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DO N ALD J . O ’ CO N N OR
1922–1997
Elected in 1978
“For leadership in the field of mathematical modeling to gauge the
effects of pollution and abatement measures.”
BY KEVIN J. FARLEY
SUBMITTED BY THE HOME SECRETARY
D ONALD J. O’CONNOR, a distinguished professor at
Manhattan College and a pioneer in the field of water quality
modeling, died on April 18, 1997, at the age of 74.
Don was born in Brooklyn, New York, on November 7, 1922,
the son of a scenic artist who painted sets for films, operas, and
Broadway plays. His younger years with his mother, father,
and younger brother Robert were happy times filled with
laughter and early exposure to literature, philosophy, religion,
and the arts. His early family influences initially led Don
toward the liberal arts, with thoughts of following his father
into a career as a scenic artist. The tough economic times of the
1930s, however, led Don to ultimately pursue a more practical
career in engineering.
In 1940, Don accepted a partial scholarship to study civil
engineering at Manhattan College. Although he had very little
idea of what engineering involved, he was intrigued with its
logic and its puzzle-solving nature. It was during his studies
at Manhattan College that Don started to appreciate what he
calls the beauty and the power of mathematics. In his junior
year he was drawn to the civil engineering department’s
sanitary engineering option, where he studied under Professor
Clarence J. Velz. It was Professor Velz who introduced Don
to the Streeter-Phelps dissolved oxygen equation, which
served as a focal point of Don’s seminal work on water quality
modeling over the next two decades.
207
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208 MEMORIAL TRIBUTES
After receiving his bachelor’s degree in civil engineering
from Manhattan College in 1944, Don served in the U.S. Army
Medical Corps in Europe during the final years of World War II.
He returned home in 1946 ready to continue his studies and
pursue his career. He completed his master’s degree in civil
engineering at the Polytechnic Institute of Brooklyn in 1947
and accepted a job as a structural engineer with the design
firm Parsons, Brinckerhoff, Hall and MacDonald. Away from
the office, Don’s fancy was soon captured by Anita Lordi, a
dress buyer for a New York–based department store. They
married in 1948 and soon after had three children—Dennis,
Arlene, and Jeanette.
While juggling the responsibilities of a full-time job
and a new family, Don began his doctoral work in sanitary
engineering at New York University. Shortly after, he left his
full-time job as a structural design engineer to assume a full-
time teaching position at Manhattan College. He continued
his doctoral studies at night. Don’s research initially focused
on the hydraulics of side-channel weirs for combined storm
water systems. However, he found water quality issues much
more challenging, and he was particularly intrigued by what
happened to oxygen levels in streams impacted by wastewater
discharges. This led Don to reexamine the Streeter-Phelps
equation, which he had first studied at Manhattan College 10
years earlier.
Don received his doctorate in engineering science from
New York University in 1956 for his dissertation titled
“The Mechanism of Reaeration in Natural Streams.” This
work established the basis for quantitative definition of the
reaeration coefficient in streams. It is still being used today
and is the basis of the O’Connor-Dobbins equation, named
after Don and his doctoral adviser, William Dobbins.
Don’s work on reaeration was followed by further work on
dissolved oxygen depletion in streams. He extended the range
of applicability of the Streeter-Phelps dissolved oxygen equa-
tion with the addition of the photosynthetic source, nitrification,
and benthic sinks. His most lasting accomplishment, though, was
his solution to the estuary problem, which involved application
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DO N ALD J . O ’ CO N N OR 209
of the Streeter-Phelps dissolved oxygen framework to what
appeared to be a hopelessly complex physical setting that
included tidal motion, stratification, and irregular geometry.
His solution was to model the slack water distributions and
represent longitudinal mixing using a dispersion coefficient.
According to his colleagues, “This was vintage O’Connor: an
insightful manipulation of the data (slack time concentrations
translated to mean tide positions) combined with an intuitive
leap to a mathematical model (tidal- and density-driven
mixing modeled as a dispersion coefficient).” His 1960 paper
in the sanitary engineering journal on the subject is considered
by many to mark the beginning of modern water quality
modeling.
Realizing the need for expert services in sanitary engineering
and water quality modeling, Don and fellow faculty colleague
Wes Eckenfelder founded Hydroscience, Inc., in 1962. This
was one of the first consulting firms in the country to specialize
in combined wastewater treatment planning and analysis of
water quality impacts. One of the firm’s early projects was a
comprehensive water quality study of the New York–New
Jersey Harbor complex. The work, which was based largely
on Don’s application of the Streeter-Phelps framework to the
estuary problem, has served as a basis for subsequent water
quality studies of the harbor.
The implementation of secondary wastewater treatment
in the late 1960s and early 1970s brought tremendous
improvements in dissolved oxygen levels in streams and
estuaries, as well as a new set of water quality concerns.
During this time, Don and his colleagues at Manhattan College
turned their attention to problems of nutrient enrichment. Don
worked extensively with Bob Thomann and Dominic Di Toro
in developing eutrophication models to assess the impact of
nutrients on algal growth. Those models were applied in studies
of the Great Lakes and a number of estuaries. Expanding his
seminal work on estuaries in the 1960s, Don focused largely
on eutrophication problems in the Sacramento–San Joaquin
Delta, the Chesapeake Bay, and the New York Bight.
In the late 1970s and early 1980s, Don expanded his work
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210 MEMORIAL TRIBUTES
on estuaries to address new concerns of toxic contamination
by pesticides and other industrial chemicals. During this time
I had the honor of working with Don in developing the first
model for the pesticide Kepone in the James River estuary of
the Chesapeake Bay. The model synthesized multiple factors,
including hydrodynamics, sediment transport, and chemical
behavior, into a comprehensive analysis. This approach
continues to serve as a basis for current modeling studies of
toxic contamination in rivers, lakes, and estuaries. In the late
1980s, Don carved out a new research topic, namely, seasonal
and long-term variations of dissolved solids in lakes and
reservoirs. His final work in the 1990s led him back to his
earlier work on gas exchange in natural waters.
Don’s work in mathematical modeling of water quality
will always stand next to that of the great researchers and
practitioners in the environmental field. The insights gained
through carefully constructed analytical models of water
quality processes, developed long before the advent of modern
computers, and the steadfast insistence on comparison of
model results to observed data are hallmarks of his work.
Don’s accomplishments are documented by his many
publications and awards. He received four Rudolf Hering
medals (1959, 1966, 1984, 1989) and the J. James R. Croes Medal
(1991) from the American Society of Civil Engineers (ASCE)
Environmental Engineering Division (EED). These awards
clearly reflect the four decades of significant contributions
that Don made to the environmental engineering field. Based
on his work in water quality modeling, Don was elected to
the National Academy of Engineering in 1978. The following
decade he was named the Association of Environmental
Engineering Professors Distinguished Lecturer in 1986, the
Gordon M. Fair Distinguished Educator by the Water Pollution
Control Federation in 1989, and the ASCE-EED Simon W.
Freese Distinguished Lecturer in 1990.
In addition to his research and consulting activities, Don
gave generously of his time to serve on countless boards
and advisory panels. From 1972 to 1977, he served on the
advisory committee to chart the role of the National Oceanic
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DO N ALD J . O ’ CO N N OR 211
and Atmospheric Administration. During the 1980s and early
1990s, he served on the Environmental Engineering Committee
of the U.S. Environmental Protection Agency’s Scientific
Advisory Board and the Water Science and Technology Board
of the National Research Council.
Perhaps it is Don’s legacy as a teacher of so many members
of our profession that will stand as his greatest achievement.
Over his five decades at Manhattan College, he combined a
remarkably clear teaching style with an infectious excitement
and enthusiasm for environmental engineering. His chalk
renderings on the blackboard reminded us of the scenic artist
that he could have been, and his tales of consulting experiences
from around the world kept us glued to our seats. But it was
his enthusiasm for using mathematics to solve real-world
problems that was most contagious. Don opened our minds
to the many dynamic processes affecting streams, lakes, and
estuaries through the beauty of mathematical modeling for
which we are all forever grateful.
Don is survived by his children—Dennis O’Connor,
Arlene O’Connor Bell, and Jeanette O’Connor—and by two
grandchildren, Christopher and Kristin, as well as by many of
his former colleagues and students whom he deeply inspired
during his wonderful career.
