Prediction of wastewater dilution and indicator bacteria concentrations for marine outfall systems

This paper describes a modeling study of near-field and far-field dilution of discharged effluents from a deep sea outfall system in Antalya Bay of Turkey. Initial dilution and wastewater plume behavior were simulated by Visual Plumes-UM3 model whereas Brooks dispersion model and first order bacterial decay formulations were used to simulate far-field dilution. The input data sets were collected by detailed field and lab investigations for effluent discharges (flow rate, total and fecal coliform concentration) and ambient environment (oceanographic and current measurements). Geostatistical methods and GIS were used to visualize results of the bacteriological sampling study. Site specific bacterial inactivation rates were determined by both in-situ and lab-scale experiments. Total dilution values and bacteria concentrations were predicted. Good agreement between predicted and measured total and fecal coliform concentrations were obtained for homogeneous and density stratified ambient conditions. Discussion on wastewater dilution mechanisms was presented with recommendations for similar future studies.