Nutrified Sludge

by W. Max Frazier, Proj. Engr.; Black and Veatch, Asheboro, NC,
Kathryn Kalb, Gen. Mgr.; Operations, Orange Water and Sewer Authority, Carrboro, NC,
Ronald Williamson, Plants Mgr.; Orange Water and Sewer Authority, Carrboro, NC,

Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 8, Pg. 64-65

Document Type: Feature article


A new biological treatment process, Nutrification, enables a wastewater treatment plant to remove phosphorus from influent water at an operating and maintenance cost 35% less than that of chemical treatment methods. It is most effective for weak sewage or plants that have trickling filters—a venue that rules out other methods of biological phosphorus removal. The North Carolina Water Resources Research Institute and the Urban Water Consortium designed and built pilot facilities to evaluate several biological removal processes for treatment plants. The pilot studies indicated that the UNC process was the only one capable of reducing the wastewater phosphorus concentration to under 1.0 ppm, regardless of conditions such as temperature, flow and phosphorus loading. OWASA developed its own biological process, which is most effective at lower BOD/P ratios. Plant modifications included improvements to the trickling filters and a two-stage primary sludge fermenter designed by Black & Veatch. The fermenter features a two-compartment tank that efficiently produces volatile acids. The sludge nutrification stage creates an environment conducive to biological phosphorus treatment. This process minimizes the negative effect that nitrates from nitrification treatment can have on the biological phosphorus treatment, and conditions the process organisms for maximum subsequent phosphorus removal.

Subject Headings: Biological processes | Water treatment plants | Phosphorus | Chemical treatment | Chemical processes | Industrial wastes | Wastewater treatment plants | Water resources

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