SEWERS AND STORM W A T E R
THE COMPOSITION OF SEWER AIR
D.K.B. THISTLETHWAYTE* and E.E. GOLEB
*25 Glen Road, Roseville, Sydney 2069, Australia
INTRODUCTORY
The work reported in the following was undertaken as part of investigations into
methods for deodorizing air discharge from sewer ventilation systems. Air contaminated
during contact with sewage has always been associated with odour nuisance, indeed the
possibility of such nuisance often places restraints on sewerage works' designs.
Latham (1878) devotes considerable space in his book "Sanitary Engineering" to
sewer ventilation, with much emphasis on the odour problems, which are attributed
mainly to ammoniacal compounds. At that time it was commonly believed that odours
could be a direct cause of "pestilence and diseases". Folwell (1898), Rideal (1900),
Dibdin (1903) and Fuller (1912) all pay attention to sewer design and maintenance
practice, including "flushing", in relation to odour nuisance from sewers as problems of
aesthetics. Folwell refers to the composition of sewer atmospheres as including "an
ever-varying mixture of gases; and of those that are more deleterious the more prominent
are sulphuretted hydrogen, sulphide of ammonium, and carburetted hydrogen; while
ammonium, carbonic acid and occasionally carbonic oxide derived from leakage of
illuminating gas also occur". Dibdin and Rideal between them mention carbon dioxide
(then called carbonic acid) and the alkylamines as the major constituents.
Fuller says "while sulphuretted hydrogen seems to have the reputation of being the
most offensive product in the decomposition of sewage, it is doubtful if this statement is
correct. Indole, skatole, cadaverin, mercaptan and some other compounds are considered
more repulsive, found in sewage only in a soluble non-gaseous state".
Carlson and Leiser (1966) refer to various products of putrefaction as comprising four
categories of odorous substances, including (a) the inorganic gases including hydrogen
sulphides (?) and ammonia, (b) the acids - acetic, lactic and butyric, (c) the toxics -
indole, skatole, phenols, and the mercaptans, and, (d) the amines - cadaverine and
putrescine. Their practical work however was confined to deodorization studies with
hydrogen sulphide and ethyl mercaptan.
Glaser (1970) discusses the analysis of polluted air from sewage treatment, and reports
some analytical data for air samples collected in and near the raw sewage screen chamber
of a sewage treatment works. His studies recognize different types of organic vapours
defined respectively as sulphides, mercaptans (reported as butyl mercaptan), aldehydes
(reported as formaldehyde), and "total organics". The concentrations, presented only
graphically, include sulphides, daytime values between about 0.2 to odd peaks around 1.5
ppm by volume, mercaptans typically perhaps 0.02 but as high as 0.2 ppm; and aldehydes
between about 0.4 and 1.4 ppm.
Very little has been reported respecting the gases and vapours which commonly
emanate from septic sewages flowing in normal sewage systems. Earlier analytical data for
"sewer g^ses" appear to have been derived mainly by inference from information
respecting sewage decomposition rather than from studies of air in contact with flowing
281
THE COMPOSITION OF SEWER AIR
D.K.B. THISTLETHWAYTE* and E.E. GOLEB
*25 Glen Road, Roseville, Sydney 2069, Australia
INTRODUCTORY
The work reported in the following was undertaken as part of investigations into
methods for deodorizing air discharge from sewer ventilation systems. Air contaminated
during contact with sewage has always been associated with odour nuisance, indeed the
possibility of such nuisance often places restraints on sewerage works' designs.
Latham (1878) devotes considerable space in his book "Sanitary Engineering" to
sewer ventilation, with much emphasis on the odour problems, which are attributed
mainly to ammoniacal compounds. At that time it was commonly believed that odours
could be a direct cause of "pestilence and diseases". Folwell (1898), Rideal (1900),
Dibdin (1903) and Fuller (1912) all pay attention to sewer design and maintenance
practice, including "flushing", in relation to odour nuisance from sewers as problems of
aesthetics. Folwell refers to the composition of sewer atmospheres as including "an
ever-varying mixture of gases; and of those that are more deleterious the more prominent
are sulphuretted hydrogen, sulphide of ammonium, and carburetted hydrogen; while
ammonium, carbonic acid and occasionally carbonic oxide derived from leakage of
illuminating gas also occur". Dibdin and Rideal between them mention carbon dioxide
(then called carbonic acid) and the alkylamines as the major constituents.
Fuller says "while sulphuretted hydrogen seems to have the reputation of being the
most offensive product in the decomposition of sewage, it is doubtful if this statement is
correct. Indole, skatole, cadaverin, mercaptan and some other compounds are considered
more repulsive, found in sewage only in a soluble non-gaseous state".
Carlson and Leiser (1966) refer to various products of putrefaction as comprising four
categories of odorous substances, including (a) the inorganic gases including hydrogen
sulphides (?) and ammonia, (b) the acids - acetic, lactic and butyric, (c) the toxics -
indole, skatole, phenols, and the mercaptans, and, (d) the amines - cadaverine and
putrescine. Their practical work however was confined to deodorization studies with
hydrogen sulphide and ethyl mercaptan.
Glaser (1970) discusses the analysis of polluted air from sewage treatment, and reports
some analytical data for air samples collected in and near the raw sewage screen chamber
of a sewage treatment works. His studies recognize different types of organic vapours
defined respectively as sulphides, mercaptans (reported as butyl mercaptan), aldehydes
(reported as formaldehyde), and "total organics". The concentrations, presented only
graphically, include sulphides, daytime values between about 0.2 to odd peaks around 1.5
ppm by volume, mercaptans typically perhaps 0.02 but as high as 0.2 ppm; and aldehydes
between about 0.4 and 1.4 ppm.
Very little has been reported respecting the gases and vapours which commonly
emanate from septic sewages flowing in normal sewage systems. Earlier analytical data for
"sewer g^ses" appear to have been derived mainly by inference from information
respecting sewage decomposition rather than from studies of air in contact with flowing
281