AN IMPROVED PROCESS FOR THE TREATMENT OF PROVISIONAL SPECIFICATION FOR THE TREATMENT OF SEWAGE AND THE PRODUCTION OF MANURES THEREFROM
Year: 1872

page_text: LETTERS PATENT to Dugald Campbell, Consulting and Analytical
Chemist, 7, Quality Court, Chancery Lane, London, Middlesex,
for the Invention of "AN IMPROVED PROCESS FOR THE TREATMENT OF
PROVISIONAL SPECIFICATION left by the said Dugald Campbell at
the Office of the Commissioners of Patents, with his Petition, on
the 30th March 1872.
I, DUGALD CAMPBELL, Consulting and Analytical Chemist, 7, Quality
Court, Chancery Lane, London, Middlesex, do hereby declare the nature
of the said Invention for "AN IMPROVED PROCESS FOR THE TREATMENT OF
SEWAGE AND THE PRODUCTION OF MANURES THEREFROM," to be as follows:-
My Invention of "An Improved Process for the Treatment of Sewage
and the Production of Manures therefrom," consists, in obtaining a
precipitate from sewage as free or as nearly free as is possible from
either the phosphate of alumina or the phosphate of iron, and for this
purpose I use artificial or manufactured phosphates of lime, which are
of themselves practically free from alumina or oxide of iron. I dissolve
the said artificial or manufactured phosphates of lime in some mineral

page_text: acid, and in preference to others in either sulphuric or hydrochloric acid,
as being more economical, and I apply the solution so obtained to the
sewage, adding before or after, but preferably after, cither a milk or
cream of lime, or preferably a milk or cream of magnesia and lime
prepared from magnesian limestone, in quantity sufficient to neutralize 5
the acid which was in the acid phosphate of lime added to the sewage.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Dugald Campbell in the Great Seal Patent Office
on the 27th September 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME; I, DUGALD
CAMPBELL, Consulting and Analytical Chemist, 7, Quality Court,
Chancery Lane, London, Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirtieth day of March, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Dugald Campbell, Her special licence that
I, the said Dugald Campbell, my executors, administrators, and assigns,
or such others as I, the said Dugald Campbell, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AN IMPROVED PROCESS FOR
THE TREATMENT OF SEWAGE AND THE PRODUCTION OF MANURES THEREFrom,” upon
the condition (amongst others) that I, the said Dugald Campbell, my
executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
NOW KNOW YE that L. the said Dugald Camnhell do hereby declare

page_text: performed, to be particularly described and ascertained in and by the
following statement :-
Hitherto acid solutions of the natural phosphates of alumina or of
the natural phosphates containing either phosphate of iron or phosphate
of lime, or mixtures of the same, or of the natural phosphates containing
mixtures of phosphates of alumina and phosphate of iron, or of the
natural phosphates, containing mixtures of phosphate of lime or of
phosphate of iron or of phosphate of lime, either with or without the
addition of lime or of chalk, have been proposed to be employed in the
treatment of sewage so as to obtain a precipitate of the same, which
precipitate is to be employed as a manure, but in most cases of such
treatment the result has been the production of a precipitate containing
more or less of phosphate of alumina or of phosphate of iron, these
phosphates of alumina or of iron being great or little in the precipitate,
according to the natural phosphate used in preparing the acid phosphate
so employed in such treatment of the sewage, containing little or much
of the oxides of alumina or of iron. Now experience has shewn that
either of these precipitated phosphates, namely, the phosphate of
alumina or the phosphate of iron, although valuable to some extent
for agricultural purposes, are very inferior in this respect to precipitated
phosphate of lime, the phosphate of alumina and phosphate of iron
being both not easily decomposible by plants, owing no doubt to the
bases of these phosphates, namely, alumina or oxide of iron forming
practically little or no, part of the food of plants.
Now my Invention consists in applying for the purpose of obtaining
a precipitate from sewage as free or as nearly free as it is possible from
either the phosphate of alumina or the phosphate of iron, artificial or
manufactured phosphates of lime which are of themselves practically
free from alumina or oxide of iron instead of applying solutions of
these natural phosphates, to which I have herein-before referred, as and
to obtain a precipitate to be employed as a manure, and I treat the said
artificial phosphates of lime in the following manner:-I act upon the
said artificial or manufactured phosphates of lime with some mineral
acid so as to render the phosphate of lime soluble, and in preference
to others by either sulphuric or hydrochloric acid as being more
economical than most other such acids, and I apply the compound
so obtained, or a solution of the same, adding before or after, but pre-
ferably after, either a milk or cream of lime, or preferably when it is.
.

page_text: procurable, a milk or cream of magnesia and lime prepared from mag-
nesian limestone in quantity sufficient to neutralize the acid which was
in the acid phosphate of lime added to the sewage.
In carrying out my Invention of "An Improved Process for the
Treatment of Sewage and the Production of Manures therefrom," by
the use of artificial or manufactured phosphates of lime rendered soluble
by acid or acids, I prefer to use the material obtained from the calci-
nation of bones, known in the market as bone ash, as it is at present
the cheapest and best source with which I am acquainted from which
I can now derive by the treatment of an ordinary mineral acid a soluble
phosphate of lime as free or as nearly free as it is possible commercially
to obtain it from the phosphate of alumina or the phosphate of iron,
and to this bone ash I add about three-quarters of its weight of
sulphuric acid, by preference of brown sulphuric acid, made from pyrites
of 80 per cent. as the most economical, mixing or stirring up the whole
well together, and allowing the mixture, preferably, to remain undis-
turbed for a few hours, when the mixture described can be most
advantageously used either in its then existing state or preferably
dissolved in water or in sewage or any analogous liquid; this solution
of soluble phosphate of lime is then to be mixed with the sewage
to be treated, contained in a cistern or reservoir, by means of agitators
of any ordinary kind in the said cistern or reservoir, after which the
milk or cream of lime, or of magnesia and lime prepared from mag-
nesian limestone, sufficient to neutralize the acid which was in the acid
phosphate of lime added to the sewage, is added and the whole com-
pound mixture is to be well agitated and then allowed to rest until the
precipitate having subsided (which it will shortly do), the supernatant
liquid is run off from it, and where practicable such supernatant liquid
is applied to the irrigation of land, to which purpose it will be found
highly beneficial.
Instead of adding the solution of acid phosphate of lime to the sewage
in a cistern or reservoir, and agitating the mixture and afterwards
adding the milk or cream of lime or of magnesia and lime, and again
agitating the solution of acid, phosphate of lime may be run into the
upper part of an inclined trough containing the sewage, so as to produce
a running stream of the sewage and solution of acid phosphate of lime
mixed together. The milk or cream of lime or of magnesia and lime
is then to be delivered at a lower part of the trough into the stream

page_text: of sewage and solution of acid phosphate of lime, and the whole will
then be well mingled by running together until the mixture reaches
the reservoir, and then no use of agitators will be required in the
reservoirs. After the liquid is run off from the precipitate, the pre-
cipitate is collected and may be used in its then existing state as a
manure, or it may be collected and a small quantity of acid, preferably
sulphuric acid, may be added to it, and it may be dried by any of
the well-known methods employed for drying precipitates from sewage
or such like substances, and in this state it may be used or sold as
a manure.
As sewage differs very much in quality, so will the quantities of
solution of acid phosphate of lime required to be added to the sewage
differ; a strong sewage, that is a sewage containing a large quantity
of fecal matter either in solution or suspension, or both, requiring more
than a weak sewage; generally I have found that from about one and
a half parts to two and a half parts by weight of the acid phosphate
of lime to every one thousand parts by weight of raw sewage of
an average kind to answer well; a very strong sewage would require
a little more of the acid phosphate and a very weak sewage would
require a little less. The quantity of hydrate of lime or hydrate of
magnesia and lime to be added to the sewage (preferably in the form
of a milk or cream) is as near as may be about half the weight of the
acid phosphate of lime that is added to the sewage.
Having thus described my Invention, and the means which I adopt
in carrying out the same into effect, I would have it understood that
what I claim is, the employment of artificial or manufactured phosphates
of lime in the treatment of sewage and in the production of manures
therefrom, substantially as described.
In witness whereof, I, the said Dugald Campbell, have hereunto
set my hand and seal, this Twenty-sixth day of September, in
the year of our. Lord One thousand eight hundred and seventy-
two
DUGALD CAMPBELL. (L.S.)