---
title: "Biochemical Oxygen Demand"
canonical: "https://help.innovyze.com/space/infosewer/17467216/Biochemical%20Oxygen%20Demand"
format: markdown
---
Biochemical Oxygen Demand (BOD) is the most widely used parameter of organic pollution in sanitary sewer systems. The ability to model BOD is of great importance in wastewater engineering to assist wastewater utilities in (1) estimating the quantity of oxygen required to biologically stabilize the organic matter present; (2) determining the size of wastewater treatment facilities; (3) evaluating the efficiency of the treatment process; and (4) ensuring compliance with wastewater discharge permits (Tchobanoglous 2003).

InfoSewer Pro models the rate of BOD oxidation (exertion) throughout the collection system using first-order kinetics with the rate of oxygen utilization being proportional to the difference between the amount of oxygen used and the ultimate BOD as:

![image](media://04ac609f-fa8c-498f-a345-5f5c45ec0eec)

or

![image](media://84cd77dd-7a87-4725-beb0-3e6565b59636)

where

BOD = BOD exerted at time t, mg/L

UBOD = total or ultimate carbonaceous BOD, mg/L

k = first-order reaction rate constant, 1/day

t = time, day

The value of the first-order reaction rate constant k varies with the type of waste and normally ranges from 0.05/day to 0.46/day or more, with a typical value of 0.23/day. This constant can also be expressed as a function of temperature as:

![image](media://1252fd8a-5a76-4ca6-818f-10e9bca5ac68)

where k20 is the first-order reaction rate constant at 20oC (1/day) and T is the temperature (degree Celsius). The value of θ is 1.056 in the temperature range between 20oC and 30oC and 1.135 in the temperature range between 4oC and 20oC, with a typical value of 1.047.InfoSewer Pro determines and uses appropriate values of k and θ based on the user-specified temperature. The default values used by InfoSewer Pro for k, θ, and T are 0.23/day, 1.047, and 20oC, respectively.

![image](media://1828c376-110f-4156-9540-527934289a9a)