Evaluating the Effect of
Industrial Wastes on Lagoon Biota
HARDAM S. AZAD, Graduate Research Assistant
DARRELL L. KING, Assistant Professor
Department of Civil Engineering
University of Missouri
Columb ia,  M issouri
INTRODUCTION
Waste-stabilization ponds or lagoons represent one of the most rapidly expanding forms of waste treatment advanced within the past fifty years. The low
construction and maintenance costs are well-known features of lagoons and are the
dominant factors leading to widespread adoption of this form of treatment by
many municipalities. Many urban areas now installing lagoons are faced with the
problem of treating wastes from small industries along with the more traditional
domestic wastes. The addition of industrial wastes to municipal lagoons represents a possible threat to the successful operation of these waste-treatment facilities. However, little is known about the effect of toxic substances on the mixed
populations of microbiota responsible for the successful operation of waste-stabilization lagoons.
Despite a considerable amount of research (1,2,3,4, 5), the actual metabolic
mechanism within lagoons remains an enigma. This is due largely to the varied
nature of different lagoons, and especially to the diverse biotic populations undergoing constant change both in time and space within the lagoon environment.
Very little is known about the tolerance of these mixed biotic populations to extrinsic toxic substances, and since the biota differs from one lagoon to another,
there is a real need for a method of estimating the impact of toxic wastes on a
given installation. This paper deals with a method which may prove useful in
evaluating the shock-load toxicity of a particular waste to the biota peculiar to a
given lagoon.
The toxic substances considered in this study were copper, added as copper
sulfate, and chromium, added as potassium dichromate. In addition to being a
common component of electroplating wastes, copper is widely used as copper sulfate to control unwanted growths of aquatic plants. Chromium gains access to
treatment facilities from many sources ranging from plating wastes to treatment
for corrosion inhibition.
METHODS
The metabolic degradation of domestic wastes has been evaluated by at least
four different methods and for a wide variety of biotic communities. Indirect
measurement includes the conventional BOD bottle test and estimation of the carbon dioxide evolved during biochemical oxidation (6,7). Direct measurement includes the use of manometric techniques and a variety of specialized apparatus
(8). Manometric techniques were first introduced as a method of investigating
the metabolic changes in domestic wastes by Wooldridge and Standfast (9) and,
since the time of Caldwell and Langelier (10), the Warburg respirometer has been
used extensively for studies of this type. Dawson and Jenkins (11) used a Warburg
apparatus to determine the oxygen requirements of activated sludge subjected to
- 410 -