Here are the answers to the April 15, 2021 edition of TPO's Exam Study Guide:

1. The MPN (Most Probable Number) method for fecal coliform testing has become one of the most common methods for testing. What is a disadvantage for MPN fecal coliform analysis?

The answer to the question is D, results are not very accurate and there's a high probability of false positives. Understanding the many types of laboratory procedures and analysis is important for the operators understanding and ability to properly operate a wastewater treatment facility. Fecal coliform testing is required on most if not all NPDES permits. MPN has become the most common method. The advantages of MPN are ease of interpretation, sample toxins are diluted, it's very effective on highly turbid samples, and the samples cannot be analyzed by membrane filtration. They have distinct disadvantages that need to considered, such as the amount of time to get the results (up to 48 hours), requiring more glassware and media, probable false positives, and results are sometimes inaccurate. 

2. In the distribution of potable water, where is the beginning of the service line located? 

The correct answer is C, at the corporation stop. Corporation stops are either treaded directly into the distribution main or a service saddle. The corporation stop is then connected to the service line which provides water to the customer. It is recommended that the service line be installed in an S-curve down from the tap so the line has plenty of slack to allow for earth settlement and pipe expansion/contraction. In addition, the service line should be buried at a depth below the maximum frost line for freeze protection. 



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