Learning how to curtail phosphorus

A pilot project pointed the way for full-scale treatment of phosphorus at Metro.

The Metropolitan Syracuse Wastewater Treatment Plant (Metro) is considered a major source of the phosphorus that reaches Onondaga Lake. Phosphorus removal with conventional technologies is expensive. The Onondaga County Department of Water Environment Protection (WEP) implemented a $1.9 million pilot project—completed 6 years ahead of schedule—to evaluate six different phosphorus treatment technologies.

This pilot project concluded that high-rate flocculated settling (HRFS) could reduce phosphorus in Metro's discharge to extraordinarily low levels (0.12 mg/L as a 12-month rolling average). On the basis of this work, WEP can use HRFS to meet New York State effluent requirements.

The pilot project also provided a basis of design for the full-scale phosphorus treatment facility that WEP is now building.

It appears today that the HRFS technology may be able to achieve lower limits than Onondaga County currently must meet. Moreover, because of the high efficiency of the HRFS system, WEP has projected significant savings over more traditional filter technologies.

By 2012 Onondaga County must reduce the phosphorus discharges to 0.02 mg/L, the most restrictive in the U.S. and perhaps in the world. To meet such a low limit, the County is again testing technologies.