34    REMOVAL OF ORGANIC COMPOUNDS BY
MICROBIAL BIOMASS
Ariamalar Selvakumar, Graduate Student
Hsin-Neng Hsieh, Assistant Professor
Department of Civil & Environmental Engineering
New Jersey Institute of Technology
Newark, New Jersey 07102
INTRODUCTION
Development of sophisticated industrial societies has led to proliferation of a vast number and
variety of complex chemicals for industrial, agricultural, and domestic use. Many of these compounds
exhibit toxic, carcinogenic, mutagenic or teratogenic properties. Many compounds of such concern
eventually find their way into municipal and industrial wastewaters, and, unless specifically removed
by waste treatment processes, ultimately appear in receiving waters and drinking water supplies and
can have harmful effects on human and other organisms in the environment.
The fate of hazardous organic pollutants discharged into conventional biological wastewater treatment processes is not well understood. These compounds may be removed from the wastewater
stream by biodegradation, volatilization (air stripping), sorption by the biomass, precipitation,
hydrolysis, etc. Of these processes, sorption would accumulate pollutants in the sludge and create
potential environmental hazards when released back into the environment upon sludge landfilling or
spreading the sludge on the land surface.
LITERATURE REVIEW
Recent studies have shown that the microbial cells tend to concentrate chemicals from their aquatic
environment. Tsezos and Seto1 studied the adsorptive capacity of 1,1,2-trichloroethane (TCE) and
1,1,2,2-tetrachloroethane (TTCE) onto mainly two types of biomass. Their results showed that the
combination of lower solubility, the higher octanol/water partition coefficient and reduced volatility
favors the uptake of TTCE by microbial biomass. Bell and Tsezos^ found that the uptake capacity of
biomass is generally less than that of activated carbon, but it is high enough to provide significant
removal of trace quantities of hazardous compounds combined with domestic and industrial pollutants. The adsorptive capacity was very well correlated with octanol/water partition coefficient but
not as well correlated with water solubility of the compounds.
The extent of biosorption by the microorganisms varies from species to species. One suggestion that
has often been mentioned in describing biosorptive phenomena is that the bioaccumulation of highly
hydrophobic compounds is directly related to the lipid content of the organism.3-4 But experimental
results of Tsezos and Seto1 did not confirm this. However, a comparison of the relative adsorptive
capacities with the organic carbon content indicated a trend.
Petrasek et al.5 concluded that the organic compounds are accumulated in the primary and secondary sludge in the treatment plants. Sorption of organic compounds to the biomass could be an
important removal mechanism in the activated sludge process according to Ullrich and Smiths. Leo et
al. i have shown that the octanol/water partition coefficient is a very useful tool in many situations
where a substance's behavior is influenced by its partition into a lipid phase. Matter-Muller et al.8
have determined the partition coefficients, Kp, of several refractory organic compounds in a batch
activated sludge process and found a linear dependence of log Kp upon log Kow. Karickhoff et al.9
concluded that the linear partition coefficients were directly related to organic carbon content for
given particle size isolates in the different sediments.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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