The Effect of Chromium on the
Activated Sludge Process of
Sewage Treatment
W. ALLEN MOORE, in Charge, Analytical Methods
G.N. McDERMOTT, Sanitary Engineer
MILDRED A. POST, Chemist
J. W. MANDIA, Chemist
M. B. ETTINGER, Chief, Chemistry and Physics
Robert A. Taft Sanitary Engineering Center
Bureau of State Services
Public Health Service
Department of Health, Education, and Welfare
Cincinnati 26, Ohio
This study is planned as the first of a series of studies on the effect of
metallic wastes on the operation of sewage disposal plants. The objectives of
these studies are:
To determine the extent to which sewage treatment processes can tolerate
metallic wastes without losing efficiency in their treatment of the organic pollutants in sewage;
To determine the extent of removal of metallic wastes in sewage treatment plants and to follow their travel and concentration in various units of
conventional sewage disposal processes;
Where a need exists and where practical, to develop modifications of
sewage treatment procedures which will make them more tolerant of metallic
wastes, or to make them more efficient in the removal of metals from sewage.
It is believed that the objectives outlined above will serve a number of
purposes. It is expected that the data gathered will assist sewage disposal
authorities in determining the quantity and characteristics of metallic wastes
which they may accept without fear of damaging operation. Further, it is frequently efficient and desirable for industry to be able to use municipal resources to handle its wastes. Viewing the community and its industries as a
mutually dependent group, it is obviously desirable to have ground rules for
determining optimum distribution of waste treatment effort between the municipal facility and industrial waste treatment facilities.
Numerous studies have appeared in the literature in recent years on the
effect of metals on biological processes. Unfortunately, practically all of
these have been confined to bench experiments which have not reasonably
simulated plant situations and the results obtained are not necessarily applicable to either the pilot plant or large-scale treatment of sewage. Forthis
reason the literature covering these experiments will not be reviewed and only
those references which might apply to the present study will be cited. These
studies, for instance, do not show the effects a given metal will have on the
efficiency of a treatment plant when received continuously in the influent
sewage or in slug doses.
In view of the conflicting data appearing in the literature it was decided
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