Removal Of Cyanotoxins Research Articles

Effective electrochemical inactivation of Microcystis aeruginosa and degradation of microcystins via a novel solid polymer electrolyte sandwich

The treatment of toxic Microcystis aeruginosa (M. aeruginosa) by electrolysis using a boron-doped diamond (BDD) anode with a solid polymer electrolyte (SPE) was investigated. In order to examine the role of oxidizing agents, the electrolysis of M. aeruginosa was conducted in distilled deionised water (DIW) with and without sodium chloride aqueous electrolyte. Furthermore, to verify the system’s ability for freshwater treatment without the addition of chemicals, we also tested filtered local reservoir water. M. aeruginosa cell inactivation and microcystins degradation occurred in the DIW system without a supporting aqueous electrolyte, but cell inactivation occurred at slightly slower rate compared to when 30 mg/L Cl− was added. Even though these rates were even slower in the pre-filtered reservoir water, around 90% inactivation and toxin degradation was still observed after 30 min, and cells were not able to re-grow when subsequently exposed to optimum growth conditions. These results for the first time demonstrate the ability of the SPE system to efficiently treat contaminated freshwaters, even without the addition of chemicals or adjustment of electrical conductivity. Importantly, significant changes in cell morphology after electrolysis in different water matrices were observed. In the DIW with 30 mg/L Cl− test based on the significant differences in oxidants concentrations in the presence and absence of M. aeruginosa suggest that there was a synergistic effect of in situ electro-generated ozone and chlorine species in cell inactivation, however, hydrogen peroxide did not seem to assist in the treatment performance. This study suggests that the electrochemical treatment of BDD with SPE, with and without supporting electrolyte is an effective method for the removal of both toxic cyanobacteria and cyanotoxins.

English

Recent increases in the frequency and severity of toxic algae blooms in freshwater lakes has been a major concern for small communities that rely on them for drinking water supply. A hazard quotient approach to risk characterization is employed to analyze the effectiveness of five conventional treatment methods for removal of cyanotoxins. The application of the method for risk assessment and mitigation is demonstrated for five case studies, including Lake Champlain (Quebec), Coal Lake (Alberta), Butte Lake (Alberta), Kubbani Lake (Nigeria) and Bomo Lake (Nigeria). Key words: Cyanotoxins, human health, hazard quotient, lake water intake, water quality.

Cyanotoxins removal from the water: a review

The aim of this work is to show the state-of-the-art about powdered activated carbon and cyanotoxins removal, normally used to avoid health problems in drinking water. The work is part of the PhD research of the second author. Brazilian government has one important law about the subject, named as ordinance 2.914, which provides procedures for water quality control and monitoring. In addition, the standards of portability. Problems caused by cyanotoxins are discussed as one the most dangerous for the public health. The problems linked with cyanobacteria for a long time have been neglected. Some of the problems caused for the presence of this toxins in the water are gastroenteritis, hepato-enteritis and other diseases of the liver and kidney, cancer, skin irritations, allergies, conjunctivitis, vision problems, muscle weakness, respiratory problems, asphyxia, seizures and in extreme cases death. Papers from different bases were consulted as materials in this research. The main bases were Scopus, Science Direct, and SciELO.

Toxic cyanobacteria and cyanotoxins in European waters – recent progress achieved through the CYANOCOST Action and challenges for further research

This review aims to summarise the outcomes of some recent European research concerning toxic cyanobacteria and cyanotoxins, with an emphasis on developments within the framework of the CYANOCOST Action (COST Action ES1105, Cyanobacterial Blooms and Toxins in Water Resources: Occurrence, Impacts and Management). State of the art research and management capabilities in Europe on cyanobacteria have benefitted from input from the pure and applied life sciences, the human and animal health sectors, water engineers, economists and planners. Many of these professional groups have been brought together and they interacted favourably within the framework of CYANOCOST.Highlights of the Action include phycological and ecological studies, development of advanced techniques for cyanotoxin analysis, elucidation of cyanotoxin modes of action, management techniques to reduce cyanobacterial mass development, and research on methods and practices for cyanotoxin removal during drinking water treatment. The CYANOCOST Action has had an active outreach policy throughout its lifetime, resulting in e.g. three handbooks, two special issues in scientific journals and activities in the social media. The many contact channels to end-users, including environmental and drinking water supply authorities, health professionals and the general public are described in this review.Furthermore, the authors have identified a number of gaps in knowledge. Proposed directions for future research in the field of toxic cyanobacteria and cyanotoxins are also discussed.

Removal of cyanobacteria and cyanotoxins from lake water by composites of bentonite with micelles of the cation octadecyltrimethyl ammonium (ODTMA)

Cyanobacteria and their toxins present potential hazard to consumers of water from lakes, reservoirs and rivers, thus their removal via water treatment is essential. The capacity of nano-composites of Octadecyltrimethyl-ammonium (ODTMA) complexed with clay to remove cyanobacterial and their toxins from laboratory cultures and from lake water, was evaluated. Column filters packed with micelles of ODTMA complexed with bentonite and granulated were shown to significantly reduce the number of cyanobacteria cells or filaments and their corresponding toxins from laboratory cultures. Fluorescence measurements demonstrated that cyanobacteria cells lost their metabolic activity (photosynthesis) upon exposure to the micelle (ODTMA)–bentonite complex, or ODTMA monomers. The complex efficiently removed cyanobacteria toxins with an exceptional high removal rate of microcystins. The effectiveness of the complex in elimination of cyanobacteria was further demonstrated with lake water containing cyanobacteria and other phytoplankton species. These results and model calculations suggest that filters packed with granulated composites can secure the safety of drinking water in case of a temporary bloom event of toxic cyanobacteria.

CyanoTOX: Tools for Managing Cyanotoxins in Drinking Water Treatment With Chemical Oxidants

CyanoTOX is a spreadsheet tool developed to estimate the removal of extracellular cyanotoxins and help utilities address the complexities of the oxidation of cyanotoxins.

The effectiveness of conventional water treatment in removing <i>Ceratium furcoides</i> (Levander) Langhans, <i>Microcystis</i> sp. and microcystins

Algal blooms are a global problem due to various negative effects that can compromise water quality, such as the production of metabolites that are responsible for odour, colour, taste and toxins. In drinking water supplies algae can reduce the aesthetics of potable water when not readily removed by conventional water treatment processes. One of the major challenges in water treatment is the removal of cells without leading to lysis and the consequent release of dissolved metabolites in the water. The Maestra Reservoir, which is located in Caxias do Sul, RS – Brazil, is a small meso- to supereutrophic reservoir. The reservoir provides water for the Celeste Gobatto water treatment plant (Celeste Gobatto WTP) which uses the conventional method of treatment. This study aimed to evaluate the efficacy of conventional water treatment for the removal of algae, cyanobacteria and cyanotoxins. A bloom of Microcystis (Kutzing) ex Lemmermann with a density of 23 163 cells∙mL -1 , Ceratium furcoides (Levander) Langhans, (5 356 cells∙mL -1 ) and a microcystin concentration of 1.97 μg∙L -1 was found in the raw water reservoir. Samples sites were assigned the following numbers: (1) raw reservoir water; (2) WTP entry; (3) after sedimentation; (4) filtered water; and (5) treated water. Cell removal was evaluated by cell counting conducted with an inverted microscope, chlorophyll-a by a colorimetric method and microcystin by an enzyme immunoassay kit. Conventional water treatment was effective in removing chlorophyll-a, Microcystis sp. and Ceratium furcoides , mainly in the early treatment steps. Microcystin persisted until the last treatment step, when approximately 50% of the microcystin that had arrived at the WTP was removed by disinfection. Removal of these taxa and toxin was above 98%. Despite the efficacy of Ceratium furcoides removal, the presence of this dinoflagellate in treated water is considered to be large because of its large size. Keywords: Ceratium furcoides , Microcystis sp., microcystins

Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study.

Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity.

Potential of Fuzzy-ELECTRE MCDM in Evaluation of Cyanobacterial Toxins Removal Methods

Cyanobacteria blooms and toxins released from cyanobacteria, called cyanotoxins, have become a serious environmental issue because of their potential toxicity toward human health. Several conventional and advanced water treatment methods are available for degradation of cyanotoxins from surface water, but a cost-effective and efficient water treatment technique can greatly reduce the processing time and improve the quality of treated water. Selection of an optimum treatment technique for cyanotoxins degradation is a multi-criteria decision-making problem owing to the involvement of several conflicting criteria and constraints. In this paper, an integrated Fuzzy-ELECTRE model was proposed and its potential toward evaluation of different cyanotoxins removal techniques has been explored to select the most suitable technology. In this integrated model, criteria importance weights were determined by Fuzzy process, while the ranking of alternatives was performed using ELECTRE process. The result obtained from the model shows that ‘advanced oxidation by titanium dioxide \({({\rm TiO}_{2})}\)’ is the most suitable technology among all considered technology for the removal of cyanotoxins. The developed methodological approach was also used to rank the available treatment techniques within the main group of conventional and advanced oxidation methods (AOMs). The results clearly depict that ozonation and photocatalysis by \({{\rm TiO}_{2}}\) are the best methods within the group of conventional and AOMs, respectively. The ability of the proposed model for providing complete and clear ranking of all considered alternatives confirms its potential for evaluation of cyanotoxins removal methods.

Degradation of cyanotoxins (microcystin) in drinking water using photoelectrooxidation.

The discharge of sewage and industrial effluents containing high concentrations of pollutants in water bodies increases eutrophication. Cyanobacteria, some of the organisms whose growth is promoted by high nutrient concentrations, are resistant and produce several types of toxins, known as cyanotoxins, highly harmful to human beings. Current water treatment systems for the public water supply are not efficient in degradation of toxins. Advanced oxidation processes (AOP) have been tested for the removal of cyanotoxins, and the results have been positive. This study examines the application of photoelectrooxidation in the degradation of cyanotoxins (microcystins). The performance of the oxidative processes involved was evaluated separately: Photocatalysis, Electrolysis and Photoelectrooxidation. Results showed that the electrical current and UV radiation were directly associated with toxin degradation. The PEO system is efficient in removing cyanotoxins, and the reduction rate reached 99%. The final concentration of toxin was less than 1 µg/L of microcystin in the treated solution.

Oxidation of microcystin-LR and cylindrospermopsin by heterogeneous photocatalysis using a tubular photoreactor packed with different TiO2 coated supports

The photocatalytic degradation of cyanotoxins in aqueous solutions using slurry suspensions of TiO2 implies a post-filtration step to retain the photocatalyst. In this work, 2D and 3D TiO2 thin films supported in inert surfaces was proposed for the solar photocatalytic removal of cyanotoxins microcystin-LR (MC-LR) or cylindrospermopsin (CYN) in distilled and natural water under neutral pH conditions. The photocatalytic experiments were performed in a lab-scale tubular photoreactor with a compound parabolic collector (CPC) using simulated and natural solar radiation. The tubular photoreactor was packed with transparent cellulose acetate monoliths (CAM) coated with a P25 paste or sol–gel 2D TiO2 film or with a photocatalytic 3D TiO2-loaded exterior paint (PC500, VLP7000 and P25). The efficiency of the TiO2 photocatalytic system in the presence of hydrogen peroxide was also assessed. PVC or glass tubes and glass spheres, coated with a photocatalytic 3D TiO2-loaded exterior paint, were also tested as inert surfaces. The supports used in this work were chosen according to some characteristics, such as cost, surface resistance, surface area and transmissibility to UV radiation. The toxins MC-LR and CYN were purified from Microcysts aeruginosa and Cylindrospermopsis raciborskii cultures, respectively. The photocatalytic system P25-CAM/H2O2 can be considered the most effective process, considering the cyanotoxins removal efficiency, the cost and the simplicity of the preparation.

Application of Various Oxidants for Cyanobacteria Control and Cyanotoxin Removal in Wastewater Treatment

Cyanobacteria blooms are an increasing issue in wastewater-treatment systems as the associated toxins could induce health risks due to potential passage through irrigation practices using recycled water. The impacts of hydrogen peroxide (H2O2), chlorine, potassium permanganate (KMnO4), and ozone on Microcystis aeruginosa cell viability, and the concomitant toxin release and degradation in wastewater, were investigated. All of these treatments could inactivate M. aeruginosa cells to varying degrees in wastewater due to its chemically challenging matrix. In this paper chlorine was shown to be a feasible option to be used as the last barrier in wastewater-treatment plants due to its strong oxidizing potential resulting incomplete cell inactivation and subsequent degradation of the majority of cyanotoxins in 30 min. However, this was dose dependent as although the release of extracellular toxins was oxidized using 5 mg L−1 chlorine, lower doses of 3 and 4 mg L−1 chlorine were unable to effectively degrade the resultant extracellular toxins. KMnO4 was also effective when a high dose (10 mg L−1) was applied as a postoxidation step to reduce the negative impacts caused by cyanobacteria in wastewater and unlike chlorine does not form any toxic disinfection byproducts. H2O2 was also an effective oxidant as it degraded the majority of intracellular and extracellular toxins after a 2-day treatment. Although 4 and 6 mg L−1 ozone could reduce the total toxins, apparent increase of extracellular microcystins were observed for both ozone treatments.

Removal of cyanobacteria and cyanotoxins during lake bank filtration at Lagoa do Peri, Brazil

Bank filtration is presented as a barrier for cyanobacteria and their metabolites (cyanotoxins and odor compounds). Retention of cyanobacteria is supported by column and bench studies using sandy materials. Most of the removal is in the first decimeters of infiltration, where physical and biological processes take place. Cyanotoxin removal is a very complex process including sorption and/or biodegradation. Sorption depends on the type of cyanotoxin and the sediments/aquifer composition. Biodegradation depends on the type of cyanotoxin, redox conditions, previous contact with the cyanotoxin, type and content of natural organic matter, and temperature. Pilot studies at the Lake Lagoa do Peri in Brazil demonstrated the effectiveness of bank filtration in removing phytoplankton and Cylindrospermopsis raciborskii (105–106 cells/mL) before reaching a sampling well at 12-m depth located 20 m from the lakeshore. Column experiments confirmed biomass removal predominantly in the upper 2 cm of infiltration. No saxitoxins (STXs) were found in the well water and a high retention of neo-STX and STX was determined by isotherm experiments. The sorption linear coefficient (Kd 13–16 L/kg) was found to better represent the sorption processes than the Freundlich coefficient (Kf 6.5–12 L/kg).

Surface Binding of Toxins and Heavy Metals by Probiotics

Removal of toxic metals and toxins using microbial biomass has been introduced as an inexpensive, new promising method on top of conventional methods for decontamination of food, raw material and concentrated. In this article the potential application of lactic acid bacteria and yeasts as the most familiar probiotics to eliminate, inactivate or reduce bioavailability of contamination in foods and feed has been reviewed. After fast glance to beneficial health effects and preservative properties of lactic acid bacteria, the mechanisms which explain antibacterial and antifungal efficiency as well as their antifungal metabolites are mentioned. Then the article has been focused on potential application of single strain or combination of lactic acid bacteria for removal of heavy metals (copper, lead, cadmium, chromium, arsenic), cyanotoxins (microcystin-LR, -RR, -LF) and mycotoxins (aflatoxin B1, B2, B2a, M1, M2, G1, G2, patulin, ochratoxin A, deoxynivalenol, fumonisin B1 and B2, 3-acetyldeoxynivalenol, deoxynivalenol, fusarenon, nivalenol, diacetoxyscirpenol, HT-2 and T-2 toxin, zearalenone and its derivative, etc) from aqueous solutions in vitro. Wherever possible the mechanism of decontamination and the factors influencing yield of removal are discussed. Some factors which can facilitate metal removal capacity of lactic acid bacteria including the strains, surface charge, pH, temperature, presence of other cations are introduced. The cell wall structure of lactic acid bacteria and yeasts are also introduced for further explanation of mechanism of action in complex binding of probiotic to contaminants and strength of mycotoxin- bacterium interaction.

Cyanobacterial and microcystins dynamics following the application of hydrogen peroxide to waste stabilisation ponds

Abstract. Cyanobacteria and cyanotoxins are a risk to human and ecological health, and a hindrance to biological wastewater treatment. This study investigated the use of hydrogen peroxide (H2O2) for the removal of cyanobacteria and cyanotoxins from within waste stabilization ponds (WSPs). The daily dynamics of cyanobacteria and microcystins (commonly occurring cyanotoxins) were examined following the addition of H2O2 to wastewater within both the laboratory and at the full scale within a maturation WSP, the final pond in a wastewater treatment plant. Hydrogen peroxide treatment at concentrations ≥ 0.1 mg H2O2 μg−1 total phytoplankton chlorophyll a led to the lysis of cyanobacteria, in turn releasing intracellular microcystins to the dissolved state. In the full-scale trial, dissolved microcystins were then degraded to negligible concentrations by H2O2 and environmental processes within five days. A shift in the phytoplankton assemblage towards beneficial Chlorophyta species was also observed within days of H2O2 addition. However, within weeks, the Chlorophyta population was significantly reduced by the re-establishment of toxic cyanobacterial species. This re-establishment was likely due to the inflow of cyanobacteria from ponds earlier in the treatment train, suggesting that whilst H2O2 may be a suitable short-term management technique, it must be coupled with control over inflows if it is to improve WSP performance in the longer term.

Genetically Engineered Bacteria Immobilized in Alginate as an Option of Cyanotoxins Removal

Genetically Engineered Bacteria Immobilized in Alginate as an Option of Cyanotoxins Removal

Removal of Cyanobacteria and Microcystin by Natural Plant-Mineral Combinations in Eutrophic Waters

The removal or mitigation of cyanobacterial bloom and cyanotoxins is a necessity to ensure safe drinking water and recreational water. As a feasible agent to control cyanobacterial bloom, a novel plant-mineral composite (PMC) was developed and optimized through laboratory and field testing over the past 3 years. Based on previous studies, we treated cyanobacterial bloom water (mainly Microcystis and Synechocystis) with 0.05 mg/L PMC at the small eutrophic reservoir; 2 h later, we collected samples and analyzed them in the laboratory. The intra-cellular (c-MC) and dissolved microcystin-LR (d-MC) were measured using an ELISA method. The PMC exhibited a remarkable removal of both c-MC (47.3 %) and d-MC (95.8 %) within 2 days. In addition, notable decreases (on average, 78 % of the control) in the chlorophyll-a, suspended solids, total phosphorus and biochemical oxygen demand values, in zooplankton and in the phytoplankton density (83.9 %) were verified after 48 h. These results indicate that the PMC is more effective in controlling d-MC than c-MC, suggesting a possible method to mitigate such hazardous chemicals as agrochemicals and endocrine disrupters in aquatic ecosystems.

Special Issue on Toxics and Pathogens in the Environment

Special Issue on Toxics and Pathogens in the Environment

Removal of cyanotoxins from surface water resources using reusable molecularly imprinted polymer adsorbents

Microcystins (MCs; cyclic heptapeptides) are produced by freshwater cyanobacteria and cause public health concern in potable water supplies. There are more than 60 types of MCs identified to date, of which MC-LR is the most common found worldwide. For MC-LR, the WHO has established a threshold value of 1 μg L(-1) for drinking water. The present MCs removal methods such as coagulation, flocculation, adsorption, and filtration showed low efficiency for removing dissolved MC fraction from surface waters to the stipulated limit prescribed by WHO based on MC health impacts. The search for cost-effective and efficient removal method is still warranted for remediation of dissolved MC-LR-contaminated water resources. Molecularly imprinted polymer (MIP) adsorbent has been prepared using non-covalent imprinting approach. Using MC-LR as a template, itaconic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking monomer, a MIP has been synthesized. Computer simulations were used to design effective binding sites for MC-LR binding in aqueous solutions. Batch binding adsorption assay was followed to determine binding capacity of MIP under the influence of environmental parameters such as total dissolved solids and pH. The adsorptive removal of MC-LR from lake water has been investigated using MIPs. The MIP showed excellent adsorption potential toward MC-LR in aqueous solutions with a binding capacity of 3.64 μg mg(-1) which is about 60% and 70% more than the commercially used powdered activated carbon (PAC) and resin XAD, respectively. Environmental parameters such as total organic carbon (represented as chemical oxygen demand (COD)) and total dissolved solids (TDS) showed no significant interference up to 300 mg L(-1) for MC-LR removal from lake water samples. It was found that the binding sites on PAC and XAD have more affinity toward COD and TDS than the MC-LR. Further, the adsorption capacity of the MIP was evaluated rigorously by its repeated contact with fresh lake water, and it was found that the adsorption capacity of the MIP did not change even after seven adsorption/desorption cycles. The contaminated water of MC-LR (1.0 μg L(-1)) of 3,640 L could be treated by 1 g of MIP with an estimated cost of US $1.5. The adsorption capacity of the MIP is 40% more than commercially used PAC and resins and also the polymer showed reusable potential which is one of the important criteria in selection of cyanotoxins remediation methods.

Characterization of microcystin-LR removal process in the presence of probiotic bacteria

Toxic cyanobacteria have been reported in lakes and reservoirs in several countries. The presence of toxins in drinking water creates a potential risk of toxin transference for water consumers. Besides chemical and physical methods of cyanotoxin removal from water, biodegradation methods would be useful. The aim of the current study was to identify bacterial removal mechanisms of the hepatotoxin microcystin-LR. This was studied by testing the hypothesis of enzymatic degradation of microcystin-LR in the presence of probiotic lactic acid bacterial and bifidobacterial strains and the participation of the proteolytic system of the bacteria in this process. The results suggest that extracellularly located cell-envelope proteinases are involved in the decomposition of microcystin-LR. In particular, a correlation between proteolytic activity and microcystin removal was found and both these parameters were dependent on glucose as an energy source. In addition, EDTA, which was indicated as a main inhibitor of proteinases of the investigated strain, was shown to limit the rate of microcystin removal. The removal of microcystins was shown to be different from the known microcystin-degradation pathway of Sphingomonas. 14C-labeled microcystin was not found inside the cells and bacterial cell extracts were not able to remove the toxin, which supports the involvement of extracellularly located proteinases. The results confirm the hypothesis of enzymatic degradation of microcystins in the presence of probiotic bacteria.