Expanded use of Iron in Wastewater Treatment and role in toxic cyanobacterial resurgences
Ann Arbor, MI — Resurgences in toxic cyanobacterial blooms in the lower Great Lakes over the last decade led to an examination of total phosphorus (TP) and iron loading from wastewater treatment plants (WWTPs) in the Hamilton Harbour and Toronto. Compliance with regulatory standards for maximum TP concentration in wastewater has led to increased dependence on the use of iron chloride for phosphorus removal from effluent. However, ecological research suggests that increased supply of biologically available forms of iron may stimulate cyanobacterial growth.
"With governments very focused on reducing phosphorus in aquatic systems, additional research on other nutrients, such as iron, is necessary."
The researchers found that TP loadings from the Hamilton and Toronto WWTP's have, in general not increased over the last 10-15 years. Effluent sampling frequency for iron is much lower than for a regulated parameter such as TP, consequently there is greater uncertainty in loading estimates. Iron loading estimates are available for only a single plant from 1996 and 3 plants from 1999, precluding analysis of long-term iron loading trends. Iron use in the Humber WWTP in Toronto has increased 30%, while iron loading to Lake Ontario has increased 5-fold between 2001 and 2004. Iron loading from the Woodward Avenue WWTP that discharges into Hamilton Harbourt is 25% larger than the load from Toronto's Ashbridges Bay WWTP. The latter is the largest WWTP in Ontario, although it has only about 1/2 of the flow.
The possibility of industrial and municipal sources of iron stimulating cyanobacterial blooms raises questions about the impact of current point-sources of iron loading in the lower Great Lakes. In order to determine the full impact of the increased discharge of iron in wastewater effluents, increased monitoring of total iron concentrations in effluent needs to be undertaken by all WWTP operators. Additional research is needed to assess the nature of the relationship between iron and cyanobacteria blooms. Moreover, improved reporting to government is necessary.
Original Publication Information
Results of this study "Trends in Iron and Phosphorus Loading to Lake Ontario from Waste Water Treatment Plants in Hamilton and Toronto," are reported by Andrew S. Medeiros and Lewis A. Molot in the latest issue (Volume 32, No. 4, pp. 788-797) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2006.
Contacts
For more information about the study, contact Andrew Medeiros, Department of Biology, York University, Toronto, Ontario, M3J1P3; fraggle@yorku.ca; (416) 736-2100 x40076.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.
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