Exam Study Guide: Dealing With Flow Surges

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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 study and prepare for exam questions. Take a look at this sample water treatment licensing question along with an explanation of the correct answer.

Sample question:

One of the most difficult aspects of wastewater treatment is consistency with operations. This is difficult to maintain because flows entering the treatment facility vary greatly depending on time of day. Most wastewater treatment plants have two surges each day: one in the morning and one in early evening. These fluctuations make treatment difficult because contact times, settling rates and detention times are reduced during peak flows.

With wastewater operations, we rely on composite sampling so an average can be measured on discharge concentrations each day. However, if a facility is undersized, and the surges constantly put the utility at risk of discharge violations, which corrective action can be taken?

A)  Work with the public to establish flow and discharge patterns into the collection system
B)  Increase the size of the primary clarifier only
C)  Increase the size of the disinfection tank
D)  Create an equalization basin

Although any corrective action will be expensive, the best fix is D) Create an equalization basin.

This basin would be located before the first phase of the treatment process right after bar screening. This might involve creating a channel to direct the flow to the equalization basin before it enters the primary treatment clarifier. The basin would receive 100 percent of the flow but be screened of waste debris. The effluent from the basin is then a fixed constant flow throughout the day. Only the equalization basin would see different flows entering the plant. This is expensive, but far less costly than upgrading the size of the entire system. It also requires a sizable amount of land space to hold enough volume to control daily flow.

About the author
Mike Smith is program coordinator and lead faculty of the Water Quality Management program at Red Rocks Community College in Lakewood, Colo.

He has been in charge of the multi-faceted training program since 1996.


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