The Sun.
London, England, 1860-04-30 00:00:00

DEODORISATION OF THE THAMES.

ThrJ following report on the practicability and
probable efficacy of the plan proposed by the
Metropolitan Board of Works, for deodorising the

sewage of London by means of perchloride of iron,
has been presented to the Improvement Committee

of the City Commission'of Sewers, by Dr. Letheby,

their Medical Officer of Health :

To the Hon. Commissioners of Sewers of the City

of London.
Gentlemen,—ln accordance with your instruc-
tions I have considered the question submitted
to me at the last meeting of the board—viz.,
the probable efficacy of the proposed plan for
deodorising the sewage of London by means of
perchloride of iron, an I have the honour to sub-
mit my report thereon.
The question is manifestly of the greatest im-
portance, and it must be acknowledged that it is
surrounded with difficulties ; nevertheless it must
be dealt with, for the state of the river during the
last two summers, and the certainty of its becom-
ing as bad as ever during the hot months of the
present year, are matters for serious consideration.
It is true that little or no mischief, as far as we can
discover, has yet been done to the public health ;
but in the face of all experience, it would be rash
indeed to conclude that our present immunity from
disease is sufficient proof of a total absence of dan-
ger, and of the non-necessity for interference.
Who, indeed, can say what little or last condition
may be necessary, or what accident may happen to
call into activity the zymotic powers of disease which
may now only be waiting for their finaldevelopment ?
For my own part, I have looked with anxiety upon
the subject, and I have watched with care the state
of the river during the last two years, and the con-
comitant condition of the public health ; for I could '
not shut my eyes to the fact that all knowledge de-
rived from antecedents has proved beyond doubt
that cholera and its congeners have shown a special
affinity for those places where putrid miasms are
abundant. There the visitations of epidemic disease
are most frequent, and there they acquire the
strength which enables them to migrate into sur-
rounding districts. As your medical adviser, there-
fore, on matters connected with the public health of
this city, I have considered it to be my duty to direct
your attention again and again to the state of the
river ; and to this end I have kept myself constantly
informed of its chemical condition, and have sought,
by the aid of experiment and observation, to discover
the true cause of the mischief, and to find a remedy
for it.
Not only have I tested in the laboratory the
powers of almost ee cry disinfectant that has been
proposed, but I have also visited the principal
towns in England where processes of deodorisation
are largely carried out, and I am bound to state
that the result of all these inquiries, guided by the
principles of chemistry and hygiene, is not favour-
able to the proposed scheme of the Metropolitan
Board.
The plan which is recommended is to cast into
the sewers during the hot weather a concentrated
solution of perchloride of iron. This is to be used
in the proportion of about six grains to the gallon
of sewage ; and the precipitate which it forms with
the sewage is not to be removed, but is to be allowed
to flew into the Thames with the rest of
the liquor. The result of this will be, not
a prevention of the putrefactive process, but
merely a delaying of it. At the utmost its effects
will last for only about nine days, and then the
putrefactive change will continue in its usual way.
This is not only the result of my own experience of
the process, but it is also admitted to be the expe-
rience of Drs. Hofmann and Frankland, who have
advised the board on the subject •, for they say
" that the suspended matter, even when separated
from the deodorised sewage, rapidly passes, in warm
weather, into a state of active putrefaction." The
same opinion has been again and again expressed
by Dr. Hofmann in respect of the solid matter
which is cast down from sewage by the addition of
lime. He has even gone so far as to say that, on
sanatory grounds, no process of disinfection is per-
fect that does not destroy the organic matter of
sewage, as is the case with chlorideof lime, and the
permanganates of potash and soda.
When chloride of iron is added to sewage, the
Wmost effect of it will be but to fix a small portion
—about one-third—of the ammonia contained in
sewage, and to precipitate the sulphuretted hyro-
gen as a black and filthy-looking compound. This
precipitate will be rapidly cast down, and will
carry with it the suspended matters of sewage, ,
learieg a clear liquor in which the organic miasms
are untouched; and here it is that chemistry, when
unassisted by pathology, physiology, and hygiene,
is liable to the most serious errors, and may give
rise to a dangerous confidence in her abstract specu-
lations. Doubtless the removal of a filthy odour
like that of sulphuretted hydrogen may in some
degree be an advantage ; but there is not the re-
motest proof that these are the only or even the prin-
cipal agents which excite disease, and there is no
scientific reason whatever for believing that their
removal is sufficient to interfere with the origin or
spread of epidemic disease.
But worse yet. Not only is the clear liquor still
charged with ammonia and organic iniasms, and so
far is not disinfected, but the bulky precipitate,
which contains all the suspended organic matter,
will soon subside, because of its high specific gra-
vity, and will settle upon the banks of the river,
where it will be left by the receding tide, and where
its disgusting appearance will assuredly excite
alarm; besides which the putrefactive changes
through which it will pass will render it no lss
offensive than the present mud, which Dr. Hofmann
has characterised "by far the most serious evil
which results from the discharge of the London
sewage into the river."
If the process recommended to the board had for
its object the separation of suspended matters from
the sewage, and the disposal of the clear defcecated
liquor, it might perhaps have been applied with
sonic prospect of success ; for this, in truth, is the
basis of the plans adopted by the Metropolitan
Board, and now in process of execution. Those
plans are the result of careful inquiry and delibe-
ration ; for when with Messrs. Bidder, Hawlesley,
and Bazalgette, I examined the processes which are
already in practice at Leicester and elsewhere for
the drtweation of sewage, I was fully convinced
that no process ot' disinfection would be successful
that did not provide for the final and complete re-
moval of the suspended matters of sewage. The
mere addition of a precipitant, without the separa-
tion of the feculent matter so precipitated, was
abundantly proved by experiment and observation
to he a wasteful and worthless proceeding.
Even in the case of the iron solution, which is
props-ell to the board, it has in every instance most
signally failed as a practical deodoriser. More than
two years ego I made a larce nuaileft of experi-
ments on the deodorising power of perchloride of
iron, and the results were communicated to you in
my report on sewage and sewer gases. I found
that it was the least effective, and at that time
the most expensive of all the deodorisers known.
I calculated that, if it were mused in proper propor-
tion to check finally and completely the putrefac-
tion of sewage, it would cot nearly forty-eightmil-
lions a year to deodo:ise the sewage of London.
Since that time, the price of the solution has fallen
to a twelfth part of what it then was; but its cost
as an effective deodoriser is still enormous. It is
not ten or twenty or forty grains of the solution,
that will have the proper hygienic effect upon the
river; but it must be used in the proportion of hun-
dreds of grains to the gallon, to put a final check
upon the putrefactive process. This I have demon-
strated by actual expc,-Tialent, and therefore speak
of it with confidence.
Nor do the results of my experiment stand alone,
as proof of this conclusion ; for your own engineer,
Mr. Haywood, inquired into this matter, at your
request, as far back as the month of March in
1848 ; and he reported to you that when Elierman's
solution was used in the proportion of three gallons
to a cubic yard of night soil, it was not so perfect
in its deodorising power as five pints of a solution
of chloride of zinc. The solution of perchloride
used by Mr. Haywood was supplied to him by
Mr. Ellerman himself. •
Later still the subject was inquired into by Mr.
Hoigson, and reported on to the Metropolitan
Sewers Commission. His report bears the dateof
April, 1848; and, like Mr. Haywood, he found
that Ellerinan's solution was but an imperfect deo-
doriser ; in point of fact, he only sought to remove
ammonia and sulphuretted hydrogen, and these
required ns mueli as eleven and a half quarts, or
nearly three gallons of Ellerman's liquid for a cubic
yard of night soil, whereas the fluid of Sir Wm.
Burnett (chloride of zinc) required but one quart.
These and other experiments were so unsatisfac-
tory that the liquid was not used either by the City
or the Metropolitan Commissioners.
Again :—About four years ago, Mr. Davy, the
Professor of Agricultural Chemistry to the Royal
Dublin Society, undertook a series of experiments
for tho purpose of ascertaininr, what substances
might be successfully used as deodorieers nightsoil'. The salts of iron were used among other,
cad he says of Ell pilaf of iron, which is the hotno--
' Iceme of the pErehLaide, that its efficacy was but
lit tl:3 superior to that said.
And lastly, we have the evperimental and prae_
tieal failure of Mr. Eilerman's plan, under his own
immediate supervision, as the hest of all reasons
for concluding that the re•ocees is not effective.
Seine rears ago his dendori:Ang eetablisliment was-
at '‘',7hitechapel, said although it was in a colony of
nuisances, and sanatory measures were not then
prosecuted with the rigour which they now are, yet
his works were so intolrrably offensive, that the