Note: Descriptions are shown in the official language in which they were submitted.
10755S9
The present invention relates to the production of
phosphate removal agents; more particularly it relates to
the production of an expanded porous calcium, aluminous-
iron material for such a purpose.
In the treatment of municipal, domestic, industrial,
manufacturing and agricultural wastewater effluents, it
is common to convey such effluents to a treatment plant
such as a primary sewage treatment plant, or a Primar
then secondary ~ewage treatment plant,or a septic tank
for the purpose of removing the pollutants therefrom.
Tertiary sewage treatment is ~ometimes added for the
removal of phosphates from the wastewater but it suffers
from the disadvantage in that its phosphate removal effect-
lveness i8 not as high as other materials which might
be used as for example, calcium, aluminous and iron
compounds.
It i6 an object of the present invention to provide a
method of producing an expanded porous product containing
therein in concentrated form the compounds of calcium,
alumina and iron suitable as a phosphate removal agent
which when u9ed as a phosphate removal agent in the treat-
- ment of wastewa~ers tends to overcome the aforementioned
disadvantages associated with conventional wastewater
treatment systems.
According to one asPect of the present invention there
is provided a method of producing an expanded porous cal-
cium, aluminous, iron material suitable as a phosphate
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` 1~)755S9
removal agent in the treatment of phosphate containing-
wastewater, which method comprises calcining an aggregate
containing therein a high proportion of the compounds of
calcium, aluminum and iron at a temperature of from between
600 to 1400 degrees Fahrenheit until the organic matter
and volatiles in the aggregate are driven off, the chem-
ical and mineralogical composition of the aggregate is
changed, the calcium, aluminous and iron content of the
aggregate in changed and concentrated form ~i8 held within
the calcined aggregate material, the external and inter-
nal structure of the calcined aggregate opened up and
made more porous, and also a greatly increased surface
area~ developed therein.
The raw material aggregates ~table for use in the
production of phosphate-removing agents are chosen from
the group of aggregates consisting of clays, rock, shales,
mineral wastes, industrial wastes, coal or burnt coal was- -
tes, coal slag wastes or any form of wastes, containing
therein the compounds of calcium, aluminum or iron in
which they form a major part of the aggregate either as
individual parts thereof or in combination.
It has been found that the temperature of calcination
of the aggregate is a very important factor with the
optimum temperature of calcination being that which will
produce a product therefrom having the de~ired soft-burned
; porous physical characteristics and a desired concentration
of the phosphate removing agents calcium, alumina and
iron retained therein.
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:1075559
As the physical, chemical and mineralogical composition
of the raw aggregate may vary considerably from one
recovery site to another, the exact temperature of calcin-
ation should be determined for aggregates from each part-
icular site-
Because of the aforementioned variations in calcin-
ation temperatures which may range from a low of 600 F.,
to a high of 1400 degrees Fahrenheit, it should be noted
that the temperature of calcination of the aggregate
10 should be that from which a soft-burned product having
a porous structure may be produced while at the same :
time leaving therein the greater portion of its original
calcium, alumina and iron content in more concentrated
form~ It should also be noted that the temperature of cal-
conation should be below that which would be classed as
hard burned in `a. brick works and should be at least
50 degrees Fahrenheit below the melting point of the
aggregate U8 ed -
m e calcium-aluminous-iron material ofthe.invention
20 i8 also formed to expand on heating to give a product with
an expandPd porous structure- Thi~ expansion is advantag-
eous because after crushing and grinding the product obt-
ained is in the form of particles with a desirable ang-
ularity sufficient to interlock one with the other to form
. therefrom an extremely effective filter media having a very
large surface area as compared to normally u6ed filt~r media
and sufficiently large numbers of angles to Provide maximum
micro-straining filter-efffctivene8s. Thus in carrying out
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~" 1075559
calcining it is essential to calcine below the afore-
mentioned "hard burned" formation temperature ~or a time
sufficient to impart a "soft burned" expanded porous
structure to the product of calcining.
According to another aspect of the present invention
there is provided a method of preparing phosphate remov-
ing compounds contained in a wastewater treatment material,
which method consists of incorporating in, concentrated
phosphate-removing compounds or a phosphate-removing
compound contained in a wastewater treatment material,
an expanded porous calcium-aluminous-iron material prod-
uced by the above method.
For the purpose of this specification the term calcium-
aluminous-iron aggregate is intended to cover calcium-
aluminous-iron materials known to form light weight agg-
regates by expanæion on calcining.
..
The calcium, aluminum and iron raw material aggregatesmay be calcined by the application of heat under cont-
rolled conditions of firing in a kiln, open pit, under-
ground ~iring or other suitable means, and thereafter thecalcined materials are crushed, ground and screened to
provide therefrom the desired range of phosphate-removing
wastewater treatment sizings.
It has been found that the phosphate-removing capab-
: ility and the micro-straining capability as well as the
backwashing capability of a filter medium and filter can
be increased without alteration or impairment of the
other qualities demanded of the filter medium or filter,
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1075Ci59
by substituting, for preference, a specified amount or
all of the calcium-aluminous-iron materia~ produced in
- the method of the invention for an equal weight or all of
the filter sand or other conventional types of filter
medium in the filter.
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Observation of the action of the calcined calcium-alum-
inous-iron materials produced in the method of the inven-
tion has disclosed that the angular calcium-aluminous-
iron material after crushing, grinding and screening
to the desired size wil~ interlock the various sized
filter media particles together to provide desirable
micro-straining effect in the filter media so that the
resultant ~ilter media surface will offer a greater res-
istance to wa5tewater pollutant passage through the filter
media while still allowing for a desirable effluent flow
rate therethrough and for maximum flexibility during
backwashing.
I have found it best to crush, grind and screen the
calcined phosphate-removing aggregate to produce there-
from a coarsely granular down to a finely granular prod-
uct and a finely ground product.wherein the maximum size
of the coarsely crushed granular product is that size
passing through a standard screen with a ~ 1/2 inch mesh
size and the minimum size of the finely ground granular
product is that retained on a standard screen with a
60 mesh size, and wherein the finely ground phosphate-
removing product includes all those sizings pas~ing
through a standard screen of 60 mesh size~ although it
10755S9
should be understood that the descrip~ion here is merely
an optimum condition and other degrees of coarseness and
fineness could be used.
I have also found it best to provide a wide range of
phosphate-removing sizings from the coarsely-crushed,
and finely-crushed and ground gran~lar sizings of the
- calcined aggregates. This makes possible the Provision
of filter-media having the property of phosphate rem-
oval graduated according to the desired sizings ranging
from coarsely granular down to finely granular in segreg-
ated aggre~ations thereof when placed within pervious
plastic bags or containers.
The aforementioned pervious bags may be made from
plastic netting, waterPrOOfed woven material, polyprop-
ylene or other suitable materials. The mesh size of the
bags may be of any suitable size but the perforations
in the pervious bags should have a smaller diameter sizing
; than the diameter of the phosphate-removing filter media.
Since most of the plastic or polypropylene netting used
today for bag making is in tubular form it is essential
tha~ a large enough diameter sizing be used. I have
; found it best to use a bag size of about 24 inches wide
and 36 inches long. A narrower bag becomes to bulky and
a longer bag to heavy to handle particularly when wet~ It
should be understood that the description here is mere-
ly an optimum sizing and other sizings or shapes could
be used as may be required or be necessary to conform
to the filter de~ign or configuration.
This artificially prepared product will in the presence
of phosphate-containing wastewater react with its phosph-
ate content to remove it therefrom by chemical precipitat-
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~75559
ion, sorptive processes or biological activity.
In the practice of the present invention, it is desir-
able in most wastewater treatment applications such as
domestic, industrial, manufacturing and agricultural
wastewaters to pre-treat the wastes to remove solids, org-
anics, toxic substances and heavy metals prior to treating
the wastewater to remove phosphate sewage-fertilizer
nutrients therefrom. This can be done by passing the
wastewater through a conventional type primary, secondary
and tertiary sewage treatment plant, or a septic tank
sewage treatment system followed by a biological- oxid-
ation bed containing granular adsorptive coal filter media
therein, then Passing the effluent through the phosphate-
removing filter media prepared by the method of the pres-
ent invention prior to its discharge to surface waters.
` m e following tables are o~ ash analysis of typical
raw material aggregates suitable for use in preparing
the phosphate removing wastewater treatment materials of
the invention.
Table 1
Aggregate in which calcium predominates.
Analysis of Ashs ~A12O3 Fe203 CaO (calcium)
.. ,............. , l302 5.9 22.5
Table 2
Aggregate in which alumina predominates.
Analysis of Ash: ~1203 Fe203 CaO
%.................. 38.2 2.9 1.
Table 3
Aggregate in which Iron predominatess
30 Analysis of Ashs A12O3 Fe2O3 CaO
.................. 12.0 59.3 3.4
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10~5559
The calcined materials of the invention after crushing,
grinding and screening to a desired sizing are very
porous and extremely abrasive with a desirable Particle
angularity. They have a specific gravity of from between
1.80 to 3.5 and a grindability index of from between
30 to 50, with a hardness of from 2 to ~ on the Mohrs
scale of hardness.
It has been found desirable to treat larger water areas
such as lagoons, lakes and the like whose waters are
loaded with phosphates and whose sediments are polluted
with all manner of undesirable toxic substances, heavy
metals and sewage fertilizer nutrient~. In treatment app-
lications such as these it is not always possible to treat
- the waters in filters or the like. I have found that the
use of the finely ground phosphate removing materials
when dusted over the water tend to cleanse the pollutants
therefrom and on settling tend to bind the phosphates with-
in the calcined phosphate removing treatment media.
It will be evident to those skilled in the art that
it would be advantageous to form a treatment mixture
of both the finely ground phosphate removing materials
of the invention and the adsorptive coal in ~inely ground
form where a complete form of wastewater trea~ment may
be provided to serve the needs of larger water areas~ Such
uses are intended to come within the scope of the present
invention.
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1075559
For the purpose of this invention micro-straining
is intended to mean the removal from wastewater of
extremely fine suspended mattex from water due to
the porous9 rough and very abrasive nature of the
phoæphate-removing filter medium and the ability
of the filter medium to interlock one with the other
due to the tr~mendou~ number of angles presented to -
the incoming wastewater due to the angularity of the
calcined phosphate-removing filter-medium
Having described a pr0ferred embodiment of the
invention, it should be apparent to those skilled
in the art that the invention permit~ of modification
in arrangement and detail. I claim as my invention
all such modifications as come within the true
spirit and scope of the aPPended claims.
.
No corresponding United States patent application
has been filed.
