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November 6, 2017


In a recent post I focused on the importance and value of total kjeldahl nitrogen (TKN) testing. That post addressed the need to run the full gamut of nitrogen tests which include TKN, ammonia, nitrate, and nitrite, the sum of which equate to the total nitrogen concentration as illustrated in Figure 1. In this post I want...

November 3, 2017


After all the many years I've been working in water and wastewater treatment it's really just this past year that I have come to better appreciate the value and importance of measuring the total kjeldahl nitrogen in addition to the ammonia nitrogen concentration entering and leaving industrial biological treatment systems....

July 10, 2017

In former days, when I did a lot of polymer-focused jar testing, I had three products in my polymer test kit that I never fully understood. The products themselves were straightforward enough as they were PACls or polyaluminum chloride coagulants. Where my understanding stalled out was the additional description of these products in t...

May 2, 2017

The nitrogen cycle and other graphics are shown here. These graphics are intended to inform those who operate (or need to know about) nitrifying wastewater treatment systems. The first graphic below is one of the most common and you will come across this in several different textbooks.

May 1, 2017

Testing Equipment for Water, Reverse Osmosis, and Wastewater

There are several "sets" of laboratory equipment that are critical for evaluating water (including reverse osmosis) and wastewater treatment systems. One set is for doing oxygen uptake rate (OUR) analysis in wastewater systems. Another set is for conducting adenosine triphosp...

May 1, 2017

Composition of a Bacterial Cell

There are two formulas used to describe a bacterial cell. Both are discussed below.

The most widely used empirical formula for the organic fraction of bacteria cells is shown below. About 53 percent by weight of the organic fraction is carbon.

A more complete formula for the composition of a bacteria cell...

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...

State Point Analysis

With just six data inputs, state point analysis (SPA) would seem to provide a simple mathematical model for evaluating clarifier performance. But in fact, the graphical output of SPA does require careful review and interpretation.

Before going through the specifics of SPA I’d like to quote from an excellent textbook...

December 19, 2016


Before going into a detailed discussion of the F:M (food-to-mass or food-to-microorganism) ratio I want to let you know about changing views toward this process control parameter. Here are two opposing examples, the first from 1988 and the second from 2011.


This ratio, called the food-to-microorganism or food/mass (F/M) r...

December 19, 2016

Oxidation Reduction Potential (ORP)

Measuring the oxidation reduction potential (ORP) is such an easy, insightful test to perform, it’s a shame this poorly understood parameter is so underutilized. Of course, it’s that very lack of understanding that leaves ORP testing hidden away in the shadows. Though the science of ORP measurement i...

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...

December 19, 2016

Refinery Wet Gas Scrubber

This may seem a little odd, perhaps, but there is one unit process in particular that I really enjoy evaluating and that is wet gas scrubbers at refineries. Of most interest to me is the choice of chemistry used to settle solids (catalyst fines) in the scrubber blowdown. My focus here, but only in fairly gener...

December 19, 2016

Adenosine Triphosphate (ATP)—An Introduction

I’ve stated previously (OUR Level 1 Testing) that 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 analysis provide a very complete...

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