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1.
Environ Technol ; : 1-14, 2024 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-38723193

RESUMO

ELISA assays are a potential tool to screen for dissolved or cell bound microcystins in drinking water treatment sludges. In order to evaluate this potential more thoroughly, experiments were performed in alum sludges to: (1) evaluate the impacts of sample storage times, temperatures, and sludge composition on spiked microcystin-LR recovery by ELISA; (2) examine the linearity of ELISA responses to spiked microcystin-LR as a function of sludge composition; and (3) examine the sensitivity ELISA and LC/MS/MS to five different concentrations of microcystin-producing cyanobacteria entrained in sludges of two different compositions. During storage experiments, microcystin recovery efficiencies ranged from 85% to 125% across the range of 12 storage time and temperature combinations with recovery efficiencies in 7 of the 12 combinations falling into the 90% to 110% range. During the linearity experiments, linear models fit ELISA responses in all sludge compositions with R2 values ≥ 0.95. During the sensitivity studies, simple freeze/thaw/centrifugation processing combined with ELISA or LC/MS/MS analyses resulted in detection of microcystins in thickened sludges derived from pre-coagulation cell suspensions of 102-106 cells/mL. In addition, the relationships between toxin concentrations in sludges and the original cell titers were linear regardless of analytical method.

2.
Front Microbiol ; 14: 1260460, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37915853

RESUMO

Opportunistic premise plumbing pathogens (OPPPs) have been detected in buildings' plumbing systems causing waterborne disease outbreaks in the United States. In this study, we monitored the occurrence of OPPPs along with free-living amoeba (FLA) and investigated the effects of residential activities in a simulated home plumbing system (HPS). Water samples were collected from various locations in the HPS and analyzed for three major OPPPs: Legionella pneumophila, nontuberculous mycobacterial species (e.g., Mycobacterium avium, M. intracellulare, and M. abscessus), and Pseudomonas aeruginosa along with two groups of amoebas (Acanthamoeba and Vermamoeba vermiformis). A metagenomic approach was also used to further characterize the microbial communities. Results show that the microbial community is highly diverse with evidence of spatial and temporal structuring influenced by environmental conditions. L. pneumophila was the most prevalent pathogen (86% of samples), followed by M. intracellulare (66%) and P. aeruginosa (21%). Interestingly, M. avium and M. abscessus were not detected in any samples. The data revealed a relatively low prevalence of Acanthamoeba spp. (4%), while V. vermiformis was widely detected (81%) across all the sampling locations within the HPS. Locations with a high concentration of L. pneumophila and M. intracellulare coincided with the highest detection of V. vermiformis, suggesting the potential growth of both populations within FLA and additional protection in drinking water. After a period of stagnation lasting at least 2-weeks, the concentrations of OPPPs and amoeba immediately increased and then decreased gradually back to the baseline. Furthermore, monitoring the microbial population after drainage of the hot water tank and partial drainage of the entire HPS demonstrated no significant mitigation of the selected OPPPs. This study demonstrates that these organisms can adjust to their environment during such events and may survive in biofilms and/or grow within FLA, protecting them from stressors in the supplied water.

3.
AWWA Water Sci ; 6(3)2023 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-39376724

RESUMO

The feasibility of using a 26-1 fractional factorial design to screen the relative importance of six water quality and operational factors in the removal of microcystin-LR (MC-LR) by powdered activated carbon (PAC) was evaluated through jar testing. The factors were: PAC type, PAC dose, total organic carbon (TOC) concentration, turbidity, alum dose, and timing of PAC versus coagulant application. Follow-up tests were performed to examine the interaction of PAC dose and TOC concentrations. All MC-LR analyses were performed by enzyme linked immunosorbent assay (ELISA) and liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The top three effect magnitudes were the same by ELISA and LC/MS/MS:PAC dose > PAC type > PAC application time. Correlation coefficients between removals estimated by ELISA and LC/MS/MS were >0.9 (p « .05). With both methods, the effects of PAC type and dose were found to be markedly larger than the other factors. The follow-up tests indicated a greater impact of PAC dose at higher natural organic matter concentrations. Factorial designs are not commonly used to plan drinking water jar test experiments. The results generated in this study were plausible with respect to the existing body of adsorption knowledge, thus helping to demonstrate the feasibility of the factorial approach.

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