PLANT-SOIL ASSIMILATIVE CAPACITY FOR
ORGANIC SOLVENT CONSTITUENTS IN INDUSTRIAL WASTES
D. Pal, Research Associate
M. R. Overcash, Associate Professor
P. W. Westerman, Assistant Professor
Department of Biological and Agricultural Engineering
North Caroline State University
Raleigh, North Carolina 27607
INTRODUCTION
Organic solvents are important chemicals in a wide variety of industrial processes, such
as absorption separation, extraction, crystallization, distillation, etc.   Because of solubilization characteristics, these constituents serve as carriers and reaction media.   As a consequence of the wide use of solvents in manufacturing processes, industrial wastes inevitably
contain organic solvents which must be treated to eliminate any adverse environment impact.
Organic solvents occur largely in the wastes of (a) synthetic fiber industries, (b) organic
chemicals manufacturing plants,((c) oil refineries and petrochemicals processing, (d) coke
ovens, (e) meat smokehouses and (f) other industries as listed in Table I.   Most organic
solvents are difficult to work with because of their volatility and potential toxic nature.
These include phenols, phthalates, benzene, toluene, quinones, hydroquinones, pyridines,
aldehydes, acetone, chloroform, glycols, alcohols, ethers, organic acids and esters (Table I).
Therefore, treatment systems which satisfactorily assimilate organic solvents have a broad
use in the field of industrial wastes.
The environmental manager responsible for industrial wastes containing organic solvents
has certain alternative procedures available when considering the overall concept of waste
management.   These alternatives are depicted in Figure 1 and are fairly universal for industrial processes.   The selection among these approaches is based on the relative economics of each, subject to satisfying environmental regulations, over the life of the plant being
considered.   Obviously, in existing facilities somewhat less flexibility exists than for the
planning of a new plant or process.   Each alternative for wastes containing organic solvents must be evaluated, after a thorough design for satisfactory long-term treatment performance, for the least-cost total waste management system.
The use of a plant-soil system as the terminal receiver for organic solvents is a viable
alternative for industrial wastes and is the basis of this paper.   The evaluation of land-
based receiver systems for organic solvents involves total waste management, thus including in-plant source control, pretreatment and land application (Figure 2).   In order to
establish the pretreatment-land application alternative for industrial wastes certain definitions are necessary.
Waste assimilatory capability is the unit rate, expressed as mass per unit time per volume or area of receiver by which a constituent or family of constituents are stabilized,
separated or converted in an environmentally acceptable manner.   The important factor
is the particular receiver chosen, either water-based or land-based; e.g., kg toluene decom-
posed/yr/ha of plant-soil systems.
Land limiting constituent (LLC) or stream limiting constituent (SLC) is determined
from the ratio of waste generation to waste assimilation capability.   This ratio for each
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