Here are the answers to the June 17, 2021 edition of TPO's Exam Study Guide:

1. What term is defined as: “A measurement of how much acid can be added to water before there is a big change in pH.”

The answer to the question is D, alkalinity. Alkalinity is discussed in aerobic and anaerobic digestion. Biological treatment works best when the pH is maintained in the 6.5 to 9.0 range and there is enough residual alkalinity to keep the pH in that range. Alkalinity is expressed as mg/l as CACO₃. Understanding some chemistry in aerobic and anaerobic digestion and the wastewater process will be helpful in achieving higher certifications.

2. A filter with unknown dimensions is in operation. The operator closed the influent valve and the water level in the filter dropped 17 inches in five minutes. What is the filtration rate in gpm per square foot?

The correct answer is C, 2.1. Filtration rates are typically reported as gpm per square foot. In this case, we do not know the square surface area so we will need to use a 1-square-foot area. First, convert the change in depth to feet by dividing 12 inches into 17 inches. Second, calculate the volume of water that passed through the 1-square-foot area. Third, divide the volume of water by the time frame in which it occurred.