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9. Oxidation of Microcystis aeruginosa and Microcystins with Peracetic Acid.

Author

Alnahas, Mennatallah, Almuhtaram, Husein, and Hofmann, Ron

Subjects
*CYANOBACTERIAL blooms, *MICROCYSTIS aeruginosa, *WATER purification, *DISINFECTION by-product, *PERACETIC acid, *CYANOBACTERIAL toxins
Abstract

Peracetic acid (PAA) shows potential for use in drinking water treatment as an alternative to prechlorination, such as for mussel control and disinfection by-product precursor destruction, though its impact as a preoxidant during cyanobacterial blooms remains underexplored. Here, Microcystis aeruginosa inactivation and microcystin-LR and -RR release and degradation using PAA were explored. The toxin degradation rates were found to be higher in alkaline conditions than in neutral and acidic conditions. However, all rates were significantly smaller than comparable rates when using free chlorine. The inactivation of M. aeruginosa cells using PAA was faster at acidic pH, showing immediate cell damage and subsequent cell death after 15–60 min of exposure to 10 mg/L PAA. In neutral and alkaline conditions, cell death occurred after a longer lag phase (3–6 h). During cell inactivation, microcystin-LR was released slowly, with <35% of the initial intracellular toxins measured in solution after 12 h of exposure to 10 mg/L PAA. Overall, PAA appears impractically slow for M. aeruginosa cell inactivation or microcystin-LR and -RR destruction in drinking water treatment, but this slow reactivity may also allow it to continue to be applied as a preoxidant for other purposes during cyanobacterial blooms without the risk of toxin release. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Defining the Chemical Additives Driving In VitroToxicities of Plastics

Author

Chen, Wanzhen, Gong, Yufeng, McKie, Michael, Almuhtaram, Husein, Sun, Jianxian, Barrett, Holly, Yang, Diwen, Wu, Menghong, Andrews, Robert C., and Peng, Hui

Abstract

Increases in the global use of plastics have caused concerns regarding potential adverse effects on human health. Plastic products contain hundreds of potentially toxic chemical additives, yet the exact chemicals which drive toxicity currently remain unknown. In this study, we employed nontargeted analysis and in vitrobioassays to identify the toxicity drivers in plastics. A total of 56 chemical additives were tentatively identified in five commonly used plastic polymer pellets (i.e., PP, LDPE, HDPE, PET, and PVC) by employing suspect screening and nontargeted analysis. Phthalates and organophosphates were found to be dominant in PVC pellets. Triphenyl phosphate and 2-ethylhexyl diphenyl phosphate accounted for a high amount (53.6%) of the inhibition effect of PVC pellet extract on human carboxylesterase 1 (hCES1) activity. Inspired by the high abundances of chemical additives in PVC pellets, six different end-user PVC-based products including three widely used PVC water pipes were further examined. Among them, extracts of PVC pipe exerted the strongest PPARγ activity and cell viability suppression. Organotins were identified as the primary drivers to these in vitrotoxicities induced by the PVC pipe extracts. This study clearly delineates specific chemical additives responsible for hCES1 inhibition, PPARγ activity, and cell viability suppression associated with plastic.

Published
2022
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26. Cyanotoxins and cyanobacteria cell accumulations in drinking water treatment plants with a low risk of bloom formation at the source

Author

Almuhtaram, Husein, Cui, Yijing, Zamyadi, Arash, Hofmann, Ron, Almuhtaram, Husein, Cui, Yijing, Zamyadi, Arash, and Hofmann, Ron

Abstract

Toxic cyanobacteria have been shown to accumulate in drinking water treatment plants that are susceptible to algal blooms. However, the risk for plants that do not experience algal blooms, but that receive a low influx of cells, is not well known. This study determined the extent of cell accumulation and presence of cyanotoxins across the treatment trains of four plants in the Great Lakes region. Samples were collected for microscopic enumeration and enzyme-linked immunosorbent assay (ELISA) measurements for microcystins, anatoxin-a, saxitoxin, cylindrospermopsin, and beta-methylamino-L-alanine (BMAA). Low cell influxes (under 1000 cells/mL) resulted in significant cell accumulations (over 1 x 10(5) cells/mL) in clarifier sludge and filter backwash samples. Microcystins peaked at 7.2 microg/L in one clarifier sludge sample, exceeding the raw water concentration by a factor of 12. Anatoxin-a was detected in the finished drinking water of one plant at 0.6 microg/L. BMAA may have been detected in three finished water samples, though inconsistencies among the BMAA ELISAs call these results into question. In summary, the results show that plants receiving a low influx of cells can be at risk of toxic cyanobacterial accumulation, and therefore, the absence of a bloom at the source does not indicate the absence of risk.

Published
2018

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