Article

Toxic cyanobacterial breakthrough and accumulation in a drinking water plant: A monitoring and treatment challenge

École Polytechnique de Montreal, Civil, Mineral and Mining Engineering Department, P.O. Box 6079, Station Centre-ville, Montreal, Quebec, Canada.
Water Research (Impact Factor: 5.53). 11/2011; 46(5):1511-23. DOI: 10.1016/j.watres.2011.11.012
Source: PubMed

ABSTRACT

The detection of cyanobacteria and their associated toxins has intensified in recent years in both drinking water sources and the raw water of drinking water treatment plants (DWTPs). The objectives of this study were to: 1) estimate the breakthrough and accumulation of toxic cyanobacteria in water, scums and sludge inside a DWTP, and 2) to determine whether chlorination can be an efficient barrier to the prevention of cyanotoxin breakthrough in drinking water. In a full scale DWTP, the fate of cyanobacteria and their associated toxins was studied after the addition of coagulant and powdered activated carbon, post clarification, within the clarifier sludge bed, after filtration and final chlorination. Elevated cyanobacterial cell numbers (4.7 × 10(6)cells/mL) and total microcystins concentrations (up to 10 mg/L) accumulated in the clarifiers of the treatment plant. Breakthrough of cells and toxins in filtered water was observed. Also, a total microcystins concentration of 2.47 μg/L was measured in chlorinated drinking water. Cyanobacterial cells and toxins from environmental bloom samples were more resistant to chlorination than results obtained using laboratory cultured cells and dissolved standard toxins.

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    • "These compounds also minimize the issues associated with more environmentally damaging mitigation methods such as the use of copper sulfate (CuSO 4 ) on K. brevis blooms in the 1950s (Rounsefell and Evans, 1958 as cited in Kim, 2006). However, CuSO 4 and chlorination are still used routinely to rid drinking water reservoirs of nuisance algae and toxins (McKnight et al., 1983; Zamyadi et al., 2012). Clay minerals such as kaolinite and loess compounds have been used effectively to control blooms in Asia, Europe, and the United States. "
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    ABSTRACT: Harmful algal blooms (HABs) are extreme biological events with the potential for extensive negative impacts to fisheries, coastal ecosystems, public health, and coastal economies. In this chapter, we link issues concerning the key drivers of HABs with the various approaches for minimizing their negative impacts, emphasizing the use of numerical modeling techniques to bridge the gap between observations and predictive understanding. We review (1) recent studies on the environmental pressures that promote HABs; (2) prominent strategies for preventing or controlling blooms; (3) modeling methods, specifically addressing harmful algal species dynamics, and their use as a predictive tool to facilitate mitigation; and then (4) highlight several coastal regions where the mitigation of HABs is generally approached from a regional Earth system and observation framework. Lastly, we summarize future directions for “living with” HABs in an era of limited financial resources for ocean observing.
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    • "Nowadays, many lakes and reservoirs are suffering from eutrophication resulting in seasonal algal blooms [1]. Toxic cyanobacteria species are considered to be the most threatening and undesirable species for drinking water plants, not only because the tiny cyanobacteria cells are difficult to be removed by traditional processes but also these easily broken cyanobacteria cells may release intracellular toxin and odour compounds that severely threaten the quality of water supply [2]. "
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    ABSTRACT: The presence of seasonal algal blooms with harmful algae-derived organic matters threatens the performance of ultrafiltration in drinking water treatment. The hybrid process of in-situ ozonation with ceramic ultrafiltration membrane was proposed for the treatment of algal-rich water with effective removal of algal cells and mitigation of membrane fouling. The mechanism of membrane fouling mitigation with in-situ ozonation was systematically investigated from the perspective of cake layer, gel layer and membrane pore blocking. The results showed that in-situ ozonation treatment can effectively mitigate membrane fouling. For instance, transmembrane pressure was reduced by 75.8% with in-situ ozonation at 1 mg/L. In-situ ozonation resulted in the formation of a more porous and thinner cake layer due to the disintegration of extracellular organic matters that attached on the algal surface. Besides, the portion of very high molecular weight biopolymers (around 100 kDa) and the hydrophobic fraction of algae-derived organic matters, the main component intercepted by the ceramic membrane, were reduced with in-situ ozonation and thus leaded to less severe gel layer fouling. Furthermore, in-situ ozonation induced the accelerated organics degradation within the ceramic membrane pores, alleviating the membrane pore blocking.
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    • "SYTO9 marking all cell membranes and propidium iodide (PI) binding only cells with lethally damaged membranes (Boulos et al., 1999; Stocks, 2004; Berney et al., 2007). Cyanotoxin analyses were conducted via an online solid phase extraction-liquid chromatography coupled to tandem mass spectrometry (online SPE-LC-MS/MS) as previously described by Zamyadi et al. (2012b) "
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    ABSTRACT: Intense accumulation of toxic cyanobacteria cells inside plants, unsuccessful removal of cells and consequent breakthrough of cells and toxins into treated water have been increasingly documented. Removal or destabilisation of cells in the pre-treatment stage using pre-ozonation could be an efficient practice as ozonation has been proven to be effective for the removal of cells and toxins. However, several unknowns including the ozone demand, the potential release of cell-bound toxins and organic matter and their impact on treatment train needs to be addressed. The general objective of this work was to study the impact of direct ozonation on different potentially toxic cyanobacteria genera from natural blooms. Water samples from five cyanobacterial bloom events in Lake Champlain (Canada) were ozonated using 2e5 mg/L O 3 for a contact time of maximum 10 min. Cyanobacterial taxonomic enumeration, cyanotoxins, organic matter and post-chlorination disinfection by-product formation potential analyses were conducted on all samples. Anabaena, Aphanizomenon, Microcystis and Pseudanabaena were detected in bloom water samples. Total cell numbers varied between 197,000 and 1,282,000 cells/mL prior to ozonation. Direct ozonation lysed (reduction in total cell numbers) 41%e80% of cells and reduced released toxins to below detection limits. Microcystis was the genus the least affected by ozonation. However, DOC releases of 0.6e3.5 mg/L were observed leading to maximum 86.92 mg/L and 61.56 mg/L additional total THMs (four trihalomethanes) and HAA 6 (six haloacetic acids) formation, respectively. The results of this study demonstrate that vigilant application of pre-ozonation under certain treatment conditions would help to avoid extreme toxic cells accumulation within water treatment plants. ScienceDirect journal homepage: ww w.else vier.com/locate /wa tres w a t e r r e s e a r c h 7 3 (2 0 1 5) 2 0 4 e2 1 5
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