Use of online nutrient monitoring for automatic aeration and nitrate recycle pump control

The Northside Wastewater Treatment Plant (WWTP) in Kinston, NC was expanded and upgraded in 2006 for biological nutrient removal (BNR) to meet limits of 3 mg/L total nitrogen (TN) and 1 mg/L total phosphorus (TP). In addition to the traditional approach of controlling the blowers based on dissolved oxygen (DO) readings, the City decided to implement an aeration basin blower control system using readings from an online nutrient monitoring system. With the availability of online nutrient readings, the blower system has the capability to operate based on the actual level of wastewater treatment desired and obtained. The online nutrient monitoring system also can be used to control nitrate recycle pump speed to optimize anoxic zone performance. This paper will provide a discussion of the aeration and nitrate recycle control schemes, challenges encountered during the preparation of specifications for contractor bidding for the development of these tailored control schemes, and results from the troubleshooting and start-up of the control system.

The City of Kinston had two existing WWTPs, Northside and Peachtree, and both consisted of an extended aeration activated sludge process in concrete lined basins. The City needed to upgrade the plants to meet an effluent TN limit of 3.5 mg/L, and due to flooding issues at the Peachtree site, ultimately decided to consolidate treatment at the Northside site. The plant was expanded, upgraded, and renamed the Kinston Regional Water Reclamation Facility.

The new plant consists of a Johannesburg activated sludge BNR process (Figure 1) followed by deep-bed denitrification filters. An online nutrient analyzer was installed at the denitrification filters facility to provide nitrate readings for use in the automatic methanol feed control scheme. To enable close tracking and optimization of the upstream activated sludge BNR system performance, an online analyzer capable of measuring ammonia, nitrate, nitrite and soluble phosphorus was installed to provide real-time nutrient data throughout the BNR process zones.  Sampling locations include the BNR basin influent, the last anoxic zone (Zone E), Zone F and Zone G (corresponding to locations at one-third and two-thirds the length of the aerated zone), and at the secondary clarifier influent splitter box.

Customer comments

  1. By Engr.A.Kh.M.Emdad Hossain on

    Auto aeration of controlled compost pile increase organic nitrate.