OXYGEN SAG EQUATION FOR 2ND-ORDER BOD DECAY

A dissolved oxygen (DO) equation for a stream is developed in which th e biochemical oxygen demand (BOD) deoxygenation rate is described as a second-order reaction. Rate constants for a second-order BOD equation may be evaluated by graphical or numerical methods. The DO sag equati on incorporates exponential integral functions. These functions are av ailable in tabular form or they may be calculated by exact or approxim ate series. The time at which the minimum DO concentration occurs is c alculated numerically. The DO sag equation using. second-order BOD mod el fills a gap in the literature, as a number of in investigators had explored describing BOD decay as a second-order reaction but the corre sponding DO sag equation was not available to predict the impact of su ch wastes on a river. (C) 1998 Elsevier Science Ltd. All rights reserv ed.