___ is the biggest threat to receiving waters when meat packing wastes are discharged.

• A. Oxygen Demand
• B. Biochemical Oxygen Demand
• C. pH Change
• D. Temperature Rise

Answer: (A)

The key idea is that the main danger to receiving waters from meat processing wastes is the consumption of dissolved oxygen caused by the organic material in the waste. When these wastes are discharged, microbes rapidly break down the organic matter, pulling in oxygen from the water. This creates an oxygen demand on the stream or river—the more oxygen that is required to oxidize the waste, the lower the dissolved oxygen available for fish and other aquatic life.

Oxygen Demand is the broadest way to describe this effect because it encompasses all the oxygen that will be used up to oxidize the waste, not just the portion accounted for by biological processes. Biochemical Oxygen Demand is a specific measure of the oxygen that microbes would use biologically, which is a major part of the total demand, but the overall threat to the water quality comes from the total oxygen depletion that results from that demand.

While changes in pH and temperature can stress aquatic life, they do not inherently represent the same direct, immediate risk of depleting dissolved oxygen that high oxygen demand does from organic discharge.