Onondaga to Ontario: Management of bioavailable phosphorus in municipal wastewaters for control of Cladophora

Document Type


Publication Date



© 2015 International Association for Great Lakes Research. Phosphorus (P) concentrations in the open waters of Lake Ontario have been reduced markedly through load management. Yet, nuisance growth of Cladophora persists in the nearshore where urban P inputs are received. Elimination of nuisance conditions will require application of more effective phosphorus treatment technologies with particular attention to phosphorus bioavailability. One such technology, ballasted flocculation, was implemented in 2005 at the Metropolitan Syracuse Wastewater Treatment Plant (Metro) in Syracuse, NY which discharges 68 MGD (257 MLD, million liters per day) to Lake Ontario via the Seneca-Oneida-Oswego River system. Wet chemistry measurements and soluble- and particulate-phase bioassays of phosphorus bioavailability are used here in assessing the efficacy of the technology. Effluent total (TP) and soluble reactive (SRP) phosphorus concentrations using ballasted flocculation technology over the period 2005-2012 averaged 86 and 3. μg P/L, respectively, and the effluent BAP (bioavailable phosphorus) concentration was 10. μg P/L. In operation now for a decade, Metro has reduced its effluent total phosphorus by 86%, soluble reactive phosphorus by 99% and bioavailable phosphorus by 97% compared with the conventional chemical treatment used previously (iron salts and gravity clarification). The reduction in BAP was accomplished through direct removal of the SRP, dissolved organic (DOP) and particulate (PP) phosphorus fractions, but also by reducing the bioavailability of DOP and PP. Retrofit implementation of ballasted flocculation at Metro is described and the effectiveness of load reductions in altering the trophic state of the immediate receiving water, Onondaga Lake, is examined. The role of ballasted flocculation in an integrated phosphorus management program for the Lake Ontario nearshore is considered.

Publication Title

Journal of Great Lakes Research