Brown and Caldwell Home Page

Brown and Caldwell engineers and scientists are technical and thought leaders in the environmental sector. Meet the people who have been advancing innovation for more than 70 years.
Author      Title/Abstract      

Author: Andre van Niekerk, Janice Ruhl, and Paul Pitt (Hazen and Sawyer); Denny Parker (Brown and Caldwell); Salil Kharkar and Aklile Tesfaye (District of Columbus Water and Sewer Authority)
Date: 10/03
WEFTEC Conference 2003

The District of Columbia Water and Sewer Authority's Blue Plains Advanced Wastewater Treatment Plant, which has a design average daily flow of 370 mgd and a design peak flow of 1,076 mgd, discharges to the Potomac River, a major tributary to the Chesapeake Bay. In order to satisfy the NPDES permit and the nutrient load reduction goals of the Chesapeake Bay Agreement (i.e. 40% load reduction from 1985 levels), strict seasonal nitrogen and phosphorus effluent discharge limits, shown in Table 1 below, must be met. Table 1: NPDES Permit Requirements. Summer (May 1 – October 31) Winter (November 1 – April 30) Monthly Maximum Weekly Maximum Monthly Maximum Weekly Maximum NH3-N (mg/L) 1.0 1.5 6.5 9.8 TN (mg/L) 5.5 - 8.58 - TP (mg/L) 0.18 0.27 0.18 0.27 The Nitrification/Denitrification facilities are currently being upgraded to reliably achieve strict Nitrogen and Phosphorus limits, and to provide for future centrate and increased influent loads. This paper presents the evaluation of alternative Nitrification/Denitrification (N/DN) processes, for both dry weather and wet weather operations, using the Biowin™ model. Results are presented in terms of solids inventory concentrations, ammonia and nitrate concentrations, and sedimentation basin factor of safety. Step feed with a dedicated stage for centrate treatment was determined to be the most beneficial process configuration for the N/DN reactors. Additional process modifications including automated control of the Secondary Effluent feed to the reactors, automated process air control, polymer addition to the mixed liquor channels and an increase in RAS pumping capacity are recommended to provide reliable process performance under wet weather scenarios.

This library contains published materials for which copyrights may be owned by entities other than Brown and Caldwell, but which are stored for limited uses by BC employees. Technical papers authored by BC employees generally may be printed and shared electronically with clients and prospective clients outside BC. Technical papers cannot be sold, and technical papers shared outside BC must have proper attribution of the original sponsoring organization or conference where the paper was presented. This attribution is embedded in each technical paper file when it is loaded into this library. Published articles from magazines or trade journals which are stored in this library are FOR INTERNAL USE ONLY and SHOULD NOT be distributed to clients or others outside BC, without express permission of the copyright owner. For questions regarding copyrights associated with any document in this library, or questions regarding copyrights in general, contact the Legal Department.