Respirometry Plus, LLC

Respirometry Plus, LLC

Respirometry Plus, an Arthur company that since 1968 has been recognized as the leader in developing respirometers, as well as a wealth of test methods. The tests, which are known as respirometry are tools for observing metabolic activity in any living system. Both models have been sold in the wastewater, compost & biosolids and education fields worldwide for over 40 years. Some 16 different tests have been developed for these instruments to provide both short term rapid results and longer term comparative tests.

Company details

P.O. Box 1236, , Fond du Lac, , 54936-1236 Wisconsin USA

Locations Served

Business Type:
Industry Type:
Monitoring and Testing
Market Focus:
Globally (various continents)
Year Founded:
$1,000,000 US - $10,000,000 US

Respirometry Emerges As An Operation Tool In The Wastewater Treatment Field

The Birth of an Idea

The saying, 'Necessity is the mother of invention.' certainly applied to the invention of the Arthur Respirometer.   The need to show wastewater treatment plant operators what is actually happening inside the activated sludge process is what stimulated Bob Arthur to invent and patent (in 1962) the Arthur Large Volume Respirometer.   He, in fact, needed to know what was happening within the process biologically so he could do a better job of training plant operators, and getting them to appreciate that they were working with a living, breathing system, not just a mass of solids.  He felt that if he could get bioactivity information in a timely manner, this would be a real breakthrough, resulting in better process control.

Arthur had to be involved in training operators, for he was part of the operation service division of a major wastewater treatment equipment manufacturer. It was his job to start up plants nationwide and train the operators in all aspects of equipment operation and maintenance.   He also had to teach them bench tests to obtain process control information.   He usually started by showing an operator how to perform a settling test with a one-liter graduated cylinder.   If he was lucky, he might find that the lab (quite limited in those days) included a hand operated centrifuge (there were no drying ovens and scales) so he could tell the operator about the importance of solids concentration.   He might then even introduce the operator to a control strategy - the Sludge Volume Index (SVI).

Physical vs. Biological Tests

Performing these physical tests of settling and solids on the mixed liquor just did not make sense to Arthur. Activated sludge is a living, breathing process. 'How,' he wondered, 'is it possible to learn what is happening in a biological process by performing physical tests?' Arthur certainly recognized that physical tests were necessary to determine what was happening in the physical part of the process, i.e.settling, but it bothered him that no tests were performed to see what was happening in the biological part, which is usually 50% or more of the treatment process.

When Arthur started his own engineering firm (Arthur Technology Inc.) to design wastewater treatment plants, he was again involved in operator training, and again was frustrated by the lack of bioactivity information when operating a biological wastewater treatment plant.   He decided to do something about this.   After several years of work to design an instrument especially for use with activated sludge and by operators, the Arthur Respirometer was introduced in a paper given at the Purdue Industrial Waste Conference in 1964.

Educating the Public in Respirometry

Shortly after introducing the instrument, Arthur realized that few people understood how to use a respirometer, or realized the importance of the information it could provide, so he began to develop new respirometer-based operation strategies. This technology was called 'respirometry'.   Aware that the only way to sell a new technology was to demonstrate it, Arthur loaded a van with a respirometer, slide show and other props and toured the USA and Canada for several weeks every year, demonstrating his respirometer and his technology to rooms full of operators, technicians and consultants. The strategies, which all utilized timely, bioactivity information obtained from the respirometer, made a great deal of sense to his audiences. The important thing they learned was that they could use this tool to actually determine what was going on inside the treatment process from start to finish, and that they could detect and avoid small treatment problems before they became major problems. In fact, the most common question from the audience was, 'Why hasn't anyone done this before?'  The rest is history, as they say. Today, hundreds of plant operators worldwide are using Arthur's operation strategies.

Respirometry Plus, LLC is currently looking for distributors in Asian and Latin American countries. A good knowledge of the activated sludge wastewater treatment process is required.