Water Pollution Problems Associated with
Control of Stack Gas Emission
CLIFFORD J. LEWIS, Environmental Consultant
The National Lime Association
Washington, D.C.
INTRODUCTION
The purpose of this discussion is to focus attention on the water pollution potential
involved in the clean up of stack gases. The water pollution which could result from this
effort is considerable. The environmental program should evaluate the water pollution
potential of any stack gas clean up program. Technologies for water preservation are well
advanced while the technologies for air pollution abatement are yet largely in the
development stage thus allowing time, though relatively short, for all concerned to plan for
the impact of stack gas clean up on our domestic water resources.
The relationship between the preservation and improvement of water resources and
the improvement of stack gas emission resides in the fact that for the control of stack gas
emission most, if not all, presently developing technology scrubs the stack gas with an
aqueous media which, subsequently, may be a potential water pollutant. The definition of
pollutant as used in this discussion is based on standards as presently suggested by the
Environmental Protection Agency of the U.S. Government. An absolute definition is not
implied since the concept of both air and water pollution is too intricately woven into our
changing societal, political and economic structure. For example, an advocate of
environmental clean up, after asking what he could do to further the cause, became
disenchanted when it was suggested that he surrender his automobile keys.
SOURCES OF STACK GAS POLLUTANTS
There are many sources of stack gas emission which readily qualify as atmospheric
pollutants under EPA recommended standards. These range from garbage incinerators,
saw dust burners, and various chemical manufacturing operations to smelters and coal
burning power plants. This discussion will confine itself to the water pollution potential
resulting from the clean up of gases from metallurgical smelters and coal burning power
plants.
In 1969, approximately 500 million tons of coal averaging about 2 percent sulfur were
consumed in the United States. Of this amount, about 61 percent was consumed by coal
burning power plants. This calculates to around 12,000,000 tons of sulfur dioxide
discharged into the atmosphere. In addition, if it is assumed that this coal averaged 10
percent ash, of which 90 percent was removed by dry precipitators, then at least 3,000,000
tons of fly ash as particulate matter were available for atmospheric discharge. In the case of
metallurgical smelters, the copper industry alone processed approximately 2,300,000 tons
of copper sulfide concentrates during 1969 representing about the same quantity of sulfur
dioxide for emission into the atmosphere. This is a generalization without correction for
sulfuric acid production and it is intended only to reflect the magnitude of the potential
water pollution.
When the pollutants in the stack gas of coal burning power plants are considered, it is
common practice to speak in terms of particulate matter, oxides of nitrogen, sulfur dioxide
and carbon dioxide. However, this is only part of the story since coal being of an earthy
nature may contain many elements which volatilizes in one form or another and report
under the generalized heading of particulate matter. For example, many coals contain
limestone which converts to quick lime during the firing process and ends up as alkalinity in
the aqueous scrubbing medium. When smelter stack gases are considered, it is usually in
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