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Discussion
G.E. Eden, UK
It is known from measurements in the UK and Germany that anionic surfactants of the LAS type
are apparently removed (i.e. rendered undetec table by the methylene blue test) to an appreciable
extent in sewers. In the UK using radioactively labelled material 15% was apparently removed in 4
miles. Newer materials of the aliphatic sulphate type are much more rapidly biodegradable, and much
greater apparent removal is to be expected.
W.J. Kaufman, USA
Normally the soluble fraction of the BOD is most rapidly exerted and removed from solution by an
active biota. Thus, it appears that one role of enhanced in-sewer soluble BOD removal is to make
possible more effective chemical precipitation treatment at the treatment plant. It should be noted
that precipitation with lime or iron does not remove the soluble BOD fraction, but does remove very
effectively the suspended fraction. Studies at Chicago in 1955 demonstrated chemical treatment
improved with the advancing season and increasing temperature. This was probably accompanied by
enhanced in-sewer biological activity which probably accounts for the better summer results.