Oxygen transfer at low drop weirs

Oxygen transfer into water at low-drop weirs was studied by using a prototy pe-scale, recirculating hydraulic flume with a weir width of 0.61 m, and a downstream channel width of 1.22 m. An enhanced-oxygen environment was used to maintain sufficient difference between saturation and upstream dissolve d oxygen concentrations to reduce the experimental uncertainty. The variati on in the deficit ratio was a function of tailwater depth H was evaluated b y using unit discharges q of 167, 334, and 502 m(3)/hr m and weir heights W of 0.54, 1.04, and 1.36 m. A semitheoretical equation for predicting r as a function of jet Froude number F-J, drop height h, and H was fitted to obs erved values by nonlinear regression analysis. An assumed value of 0.667 fo r maximum H/h (found in the literature) proved acceptable. We concluded tha t tailwater depths are important to predict oxygen transfer at low-drop wei rs, but that designing for optimum tailwater depth to maximize oxygen trans fer may not be as important as was previously thought, because large optimu m ranges for H/h were observed in this study.