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Cyanobacteria Toxin and Cell Propagation through Six Lake Erie Treatment Plants
Citation:
Dugan, N., H. Mash, D. Lytle, T. Sanan, K. Kelty, M. Pham, AND C. Muhlen. Cyanobacteria Toxin and Cell Propagation through Six Lake Erie Treatment Plants. Presented at AWWA/WEA Ohio Section Annual Meeting, Columbus, OH, August 26 - 29, 2014.
Impact/Purpose:
The information in this presentation is intended for use by practicing engineers and drinking water utility managers. The information will allow these individuals in these groups to 1) better understand their facility's source water and 2) make informed decisions about how to operate their treatment facilities.
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 (OEPA) and local municipalities, sampled water throughout the treatment trains of six water treatment facilities that use Lake Erie as a drinking water source. The water samples were tested for HAB-associated toxins, chlorophyll-a, and other chemical markers commonly associated with HABs. This sampling campaign 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 two drew water from the Eastern basin. All of the facilities employed conventional treatment and seasonal powdered activated carbon (PAC) addition. Five of the six plants employed pre-oxidation with permanganate while the sixth practiced pre-chlorination. The samples were analyzed for eight microcystin variants (-LA, -LF, -LR, -LW, -LY, -RR, -WR, -YR) plus nodularin, by liquid chromatography with mass spectrometric detection. 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. Samples of the analytical data for one of the Western basin facilities are shown in Figures 1 and 2 on the second page. As the bloom developed through the summer, chlorophyll a concentrations in the treatment plant intake increased by about an order of magnitude per month (Figure 1). This observed rate of increase was typical for the Western basin facilities. In contrast, plant influent chlorophyll concentrations for the two Eastern basin facilities remained orders of magnitude below those observed in the Western basin. As the bloom approached its peak, toxins were observed in the treatment plant influent and at several locations in the treatment process (Figure 2). Toxin samples were separated by filtration, and filtrate and retentates were analyzed separately in order to generate estimates of extra- and intra-cellular toxin concentrations. For the facility and sampling date shown in Figure 2, the bulk of the toxins were observed to be intra-cellular. This distribution of toxins was typical of those observed over the summer at the other treatment facilities. It is anticipated that the information in this presentation will help Ohio drinking water providers and regulators better understand how effectively conventional treatment facilities, aided by pre-oxidation and PAC addition, cope with seasonal HABs.
