The Effect of ABS Shock Loadings on
the Activated Sludge Process
E. R. BENNETT, Assistant Professor of Sanitary Engineering
University of Kentucky
Lexington,   Kentucky
D. W. RYCKMAN, Director
Environmental and Sanitary Engineering, Graduate Studies
Washington University
St. Louis, Missouri
One of the most challenging problems for sanitary engineers in the past
decade has been the study of the metabolism of alkyl benzene sulfonate (ABS)
in the activated sludge process. The cause of this problem has been new synthetic washing products made up of tertiary alkyl benzene sulfonate compounds.
The detergent problem has merited intensive study due to the diverse
pollutional effects produced by this relatively non-amenable material. Production of large billows of unsightly, hazardous foam in activated sludge
plants, receiving streams, and water works, has been the most spectacular
result, but other effects such as the production of tastes and odors in drinking
waters, the killing of fish in streams, and the reduction of sewage treatment
plant efficiencies are probably more significant and have also prompted many
investigations.
The problem has been an ever increasing one as the production of these
synthetic cleaning agents has increased yearly and at the present time is
estimated at approximately three and one-half billion pounds a year (1). Even
with the rising popularity of nonionic detergents, the sales of ABS have increased to the point where the concentration in waste streams has become
critical in areas of this country where multiple re-use of river waters must be
practiced. The thorough study at Chanute, Kansas, in 1957 has presented a
significant example of the problem (2).
Some of the first results of studies on detergents made by Bogan and
Sawyer (3) and Hammerton (4) established that the anionic detergents composed of ABS were the most troublesome and that the failure of these compounds to be completely degraded biochemically was probably due to the
branching of the alkyl chain. Later Sawyer and Ryckman (5) further demonstrated that the quaternary carbon connecting the alkyl chain to the benzene
ring in the tertiary ABS compounds was the important link which was inhibiting complete metabolism. It is significant that over half of the detergents
produced are of the tertiary ABS type.
The purposes of this investigation were to study the effect of shock load -
ings of ABS on the activated sludge system to determine the ability of activated sludge to oxidize increasing concentrations of detergent, and to determine the effect of sudden increases of ABS on the oxidation of other pollutional and organic matter present in a waste. It was also hoped to gain an
insight into the mechanism involved in the interaction of ABS and the activated sludge micro-organisms.
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