Treatment of Acid, Cyanide, and
Chromium Wastes
C. F. Waite
Chief Chemist, King-Seeley Corporation
Ann Arbor, Michigan
The location of the new King-Seeley Plant on the Huron River
in the country eight miles west of Ann Arbor at Scio, Michigan,
necessitates construction of adequate waste-disposal facilities as an
integral part of the plant. There are no waste-disposal services of
any kind other than the river. Sportsmen in the area are ultra-sensitive
to pollution as a result of the intermittent dumping of oil wastes by
a laundry at Dexter two miles west of the King-Seeley Plant. Re¬
peated reprimands from the Stream Control Commission had just
been effective in removing this contamination. However, of more
importance than the danger to aquatic life is the danger to human
life. The city of Ann Arbor takes up to 50 percent of its drinking
water from the river about six miles below the King-Seeley Plant.
All of this made it necessary to correct and render innocuous all
wastes before they entered the river. All sanitary wastes are treated
adequately by standard septic-tank and filter-bed treatment. The prob¬
lem was with the industrial wastes, which are separated into the
following five classifications: (1) acid and alkali, (2) cyanide, (3)
chromium,   (4)   nickel, and   (5)   roto-finish wastes.
The acid-alkali wastes, consisting of 75,000 gallons per 16-hour
working day of waste, with a pH of about 10, posed no serious problem
but merely one of neutralization.
The cyanide problem was more serious. There are about 25,000
gallons per 16-hour working day of waste containing 12 to 20 ppm of
cyanide as KCN. The cyanide wastes are of course extremely poisonous;
most authorities agree that any concentration over 0.1 ppm is dan¬
gerous to aquatic life. Many methods have been proposed to destroy
cyanide. Four of these were investigated: the acid treatment, ion
exchange, electrolysis, and oxidation methods. The acid treatment con¬
sists, of course, of adding an acid (usually sulfuric) and bubbling air
through the acidified waste to carry off the hydrogen cyanide which
is evolved.  Aside from the poisonous character of the hydrogen cyanide
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