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The Water Break Podcast, Episode 1: Wastewater Nitrification and Denitrification

“Where we bridge the gap between water plant operators and engineers”

In our first podcast episode, host Heather Jennings, PE, discusses the wastewater nitrification-denitrification cycle with two guests, John Souza and Diego Lopez. John Souza is Utilities Manager for the City of Lemoore, California. He is also a Grade T-4 Water Operator, Grade 3 Wastewater Operator, and D-3 Distribution Operator. Diego Lopez, also with the City of Lemoore, is a Grade 2 Wastewater Operator working toward his Grade 3 exam.

Nitrification-denitrification is the great “teeter-totter” of wastewater treatment. Nitrogen is one of the most abundant elements on earth, so why do we spend millions of dollars removing it from water? And how do we do it?

Podcast reference:

Podcast reference for Wanda’s Water Tidbit:

Supplemental reading:

Nitrification and Denitrification in Wastewater Activated Sludge

By Heather Jennings, PE

The great teetertotter of wastewater is the nitrification and denitrification cycle in activated sludge wastewater systems. It takes both to convert ammonia to nitrogen gas! Both processes feed off of and support each other but, in some ways, they have competing needs.

Nitrification consists of ripping off the hydrogen in ammonia and adding oxygen to make nitrates and nitritesthis is accomplished by bacteria that we call nitrifiers. You might be already familiar with some of these nitrifiers, such as Nitrosomonas, Nitrobacter, etc. I, personally, call nitrifiers the “divas” of wastewater. They can only tolerate specific conditions to really thrivesuch as a pH range of 6.58.0. They also require 7.1 lb of alkalinity for every 1 lb of ammonia that is oxidized, and they prefer temperatures at 77°F with DOs (dissolved oxygen levels) above 2mg/L. Retention times need to be longer than five hours, and the F:M (food to microorganism) ratios must ideally be less than 0.25. Basically, nitrifiers are screaming for their lattes to be a specific temperature and everything just right or they will refuse to work! Sadly, we can’t fire them. We have to learn how to meet their needs to get any nitrification done.   [Read more…]

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