COMPATIBILITY OF ORGANIC WASTE AND CYANIDE DURING
TREATMENT BY THE EXTENDED AERATION PROCESS
A.F. Gaudy, Jr., Professor, Civil Engineering Department
University of Delaware
E. T. Gaudy, Environmental Microbiologist
Newark, Delaware 19711
Y. J. Feng, Environmental Engineer
Oklahoma State Health Department
Oklahoma City, Oklahoma 73102
G. Brueggemann, Environmental Microbiologist
Enid, Oklahoma 73701
INTRODUCTION
Treatment of cyanides in waste waters continues to be an important concern in the
plating, pharmaceutical, synthetic fiber and plastics industries and may become even more
important due to reemergence of coal gasification operations in the energy industry. Much
work has been accomplished on the treatment of cyanide wastes, and their amenability
to treatment by biological processes is well-documented. Studies made in the 1940s and
1950s by Pettet and co-workers [1-3] at the Water Pollution Research Laboratory in
England and by Ludzack and co-workers [4-6] at the Taft Center of the U.S. Public Health
Service established that trickling filters and activated sludge could be acclimated to treat
wastes containing inorganic and organic forms of cyanide as well as complexes of cyanides
with heavy metals. A number of subsequent studies, e.g., those by Nesbitt and co-workers
[7-8], Mikami and Misono [9] and Howe [10-11] have confirmed the ability of biological
systems to remove cyanide. Cyanide-metabolizing microorganisms have been isolated by
several workers [3, 12-16]. However, the unique chemical reactivity and volatility of
cyanide have recently caused some investigators, e.g., Raef et al. [17, 18] to question
the validity of some of the reported data. Both for this reason and because biological treatment of cyanide wastes is not widely practiced, it would seem that further research is
warranted.
The more expensive chemical methods of treating cyanide wastes have been employed
in many cases in preference to biological methods because of the very low allowable discharge concentrations for cyanide. However, in cases where a producer discharges to a
municipal sewer, pretreatment by less expensive biological processes may reduce the level
of cyanides sufficiently to warrant admission to publicly owned treatment works (POTWs),
which usually employ biological processes. Considerable investigational effort is needed
to provide information on the cyanide concentrations that can be successfully handled
without undue stress to the POTW. This aspect requires regulatory policy decisions and
perhaps continuing reevaluation of technological and economic policies on the part of
the regulators and the regulated. Moreover, it demands investigative efforts to provide a
definitive data base for making regulatory decisions. This is particularly important regarding
the granting of reasonable variances in pretreatment requirements for industrial discharges,
in compliance with provisions of the Clean Water Act of 1977. In addition to concern
about the effects of small amounts of industrially produced toxicants on the POTW, there
is also need for consideration of the possibility of changes in operational modes of the
municipal plants which could enhance their ability to accomodate industrial wastes containing priority pollutants that have been reduced by pretreatment to levels that are relatively
low but still higher than those permitted under direct discharge standards.
The weight of information indicates that perhaps the best operational strategies for
accomodating stress due to the presence of toxicants in biological treatment processes
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