Construct a BOD demand curve for a sample that has a first s

Construct a BOD demand curve for a sample that has a first stage rate constant K of 0.16 d1 (base 10) and a nitrogenous rate constant KN 0.08 d1(base 10). Nitrification is not significant until a period of 7.5 days have passed. The ultimate first stage BOD is 335 mg/L and the ultimate nitrogenous demand is 120 mg/L. What is the total BOD exerted at 10 days? How many complete days are required to exert at least 90% of the expected demand?

Solution

The test for biochemical oxygen demand (BOD) is a bioassay procedure that measures the oxygen consumed by bacteria from the decomposition of organic matter (Sawyer and McCarty, 1978). The change in DO concentration is measuredover a given period of time in water samples at a specified temperature.

Conversions:

ultimate BOD (L)

= 335

kilogram/meter^3

= 335000

milligram/liter

deoxygenation rate constant (k)

= 0.16

second^-1

= 13823.999999969

day^-1

time (t)

= 10

day

= 10

day

Solution:

biochemical oxygen demand (BOD_t)

= 335000

milligram/liter

ultimate BOD (L) = 335 kilogram/meter^3 = 335000 milligram/liter