Sampling of Wastewater Effluent

Abstract

Sampling in an incompletely mixed effluent was studied with the aid of a hydraulic model. The effluent was the discharge from a major wastewater treatment facility. Residual chemicals from the chlorination/dechlorination process were of concern. Concentration time‐series data obtained in a 1:12 scale model were used to determine the best sampling location and duration and to predict expected sampling errors relative to spatially and temporally averaged concentration values. Some general concepts for sampler placement in not fully homogeneous streams were derived. Spatial concentration gradients have to be determined to select number and location of multiple sampling points. When concentrations fluctuate in time due to process controls, the flow patterns and velocity distributions have to be known to select representative sampling points. For example, representative sampling within a separated flow region requires carefully selected probe placement and long sampling durations. Physical model simulations can provide the information on flow and concentration time series that are necessary to select the sampling strategy.