UPGRADING OF ACTIVATED SLUDGE UNITS VTA THE ADDITION
OF COALS AND COAL GASIFICATION PLANT CHARS
Precha Yodnane, Graduate Student
Ronald D. Neufeld, Assistant Professor
Department of Civil Engineering
University of Pittsburgh
Pittsburgh, Pennsylvania 15261
INTRODUCTION
Increasing population and industrialization has placed critical demands on the nation's
clean water supply.   Public and social pressures are forcing the construction of new and
costly wastewater treatment facilities.   Upgrading of existing facilities is also mandated.
About 85% of the organic pollutants present in municipal waste can be removed by
the conventional secondary treatment process.   Less efficient or primary treatment plants
remove only 25 to 35% of the organic load.   The residual contaminants are discharged
into surface waters, and thus are able to contaminate the intake supply of downstream
users.   Accordingly the general goal of this research is the upgrading of secondary treatment facilities particularly of smaller plants in an economical way.
In the past, activated carbon was considered and used as an adsorbent to remove
residual organic pollutants in sewage effluents.   Activated carbon was shown to be highly
effective in the removal of organic contamination.   However, the cost of activated carbon
is too great for the volumes of sewage considered.   Thus more economical and efficient
treatment methods are needed.   Coals and chars are excellent candidates for use as adsorbents because of their relatively low cost and their availability.   With the advent of increasing coal mining, additional coals will become available for ultimate energy production.
Chars, a solid waste product of coal gasification plants, will also become increasingly
available in the future as the demand for energy increases.   The concept behind this research is to explore the feasibility of obtaining an additional societally useful function
from coals prior to ultimate incineration and   from chars prior to ultimate disposal.   For
reasons of applicability, the organic matrix considered was fresh primary effluent of raw
settled sewage, the nemesis of small, already overloaded municipal wastewater treatment
plants.
REVIEW OF LITERATURE
Little research is reported concerning the adding of coal in activated sludge to determine the adsorption ability, but considerable research is reported regarding the filtration
of solids in wastewater by coal in a fixed bed.   Carlton, et al. [1] investigated the use of
coal as a medium for the filtration of sewage and wastewater.   It was concluded that all
American coals above the rank of lignite were suitable for use as a filter bed to remove
suspended solid matter.   In addition, it was found that any coal except lignite could be
employed to remove 50% or more of BOD or COD and more than 90% of suspended
solids.   High-volatile B to sub-bituminous coals were reported as the best for removal of
BOD and COD.   No coal was found to contribute soluble oxygen demand to water.
Johnson et al. [2] investigated the effectiveness of coal and coal-derived materials in
removing COD and ABS or alkylbenzenesulfonate, (common household detergents) via
sorption from the final effluent of secondary-treated wastewater.   At least one sample
of each rank of American coal was used as the adsorbing media in batch tests.   High-
volatile bituminous C coal was found to have about one-fourth the capacity of most act1'
vated carbon for COD; high-volatile bituminous C adsorbed COD to about 4% of its weight
before it became saturated.   Some of the fly ashes tested were also quite effective, removing as much as 66% of the COD at the maximum adsorbent concentration of 8 g/1.
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