HR: 12:10h
AN: OS52A-08    [Abstracts]
TI: Modeling the Effects of Changing Seasonal River Flow Rates on the Mixing of Reverse Osmosis Plant Effluent into the Pasquotank River in North Carolina
AU: * Fischer, K M
EM: kmfischer@mail.ecsu.edu
AF: Elizabeth City State University, Department of Geological, Environmental and Marine Sciences, Elizabeth City, NC 27909 United States
AU: Hankinson, S D
EM: sdhankinson@mail.ecsu.edu
AF: Elizabeth City State University, Department of Geological, Environmental and Marine Sciences, Elizabeth City, NC 27909 United States
AB: The goal of this research, begun Fall 2004, is to assess the seasonal impact of effluent from a reverse osmosis (RO) plant on the water of the Pasquotank River, a trunk river of Albemarle Sound in northeast North Carolina. Currently, the plant discharges about 103,000 gallons of high salinity (16 ppt) processed groundwater into Chantilly Bay in the Pasquotank River (0-3 ppt, depending on season) over an eight-hour operational day. The impact of the RO effluent on water chemistry and physical properties along the river bottom depends on the flow rate of the river. The Pasquotank is slower flowing (anecdotally, reverse flowing at times) during the generally dry summer season and faster flowing during the rainy winter season. This varying river flow rate may result in various effluent zones: a pool of effluent on the riverbed, a plume of effluent dissipating with downstream distance, or a minimal effluent signal near the outlet manifold. Modeling of seasonal data for the current rate of effluent discharge allows prediction of the effects of tripling the daily volume of RO plant discharge through round-the-clock plant operation, an outcome that seems likely in the near future due to residential growth in the county served by the plant. Data from fall and early winter 2004 will be presented. Water parameters (salinity/conductivity, temperature, pH, turbidity, Secchi depth, dissolved oxygen content, and dissolved major cation concentrations) are measured biweekly at nine surface stations (three water depths at each station) in the general vicinity of the effluent discharge outlet. Similar parameters are measured biweekly for Pasquotank River water at two stations upstream and two stations downstream of the outlet. River flow rates and discharge rates are measured weekly. The results of modeling using a two-end member mixing model and a normative analysis treatment will be presented. Additionally, modeling results for various possible changes (relocation of discharge outlet, outlet manifold redesign, reselection of wells for plant influent, rescheduling of discharge periods, effluent pre-discharge dilution, etc.) will be discussed.
DE: 4235 Estuarine processes
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
DE: 0400 Biogeosciences
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting