Algae and cyanotoxins removal by coagulation/flocculation: A review

2015

Environ. Sci. Technol.

Cyanobacterial harmful algal blooms (cyano-HAB) and microcystins (MCs) can cause a potential threat to public health. Here, a method for simultaneous removal of cyano-HAB and MCs was developed using chitosan-modified local soil (MLS) flocculation plus microorganism-modified soil capping. The experiment was conducted in simulated columns containing algal water collected from Lake Taihu (China). More than 90% of algal cells and intracellular MCs were flocculated and removed from water using chitosan-MLS and the sunken flocs were treated by different capping materials including Pseudomonas sp. An18 modified local soil. During 40 days of incubation, dissolved MC-LR and MC-RR showed 10-fold increase in the flocculation-only system. The increase of MC-LR and MC-RR in water was reduced by 30 and 70% in soil capping treatments; however, the total content of MCs in the sediment−water column remained similar to that in the control and flocculation only systems. In contrast, both dissolved MCs and total MCs were reduced by 90% in Pseudomonas sp. An18 modified soil capping treatment. The high performance of toxin decomposition was due to the combined effects of flocculation and MC-degrading bacteria that embedded in the capping material, which prevents dilution of bacteria biomass, concentrates algal cells, confines released toxins, and enhances toxin biodegradation.

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…Evaluation of Pseudomonas sp. An18 carrying capability revealed the modified soil was capable of embedding 10 15 bacterial cells/g soil ( Figure S3, Supporting Information). Proliferation tests showed that the biomass of Pseudomonas sp.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Simultaneous Removal of Harmful Algal Blooms and Microcystins Using Microorganism- and Chitosan-Modified Local Soil

2015

Environ. Sci. Technol.

“…6). Sedimentation was regarded as a major challenge for chemical coagulation and flocculation treatment of cyanobacteria cells because of the buoyant properties (Ghernaout et al, 2010) and low density of algal flocs (Pieterse and Cloot, 1997). Unlike in the constructed water treatment systems, sufficient sedimentation time can be provided to allow the small flocs to settle by creating static water condition and/or appropriate water retention time, or dissolved air bubbles can be generated to float the flocs with a low density (Edzwald, 1993).…”

Section: Algal Floc Formation Size Growth and Sedimentationmentioning

confidence: 99%

Influence of zeta potential on the flocculation of cyanobacteria cells using chitosan modified soil

Zhang

Journal of Environmental Sciences

2015

Using chitosan modified soil to flocculate and sediment algal cells has been considered as a promising strategy to combat cyanobacteria blooms in natural waters. However, the flocculation efficiency often varies with algal cells with different zeta potential (ZP) attributed to different growth phases or water conditions. This article investigated the relationship between ZP of Microcystis aeruginosa and its influence to the flocculation efficiency using chitosan modified soil. Results suggested that the optimal removal efficiency was obtained when the ZP was between − 20.7 and − 6.7 mV with a removal efficiency of more than 80% in 30 min and large floc size of > 350 μm. When the algal cells were more negatively charged than − 20.7 mV, the effect of chitosan modified soil was depressed (< 60%) due to the insufficient charge density of chitosan to neutralize and destabilize the algal suspension. When the algal cells were less negative than − 6.7 mV or even positively charged, a small floc size (< 120 μm) was formed, which may be difficult to sink under natural water conditions. Therefore, manipulation of ZP provided a viable tool to improve the flocculation efficiency of chitosan modified soil and an important guidance for practical engineering of cyanobacteria bloom control.

“…On the other hand, it is also well recognized that biodegradation is one of the elimination pathways to reduce its concentration in natural waters and sediment (Chen et al, , 2010. However, in severe cyano-HABs lakes, dramatic increased concentration of MCs after the cyano-HAB may exceed the endurance of indigenous MCs-degrading microorganisms (Ghernaout et al, 2010;Cai et al, 2010). Therefore, the application of exogenous MCs-degrading bacteria may become an important engineering measure for the elimination of MCs.…”

Section: Introductionmentioning

confidence: 99%

Enhanced and continued degradation of microcystins using microorganisms obtained through natural media

Hong

Journal of Microbiological Methods

2014

Microorganisms isolated through artificial media are often unsustainable in biodegrading microcystins (MCs) in natural water. Here we studied alternative approaches to isolate MCs-degrading bacteria using natural media. In comparison to two species (MS-1 and MS-2) isolated from artificial media and the failure of bacterial colonies formation using water extracts of sediment (10%, w/v), five colony species (WC-1 to WC-5) appeared using concentrated water extracts of sediment that is 10-fold enhancement of nutrient level. In the simulated biodegradation test in Lake Taihu water with continuous supply of MCs, a lag phase of 6 days was required for MS-1 and M-2 to degrade 13% and 15% of the added MC-RR and MC-LR, respectively, whereas the lag phase was only 3 days with approximately 44% and 31% removal of the added MC-RR and MC-LR by WC-1 to WC-5. During the continuous supply experiment, degradation of MCs by MS-1 and MS-2 stopped after 3 days, while degradation of MCs by WC-1 to WC-5 lasted continuously throughout the 18 day test period with 2 to 6-fold enhancement of removal rate. 16S rRNA gene sequences and phylogenetic analysis indicated the potential to amplify species of MCsdegrading bacteria when natural media were used. The results suggested that the increased adaptability of bacteria obtained through concentrated natural media was responsible for the enhanced and continued biodegradation under simulated natural water conditions.