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Digital Environmental Engineer & Scientist: Winter 2014 (V50 N1) - Special Activated Sludge Issue
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This special edition of the Environmental Engineer and Scientist is devoted to the 100-year anniversary of the Activated Sludge process. As we commemorate this significant milestone in wastewater treatment, we pause to reflect on the great contributions of the early pioneers and many who have contributed to the development and enhancement of the process over the years.

It was the presentation by Edward Ardern and William Lockett in April 1914 to the Society of Chemical Industry in Manchester England entitled: "Experiments on the Oxidation of Sewage Without the Aid of Filters" which was based on lab-scale experiments conducted at Manchester - Davyhulme wastewater treatment plant under the direction of Dr. Gilbert Fowler of the University of Manchester that marked the discovery of the activated sludge process. In this paper, Ardern and Lockett described all of the essential components of the activated sludge wastewater treatment process, as it is used today, and made the first reported use of the term "activated sludge" to refer to biological solids that settled out of aerated wastewater and recycled back into the treatment process.

Prior to this, in 1912, Fowler was invited to the United States to review the New York Harbor pollution problem. During this trip, he had an opportunity to witness first-hand ongoing sewage treatment experiments at the Lawrence Experimental Station in Lawrence, Massachusetts. Fowler later credited this visit as the impetus for his "illuminating idea" regarding activated sludge, referring to Lawrence as the "Mecca of sewage purification."

Following successful pilot-scale and full-scale testing, the activated sludge process soon found widespread application in the United Kingdom, United States of America, Germany, India, Australia, and South Africa. The first experimental activated sludge plant in the USA was built in Milwaukee, WI in 1915, and the first activated sludge plant built in 1916 in San Marcos, TX. Subsequently, the activated sludge process has rapidly become the most flexible and most widely used biological wastewater treatment process worldwide, with applications ranging from small package plants to large custom designed activated sludge plants treating flows up to hundreds of million gallons per day.

However, "the activated sludge process is currently a treatment process that is capable of producing a high quality effluent low in carbonaceous organic material, nitrogen, phosphorus and suspended solids, and where necessary a reduced pathogen content. But this still remains a linear process in which the contents of the wastewater are considered to be disposable wastes, with limited potential for recovery, recycle or re-use. The challenge for activated sludge in the 21st century is to make this a circular process in which the wastewater is viewed as a source of raw materials and the treatment plant becomes a production facility to produce: clean water, nutrients, fertilizer in the form of nitrogen and phosphorus, soil conditioner, and energy in the form of heat and electricity."

As we strive towards the goal of energy neutral or energy producing facilities, environmental engineers and scientists are rising to the challenge to make this a reality in the 21st century.

I hope you enjoy the articles, anecdotes, and personal reflections presented in this special edition of the activated sludge process. Happy reading!

Christian Davies-Venn, Ph.D., P.E., BCEE
President, AAEES

What you will find in Volume 50, Number 1 - Winter 2014

News and Features

  • 100th Anniversary of the Activated Sludge Process: Introduction by Brian Flynn, P.E., BCEE
  • Who Invented Activated Sludge? by Daniel W. Schneider
  • Experiments on the Oxidation of Sewage Without the Aid of Filters by Edward Ardern, M.Sc., and William T. Lockett, M.Sc.
  • The Sludge Age Concept and the Activated Sludge Process: A 45 Year Retrospective Commentary by Alonzo W. Lawrence, Ph.D., P.E., BCEE, and Andrew C. Middleton, Ph.D., P.Eng., BCEE
  • Complete Mixing Activated Sludge by Ross E. McKinney
  • Solids Separation in the Activated Sludge Process - the First 100 Years by Richard I. Dick, Ph.D., P.E., BCEE
  • Designing Activated Sludge Systems for Nitrogen Removal by Glen T. Daigger, Ph.D., P.E., BCEE, NAE
  • Phosphorus Removal in the Activated Sludge Process by James L. Barnard, Ph.D., BCEE, WEF Fellow, IWA Senior Fellow, Dist. MASCE
  • The Future of Activated Sludge by George Tchobanoglous, Ph.D., P.E., BCEE, NAE, and H. David Stensel, Ph.D., P.E., BCEE


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