CA1117042A

CA1117042A - High nitrogen and phosphorous content biomass produced by treatment of a bod containing material

Info

Publication number: CA1117042A
Application number: CA000305326A
Authority: CA
Inventors: Marshall L. Spector
Original assignee: Air Products and Chemicals Inc
Current assignee: Air Products and Chemicals Inc
Priority date: 1977-07-25
Filing date: 1978-06-13
Publication date: 1982-01-26
Also published as: DE2827474C2; JPS6366516B2; FR2398700B1; JPS5424774A; FR2398700A1; DE2827474A1

Abstract

ABSTRACT
An organic product material having a high nitrogen and phosphorous content is produced as the product of a biological system for the treatment of a BOD-containing influent which also contains phosphorous and fixed nitrogen. The biological treatment system comprises the reaction of a mixed liquor composed of an activated biomass and a BOD-containing influent initially under anaerobic conditions and thereafter treating such mixed liquor under oxic conditions. The treated material is them separated into a supernatent liquid in which the BOD is depleted and a dense, activated biomass. A portion of this biomass is employed in forming the mixed liquor for the initial anaerobic treatment, while the remaining portion of the biomass is recovered as product.
The living biomass product can be used in the fermentation indus-tries. Alternatively, the product can be used as such or further processed, e.g. dried, for employment as a fertilizer or a nutrient in animal feeds.

Description

~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.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An improved high nitrogen-, and phosphorus- content biomass produced by:
(a) forming a mixed liquor by mixing activated biomass with nitrogen-, phosphorus-, and BOD-containing influent under anaerobic conditions such as to be substantially free of No? and to have a dissolved oxygen content of less than 0.7 ppm; thereby effecting selective production of nonfilamentous microorganisms capable of sorbing BOD under anaerobic conditions;
(b) oxidizing BOD in the mixed liquor to cause removal of BOD by contact with oxygen containing gas under conditions selected to maintain a dissolved oxygen content of at least 1 ppm;
(c) settling the oxidized mixed liquor so as to separate a supernatant liquid from a more dense biomass;
(d) employing a portion of the separated biomass as the activated biomass in an initial mixing with BOD-containing influent; and (e) recovering another portion of the settled and separated biomass as product.

2. The biomass product of Claim 1 wherein the anaerobic conditions are selected so as to have a dissolved oxygen concen-tration of less than about 0.5 ppm.

3. The biomass product of Claim 1 wherein the anaerobic conditions are maintained by contacting the mixed liquor with nitrogen gas.

4. The biomass product of Claim 1 wherein the product is to be employed as a plant or animal nutrient and the BOD-containing influent is wastewater.

25.

5. The biomass product of claim 1 wherein the influent also contains ammonia values and wherein the mixed liquor, sub-sequent to the anaerobic treatment and prior to the oxidizing treatment, is treated under anoxic conditions including a dis-solved oxygen content not in excess of 0.7 ppm and wherein oxidized mixed liquor having a concentration of nitrates and /or nitrites in excess of about 2 ppm, expressed as elemental nitro-gen, is admixed during the anoxic treatment.

6. The biomass product of claim 5 wherein the oxidized mixed liquor added to the anoxic treatment is added in a quantity corresponding to from 100 to about 400% by volume based upon the fresh influent employed in the initial anaerobic treatment.

7. The biomass product of claim 5, wherein the activated biomass feed to the anaerobic treatment is admixed with the in-fluent in a quantity corresponding from about 10 to about 50%
by volume of the influent.

8. The biomass product of claim 4 wherein the total treat-ing time under anaerobic conditions and under oxidizing con-ditions does not exceed about 3 hours.

9. The biomass product of claim 5 wherein the total treating time under anaerobic conditions, anoxic conditions and oxidizing conditions does not exceed about 3 hours.

10. The biomass product of claim 1 wherein the product is to be employed as a live micro-organism in fermentation and steps (a) through (e) are performed in a batch-type process.

11. The biomass product of Claim 1 wherein the process steps are performed in a continuous flow process in separate zones and the portion of separated biomass employed as the activated biomass is recycled to the initial anaerobic zone.

12. The biomass product of Claim 5 wherein the process steps are performed in a continuous flow process in separate zones, the portion of separated biomass employed as the activated biomass is recycled to the initial anaerobic zone, and oxidized mixed liquor from the oxic zone is recycled to the anoxic zone.

13. The biomass product of Claim 11 or 12 wherein the oxic zone comprises a series of at least two hydraulically distinct sections in sequential liquid flow communication.

14. The biomass product of Claim 1 wherein the BOD-containing influent is a carbohydrate solution or suspension.

15. The biomass product of Claim 11 or 12 wherein the anaerobic zone comprises a series of at least two hydraulically distinct sections in sequential flow communication.

27.