WILL BIOLOGICAL NITROGEN REMOVAL IMPROVE MY RECEIVING STREAM? WATER QUALITY MONITORING AS AN INVESTIGATIVE TOOL

摘要

The Hopewell Regional Wastewater Treatment Facility (HRWTF) initiated the HopewellEstuary Region Monitoring and Assessment (HERMA) project to evaluate the status ofwater quality and living resources in the region, and predict the benefits of biologicalnitrogen removal (BNiR) on the receiving stream. A watershed screening assessmentrevealed that dissolved oxygen (D.O.) conditions were generally good, but that highturbidity caused poor conditions for the growth of submerged aquatic vegetation(SAV). To further investigate near-field water quality and the causes of lightattenuation, HRWTF initiated a biweekly sampling and continuous monitoring programin the James River and Baileys Creek. Results indicate that the approved mixing zoneis fulfilling its regulatory purpose of reducing ammonia concentrations. However, theHRWTF discharge contributes to low D.O. conditions within the mixing zone. Althoughincreased nitrification by HRWTF would reduce ammonia and NBOD in the near-fieldarea, BNiR alone will not significantly reduce eutrophic conditions in this area becausephytoplankton growth is limited by light and phosphorus. Large reductions in pointsourcenitrogen loads are expected to decrease phytoplankton growth downstream ofHopewell and thereby cause small increases in light availability downstream ofHopewell. However, light conditions would remain poor in most of the Hopewell estuaryregion due to the preponderance of inorganic suspended sediment, much of which isderived from local resuspension processes.