Here are the answers to the Feb. 3, 2021 edition of TPO's Exam Study Guide:

1. When defining confined spaces in your facility, who makes the determination whether the space is non-permit confined space or permit-required confined space?
The answer to this question is D, the employer. Confined spaces are very common in the water and wastewater industry. The OSHA standards (29 CFR 1910.146) states the employer evaluates each workplace and makes the determination of what type of confined space each one is. The definition of confined spaces can be found in the standard. If the space is defined as a "permit-required confined space," then the employer must inform the employees of its existence, location and hazards it poses. These procedures are important for the operator to understand, especially when performing duties in confined spaces. Remember, safety first.

2. The operator fed 10 pounds of H2SiF6 (25% commercial purity, 79.2% fluoride) into 600,000 gallons of water that contained 0.3 mg/L naturally occurring fluoride. How many pounds of fluoride did the operator add to the water and what should the finished water fluoride concentration be?
The correct answer is D, 1.98 pounds, 0.7 mg/L. It is important to note that the operator fed 10 pounds of H2SiF6, which is a fluoride compound that contains components other than fluoride. In order to determine the pounds of actual fluoride, you need to multiply the pounds of compound fed by the commercial purity percent and fluoride percent.

(10 pounds of H2SiF6)(0.25 commercial purity)(0.792 fluoride) = 1.98 pounds of fluoride.

If the operator added 1.98 pounds of fluoride, the finished water fluoride concentration should be 0.7 mg/L.

1.98 pounds of fluoride / (0.6 MG * 8.34) = 0.40 mg/L fluoride dosage.

0.40 mg/L fluoride dosage + 0.3 mg/L naturally occurring fluoride = 0.7 mg/L fluoride concentration.

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