ABS Removal in Physical and
Chemical Systems
EDWIN L. BARNHART
Hydroscience, Inc.
W. WESLEY ECKENFELDER, JR., Associate Professor of Civil Engineering
Manhattan College
New York, New York
Over the past several years there has been an increasing appearance of ABS in
surface and ground waters in various parts of the country. This has resulted in undesirable foaming in potable and recreational waters. Because of the non-degrad-
able nature of these surfactants, there is a tendency for an accumulation of ABS,
particularly in ground waters. In an attempt to minimize this contamination,
health agencies have prohibited the installation of coin-operated laundries in
many areas of the country.
In an effort to relieve this prohibition, a research program was initiated to investigate various methods of treatment for the removal or ABS prior to discharge to
receiving waters.   This paper summarizes the results of these investigations.
Four processes applicable to the removal of ABS from solution were investigated. These were: (1) Foam separation; (2) Coagulation and adsorption; (3)
Adsorption in carbon towers; and (4) Complexing and precipitation.
FOAM SEPARATION
Theory
The foam separation process consists basically of three phases: a bulk liquid
phase, a boundary layer (air-liquid interface), and a foam column. The bulk
liquid phase is a completely mixed solution in which the concentration of ABS is
equal to the effluent concentration. Surface active material concentrates at the
boundary layer which is the air-liquid interface created by the air bubbles diffused
into the system and is removed in the foam column. At some point an equilibrium
will be established between the concentration of ABS in the bulk solution and the
concentration of the air-liquid interface. If foam is continuously removed from
the system, the concentration in the bulk solution will be reduced to very low
values. The primary variables which influence this process are temperature, pH,
size and number of air bubbles, and the character of the foaming material. The
foam generated in the process will have defined characteristics as to stability and
drainability.   Temperature influences these foam characteristics.
Studies
Experiments were conducted on a batch and a continuous system to evaluate
the efficiency of ABS removal from pure solution and from laundromat wastes and
the factors which affect this removal. The laboratory unit employed in these
studies is shown in Figure 1. For studies involving high ABS concentration, this
system was modified to employ an enlarged section for foam drainage. During
tne batch studies the feed and drawoff lines were not employed.
In the batch studies a sample of known volume, temperature, and ABS concentration was added to the unit. (In all the preliminary studies, sodium lauryl
sulfate was employed as the feed material.)  Aeration was initiated at the min-
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