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May 25, 2020


Hydrogen peroxide can be used to increase the dissolved oxygen (DO) concentration in an aerobic bioreactor, often referred to as “DO supplementation.” Using peroxide is rarely a first choice because chemically increasing DO is more expensive than using a mechanical method (diffused aeration, mechanical mixing, etc.). But i...

March 9, 2017

What to Consider When You Actually Perform the OUR Test

You have two key concerns when you collect a mixed liquor suspended solids (MLSS) sample to run your initial oxygen uptake rate (OUR) test. The first concern is to perform the OUR test on an MLSS sample as soon after you have collected it as is reasonably practical. In contrast, w...

March 8, 2017

Level 3: Treatability OUR Testing

This level of oxygen uptake rate (OUR) testing is used to evaluate the impact of different chemical compounds or waste streams on a biological treatment system. In particular, Level 3 OUR testing allows you to determine if a waste stream or chemical is desirable, inhibitory, or toxic to the microorgani...

Level 2: Time to Endogenous Respiration

Many activated sludge systems do not achieve endogenous respiration by the time the mixed liquor leaves the bioreactor, indicating that treatment is not complete. When this is the case, extended oxygen uptake rate testing can be used to determine how long it takes for the system to reach a state...

December 19, 2016

Level 1: Oxygen Uptake Rate—An Introduction

Whenever I evaluate a biological treatment system there are two sets of tests I always run:

1) Oxygen uptake rate (OUR), and

2) Adenosine triphosphate (ATP) analysis.

When combined, the results of the OUR and ATP analyses can provide you with a very insightful picture of conditions in the biorea...

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