Removal efficiency of phosphorus, cyanobacteria and cyanotoxins by the “flock &amp; sink” mitigation technique in semi-arid eutrophic waters

Lucena-Silva, Daniely de; Molozzi, Joseline; Severiano, Juliana dos Santos; Becker, Vanessa; Barbosa, José Etham de Lucena

doi:10.1016/j.watres.2019.04.057

Cited by 39 publications

(18 citation statements)

References 51 publications

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“…Our results indicated that biomass composed predominantly of Dolichospermum circinalis and Microcystis aeruginosa could be efficiently removed from the water column using a mixture of low-dose coagulants and ballasts. PAC in combination with LMB or LRS had similar efficacy, and this result is in agreement with previous studies carried out in tropical systems [21][22][23][24]. At odds with what was observed by Miranda et al [21] and Lucena-Silva et al [22], we recorded the release of MCs with a low dose of PAC (3 mg Al L −1 ) and in all combinations of PAC and ballast.…”

Section: Discussionsupporting

confidence: 92%

“…The coagulation and precipitation of cyanobacteria biomass and phosphate (P) is a promising tool to manage eutrophication and its nuisance [19]. This technique combines a ballast and a coagulant (Floc and Sink) that moves intact cells and P out of the water column, bound to ballast, toward the sediment, and is proven safe [19][20][21][22][23]. However, the coagulation step is a critical part of this technique because the coagulant can cause physiological or chemical stress to cell membranes, releasing intracellular toxins and P into water [20,21,24].…”

Section: Introductionmentioning

confidence: 99%

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‘Floc and Sink’ Technique Removes Cyanobacteria and Microcystins from Tropical Reservoir Water

Arruda

Noyma

Magalhães

et al. 2021

Toxins

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Combining coagulants with ballast (natural soil or modified clay) to remove cyanobacteria from the water column is a promising tool to mitigate nuisance blooms. Nevertheless, the possible effects of this technique on different toxin-producing cyanobacteria species have not been thoroughly investigated. This laboratory study evaluated the potential effects of the “Floc and Sink” technique on releasing microcystins (MC) from the precipitated biomass. A combined treatment of polyaluminium chloride (PAC) with lanthanum modified bentonite (LMB) and/or local red soil (LRS) was applied to the bloom material (mainly Dolichospermum circinalis and Microcystis aeruginosa) of a tropical reservoir. Intra and extracellular MC and biomass removal were evaluated. PAC alone was not efficient to remove the biomass, while PAC + LMB + LRS was the most efficient and removed 4.3–7.5 times more biomass than other treatments. Intracellular MC concentrations ranged between 12 and 2.180 µg L−1 independent from the biomass. PAC treatment increased extracellular MC concentrations from 3.5 to 6 times. However, when combined with ballast, extracellular MC was up to 4.2 times lower in the top of the test tubes. Nevertheless, PAC + LRS and PAC + LMB + LRS treatments showed extracellular MC concentration eight times higher than controls in the bottom. Our results showed that Floc and Sink appears to be more promising in removing cyanobacteria and extracellular MC from the water column than a sole coagulant (PAC).

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

‘Floc and Sink’ Technique Removes Cyanobacteria and Microcystins from Tropical Reservoir Water

Arruda

Noyma

Magalhães

et al. 2021

Toxins

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“…poly-aluminium chloride (PAC) and iron(III)chloride (Pan et al, 2011a;Lürling and Oosterhout, 2013;Waajen et al, 2016a;de Lucena-Silva et al, 2019), organic polymers like chitosan (Pan et al, 2006(Pan et al, , 2011bNoyma et al, 2016Noyma et al, , 2017 and cationic starch (Shi et al, 2016), synthetic organic coagulants like cationic polyacrylamides (Jančula and Maršálek, 2011) and cationic polyamine (Dai et al, 2015), or extracts derived from Moringa oleifera seeds (Oladoja and Pan, 2015;Camacho et al, 2017;de Oliveira Ruiz Moreti et al, 2019). Ballast compounds may be local soils, clay, bauxite, gravel (e.g., Pan et al, 2006Pan et al, , 2011aLi and Pan, 2015;Noyma et al, 2016Noyma et al, , 2017Miranda et al, 2017;de Lucena-Silva et al, 2019), or modified clays and products with P adsorption capacity (e,g., Lürling and Oosterhout, 2013;Noyma et al, 2016Noyma et al, , 2017Waajen et al, 2016a). The latter is a special case of "Floc and Sink" (Noyma et al, 2016) as it is also aimed at removing phosphate from a water column and reducing sediment P release: a "Floc and Lock" approach (Lürling and Oosterhout, 2013), which will be discussed in detail in the next section.…”

Section: Figmentioning

confidence: 99%

Coagulation and precipitation of cyanobacterial blooms

Lürling

Kang

Mucci

et al. 2020

Ecological Engineering

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Eutrophication is the prime water quality issue in inland waters. Eutrophication and its key symptom, harmful cyanobacterial blooms, is expected to further increase in the future, which highlights the importance of managing the issue. The reduction of external nutrient load is crucial but might not bring fast relief to eutrophic waters due to ongoing diffuse pollution and legacy nutrients in the sediment. In this context, in-lake measures are needed to speed-up recovery. In this review, we discuss different in-lake measures based on coagulation and precipitation of cyanobacteria and/or phosphate for different lake categories (e.g., shallow or deep, mainly external or internal nutrient load, occurrence of perennial or summer blooms). In deep lakes with an external nutrient load higher than the internal load, a "Floc and Sink" method could be used in which a coagulant (e.g. aluminium salts, Al-salts; chitosan) combined with a ballast (e.g. soil, clay) removes a cyanobacterial bloom out of the water column. In case the deep lake suffers from high internal load, a phosphate (P)-fixative (e.g. lanthanum modified bentonite or Al-salts) can be used to "Lock" the legacy P, possibly combined with a coagulanta "Floc and Lock" technique. The latter approach will target both the particulate P in a bloom and the internal P load. A shallow lake that suffers from summer blooms and in which the internal load is higher than the external load, a "Lock" strategy of winter application of a P-fixative is proposed to prevent bloom development. In shallow lakes with perennial blooms, an agent to damage the cells (such as H 2 O 2 ) is required together with a coagulant and a ballast to avoid recolonization of the water column due to resuspension -a "Kill, Floc and Sink/ Lock" method. The selection of the most promising in-lake measures and materials should be based on a proper system diagnosis and tests prior to a full-scale intervention. These methods can be effective, but evidently reduction of external nutrient loads, both from point-and non-pointed sources, is an absolute necessity to restore aquatic ecosystems in a holistic sense. recyclable sediment phosphorus (P) pool (Moss, 2010). The most notorious symptom of eutrophication is a massive proliferation of cyanobacteria (Paerl et al., 2011). Blooms of cyanobacteria are viewed problematic as they may produce nasty odours, cause fish kills due to hypoxia/anoxia, and may impair ecosystem services, such as drinking water production, irrigation, recreation, aquaculture and fisheries (Paerl and Paul, 2012). Eutrophication is expected to further increase in the upcoming decades because of human population growth, intensified

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“…Several studies have used chitosan to remove cyanobacteria or dinoflagellates from the water column, some using chitosan-Modified Local Soils/Sand (MLS, e.g., [ 21 , 25 , 35 , 36 , 37 , 38 , 39 ]), others adding first only chitosan, followed by soils/clays (e.g., [ 40 , 41 , 42 , 43 ]) and recently a chitosan fiber has been used [ 44 ]. However, in only a few of these studies, the possible chitosan effects on the algal cells viability were investigated.…”

Section: Introductionmentioning

confidence: 99%

Chitosan as a Coagulant to Remove Cyanobacteria Can Cause Microcystin Release

Mucci

Guedes

Faassen

et al. 2020

Toxins

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Chitosan has been tested as a coagulant to remove cyanobacterial nuisance. While its coagulation efficiency is well studied, little is known about its effect on the viability of the cyanobacterial cells. This study aimed to test eight strains of the most frequent bloom-forming cyanobacterium, Microcystis aeruginosa, exposed to a realistic concentration range of chitosan used in lake restoration management (0 to 8 mg chitosan L−1). We found that after 1 h of contact with chitosan, in seven of the eight strains tested, photosystem II efficiency was decreased, and after 24 h, all the strains tested were affected. EC50 values varied from 0.47 to > 8 mg chitosan L-1 between the strains, which might be related to the amount of extracellular polymeric substances. Nucleic acid staining (Sytox-Green®) illustrated the loss of membrane integrity in all the strains tested, and subsequent leakage of pigments was observed, as well as the release of intracellular microcystin. Our results indicate that strain variability hampers generalization about species response to chitosan exposure. Hence, when used as a coagulant to manage cyanobacterial nuisance, chitosan should be first tested on the natural site-specific biota on cyanobacteria removal efficiency, as well as on cell integrity aspects.

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Removal efficiency of phosphorus, cyanobacteria and cyanotoxins by the “flock & sink” mitigation technique in semi-arid eutrophic waters

Cited by 39 publications

References 51 publications

‘Floc and Sink’ Technique Removes Cyanobacteria and Microcystins from Tropical Reservoir Water

‘Floc and Sink’ Technique Removes Cyanobacteria and Microcystins from Tropical Reservoir Water

Coagulation and precipitation of cyanobacterial blooms

Chitosan as a Coagulant to Remove Cyanobacteria Can Cause Microcystin Release

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