Treatment Plant Operator Exam Study Guide Answers

Given the following data:

Analyzing BOD readings of raw influent 10 ml samples 
Initial DO reading sample 1: 8 mg/L
Final DO reading sample 1: 1.4 mg/L
Initial DO reading sample 2: 8 mg/L
Final DO reading sample 2: 1.6 mg/L

What is the average BOD reading for this sample? This is an unseeded BOD test.

The answer to this question is B, 195 mg/L BOD. This can be solved using the BOD formula below. To perform the proper BOD analysis, prepare your sample and take the initial DO reading of each sample. Place the samples in a BOD incubator for five days (=/- four hours) at a temperature of 20 degrees C. After the five day period, retake the DO reading (final reading) and simply subtract that reading from your initial reading, multiply the reading by 300 milliliters (your sample bottle size) and divide your outcome by the milliliters of sample used (10 milliliters in this case). You should have readings of 192 mg/L and 198 mg/L, the question asked for an average of these numbers, so add them together and divide by 2. This will give you a final average of 195 mg/L BOD.

The pounds formula is as follows:

How does a venturi meter measure flow?

The correct answer is C, it measures the difference in pressure from two separate points. The venturi meter is a pressure-differential meter consisting of a converging cone, throat and diverging cone. The water flows fasters as it exits the converging cone and enters the throat. The faster moving water has a lower pressure than the slower moving water upstream of the converging cone. The difference in pressure at these two points is translated into a volume of flow. 


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