sugar and BOD 5 1

[schtroumpfette]

If a sugar refinery sends a large amount of soft liquor (liquid sugar) into the Hudson Bay, what is the BOD of the discharge? Does sugar translate directly into BOD? i.e., if the refinery releases 1,000 lbs of sugar, is that equivalent to 1,000 lbs of BOD?

 

[bimr]

Molasses has the highest BOD of approximately 900,000 mg/l. High pollution load effluents from cane sugar processing may contain a BOD of 2000 to 3000 mg/l BOD.

 

[schtroumpfette]

Thanks bimr! So this means that for every lb of sugar, we have .9 lbs of BOD!

 

[NPSEngineer]

Sugar combines with oxygen to form carbon dioxide and water through aerobic respiration to generate energy and biomass. A summary of the chemical reaction is C6H12O6 + 6O2 Arrow 6CO2 + 6H2O. The molecular weight of sugar is 180 g/mol and Oxygen (O2) is 32 g/mol. The ratio of sugar to oxygen is 180 g/mol / (6x32g/mol) = 180/192 = 0.9375. So for a 1000 lbs of sugar, you'll need 937.5 lbs of oxygen (O2). BOD is a concentration (mg O2/L or mg/L), so if you want to figure out the BOD you need to determine the amount of dilution. 1000 lbs of sugar in a pond will have a much higher BOD than 1000 lbs in Hudson Bay. If they dump it in a river, what's the flow rate of the river?

 

[schtroumpfette]

So what you're saying, NPS, is that while complete lack of DO, caused by a sky-high BOD in this instance, will be incredibly toxic to aquatic organisms -- delayed egg hatching, decreased food efficiency and growth rate, reduced size and increased defects in offsprings, decreased tolerance to some toxic substances, you name it --but by the sheer size of Hudson Bay, the unfathomably high volume of water that moves through the Bay every day, the impact of such a discharge is, essentially, nill . . . ??!! When and where do we draw the line, I wonder?

 

[shahyar]

To add clarification to what NPS said:
The oxygen calculation from a reaction shows ThOD (Theoritical Oxygen demand). COD (Chemical Oxygen demand) is a fraction of ThOD and BOD is a fraction of COD.