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Cyanobacteria Toxin and Cell Propagation through Seven Lake Erie Treatment Plants during the 2013 Algal Bloom Season - abstract
Citation:
Dugan, N., H. Mash, AND D. Lytle. Cyanobacteria Toxin and Cell Propagation through Seven Lake Erie Treatment Plants during the 2013 Algal Bloom Season - abstract. Presented at AWWA WQTC 2014 HAB, New Orleans., LA, November 16 - 20, 2014.
Impact/Purpose:
To inform the public of toxins in drinking water.
Description:
Over the past five years, Lake Erie has been experiencing harmful algal blooms (HABs) of progressively increasing severity. Cognizant of the potential health and economic impacts, the United States Environmental Protection Agency’s (USEPA’s) Water Supply and Water Resources Division (WSWRD), in partnership with the Ohio Environmental Protection Agency and local municipalities, sampled water throughout the treatment trains of seven water treatment facilities that use Lake Erie as a drinking water source. The samples were tested for HAB-associated toxins, chlorophyll-a, and other chemical markers commonly associated with HABs. This sampling campaign ran from June through November and represented a unique opportunity to characterize the development of Lake Erie’s cyanobacterial bloom, its associated toxins, and the propagation of those toxins through drinking water treatment facilities, at a high level of analytical detail. Four of the treatment facilities were located on Lake Erie’s Western basin and three drew water from the Eastern basin. The dividing line between Western and Eastern basins runs roughly North from Sandusky, Ohio, and the Western basin has historically experienced higher levels of cyanobacteria activity than the Eastern basin. All of the facilities employed conventional treatment and seasonal powdered activated carbon (PAC) addition. Six of the seven plants employed pre-oxidation with permanganate while the seventh practiced pre-chlorination. Each month, samples were collected at six to eight locations per facility, depending on treatment scheme and accessibility. The samples were analyzed for eight microcystin variants (-LA, -LF, -LR, -LW, -LY, -RR, -WR, -YR) plus nodularin. The other chemical markers included phosphate, ammonia, nitrate and nitrite. Chlorophyll a concentrations served as a proxy for the concentration of suspended cyanobacterial and algal cells. As the bloom developed through the summer, chlorophyll a concentrations in the Western basin treatment plant intakes increased by about an order of magnitude per month, ranging from 0.2 - 6 µg/L in June to 14 – 100 µg/L in September. In contrast, plant influent chlorophyll concentrations for the three Eastern basin facilities remained well below those observed in the Western basin, peaking at 1.4 - 8.5 µg/L in September. As the bloom peaked, Western basin plant influent total toxin concentrations approached 1 µg/L, with the bulk of the toxin present in the intra-cellular phase. In the Eastern basin, plant influent toxin concentrations were only detected at one facility, at a level of 0.077 µg/L. During the bloom peak, finished water toxin concentrations at all seven facilities were below detection limits (<= 0.009µg/L). The information in this presentation will help drinking water providers and regulators better understand how effectively conventional treatment facilities, aided by pre-oxidation and PAC addition, cope with seasonal HABs.
URLs/Downloads:
http://www.awwa.org/Portals/0/files/education/conferences/wqtc/wqtc14/pdfs/WQTC14FinalProgramWeb.pdf