Designing for Reliable, Cost-Effective Nutrient Removal: Lessons Learned
Authors:
- Ron J. Latimer, P.E., Ronald L. Taylor, P.E., Mark Bottin, P.E., and Paul Pitt, P.E., Ph.D.
Wastewater treatment plants have been required to meet stringent effluent limits for total nitrogen and total phosphorous for the past five years in the Chesapeake Bay drainage basin within Maryland, the District of Columbia and Virginia, and for the past ten years in the Neuse River Basin in North Carolina. Depending on plant location and flow increases, plants in these areas are required to meet total nitrogen limits between 3.0 and 8.0 mg/L and total phosphorous limits between 0.18 and 2.0 mg/l. This significant experience in designing, starting up, and optimizing operations at these plants provide important “lessons learned” that can be applied to the design and operation of reliable, cost-effective nutrient removal in Pennsylvania.
Examples of some of the lessons learned include: the importance of equal flow splitting and self-regulating flow control to biological and sedimentation process units, the need to address foam generation and provide for removal from the plant, the benefits of providing flexible aerobic, anoxic and anaerobic mass fractions, importance of DO control and minimizing DO carryover with internal recycles and post anoxic zones, the impact of analyzing and controlling recycle streams, the value of a plant specific cost-benefit analysis of chemical feed versus basin volume, supplemental carbon addition experience, the impact of properly performing nutrient analyzers, the need to accommodate wet weather flows and methods for handling low temperatures.
This paper will present examples of the above lessons learned using actual plant case studies based on full scale plant performance, upsets, special sampling results, and plant modeling efforts at BNR and ENR plants.
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