Exam Study Guide: Dissolved Oxygen Readings

Exam Study Guide: Dissolved Oxygen Readings

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When faced with a licensing exam, don't struggle with test anxiety! Use the question below and others from our Exam Study Guide series to properly study and prepare for exam questions. Take a look at this sample wastewater treatment licensing question along with an explanation of the correct answer.

Sample question:

Your plant seems to be having problems. Dissolved oxygen readings are much higher than normal and microscopic analysis shows very few to no protozoa present. What is the most likely problem?

A) Very low food to mass ratio, increase your wasting rate

B) Excessive FOG problem, check your pretreatment records

C) Plant sludge age is too high, decrease your aeration settings

D) Possible toxic shock in the treatment system

Answer: Toxic waste adversely affects the health of activated sludge. To solve the problem, increase wasting rates for about one week to purge the system, seed with sludge from another plant to build up healthy solids inventory and conduct a survey of industrial waste dischargers to identify the toxic source. Enforce your sewer-use and pretreatment ordinance. Therefore, the correct answer is D, possible toxic shock in the treatment system.

Source: WEF MOP11 20-135

About the author
Ricky Lallish is the Water Pollution Control, Program Director at the Environmental Resources Training Center of Southern Illinois University Edwardsville. He provides training for entry level operators in the wastewater field and operators throughout the state looking to further their education.



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