.8 mg L(-1) S2O8(2-) and 14.9 mg L(-1) H2O2 for further testing since is closer to industrial applications and to minimize the residual oxidant concentration. Changes of the matrix composition of the treated water were investigated with the addition of chloride, bicarbonate and humic acids at concentrations relevant to a well-water-sample, the results showed that the system least affected was UVC/H2O2. Only when bicarbonate was used, UVC/S2O8(2-) performed better. Overall, testing these systems with the mixture of micropollutants gave better insights to their efficiency than atrazine alone and UVC/S2O8(2-) is recommended for selective oxidation of challenging matrices.

Cyanobacteria are often grouped into primary and secondary metabolites, wherein the former are essential for growth, development and reproduction of the organism while the latter are indirectly involved in the organisms' survival but their absence does not result in immediate death of the organism. These secondary metabolites are the main focus of this chapter. Cyanobacteria secondary metabolites, whether constitutive or induced, play a key role in their interactions with the environment. Some of these metabolites include taste and odor compounds such as geosmin (GSM) and 2-methylisoborneol (MIB), anti-microbials, terpenoids, lactones, metal chelators, protease inhibitors, indole alkaloids and potent toxins, frequently called cyanobacterial toxins or cyanotoxins (produced by cyanobacteria commonly found in surface water supplies), known to affect a wide range of living organisms. The chapter reviews some of the hazardous secondary metabolites produced by cyanobacteria and their potential transformation products (TPs) formed during various transformation processes.

This chapter summarizes the findings of different studies on the prevention and elimination of cyanobacterial blooms in raw water resources as well as the removal of cyanotoxins during water treatment with physical processes. Treatments that can be applied at the source water and limit bloom formation include aeration and chemical addition (e.g., copper sulfate and algaecides). Efficiencies of conventional treatment processes such as coagulation, flocculation, sedimentation, filtration, and membrane processes for the removal of both cyanobacteria and cyanotoxins are also discussed. In addition, adsorption of cyanotoxins on activated carbon (AC) and several micro- and nanomaterials is presented. Finally, integrated treatment examples are reported with a specific reference to a lab study on powdered AC-ultrafiltration technologies for the removal of cyanotoxins.

The aim of the this study was to investigate the ozone dosage required to remove active pharmaceutical ingredients (APIs) from biologically treated wastewater of varying quality, originated from different raw wastewater and wastewater treatment processes. Secondary effluents from six Swedish wastewater treatment plants (WWTP) were spiked with 42 APIs (nominal concentration μg/L) and treated with different O₃ doses (0.5-12.0 mg/L ozone) in bench-scale experiments. In order to compare the sensitivity of APIs in each matrix, the specific dose of ozone required to achieve reduction by one decade of each investigated API (DDO₃) was determined for each effluent by fitting a first order equation to the remaining concentration of API at each applied ozone dose. Ozone dose requirements were found to vary significantly between effluents depending on their matrix characteristics. The specific ozone dose was then normalized to the dissolved organic carbon (DOC) of each effluent. The DDO₃/DOC ratios were comparable for each API between the effluents. 15 of the 42 investigated APIs could be classified as easily degradable (DDO₃/DOC ≤ 0.7), while 19 were moderately degradable (0.7DDO₃/DOC ≤ 1.4), and 8 were recalcitrant towards O₃-treatment (DDO₃/DOC1.4). Furthermore, we predict that a reasonable estimate of the ozone dose required to remove any of the investigated APIs may be attained by multiplying the experimental average DDO₃/DOC obtained with the actual DOC of any effluent.

This study compared several pretreatment methods for inhibiting BrO3(-) formation during ozonation of tap water, from the DTU (Technical University of Denmark) campus, including H2O2 addition (peroxone), pH depression, and NH4+ and Cl2/NH4+ addition. At the same time, the inhibition of atrazine and carbamazepine removal was evaluated for each pretreatment. The required delivered O3 dose to achieve 90% removal of atrazine in the tap water from the DTU campus was 3.5 mg/L, which produced 130-170 microg/L BrO3(-). Peroxone did not reduce the required O3 dose for contaminant removal; however, it limited BrO3(-) formation to below the drinking water limit of 10 microg/L. Depression of solution pH to 6.0, reduced BrO3(-) formation to half, but it was still well above the water limit. Pretreatment with NH4+ also reduced BrO3(-) formation by approximately 50%, though it reduced atrazine degradation to 65%. Pretreatment with Cl2/NH4+ reduced BrO3(-) formation close to the 10 microg/L limit; however, atrazine removal did not exceed 75%. Carbamazepine was completely removed under all the tested experimental conditions with the 3.5 mg/L O3 dose.

This study investigated the formation and predicted toxicity of different groups of disinfection byproducts (DBPs) from human exudates in relation to chlorination of pool water at different pH values. Specifically, the formation of the DBP groups trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs) and trichloramine (NCl(3)), resulting from the chlorination of body fluid analog, were investigated at 6.0 ≤ pH ≤ 8.0. Either the initial concentration of active chorine or free chlorine was kept constant in the tested pH range. THM formation was reduced by decreasing pH but HAN, and NCl(3) formation increased at decreasing pH whereas the formation of HAAs remained constant. Under our experimental conditions, the formation of NCl(3) (suspected asthma inducing compound) at pH = 6.0 was an order of magnitude higher than at pH = 7.5. Furthermore, the effect of the presence of bromide on DBP formation was investigated and found to follow the same pH dependency as without bromide present, with the overall DBP formation increasing, except for HAAs. Estimation of genotoxicity and cytotoxicity of the chlorinated human exudates showed that among the quantified DBP groups, HAN formation were responsible for the majority of the toxicity from the measured DBPs in both absence and presence of bromide.

Microcystins are cyclic heptapeptide toxins produced by a number of genera of cyanobacteria. They are ubiquitous in bodies of water worldwide and pose significant hazard to human, plant, and animal health. Microcystins are primarily hepatotoxins known to inhibit serine-threonine phosphatases leading to the disruption of cascade of events important in the regulation and control of cellular processes. Covalent binding of microcystins with phosphatases is thought to be responsible for the cytotoxic and genotoxic effects of microcystins. In addition, microcystins can trigger oxidative stress in cells resulting in necrosis or apoptosis. Their cyclic structure and novel amino acids enhance their stability and persistence in the environment. Humans are primarily exposed to microcystins via drinking water consumption and accidental ingestion of recreational water. Recreational exposure by skin contact or inhalation to microcystins is now recognized to cause a wide range of acute illnesses which can be life-threatening. Microcystins are primarily degraded by microorganisms in the environment, while sunlight can cause the isomerization of the double bonds and hydroxylation in the presence of pigments. Attempts to utilize these organisms in sand and membrane filters to treat water contaminated with microcystins showed complete removal and detoxification. Conventional water treatment processes may not fully eliminate microcystins when there are high levels of organic compounds especially during harmful bloom events. Combination of conventional and advanced oxidation technologies can potentially remove 100% of microcystins in water even in turbid conditions. This review covers selected treatment technologies to degrade microcystins in water.

This study explores the potential use of sulfate radical-based advanced oxidation technologies (SR-AOTs) for the degradation of the naturally occurring hepatotoxin, microcystin-LR (MC-LR). The generation of sulfate radicals was achieved by activation of the oxidants persulfate (PS) and peroxymonosulfate (PMS) through electrophilic transition metal cations (Ag+ and Co2+, respectively), radiation (UV 300 < λ < 400 nm) and/or heat (T = 30 °C). These systems were compared to more frequently used AOTs systems in industrial applications; the Fenton Reagent (FR) and hydrogen peroxide coupled with heat and radiation. Even though SO4{radical dot}- has similar redox potential to hydroxyl radical (HO{radical dot}), to the best of our knowledge, SR-AOTs have not been tested for the degradation of cyanotoxins. In this study, PMS was activated very efficiently with Co2+ at neutral pH and increasing catalyst concentration resulted in dramatic increase of the initial rates of degradation that reached a plateau for CCo(II) ≥ 1 mg. Based on the optimum pH conditions for each system, the efficiency order is Co2+/PMS > Fe2+/H2O2 ≫ Ag+/PS, which we believe is associated with the energy of the lower unoccupied molecular orbital of the oxidants. When UV (300 < λ < 400 nm) radiation was used, the PS system was more efficient than PMS and H2O2 at all different oxidant concentrations. Since, the UV lamps used in the study emit light at a range of wavelengths (300 < λ < 400 nm), the activation of the oxidants is believed to be caused by the emission spectra and not just λmax = 365 nm. At acidic conditions, the PS/UV (300 < λ < 400 nm)/pH 3 and PMS/UV/pH 3 systems were most efficient and required the least amount of energy to reduce the toxin concentration by one order of magnitude. When thermal activation was used, PMS yielded the highest degradation efficiency (∼77%) compared to 52% for the PS and less then 2.5% for H2O2.

This study investigated the use of thin transparent TiO2 photocatalytic films, prepared with novel sol–gel methods containing surfactants as templating materials, for the degradation of the cyanotoxin, microcystin-LR (MC-LR). MC-LR is an emerging contaminant from the Contaminant Candidate Lists (CCLs 1–3) of the USEPA. The effects of UV-A radiation, solution pH, initial toxin concentration, coated surface area of the TiO2 films and their structural properties (porosity, crystallinity and thickness) on the degradation rate of MC-LR were investigated. Photolysis did not occur with UV-A radiation. Acidic pH was more efficient for the degradation of MC-LR due to toxin interaction with the catalyst surface and increased adsorption into the porous films. The degradation profiles of the toxin at different initial concentrations were fitted with pseudo-first order kinetics. Films prepared with three coatings (0.3 μm thickness) had the best performance at acidic and neutral pH, while the exclusion of surfactant from the preparation method resulted in non-porous films with decreased performance. The parameter that mostly affected the degradation rate was the solution pH. The toxicity of the treated samples, evaluated by an in-house protein phosphatase 1 assay, indicated that treatment with the TiO2 photocatalytic films indeed resulted in complete removal of MC-LR's toxicity.

This study investigated the degradation pathway of creatinine (a urine metabolite) with immobilized titanium dioxide photocatalysts. The degradation of creatinine was studied at three different pH values (acidic, neutral and basic) in the absence of buffering solutions. The intermediates formed were identified by using electrospray ionization mass spectrometer (ESI-MS) in both negative and positive ion mode. Two distinct mechanistic pathways which govern the photocatalytic degradation of creatinine irrespective of the pH of the initial solution were identified. The initial solution pH affected only the selectivity between the two mechanisms. The primary oxidation steps of creatinine with hydroxyl radicals included demethylation, hydrogen abstraction, hydroxylation, oxidation, and ring opening. At acidic pH, additional transformation steps of the two mechanisms were identified. The intermediates detected in the positive ion mode, contained at least one atom of nitrogen in their structure, explaining the observed low nitrogen mineralization of creatinine with TiO(2) photocatalysis. The intermediates in the negative ion mode were low molecular weight organic acids that contained only carbon and hydrogen atoms.

The eutrophication of water resources, mainly attributed to antrophogenic activities such as sewage and agricultural runoffs, has led to a worldwide increase in the formation of cyanobacterial harmful algal blooms (Cyano-HABs). Cyano-HABs have the ability to produce and release toxic compounds, commonly known as cyanotoxins, which comprise a potent threat for human and animal health as well as negative economical impacts. This chapter presents an overview on the sources and occurrence of species of cyanobacteria and their association with the production of cyanotoxins throughout the world. The main bloom-forming cyanobacteria that have been detected include Microcystis, Cylindrospermopsis, Anabaena, Aphanizomenon, and Planktothrix. The main cyanotoxins related to these cyanobacteria are microcystins, cylindrospermopsin, anatoxin-a and saxitoxins.

Mass spectrometry was utilized for structural identification of the intermediates formed during the photocatalytic degradation of the cyanotoxin, microcystin-LR with immobilized TiO2 photocatalysts at neutral pH. Most of the intermediates reported herein have not been found in prior studies. Results indicate that MC-LR degradation is initiated at four sites of the toxin; three on the Adda amino acid (aromatic ring, methoxy group, and conjugated double bonds) and one on the cyclic structure (Mdha amino acid). Several intermediates gave multiple peaks in the TIC (m/z = 1011.5, 1029.5, 1063.5), which were deduced to be geometrical or constitutional isomers. This is the first study that reports the hydroxylation of the aromatic ring and the demethoxylation of MC-LR with TiO2 photocatalysis. The most targeted site was the conjugated diene bonds because of their location in the MC-LR structure. Isomerization at the C4-C5 and C6-C7 of the diene bond of the Adda chain was a direct result of hydroxyl radical addition/substitution. Based on the above, we concluded that oxidation and isomerization of the diene bonds of MC-LR occurred simultaneously. Other steps included hydroxyl substitution, further oxidation, and bond cleavage. As the reaction time progressed, simultaneous oxidation of the Adda chain and the cyclic structure occurred.

Microcystin-LR (MC-LR), a cyanotoxin and emerging drinking water contaminant, was treated with TiO(2) photocatalysts immobilized on stainless steel plates as an alternative to nanoparticles in slurry. The reaction intermediates of MC-LR were identified with mass spectrometry (MS) at pH of Milli-Q water (pH(sq)=5.7). Eleven new [M+H](+) were observed in the liquid chromatography mass spectrometry (LC/MS) chromatogram with some of them giving multiple peaks. Most of these reaction intermediates have not been reported from previous studies employing TiO(2) nanoparticles at acidic conditions (pH=4.0). Investigating the effects of pH (for 3.0

In this project, immobilized titanium dioxide photocatalysis was utilized as a post-treatment technology for the destruction of model organic contaminants found in wastewater streams produced on-board during space exploration. Phenol, a known human carcinogen, and creatinine, a human metabolite found in urine, were the compounds tested in this study. Phenol and creatinine have cyclic structures consisting of six and five member rings, respectively. In addition, creatinine is a methyl guanidine derivative, with almost 40% (w/w) nitrogen. The degradation and carbon mineralization efficiencies of the target contaminants were investigated at different initial concentrations. Their photocatalytic degradation appears to follow pseudo-first-order reaction with phenol giving higher organic carbon reduction rates than creatinine. The presence and position of the functional groups of creatinine (amine, imine and peptide bond) are primarily responsible for the significantly slower mineralization. The degradation of creatinine was also tested at different pHo values. Statistical analysis showed that there is an effect of pH on the treatment of creatinine. Besides the carbon mineralization, the extent of nitrogen mineralization and the mass balance of nitrogen were conducted for three pH values (pHo 3.0, 6.2 and 11.0). Overall, the transformation of nitrogen was low, and the total maximum conversion (

Cyanobacteria, more commonly known as blue-green algae, are found worldwide in various aquatic environments as well as in water distribution systems Atikovic 2003; Carmichael 1994; Madigan et al. 2003 . Blooms of cyanobacteria have recently become spatially and temporally more prevalent in the United States and worldwide as a consequence of increasing nutrient levels such as nitrates and phosphates from fertilizers and detergents. Cyanobacterial blooms impart color, odor, and taste problems in water. More importantly, such blooms produce and release toxic compounds that dramatically impair the quality of water bodies. Up to 50% of the recorded blooms can be expected to contain toxins Carmichael 1992 . These compounds have severe and sometimes irreversible effects on mammalian health. Episodes of human and animal poisoning by consumption of water contaminated with cyanobacterial toxins have been reported since the late 1800s Carmichael 1994 . Exposure to cyanobacterial toxins can affect the number and diversity of wild animal populations, cause bioaccumulation of toxins in the tissues of fish and shellfish, and indirectly affect other organisms through the food chain. Moreover, the presence of cyanobacteria and cyanobacterial toxins in sources of drinking water supply has raised major concerns. Another major issue is the lack of guidelines or regulations of cyanobacteria and cyanotoxins in terms of maximum contaminant level MCL and analytical detection methods. In the past few years, major research effort has been targeted toward the treatment of these toxins, especially the hepatotoxin microcystin-LR MC-LR . Cyanobacteria are present in various aquatic environments, including water distribution systems and can produce scum usually greenish observed at the bottom and surface of lakes. In ecosystems, the presence of cyanobacteria is crucial as they provide oxygen to specific aerobic microorganisms symbiotic living , convert inorganic nitrogen to organic forms that plants and phytoplankton can utilize and act as a source of energy to zooplankton primary producers . Recent studies have shown that zooplankton consumes cyanobacterial algal blooms selectively depending on the availability of food. The nonconsumable blooms can be lethal to or can reduce the number and size of progeny of zooplankton Carmichael 1994 . Cyanobacteria contain and release toxins as a metabolic byproduct and also