Physico-chemical treatment for the degradation of cyanotoxins with emphasis on drinking water treatment - How far have we come?

Over the years, various physicochemical treatment processes, such as photocatalysis, membrane technology, ozonolysis and chlorination have been tested at laboratory and pilot scale for the treatment of various cyanotoxins. Most of these treatment processes are also being commonly practiced in a drinking water treatment plants (DWTPs). However, the degree of treatment widely varies among cyanotoxin variants and is mainly governed by the source water characteristics, operational parameters (temperature, pH, cyanotoxin level) which changes continuously in a DWTPs. Other common elements present in raw water, such as natural organic matter (NOMs), residual nutrients and metal ions shows competitive behaviour with the cyanotoxins. Thus, a high demand in input energy is needed for unit operations, such as photocatalysis, reverse osmosis membrane and excess chemical requirement in terms of ozone, permanganate and chlorine (for ozonation and chlorination) which can breach the guidelines and increase the toxicity level. This review provides an insight into the effectiveness of major physico-chemical operations from simple to the advanced treatment level for the removal of different cyanotoxins along with their limitations and challenges in a DWTP. The goal of this review is to provide information on the possible reaction mechanism involved in the cyanotoxin treatment, accounting mainly for the toxicity, modifications in the process that happened over the years and the process feasibility. In future, hybrid technique assisted by UV, peroxides, among others promises to assist photocatalytic, ozonation and chlorination to undergo efficient cyanotoxin removal with reduced toxicity level. Also, persistence cyanotoxins, such as anatoxin and saxitoxin need further study.Fil: Kumar, Pratik. Université du Québec a Montreal; CanadáFil: Hegde, Krishnamoorthy. Université du Québec a Montreal; CanadáFil: Brar, Satinder Kaur. Université du Québec a Montreal; CanadáFil: Cledón, Maximiliano. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Kermanshahi Pour, Azadeh. Dalhousie University Halifax; Canad

Biodegradation of microcystin-LR using acclimatized bacteria isolated from different units of the drinking water treatment plant

Bacterial community isolated from different units of a Drinking Water Treatment Plant (DWTP) including pre-ozonation unit (POU), the effluent-sludge mixture of the sedimentation unit (ESSU) and top-sand layer water sample from the filtration unit (TSFU) were acclimatized separately in the microcystin-leucine arginine (MC-LR)-rich environment to evaluate MC-LR biodegradation. Maximum biodegradation efficiency of 97.2 ± 8.7% was achieved by the acclimatized-TSFU bacterial community followed by 72.1 ± 6.4% and 86.2 ± 7.3% by acclimatized-POU and acclimatized-ESSU bacterial community, respectively. Likewise, the non-acclimatized bacterial community showed similar biodegradation efficiency of 71.1 ± 7.37%, 86.7 ± 3.19% and 94.35 ± 10.63% for TSFU, ESSU and POU, respectively, when compared to the acclimatized ones. However, the biodegradation rate increased 1.5-folds for acclimatized versus non-acclimatized conditions. The mass spectrometry studies on MC-LR degradation depicted hydrolytic linearization of cyclic MC-LR along with the formation of small peptide fragments including Adda molecule that is linked to the reduced toxicity (qualitative toxicity analysis). This was further confirmed quantitatively by using Rhizobium meliloti as a bioindicator. The acclimatized-TSFU bacterial community comprised of novel MC-LR degrading strains, Chryseobacterium sp. and Pseudomonas fragi as confirmed by 16S rRNA sequencing. Biodegradation of microcystin-LR by in-situ bacterial community present in the drinking water treatment plant without formation of toxic by-product.Fil: Kumar, Pratik. Université du Québec a Montreal; CanadáFil: Hegde, Krishnamoorthy. Université du Québec a Montreal; CanadáFil: Brar, Satinder Kaur. Université du Québec a Montreal; CanadáFil: Cledón, Maximiliano. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kermanshahi-pour, Azadeh. Dalhousie University Halifax; CanadáFil: Roy-Lachapelle, Audrey. University of Montreal; CanadáFil: Galvez-Cloutier, Rosa. Laval University; Canad

Towards the development of green plasticizers

Research was conducted to investigate the effect of chemical functional groups, including the ether function and alkyl branches, on the biodegradation mechanisms and biodegradation rates of dibenzoate plasticizers. Biodegradation of 1,6-hexandiol dibenzoate, a potential green dibenzoate plasticizer, by Rhodococcus rhodochrous, was investigated in the presence of hexadecane as a primary carbon source. The metabolites, produced in the biodegradation process were detected using GC/MS and Fourier transform mass spectroscopy techniques. None of these metabolites were stable, with all tending to biodegrade over the course of the experiments. Biodegradation mechanisms were elucidated for 1,6-hexanediol dibenzoate and two commercial plasticizers, diethylene glycol dibenzoate (D(EG)DB) and dipropylene glycol dibenzoate (D(PG)DB). Biodegradation of all of these plasticizers was initiated by hydrolysis of one ester bond to release a monobenzoate and benzoic acid. It was demonstrated that the diol fragment of 1,6-hexanediol monobenzoate was processed via a β-oxidation pathway, which was not possible for diethylene glycol monobenzoate (D(EG)MB) and dipropylene glycol monobenzoate (D(PG)MB) due to the presence of an ether function in the diols. Thus, accumulation of D(EG)MB and D(PG)MB was observed in the biodegradation broth. The biodegradation of commercial plasticizers, D(EG)DB and D(PG)DB and three alternative plasticizers, 1,3-propanediol dibenzoate, 2,2-methyl-propyl-1,3-propanediol dibenzoate and 1,6-hexanediol dibenzoate, were modeled using a Michaelis-Menten/Monod-type kinetic model. Biodegradation was conducted in an aerated bioreactor using resting cells of Rhodococcus rhodochrous, which had been grown with hexadecane as the primary substrate. Monobenzoates released from the biodegradation of commercial plasticizers degraded slower than the monobenzoates of alternative plasticizers. The rapid biodegradation of monobenzoates released from microbial hydrolysis of altDes recherches ont été réalisées pour étudier l'effet des groupes chimiques fonctionnels, y compris la fonction éther et les branches d'alkyle, sur les mécanismes de biodégradation et les taux de biodégradation des plastifiants dibenzoate. La biodégradation du 1,6-dibenzoate hexanediol, un plastifiant dibenzoate potentiel, par Rhodochrous rhodococcus, a été étudiée en présence d'hexadécane comme source de carbone primaire. Les métabolites, produits dans les processus de biodégradation ont été détectés par GC/MS et techniques de spectroscopie de masse à transformée de Fourier. Aucun de ces métabolites ne sont stables, tous avaient une tendance à la dégradation durant les expériences. Les mécanismes de biodégradation ont été élucidés pour le dibenzoate de 1,6-hexanediol et de deux plastifiants commerciaux, le dibenzoate de diéthylène glycol (D(EG)DB) et le dibenzoate dipropylèneglycol (D(PG)DB). La biodégradation de l'ensemble de ces plastifiants a été initié par hydrolyse d'une liaison ester pour libérer un monobenzoate et de l'acide benzoïque. Il a été démontré que le fragment de 1,6-diol monobenzoate hexanediol est généré par une β-oxydation, ce qui n'était pas possible pour le monobenzoate diéthylène glycol (D(EG)MB) et le monobenzoate dipropylèneglycol (D(PG)MB) en raison de la présence d'une fonction éther dans les diols. Ainsi, l'accumulation de D(EG)MB et D(PG)MB a été observée dans le bouillon de biodégradation. La biodégradation des plastifiants commerciaux, D(EG)DB et D(PG)DB et trois plastifiants de remplacement, le dibenzoate de 1,3-propanediol, le dibenzoate de 2,2-méthyl-propyl-1propanediol et le dibenzoate de 1,6-hexanediol, a été modélisée à l'aide d'un modèle cinétique Michaelis-Menten/Monod-type. La biodégradation a été effectuée dans un bioréacteur aéré à l'aide de cellules au repos Rhodochrous rhodococcus, qui avaient été cultivées avec l'hexadécane comme subs

Algal Polysaccharides-Based Hydrogels: Extraction, Synthesis, Characterization, and Applications

Hydrogels are three-dimensional crosslinked hydrophilic polymer networks with great potential in drug delivery, tissue engineering, wound dressing, agrochemicals application, food packaging, and cosmetics. However, conventional synthetic polymer hydrogels may be hazardous and have poor biocompatibility and biodegradability. Algal polysaccharides are abundant natural products with biocompatible and biodegradable properties. Polysaccharides and their derivatives also possess unique features such as physicochemical properties, hydrophilicity, mechanical strength, and tunable functionality. As such, algal polysaccharides have been widely exploited as building blocks in the fabrication of polysaccharide-based hydrogels through physical and/or chemical crosslinking. In this review, we discuss the extraction and characterization of polysaccharides derived from algae. This review focuses on recent advances in synthesis and applications of algal polysaccharides-based hydrogels. Additionally, we discuss the techno-economic analyses of chitosan and acrylic acid-based hydrogels, drawing attention to the importance of such analyses for hydrogels. Finally, the future prospects of algal polysaccharides-based hydrogels are outlined

Potential of biological approaches for cyanotoxin removal from drinking water: A review

Biological treatment of cyanotoxins has gained much importance in recent decades and holds a promise to work in coordination with various physicochemical treatments. In drinking water treatment plants (DWTPs), effective removal of cyanotoxins with reduced toxicity is a primary concern. Commonly used treatments, such as ozonation, chlorination or activated carbon, undergo significant changes in their operating conditions (mainly dosage) to counter the variation in different environmental parameters, such as pH, temperature, and high cyanotoxin concentration. Presence of metal ions, natural organic matter (NOM), and other chemicals demand higher dosage and hence affect the activation energy to efficiently break down the cyanotoxin molecule. Due to these higher dose requirements, the treatment leads to the formation of toxic metabolites at a concentration high enough to break the guideline values. Biological methods of cyanotoxin removal proceed via enzymatic pathway where the protein-encoding genes are often responsible for the compound breakdown into non-toxic metabolites. However, in contrast to the chemical treatment, the biological processes advance at a much slower kinetic rate, predominantly due to a longer onset period (high lag phase). In fact, more than 90% of the studies reported on the biological degradation of the cyanotoxins attribute the biodegradation to the bacterial suspension. This suspended growth limits the mass transfer kinetics due to the presence of metal ions, NOMs and, other oxidizable matter, which further prolongs the lag phase and makes biological process toxic-free, albeit less efficient. In this context, this review attempts to bring out the importance of the attached growth mechanism, in particular, the biofilm-based treatment approaches which can enhance the biodegradation rate.Fil: Kumar, Pratik. Université du Québec a Montreal; CanadáFil: Hegde, Krishnamoorthy. Université du Québec a Montreal; CanadáFil: Brar, Satinder Kaur. Université du Québec a Montreal; Canadá. University of York; Reino UnidoFil: Cledón, Maximiliano. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Kermanshahi-pour, Azadeh. Dalhousie University Halifax; Canad

Novel fluidized-bed biofilm reactor for concomitant removal of microcystin-LR and organics

Fluidized bed biofilm reactor (FBBR) was evaluated for the removal of microcystin-LR (MC-LR) from drinking water-sludge (0.3% w/v). Biofilm formed inside the solid media carriers (biocarriers) were studied for the MC-LR degradation in FBBRs via known MC-LR degraders: Arthrobacter ramosus (reactor A: RA) and Bacillus sp. (reactor B: RB), along with the heterogeneous bacterial community (HBC) present in the sedimentation-unit sludge as a background matrix. Their ability to form biofilm inside the immobilized biocarriers was periodically quantified for over 300 days to determine the duration of mature biofilm growth, sloughing event and then re-maturation. The bioreactor performance was mainly evaluated in terms of MC-LR, nitrate, nitrite, ammonia removal, and soluble-chemical oxygen demand (s-COD) removal. Biological degradation of MC-LR showed significant role over the physical adsorption, as the removal efficiency increased by around 30% and 26% for RA and RB respectively, as compared to the control bioreactor RD (without any bacterial cells) and an increase by over 15% and 11% when compared to reactor RC (contained only HBC). Mass spectra analysis for RA, RB, and RC strengthen the possibility of a toxic-free degradation mechanism. Overall, RA showed the best MC-LR removal efficiency of around 93.7%, which comprised no MC-LR in the supernatant phase and around 3 µg/L in the sludge-mixture phase. Toxicity assessment of biodegraded sample (using bioindicator) further revealed the toxic-free nature by RA with >80% removal for ammonia, nitrate, and nitrite. Scale-up of laboratory scale FBBR (2 L) is also proposed to handle 200 m3 of feed water per day based on a similar volumetric mass transfer coefficient (kLa) to study the feasible process economics.Fil: Kumar, Pratik. Centre Eau Terre Environnement; CanadáFil: Hegde, Krishnamoorthy. Centre Eau Terre Environnement; CanadáFil: Brar, Satinder Kaur. Centre Eau Terre Environnement; CanadáFil: Cledón, Maximiliano. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Kermanshahi pour, Azadeh. Dalhousie University Halifax; CanadáFil: Roy Lachapelle, Audrey. University of Montreal; Canadá. Environment Canada; CanadáFil: Galvez Cloutier, Rosa. Laval University; Canad

Co-culturing of native bacteria from drinking water treatment plant with known degraders to accelerate microcystin-LR removal using biofilter

The biofilm-mediated bioremediation of drinking water source for Microcystin-LR degradation under various water quality parameters was investigated using sand filter with known Microcystin (MC)-degrading bacterial genera: Arthrobacter (A), Bacillus (B) and Sphingomonas (S), both under individual (A, B and S) as well as co-culture condition (A + X, B + X and S + X) with the native bacterial strains (Pseudomonas fragi and Chryseobacterium sp. = X). These native bacterial strains were isolated from the filtration unit of a drinking water treatment plant (DWTP). Before starting the filter operation, the biofilm-forming ability of MC-degraders was evaluated using a unique experimental set-up. The study showed that the MC-LR removal was enhanced by 38% using S + X filter as compared to the uninoculated filter (control). Except for Bacillus sp., MC-degraders in the form of Arthrobacter ramosus and Sphingomonas sp. enhanced the MC removal potential of the native bacterial strains (X) by 10% and 17%, respectively. The central composite design was used to obtain an optimized input parameter (pH, temperature, initial turbidity and retention time) for the filter operation. Various output parameters including dissolved organic carbon (DOC), total coliform, turbidity, dissolved oxygen, MC-LR toxicity and ammonia were analyzed to form a well-generalized model with a desirability index of 0.638. Overall, filter S + X achieved a non-detectable MCs concentration in some cycles and showed an average of >30% DOC and >80% of total coliform removal along with an under-regulated removal of nitrite, nitrate and ammonia. However, MC-LR breakthrough occurred after 8 weeks of filter operation. These studies demonstrated the effectiveness of inoculating MC-degraders in an existing filtration unit of a DWTP to remove the seasonal occurrence of MCs in the water source.Fil: Kumar, Pratik. Université du Québec; CanadáFil: Hegde, Krishnamoorthy. Université du Québec; CanadáFil: Brar, Satinder Kaur. Université du Québec; Canadá. York University; CanadáFil: Cledón, Maximiliano. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Kermanshahi-pour, Azadeh. Dalhousie University Halifax; CanadáFil: Roy-Lachapelle, Audrey. University of Montreal; Canadá. Environment and Climate Change Canada; CanadáFil: Sauvé, Sébastien. University of Montreal; CanadáFil: Galvez-Cloutier, Rosa. Laval University; Canad