Waste Water Assimilation

[salhu]

Hello all,

I am trying to find the critical oxygen deficit that can happen in a river with the introduction of a continuous waste water from a treatment plant.

I have used the following parameters;
Initial BOD=L= 1.471 mg/L
Initial oxygen deficit = Do = 0.943 mg/L
Deoxygenation Rate constant = Kl = 1.3936
Reoxygenation Rate constant = Ka = 8.68

I have used the equation IV-46 from the US EPA manual (

http://www.epa.gov/waterscience/library/modeling/wqascreenpart1.pdf),

at its page 337.

Problem is that i am getting negative oxygen deficit, which means that with the introduction of the waste, the oxygen constant is getting even higher after the introduction of the waste. A previous report shows the result otherwise; that report however does not include detials of the rate constants and calculations.

I am using wrong equation? wrong coefficients? or....any conceptual problem?

Help needed please.

Thank you.