Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~7~4;~
This invention relates to the conversion of carbon-
aceous phosphorous and nitrogen values in BoD-containing liq-
uid into a plant or animal nutrient or a high energy biomass
useful in the fermentation industries. More particularly, the
product of this invention relates to high nutrient assay animal
feeds produced from N-, P-, and BOD-containing mixtures, such
as, for example, carbohydrate suspensions or solutions. This
invention also relates to the production of high assay fertili-
zers by the treatment of BOD-containing wastewater. It also re-
lates to an active, dense biomass useful in fermentation pro-
cesses~
The employment of biological sludge for fertilizer
values is known to the art and has been more or less success-
fully practiced (Nilorganite (trademark~ fertilizer produced
by the city of Milwaukee). Various other municipalities and
wastewater treating enterprises have attèmpted to dispose of
waste sludge for their compost or fertilizer values. Unfor-
tunately, the fertilizer value of unsupplemented sludges here-
tofore employed has been minimal due to the fact that the
phosphorous content, expressed as elemental phosphorous, has
varied from about 1 to about 2% by weight. (See C. J. Rehling
and E. Truog "Activated Sludge-Milorganite, Constituents,
Elements and Growth Producing Substances", I and E Chemistry,
Analytical Edition, Volume 11, No. 5, Pages 281 to 283).
In accordance with this invention the product which
can be employed as an animal nutrient (e.g., poultry, fish
or crustacean feed), as a plant nutrient (fertilizer), or
applied to fermentation processes, is produced by first form-
ing a mixed liquor by mixing activated biomass with a food
source in the form of a BOD-containing liquid under anaerobic
conditions, i.e., substantially free of NOX having a con-
centration of less than 0.7 ppm dissolved oxygen (DO). Pre-
ferably, the DO content
- 2 -
1117~4~
is less than 0.5 ppm with a DO content of less than 0.4 ppm being
co!~T.on. It is important to maintain the Do content in the anaero-
bic zone be~ow the specified limit throughout the entire zone and
for the total treatment pe~iod. Isolated portions of the anaerobic
zone at higher ~o levels are to be avoided. similarly, intermit-
tent time periods of higher DO are also to be avoided. It is
through the operation of this initial anaerobic treatme~t that
the formation of a nonfilamentous biomass is effected. In fact,
formation of the nonfilamentous biomass is indicative of the
maintenance of the anaerobic conditions, i.e. low DO. Conversely,
the formation of a filamelltous biomass is indicative of a failure
to maintain anae obic conditions. This is particularly so in the
earlier portions of the anaerobic operation.
When operating in a continuous flow mode, the formation
of the particular microorganism (capable of sorbing BOD under
anaerobic conditions)! in preference to other types of micro-
organism requires the maintenance of anaerobic conditions i~ the
initial zone in order to develop. The occurrence of isolated
zones of higher DO or the maintenance of a higher DO in the zone
for an intermittent period adversely affects the development of
such microorganisms. After establishment of the desired micro-
organism through the maintenance of anaerobic conditions, slightly
higher DO levels can be tolerated for short periods of time, but
if conditions of higher DO level are permitted to prevail for any
significant period of time, the effect is deleterious in that the
desired microorganisms are washed out and replaced by ordinary
biomass.
The food source must also contain nitrogen, phosphorous
and potassium values in adeguate quantities relative to BOD con-
centration to stoichiometrically produce the desired concentrations
.
4~
of these elements in the product. For this purpose, it can be
estimated that from about 30 to about 100% of the BOD removed
is converted to product. Usually, the phosphorous content is
at least about 2% by weight (expressed as elemental phosphorous),
the potassium content (expressed as elemental potassium) is at
least about 1% by weight, and the nitrogen content (expressed
as elemental nitrogen) is at least about 5% by weight of dried
product. The food source, of course, will also contain (albe-
it at times only in trace quantities) other elements normally
required to sustain life, including sulfur, magnesium, zinc,
calcium, manganese, copper and others. The full list of these
elements is believed to be known in the art and, in addition
to those specifically mentioned above, also encompasses carbon,
hydrogen, oxygen, iron and sodium. (A list of these elements
can be found in "Botany - A Functional Approach'`, Third
Edition, by W. H. Muller, Macmillan Publishing Co., Inc., N.Y.)
Generally, these elements are found in adequate supply in
ground water.
The activated biomass employed in thisstep is the same
biomass produced later in this process and it is the employment
of such biomass which is effective for the selective production
of nonfilamentous microorganisms capable of sorbing substantial
quantities of BOD under anaerobic conditions. It is theorized
that the energy for active transport of BOD values from aqueous
solution to within cell walls is derived from hydrolysis of poly-
phosphates stored either within or at cell walls and inorganic
phosphate is transferred from the biomass to the aqueous phase at
the same time. It is believed that the initial exposure of this
particular biomass to BOD-containing solutions under anaerobic
conditions favors proliferation of species most capable of storing
polyphosphates since these species are particularly able to sorb
.~,,
~ .
the availa~lc food ~der anaerobic conditions.
The ~ixed liquor from the anaerobic treatment is sub-
seguQntly contacted with oxygen-containing gas under conditions
.
selected to maintain a'dissolved oxygen content of at least about
1 ppm. This contacting is effective to oxidize the BOD previously
sorbed by the biomass in the mixed liquor, thereby su'ostantially
lowering the'internal BOD content and generating energy During
this oxic or aerobic treatment, the energy expended by hydrolysis
of polyphosphates in the anaerobic treatment is recouped and
polyphosphate is reformed and accumulated ~i~hi~ the biomass,
.thereby rernoving phosphate values from the aqueous portion of the
mi~ed liquor. .This oxidized mixed liquor is then separated into
a supernatant liquid and a more dense biomass. At least a portion
of this separated biomass is employed as the activated biomass in
the initial anaerobic mixing with ~OD-containing liquor. Another
portion ~usually the balance~ of the separated biomass is recovered
as the product. In those cases where animal or.plant nutrient is -
to be produced, the dense biomass'can be subjected to drying ' .
and/or pasteurizing procedures in order to convert it into a form
more convenient for handli~g and saf.e for application ~owever,
it may at times be preferable to add live, wet biomass to the
soil thus avoiding drying costs. Another approach would be to
mix seeds with live biomass at time of planting. The live biomass
produced in this process has properties of unusualiy hi~h density,
due to massive polyphosphate inclusion, and the ability to remain
viable for long perîods of time due to the energy contained in
the-polyphosphate. These properties obviously make the produc~
of this invention well suited to applications in the fermentation
industries. . ..
In accordance with another embodiment, particularly
1~17~4~
suited to wastewater treatment in which denitrification is desired,
a portion of the mixed liquor, subsequent to the oxic or aerob:ic
treatment, can be recycled to an anoxic zone interposed between
the anaerobic and the oxic treatmentS under anoxic conditions for
the purpose of denitrification of nitrites and/or nitrates produced
by the oxidation of a~monia in the oxic treatment. As used
herein, ~he term anoxic indicates conditions wherein the dissolved
oxygen content of the mixed liguor is maintained at a level not
in excess of 0.7 ppm (preferabl~ less ~an 0.5 ppm and particular-
ly less than 0.4 ppm) and wherein nitrates and/or nitrites are
.
added to the initial section of the anoxic treatment. As with
the anaerobic treatment, it is also ~mportant in the anoxic
tre~tment that the DO content in the anoxic ~one be maintainedbelo~ the specified limit throughout the entire ~one and for the
total treatment period. Isolated.portions of higher DO levels or
intermittent time periods of higher DO level are to he avoided,
but in this case the penalty is a loss of denitrification as
distinguished from loss of good sludge properties when excessive
~0 is present in.the anaerobic zone. In.fact, as a general rule,
it can be stated that in the anaerobic and anoxic treatments, an
oxygen containing gas is not intentionally fed to such treatments.
As distinguished from this, oxygen containing gas is intentionally
introduced into the oxic or aero~ic treatment.
: . The concentration of total nitrates and/or nitrites in
the mixed liquor recycled back to the anoxic treatment is normall~
in excess of 2 ppm, expressed as elemental nitrogen. The nitrates
and/or nitrites are reduced in the anoxic treatment to elemental
nitrogen gas. The nitrates and/or nitrites added to the anoxic
zone are obtained by recycling back to th~ anoxic treabment,
oxygenated ~ixed liquor obtained from the oxic or aerobic treatment.
6.
~ il7~4~ !
This mode of operatin~ provides a means for reducing the nitrogen
content of the effluent liquor when the product is derived from
treatment of BOD-containing wastewater.
lt will be understood that the product of this invention
can be produced either by a batch process or by a continuous flo~
process. Thus, when operating as a continuouS flow process, it
is within the scope of this invention to have an initial anaerobic
contacting zone ~herein BOD-containing influent is mixed with
recycle biomass under anaerobic conditions to prodùce the mixed
liguor and to sorb BOD from the agueous phase. The mixed liquor
from the initial anaerobic zone can then be passed to a subsequent
oxic or aerobic zone wherein it is treated under oxic conditions.
~he material from the oxic zone can then be passed to a settiing
zone (or clarifier? wherein the more dense biomass is settled
from the supernatant liquid. A portion of the biG~ass is removed
from the settling zone and recovered as product, while another
portion of the settled biomass is recycled to the initial anaerobic
zone. -
- - When the intermediate anoxic treatment is employed, an
anoxic zone can be positioned intermediate the anaerobic and oxic
zones and connected into the syste~ such that the efnuent mixed
liguor from the anaerobic zone passes to the anoxic zone, the
treated mixe~ liquor from the anoxic zone passes to the oxic zone
and a portion of the oxygenated mixed liquor from the oxic zone
is recycled to back the anoxic zone.
~ en operating as a batch process, a EOD-containing
aqueous solution is mixed with an activated biomass o~tained from
a previous cycle to form the mixed liquor which is then treated
.
initially.under anaerobic conditions.
Su~seguent to the anerobic treatment, the mixed liquor
~1~7{!!4~ ~
is thcn'treated in ~hc same vessel but under oxic conditions.
The ~aterial, after oxic treatment, is then separated into a
supernatant clear liquid and a more dense biomass phase and at
least a portion of the biomass phase recovered as product
The particular pxoduct produced by the processing steps
described above has a comparatively high phosphorus content.
This is particularly so, for example, when a comparison is made
between the phosphorus values t~pically ohtained in wastewater
sludge versùs the elemental phosphorus content typically obtained
when wastewater is employed as the BOD containing influent for
the product of this invention. Thus,'as mentioned be~ore, typical
assays of m~re traditional wastewater sludges have a phosphorus
content in the ranqe of from about 1 to about 2% by weight (express-
ed as phosphorous) while assays of from about 5 to about 10% by
eight phosphorous on the c~me basis (dry) have been obtained in
accordance with this invention. This high assay is due to the
: ..
fact that the process employed for the production of the product
herein is capable of removing all of the soluble and hydrolyzable
phosphate in the influent by incorporation into the biologically
active species employed as the biomass herein. It is to be
emphasized that these high phosphate values are produced by
incorporation of so~uble and hydrolyzable phosphate from the BOD
influent into the biomass and, as such, is incorporated at and/or
WithiD the'c~ll walls of ~he biota, largel~ as massive inclusions
of polyphosphat~. The presence of inorganic ~olyphosphates in
biology is a widespread, but little understood phenomenon ~see
"Inorganic Polyphosphates in Biology: Structure,'~etabolism and
Function", F. M. Harold, Bacteriological Reviews, Volume 30 ~
pages 772-794, 1966) but the technique of intentionally inducing
largc concentrations of polyphosphate in biomass utilized in the
1117Q4~
treatment of BOD-containing solutions has heretofore not been
employed.
Addi~ionally, the product of this invention generally
has a nitroyr~n assay which is significantly higher, i.e. from 6
to about 8 weight percent expressed as elemental nitrogen on a
dry basis, as contrasted to nitrogen assays of less than about 5%
and going down to about 3% co~monly reported for wastewater
sludges of the prior art. Similarly, the potassium assay o the
product of this invention can also be comparatively high, i.e. in
the range of greater than about 1% expressed as K20, as contrasted
to values of about 1% or less reported for fertilizers produced
from wastewater treatment plants such as, for example, ~ilorganite.
The particularly high phosphorus values for the product
produced in accordance with this invention is due to the substan-
tially complete incorporation of phosphorus values from the BOD
containing influent to the biomass. In this connection, it is
~oted that the phosphorus content of the biomass is a function of
the mass of the phosphorus available to the system and the mass
of the biomass produced. As wili be seen in~the subsequent
examples, phosphorus, expressed as weight per c~nt P, ranges
upwardly from about 5% by weight and can conceivably be higher,
for example, up to about 20% by weight or more in the instance of
a high phosphate to BOD ratio in the influent food source.
The wet biomass product of this invention is believed
to be umlsual. This is particularly so when producing fertilizer
from waste~7ater, since there is little or no tendancy for the
biomass or sludge of this invention to have an unpleasant odor
during the drying process. It is hypothesized, without being
br,und thereby, that energy released from the high polyphosphate
content of the biomass is respons;b~e for maintaining life within
1~7Q~
the biomass until the final act of pasteurization. Thus, decay
or rotting of dead biomass is largcly avo;ded. This theory is
supported by microscopic examina~ions of the biomass which
indicate that phosphorus is stored as massive inclusions within
the ceil walls.
When the bio~ass product of this invention is employed
as a fertilizer, the phosphorus in the biomass is availcible to
plant life as is the fixed n~itrogen. Due ~o the fact tha~ the
nitrogen is combined laryely as protein and the phosphorus is
combined largely as polyphosphate, it can ~e seen that the
fertili~er product of this invention is of particular value since
the constituents can be expected to be of the slow release variety.
For the case of animal or fish feed, the BOD content of
the influent can be carbohydrates such as ~lucose, sucrose,
starch or waste liquor from pulp and paper operations. The BOD-
containing food will~ of course, also cnn~ain the i~organic
materials mentioned previously.
Further, the live ~iomass product of this invention has
utility in the fermentation industries due to its high density
~for facile separation) and energy content.
DE~CRIPTION OF T~E DRAWINGS
Figure 1 is a schematic diagram of a contimlous flow
process in accordance with this invention employing anaerobic and
oxic zones.
- Figure 2 is a schematic diagram showing processing of
biomass obtained from a continuous flow proc~ss.
Figure 3 is a schematic diagram showing a continuous
flow process employing anaerobic, anoxic, and oxic zones.
Figure 4 is a schematic diagram illustrating batch
process operation of this invention.
10.
11~7{~4~Z
Refer~inq to Figure 1 of ~le drawings, an activated
sludge wastewater treating faci~ity is shown. Incoming waste-
water or treatment, either settled sewage from a pri~ary sedi-
mentation tank or ot~erwise, is in~roduced via inlet line 10 into
tank 12 ~Jhich defines an anaerobic zone. As shown in Figure 1,
partitions 14 located within tank 12 divide the zone into a
series of intercomlected hydraulic stages 16, 18 and 20 designed
to provide staged flow through the zone defined by tank 12. Each
of the hydraulic stages is provided with stirring means 22.
While Figure 1 illustrates the division of tank 12 into three
stages each containing a stirring means, it will be understood
~hat a greater or lesser number of stages can be employed.
While various techniques can be employed in order to
maintain t~e zone defined by tank 12 ~nder anaerobic conditions,
such as, for example, by covering the tank, and/or providng a
blanXet of carbon dioxide, nitro~en, or other inert gas, the
particular technique illustrated in Figure 1 is the use of nitro-
gen purge gas aclmitted into and bubbled up through the mixed
liquor. Shown specifically, is line 24 which introduces nitrogen
into each of the stages 16, 18 and 20 through the bottom of tank
12~ It is through this technique that anaerobic conditions
including a D0 contenc of less than 0.7 ppm are maintained. A
N0x content of less than 0.3 ppm, and preferably less than 0 2
ppm is maintained by othe~ means.
The anaerobically treated mixed liquor is passed by
, . . . .
means of line 26 and introduced into tank 28 wherein the mixed
liquor is treated under oxic conditions. As illustrated in this
figure, three partitiQns 30 are employed to separate the zone
defined by tanX 28 into four serially, interconnected hydraulic
stages 32, 34, 36 and 38. Aeration of the licluid in tank 28 is
1117~4~ ~
effectcd ~y the sparging of air to the bottom of each hydraulic
stage of tank 28 by means of spargers 40. In the operation of
this zone the dissolved oxygen content is maintained above about
1 ppm in order to insure adequate oxygen presence for the metab-
olism of soD and to furnish the energy for phosphate uptake by
the biomass. Alternatively, oxygen or oxygen enriched air can be
introduced via spargers 40. When employing oxygen, oxygen enriched
air or gas containing oxygen of any desired purity, suitable
means for covering all or a part of the aerobic or oxic zone can
be considered. If desired, instead of, or in addition to spargers
the o~ygenated zone can be provided with mechanical aerators
As shown in Figure 1, tank 28 is partitioned into four
hydraulic stages, although a greater or lesser numher o~ stages
can be employed, if desired. It is preferred, however, tha~
several stages be employed since it has been observed that
phosphate uptake by the biomass is a first order reaction with
respect to soluble phosphate concentration. Accordingly, lou
values of phosphate in the liyuid effluent and, accordingly, high
values of phosphate in the biomass are rnost economically obtained
~ith stagea flow configuration.
Su~seguent to the oxic treatment in tank 28, the
treated mixed liguor is passed by means of line 41 into clarifier
42 wherein it is permitted to separate into a supernatant, clear
liquid 44 and a more dense biomass 46. The supernatant liguid 44
is withdrawn from clarifier 42 by mean~ of line 48 and removed
from the system.
The more dense biomass 46 is removed fxom the bottom of
.
clarifier 42 by means of line 50 and the stream of line S~ is
divided into streams of line S2 and line 54. As shown in Figure
1, the s~re~m of line S2 is recycled by meaIls of pump 56 and line
~1~7~?4~
58, and is returned to the first stage 16 of tank 12 to treat
BOD-containing influend under anaerobic conditions.
Referring now to Fig~re 2, there is shown the fur~her
processiny of the bio~.ass contained in the stream of line 5~.
'This portion of the biomass frorn clarifier 42 of Figure 1 is
introduced into thickener 60 where a further separation into a
second supernatant liquid phase 62 and a second more dense
biomass phase 6~, is effected. The second supernatant liguid
phase 62 is-removed from thickener 60 by means of 3;ne 66 and
xecycled via pump 68, line 70, and line 72 into tank 12 of
Figure 1.
T~e second more dense biomass phase 64 is removed from
~he thickener 60 by means of line 74 and is introduced into
filter 76 to effect further separation bet~Jee~ uid. and solids.
A centrifuge,filter press or other ~nown apparatus for the separa-
tion of liquids and solids can be used instead of filter 76. If
desired, filter aid chemicals can also be added to filter 76 by
mean:s of line 78. The,liguid separated in filter 76 is removed
vqa line 80, pump 82 and passed by means of line 84 into line 72
wherein it is-combined ~ith the second supernatant liquid of line
70 and retunled to anaerohic tank 12 as shown in Figure 1. The
solids separated.in.filter 76 are passed to a drying system 88 as
indicated by line 90.
~ s shown in Figure 2, air and fuel are introduced into
furnace 92 by means of lines 9~ and 96, respectively. -The hot
gases from furnace 92 are passed by mea~s of line 98 into dry;ng
system 88 wherein the hot gases are employed to effect,a final
drying and sterilization of the solid biomass product.
The gas from drying system 88 is removed therefrom by
means of line 100 and passed to heat exchanger 102 for the
1~7~4~ ~
recovery of hcat values tllerefrom. Thc cooled, gas~ous stream is
thcn passed from heat exchan~er 102 by means of line 104 to
cyclone separator 106 ~7hcrein any solid fines are removed from
the gaseous strc~ and are transport~d from the cyclone 106 by
means of line 108. The su~s~antially solid-free gas is exhausted
from cyclone sepaxator 106 and the system by means of line 110.
The separated solid biomass product is removed from
drying system 88 by means of line 112 and passed to product
storage facility 114. AS shown in Figure 2, the solid fines
removed from t-he ~aseous stream in separator 106 are introduced
into line 112 by means of line 108.
Figure 3 shows a schematic diagram of a cont:inuous flow
process in which an anoxic zone.is interposed ~etween the anaerobic
zone ~tank 12~ and the oxic zone (tank 28) of the scheme sho~n in
Fîgure 1. Accordingly, then, the same items in both Figure 1 and
Figure 3 will be designated ~y the same reference nu~erals.
Thus, in Eigure 3 incoming wastewater is shown being introdu~ed
via inlet line 10 into tank 12, which defines the anaerobic Zone.
Similarl~ the txeated wastewater is separated in clarifier 42
into a first supernatant liquid layer 44 and more dense biomass
phase 46, which is removed from clarifier 42 ~y means of line 50
and then divided into the streams of lines 52.and 54. As shown
in Figur~ 2, the stream of line 54 is introduced into thickener
60 and the liquid separated in thickener 60 and filter 76 is
returned via line 72 to tank 12 (again, as shown in both Figures
1 and 3).
In the specific flow scheme shown in Fisure 3, the
anaerobically treated waste water is removed from tank 12 by
means of line 26 and introduced into tank 120, which deines an
anoxic treating zone. As illustrated in Fi~ure 3, tank 120 is
14.
11~7~ 9
partitioned into three serially, intercolmected hydraulic stages
122, 12~ and 126 by means of two partitions 128.
While various techniques can be employed in order to
maintain the zone defined by tank 120 under anoxic con~itions
such as, for example, covering ~le tanX and providing it with a
blanket of carbon dioxide, nitrogen, or other inert gas, the
particular technique illustrated in Figure 3 is the use of
nitrogen gas admitted into and bubbled up through the mixed
liguor. Shown specifically is line 25 (an extension of line 24)
which introduces nitrogen into each of the staqes ~22, 124 and
126 through the bottom of tan~ 120. It is th~ough this technique
that the D0 content of the mixed liguor in tanX 120 is maintained
at less than 0.7 ppm. Each of the stages 122, 124 and 126 is
also provided with stirring means 130 to insure adeguat~ mixing
of the ~aterials in tank 120.
Also shown in Figu~e 3 is an ihternal recycle circuit
comprised of line 132, pu~p 134, and line 136. As illustrated in
this figure, oxygenated mixed liquor is removed from the last
.
hydraulic stage 38 of tank 28 by means of line 132 and is recycled
through pump 134 and line 136 to the first hydraulic stage lZ2 of
the anoxic zone in tank 120. It is by this means $hat NOX
containing materials in the form of nitrites and/or nitrates are
introduced into ~he anoxic zone.
In all other respects, the wastewater treatment system
of Figure 3 parallels the wastewater treatment system shown in
Figure 1, but results in a supernatant liquid 44 removed rom
clarifier 42 by means of line 48 which has a reduced nitrogen
content.
Figure 4 illustrates a batch process operation for the
production of hiomass product in accordance with this in~-ention.
In this figure, in~et hoppcr 210 is provided with a valve 212,
designed to permit a measured quantity of a BOD-containing food
source to entcr reaction tank 21g A stirring means 216 is pro-
vided in tank 21~ in order to provide adequate mixing of thecontents of tank 21~. Located near the bottom of tan~ 214 is a
gas sparger 218 which in turn is connected to an external inlet
~as manifold 220. As is also shown in this figure, valved nitrogen
inlet line 222 and valved oxygen inlet ~ine 224 connect to gas
manifold 220.
Located at the bottom of tank 214 is a valved b;omass
removal line 226. TanX 214 is also provided with a dissolved-
oXygen probe 228 which is capable of detectiny and indicating the
dissolved,c~ygen content of the material within tank 214.
Finally, tank 214 i5 provided with a liguid removal or outlet
system comprising co~duit 230 having its inlet e~d positioned a
pre-determined distance above the bottom of tank 214 and connected
at its other end to pump 232.
In operation a pre-determined guantity of BOD-
containing food source is introduced,Iro~ ta..k 210 into tank 214
through the operation o'f valve 212.' '5tirring means 216 operates
to effect thorough'mixing of the BOD-containing influent and
previously prepared activated biomass in tank 214 in order to
provide a mixed liguor. Dissolved oxygën probe 228 detects the
DO level in the mixed liguor in order that proper control thereo
can be maintained. Thus, during the initial anaerobic treatiny
phase, valved nitrogen inlet line 222 introduces nitrogen into
gas manifold 220 which in turn is connected to gas sparger 218;
whereby nitrogen gas can be bubbled upwardly through the mixed
liquor in tank 214. This is e~fective to ~aintain the dissolved
oxygen content below the desired level. If the DO level is too
4~ .
high, this is detected by Do probe 228 and the rate of nitrogen
introduction c~n be increased.
Upoll termination of thc anaerobic treating phase, the
introduction of nitrosen through nitrogen inlet line 222 is
discontinued and oxygen, either in the form of pure oxygen, air
or oxygen enriched air, is then introduced via valved oxygen
inlet line 224 through gas manifold 220 and into sparger 218;
~herehy oxygen is bubbled up~ardly through the mixed li~lor in
tank 214. At the termination of the oxic or aerobic treating
phase, the introduction of oxygen containing gas tbrough inlet
line 224 is discontinued
After the introduction of oxy~en has been discontinued,
the mixed liquor in tank 214 is permitted to remain at rest in
order to affect separation of a supernatant li~uid phase from a
more dense biomass phase~ A~ter such settling has taken place,
pu~p 232 is activated iIl order to withdrau supexnatant li~uid
from tank 214 ~y means of outlet conduit 230. Valved biomass
outlet line 226 is ~hen opened in order to remove a portion of
the more dense biomass phase from the bottom of tank 21~. The
remaiI~ng poxtion of the biomass phase is retained in tank 214
fox mixture with the next batch of influent BOD-containing food
source.
The portion of the biomass phase removed via valved
outlet line 226 is introduced into thic~ener 234 in order to
permit a second, mo~e co~,plete, separation into a second super-
natant liguid phase 236 and a more dense biomass phase 238. The
supernata~t liguid phase is removed from the system by means of
conduit 240, while the biomass phase is passed by means of conduit
242 to drying æone 244 wherein substantially all water is removed.
Final dried biomass product is transported from zone 244 by means
17.
~il7~4~ ~
of'line 246 to product storage 2~8.
In order to illustrate this invention in greater detail,
reference is made to the following examples
Exam~le 1
In this exa~ple, the procedure employed to proauce the
nutrient material of this invention suitable for use as a fertiliz~
er comprised an initial anaerobic treatment followed by a subse-
guent oxic or aerobic treatment. The apparatus employed comprised
an anaerobic zone partitioned into five hydraulic stages each
having a volume of i.2 liter, and each being provided with a
stirring means. The initial zone was maintained'under anaerobic
conditions by nitrogen sparging, whereby the measured DO content
~hroughout the run was maintained at all times below 0.1~ ppm.
l'he oxic or aerobic zone was aiso partitioned into ~ive equal
hydraulic stayes each having a volume of 3'1iters. Each of these
oxic stages was maintained under oxic conditions by sp~rging with
air, and the DO content in all the stages remained above 1.8 ppm
throughout this run. A clarifier or settling tank was also ' - I
'provided to'recei~e effluent from the oxic zone In the clarifier,
a'separation is effected between a supernatent, clear liquid ana
a more dense activated biomass (sludge). The supernatent liquid
was decanted and removed from the syste~, ~hile the biomass was
removed from the bottom of the clarifier and separated into two
portions. One portion was removed from the system and recovered
as product, while the other portion of the separated sludge was
pumped back to the initial stage of the anaerobic zone.
The BO~ containing food source employed in this example
was a municipal wastewater of high phosphorous content. Inspec-
tion data for the influent are shown in Table I below The
influent ~as charged to the system at a rate so as to provide an
18,.
1~17~4~ '
influent dctent;on time (IDT) of 3.66 hours, and the portion of
thc scparatcd sludge which was returned to the initial anaerobic
zone was recycled at a rate of about 18% by volume based upon
influent flow rate. This was eff~ctive to provide a nominal re-
sidence time ~NRT) of 0.176 hours per stage in the anaerobic
z~ne, and 0.442 hours per stage in the oxic zone.
The portion of the sludge or active biomass not recycled
to the initial anaerobic zone was separated from supernatent
liquid, filtered and dried for 24 hours at 105C. The inspection
data for this dried product of the inventions, together with
other inspection data of the separated supernatent liquid are
also shown in ~able I.
TA~LE I -
,
Total BOD5 Soluble BOD5 N~ -N NO -N PO -P
(mgJl) (mg/l) (m~ (m~/l) (m~
Influent 236 . 197 24 0.03-17.4
(liguid)
Effluent 8.1 1.6 - 4.4 5.10.1
(liquid)
Nutrient C H N P SSi
(dry solid) .
% by wt. . 28 42 5.71 5.46 6.81 0.48 0.60
.. . . . .
From the data shown in Table I it can be seen that the
specific process employed to produce the products of this inventi~n
is effective to provide a nutrient material having rel.atively
high nitrogen and phosophorous content. It will also be seen
that such product is produced while convertin~ substantial quanti-
ties of the ammonia content of the influent into the more acceptab~e
nitrite and/or nitrate form and that the process also e~fects
substantially total removal of phosphate from the influent.
].9.
1117a!4~ ~
Which phosphate value is recovered in the dry, solia product.
Exam~le 2
In this example, the product produced wa a nutrient
rnaterial suitable for use as an ~nimal feed. The procedure
emplo~ed to obtain such products comprise the use of init;al
anaerobic treatment f~llowed by an anoxic treatment and ulti~ately
anoxic or aerobic treatment. The particular apparatus employed
comprised an anaerobic zone partitioned into three hydraulic
stages, each having a volu~e of 1.2 liter and each being provided
with a stirring means. This initial anaerobic zone was maintainea
under anaexobic conditions by nitrogen sparqing, where~y the
measured DO content -throughout the run was maintained below 0.1
ppm. The anoxic zone was also par~itiored into three equa~
hydraulic stages each having a volume of 1.2 liter. Each of
these stages was maintained under anoxic conditions by a nitrogen
pur~e and the DO content in all of tne anoxic stages rer~ined
below 0.1 ppm throughout the run. The oxic or aerobic zone was
partitioned into four egual hyaraulic stages each having a volume
of 2 liters. Each of the oxic stages was main~ained under ox;c
conditions by sparging with a mixture of nitrogen and air so as
to provide an oxygen content in the sparged gas of about 18~
oxygen. The DO content in all o~ these stages remained above
1.75 ppm throughout thE run.
As in the apparatus of ~xample 1, a clarifier or settl-
ing tank was also provided to receive effluent from the oxic
zone Again, in the clarifier a separation was effected between
a supernatent, clear liquid and a more dense activated bioinass.
Means were provided for decanting the supernatent liq~id and
rem~ving it from the system while other means were provided for
removing biomass from the bottorn of the clarifier. This biomass
20.
Q4~ ~
waS separatcd into two portions, one of which was removed from
the system and recovered as proauct, while the other portior. of
biomass wa, pumped back to the initial stage of the anaerobic
zone.
The apparatus employed in this example also contains
an internal recycle circuit comprising conduits and a pump and
operating so as to remo-~e mixed liquor from the last stage o~
the oxic zone and recycle it to the first stage o~ the anoxic
zone.
The BOD containing food source emplo~ea i~ this example
was a glucose solution_ Inspection data for the influent are
shown in Table II belo~. The influent was charged to the anaerobic
zone a~ a rate so as to provide an influent detention time tIDT~
of 3 16 hours for the entire 3 zone system, ana the portion of
the separated sludge which was returned to the initial anaerobic
zone was recycled at the rate of 30~ by volume based upon influent
flow rate. The portion of the mixed liguor forming the last
stage of the oxic zone was returned to the initial stage of the
anoxic zone at a recycle rate of 239~ by volume basea upon influent
flow rate. This was effective to pxovide a nominal residence
time ~NRT) of 0.192 hours per stage in the anaerobic zone, 0.074
hours per stage in the anoxic zone and 0.123 hours per stage in
the oxic zone.
The portion of the active biomass not recycled to the
initial anaerobic zone was separated from supernatent li~uid,
filtered and dried for 24 hours at 105C. The inspection data
for this dried product of the invention, together with other
inspection data of the separatea supernatent liquid are also
shown in Table II.
1117~4~
TABLE II
Total BOD5 soluble BOD5 NH3-N NOX-N PO4-P
(mg/11 (mg/l) ~mg/l) (mg/l~ ~mg~l)
Influent 219 219 22 2.3 8.9
(liquid)
Effluent 3.2 1.4 4.6 1.3 1.0
(liguid)
Nutrient C ~ N P S Si X Mg
% by weight 39.57 5.97 8.40 5.~5 0.06 0.4 i.94 1.43
The data shown in Table II above demonstrates the
production of a nutrient suitable for use as an animal feed which
was produced from a pure ~arbohydrate feedstock. As can be seen,
the product has a high nitrogen, phosphorous and potassium assay
and, additionally, contain3 a signi~icant quantity of magnesium
~another element essential to life). Further these essential
values are present along with high carbon and hydrogen content.
thus making it of a type generally suitable for the nourish~ent
.
of animal life.
- - '
~XAMPLE 3
The product material produced in this example is useful
as an activated bio~ass in fermentation operations. The particu-
lar procedure employed was a batch process as aistinguished fromthe continuous flow operations illustrated in Examples 1 and 2.
The particular equipment employed was similar to that described
in Figure 3 o~ the drawings.
In this ¢xample, a measured quantity o~ a nitrogen-,
phosphorous-, and BOD- containing food source 7as introduced into
22.
~117(~
a reaction tank. During the initial treating phase anaerohic
~onditions werc maintained ~ithin the tank by introaucing nitrogen
through the sparger located at the bottom oE the tank. The
measured DO content throughout this anaerobic phase was maintained
at su~stantially zero. The nitrogen sparging was then discontinued
and the treat~ent was continued in a second, anaerobic or oxic
treating phase. The oxic conditions were maintained by means of
oxygen sparging. The DO content maintained during the oxic phase
was 5.Q.
` ~he BO~ containing food source employed in this exa~ple
was a municipal wastewater. Inspection data for the influent
are shown in Table III below. The influent was retained in the
system so as to provide an overall influent detention time (IDT)
of 1.5 hours with a nominal residence time ~NRT) of 0.5 hours
during the anaerobic phase and l.Q hours during the oxic phase.
The portion of separated sludge which was retained from this
ex~mple for use during the initial anaerobic phase of the next
batch and which was retained for use in the initial anaerobic
phase of this batch from a preceding batch was S0% by volume based
upon the total influent charged.
The portion of the sludge or active biomass not retained
for use in the initial anaerobic phase of a subsequen. batch
operation was withdrawn from the tank, filtered and dried for 24
hours at 105C. The inspection data for this dried product together
with other inspection data of the separated supernatant liquid
are sho~ in Table III.
T~BLE III
.
Total BOD5 Soluble BOD5 ~13-N ~4
. . Img/l) ~mgJl? ~mg~l) tmg/l
Influent 153 126 16.77 3.62
(liquid)
23.
1~17~
E~fluent 6.3 2.1 7.89 0_48
(liquid)
Nutrient C ~ N P S si R Mg
% by weight 39.13 5.62 7.1 3.96 0.88 1.95 1.01 0 71
The above data show the production of a high nitrogen
ana phosphorous content proauct employing a batch operation process~
It will also be noticed that the product has a relatively high
N&P assay even thouqh the corresponding nitro~en and phosphorous
values in the influont are relatively low.
