Back to Life: Charting A Course To Resurrect A Failing WWTP

摘要

Many challenges face small to mid-size utilities in meeting the demands of maintaining aged wastewater treatment plants in a down economy and a tightening regulatory climate. By way of example, this paper will present recent efforts to face those challenges for a 39,742 m3/day (10.5 mgd) ) high purity oxygen wastewater treatment plant in North Carolina. The majority of the plant is nearly 40 years old and originally designed to treat an industrial loading. The plant has aged significantly and facing many challenges including: 1.Originally designed for a 2.0 peaking factor – Seeing nearly 6.0 peak hour peaking factor 2.Failed dewatering system requiring complete replacement 3.Experiencing regulatory compliance issues with regards to effluent limits 4.Hydraulic restrictions within flow control structures 5.Direct runoff from compost area to receiving streams 6.Treatment train equipment failures 7.High O&M cost treatment system – HPO 8.Impending nutrient removal regulations A plant with many needs now and into the future and a utility that has been experiencing significant reductions in flow due to loss of industry and a declining population for over 10 years. The primary challenge was not identifying what required “fixing”, but how to fix it, how to prioritize the needs to meet current and future issues, how to finance the improvements, and how to address current regulatory compliance issues. The project employed a critical needs assessment to identify the deficiencies that required immediate action to return the plant to compliance. These were immediately assessed, designed and procured to demonstrate the plant’s commitment to improvement and to provide greater reliability. The long term solution was to complete a comprehensive evaluation of the plant process and equipment looking at current effluent limits as well as potential future nutrient limits and identifying the best long term solution to meet both criteria for the lowest cost. Utility and engineering staff worked closely with NCDENR staff to identify a phased solution to improving plant performance and negotiate a voluntary Special Order by Consent to provide the necessary time to complete the final recommendations in a fiscally responsible manner. Finally, the project was submitted for approval of a State Revolving Fund loan under the new priority points system and was the No. 1 rated project in 2010 receiving $10.6 MM in loan funds. With plan in place the utility is on course for meeting the many challenges it faces in preparing the existing wastewater treatment plant for the next 20 years.