Here are the answers to the Sept. 30, 2021 edition of TPO's Exam Study Guide:

Solids Retention Time (SRT) is an important process control measure, what does it mean?

The answer to the question is C, how long a suspended solids particle remains under aeration. Process control and process control math are very important measures the operator must understand to operate the plant efficiently. Solids Retention Time or SRT (synonymous with MCRT) is one of these controls. SRT is the measurement of how long a suspended solids particle remains under aeration and is measured as age. The formula for SRT is pounds of suspended solids in a system divided by pounds of suspended solids leaving the system in days. 

How many disinfectant byproducts (DBPs) make up the total trihalomethanes (TTHMs)?

The correct answer is C, four. A total of four disinfectant byproducts can contribute to the calculation of the total trihalomethane concentration, bromodichloromethane (MCLG zero), bromoform (MCLG zero), dibromochloromethane (MCLG 0.06 mg/L), and chloroform (MCLG 0.07 mg/L). The TTHMs may only be a portion of the DBPs in tap water. Bromate, chlorite and haloacetic acids are also regulated by the National Primary Drinking Water Regulations.


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