CONTINUOUS-FLOW RESIDENCE TIME DISTRIBUTION FUNCTION CHARACTERIZATION

Disinfection contactors are frequently characterized using tracer stud ies to determine macromixing patterns. For some applications, such as compliance with the surface water treatment rule, this information can be interpreted directly without much analysis. However, when tracer s tudies are performed to characterize residence time distributions for design purposes, this information is frequently analyzed using a metho d of moments approach. This paper shows that the method of moments app roach, when compared to a nonlinear regression approach, produces a bi ased estimate of mean residence time and dimensionless variance, and o ne with a greater mean square error. The amount of bias in moments est imators is significant in a numerical sense, and leads to qualitativel y poor estimation of the resulting residence time distribution. Exampl es are given of characterization of a pilot-scale chlorine contactor a nd a pilot-scale ozone contactor.