Here are the answers to the April 14, 2022 edition of TPO's Exam Study Guide:

What considerations should be made when locating a lift station in your collections system?

The answer to this question is B, ease of access, utility location and groundwater table. When locating a lift station, there should be many considerations to look at, such as ease of access, nearest utilities, and groundwater, as well as soil stability and gravity to force main needs. The lift station must have reliable equipment installed, and lift station reliability is the most important requirement. Safety and the local population (odors and noise) should also be considered. Lift stations are a major component of the collections system, and each of these aspects should be closely looked into. 

At what temperature will an aqueous solution of 50% by weight sodium hydroxide freeze? 

The correct answer is D, 58 degrees F.  Aqueous sodium hydroxide (NaOH) is a common chemical used in water treatment. Aqueous sodium hydroxide or caustic soda is an extremely basic solution, so safety training is pertinent before handling. In addition to the safety concerns, proper feeding applications should be considered. Aqueous sodium hydroxide at 50% by weight concentration will freeze at around 58 degrees F. This means chemical storage room temperature and chemical feed point temperature should be monitored. For example, sections of a chemical feed line can become clogged if the chemical feed line is exposed to colder temperatures than the chemical storage room. However, diluting to a 25% aqueous sodium hydroxide concentration can eliminate freezing in most instances. Aqueous sodium hydroxide at 25% by weight concentration will freeze at around 0 degrees F.



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