REMOVAL OF CHLORINATED ORGANICS BY CONVENTIONAL
BIOLOGICAL WASTE TREATMENT
Richard K. Lackmann, Graduate Student
Walter J. Maier, Professor
Civil & Mineral Engineering Department
University of Minnesota
Minneapolis, Minnesota 55455
Nadim A. Shamat, Process Engineer
Metropolitan Waste Control Commission
St. Paul, Minnesota 55106
STATEMENT OF PROBLEM
The presence of chlorine containing organic compounds in municipal and industrial
wastewaters is well documented [1-4]. Their presence poses unique problems in pollution
abatement technology. Individual compounds are present at low concentrations (micrograms
per liter) but are nonetheless potentially hazardous. A number of chloro-organics are included in EPA's list of priority pollutants and their elimination is mandated. They tend to
be biologically refractory and some are reported as "nonbiodegradable." Large quantities
enter the waste streams as solvents and surfactants from industry, as pesticides from agriculture and silviculture, and as additives in household chemicals. Source reduction of a few
specific compounds such as DDT and PCB has been mandated but protection of the environment also requires development of more effective wastewater treatment techniques
to remove low concentrations of chloroorganic materials. A related problem is the treatment
and ultimate disposal of industrial waste streams containing high concentrations of chloro-
organics.
RESEARCH OBJECTIVES
The long range objective of ongoing research is to adapt or modify existing wastewater
treatment methods to facilitate removal of manmade chloroorganic compounds. The focus
is on biological treatment because it is universally used for municipal wastewater treatment,
usually produces relatively nonhazardous products, and is relatively low cost. However,
engineering design and operation of biological treatment processes require a systematic
understanding of the biochemical behavior of the biomass and the hydraulic regime of the
reaction chambers. This includes descriptions of the growth behavior and metabloic
capabilities of the active biomass as well as the hydraulic-flocculating properties of the
biomass which influences sedimentation and residence time in the system. The immediate
objective of this research was therefore aimed at describing the kinetics of biodegradation
of selected manmade chlorine containing compounds in mixed culture and multiple substrate environments. To this end studies were carried out to:
1. develop sewage derived enrichment cultures that can decompose and utilize selected chlorine
containing compounds;
2. measure microbial parameters (growth rate, yield coefficients and half saturation constants)
that describe rates of target substrate utilization;
3. determine the cultural characteristics of these enrichment cultures when they are exposed
to alternative food (substrate) sources; and
4. analyze the results in terms of process models that relate batch test removal efficiencies to
process control variables in continuous flow reactors.
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