CA1062380A - Waste water treatment - Google Patents

Abstract

IMPROVED WASTE WATER TREATMENT
ABSTRACT OF THE DISCLOSURE
Removal of nitrogenous and carbonaceous contaminants is carried out in a single sludge two-tank system by a symbiotic two-step process whereby the second tank mainly oxidizes ammonia to nitrate and the first tank mainly reduces nitrate to nitrogen gas. Carbonaceous material is removed mainly in the first tank by a combination of biological uptake with cell growth and used as a final electron acceptor in respiratory denitrification.

Description

- ` 106Z38 The present invention is directed to the treatment of waste water, such as domestic or industrial sewage.
Waste water contains a variety of contaminants including biodegradable carbonaceous material, nitrogenous material which is mainly ammoniacal or other non-nitrate and/
or non-nitrite form and phosphate material and such contamin-ants must be removed before the waste water can be reused.
In prior art systems, these contaminants have been removed by biological oxidation of carbonaceous materials, biological conversion of non-nitrate and/or non-nitrite nitrogen to nitrate and/or nitrite forms (nitrification) followed by respiratory reduction to nitrogenous gases in the presence of a carbon source tdenitrification) and chemical treatment of phosphate.
The carbon, nitrogen and phosphorus removals have been carried out in separate reactors, leading to time-consuming operations, owing to the inability of the prior art to provide differing sets of conditions within the same treatment unit.
The present invention provides a method for the treatment of waste water containing contaminants including dissolved biodegradable carbonaceous material and nitrogenous material mainly in non-nitrate and/or non-nitrite form by biological consumption and conversion to gases using a single mixed microbial sludge. The method consists of a plurality of interlinked steps in which there are established a first reaction zone consisting of a first upright reaction tank containing liguor, a second reaction zone physically separate from but fluidly interconnected with the first reaction zone and consisting of a second upright reaction tank containing liquor, and a sludge separation zone physical-.:, ' $ ~

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~062380 ly separate from both the first and second reaction zones but !`~ fluidly interconnected with the second reaction zone and consisting of an upright sludge separator tank containing liquor.
The waste water is fed to the first reaction zone and is passed as mixed liquor in association with the single mixed microbial sludge successively through the first and second reaction zones and the sludge separation zone along a first flow path which extends from an inlet communicating with the level of liquor in the first reaction tank, down-wardly within the first reaction tank into communication with an outlet from the first reaction tank, from the first reaction tank outlet to an inlet communicating with the level of liquor in the second reaction tank, downwardly within the second reaction tank into communication with an outlet from the second reaction tank, from the second reaction tank outlet to an inlet communicating with the level of liquor in the sludge separation tank, and downwardly within the sludge separation tank into communication with a clarified ; 20 liquor outlet from the sludge separator tank.
The mixed liquor is recycled at a suspended solids concentration in each of the reaction zones of about 3000 to about 7000 mg/l within each reaction zone to maintain the mixed liquor substantially in suspension in each of the first and second reaction zones.
Mainly anaerobic conditions in the first reaction zone are established and maintained in the first reaction zone for conversion of nitrate and/or nitrite nitrogen to nitrogen ga8 and consumption of carbonaceous material in the conversion. Mainly aerobic conditions are established and maintained in the second reaction zone for conversion .'. ,11 .
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"'' ' ' ' '' '' ''''" : ,'.' '', :, ' ' ' .', ' , of nitrogenous material to nitrate and/or nitrite nitrogen and oxidation of carbonaceous material.
The steps of internal recycling and establishing the anaerobic and aerobic conditions in the respective reaction zones are effected by establishing a second flow path within each of the reaction tanks from the bottom of the respective tank to above the liquid level therein, passing a molecular oxygen containing gas into the second flow path in each of the reaction zones adjacent the lower end thereof at a rate at least sufficient to convey mixed liquor upwardly along the second flow path and maintain the mixed liquor in suspension in each of the tanks, controlling the rate of flow of the gas into the second flow path of the first reaction tank to provide a dissolved oxygen concentra-tion in the waste liquor at the upstream end of the first flow path which is less than about 0.5 mg/l and is capable - of sustaining aerobic reactions only for an initial and short portion of the first flow path through the first reac-tion tank, and controlling the rate of flow of the gas into : 20 the second flow path of the second reaction tank to provide a dissolved oxygen concentration in the waste liquor at the upstream end of the first flow path within the second reaction tank which is at least about 2 mg/l and capable .: of sustaining aerobic reactions for the major portion of the first flow path through the second reaction tank.
Mixed liquor is recycled directly from the second :: reaction zone to the first reaction zone at a flow rate greater than the flow rate of waste water to the first reaction zone by establishing a third flow path directly from the bottom of the second reaction tank to above the liguor level in the firot reaction tank, and passing a ~ - 2b -, molecular oxygen containing gas into the third flow path adjacent the lower end thereof at a rate sufficient to convey the mixed liquor from the second reaction tank to the first reaction tank at a flow rate greater than the flow rate of waste liquor into the first reaction tank.
The dissolved oxygen concentrations in the first and second reaction zones are controlled to provide a dissolved oxygen concentration in the mixed liquor entering the third flow path for recycle from the second reaction tank to the first reaction tank which is approximately the same as the dissolved oxygen concentration in the mixed liquor at the upstream end of the first flow path in the first reaction tank and a dissolved oxygen concentration in the mixed liquor at the downstream end of the first flow path in the first reaction zone which is less than about 0.1 mg/l.
Gas formed in the first and second reaction zones are vented. During passage of treated waste water along the first flow path within the sludge separation tank, suspended sludge is at least partially flocculated, separated and settled from the treated waste water.
Settled sludge is recycled directly from the sludge separator tank directly to the second reaction zone at a flow rate greater than the flow rate of waste water to the first reaction zone and at a rate at least sufficient to prevent anaerobic decomposition of the sludge in the sludge separation zone by establishing a fifth flow path directly from the bottom of the sludge separator tank to above the liquor level in the second reaction tank, and passing a molecular oxygen containing gas into the fifth flow path adjacent the lower end thereof at a rate sufficient to draw ~ .
~ - 2c -the settled sludge into the fifth flow path and convey the ! same to the second reaction tank at a flow rate greater than -the flow rate of waste liquor into the first reaction tank.
Clarified and treated liquor is removed from the sludge separation zone at a rate which is the same as the rate of feed of waste water to the first reaction zone.
The removed liquor may be subjected to chemical treatment to remove phosphorus contaminants and other treatments, as desired.
The present invention, therefore, effects the manipulation of biological oxidation of carbonaceous material, nitrification and denitrification within the same treatment unit using a single sludge in a symbiotic two-step process combined with sludge separation and recycle procedures.
The present invention also includes apparatus for effecting such process. Accordingly, the present invention also provides an apparatus for the treatment of waste water containing contaminants including dissolved biodegradable carbonaceous material and nitrogenous material mainly in non-nitrate and/or non-nitrite form by biological consump-tion and conversion to gases using a single mixed microbial sludge, which comprises: a first reaction tank; a first inlet to the first reaction tank for the inlet of waste water to the first reaction tank; an outlet from the first reaction tank connected to a first inlet of a second reaction tank for feed of liquor to the second reaction tank from the first reaction tank; a first outlet from the second reaction tank connected to an inlet of a sludge separator tank for feed of liquor from the second reaction tank to the sludge se~arator tank, a first outlet from the sludge separator tank for the discharge of treated waste water, ' 11 ~ ~ ~ ~ - 2d -.. .

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a second outlet from the sludge separator tank connected to a second inlet of the second reaction tank for recycle of :-flocculated sludge from the sludge separator tank to the second reaction tank and first means for effecting the recycle, a second outlet from the second reaction tank connected to a second inlet of the first reaction tank for recycle of mixed liquor from the second reaction tank to the first reaction tank and second means for ~ffecting the latter recycle, means for recycling mixed liquor within the first reaction tank, means for recycling mixed liquor within the second reaction tank, means for feeding controlled quan-tities of oxygen to the first reaction tank to establish ; and maintain predominantly anaerobic conditions therein, and means for feeding controlled quantities of oxygen to the second reaction tank to establish and maintain predominantly aerobic conditioos ther~in.

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The invention is described further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a flow sheet of a waste water treatment plant in accordance with the present invention;
Figure 2 is a schematic sectional view of the carb~n and nitrogen removal unit of the treatment plant of Figure l; and Figure 3 is a plan view of the clarifier unit.
Referring first to Figure 1, there is illustrated a waste treatment plant 10 comprising a number of renovation steps for the removal of contaminants from the waste water.
Raw ~ sewage, or,other waste mate~ial to be treated, is fed by line 12 to a gross solids screen 14 for the removal of gross solids which are collected by line 16 for disposal. 3 Any desired form of screen may be used. If desired, the gross solid screen 14 may be omitted.

Raw screened sewage then is fed by line 18 to an integrated carbon and nitrogen treatment unit 20, described in more detail be]ow with reference to Figures 2 and 3, wherein carbonaceous material and nitrogenous material together with some phosphate material, are removed by biological reaction of oxidation and reduction with activa-ted sludge and air fed by line 22 and by cell growth.
The raw screened sewage passes by line 18 to a first reactor tank 24, by line 26 to a second reactor tank 28 and by line 30 to a sludge separator 32 before discharge of carbonaceous material- and nitrogenous material-depleted water from the treatment unit 20 by line 34.
Within the treatment unit, settled activated sludge is recycled from thesludge separator 32 to the second reactor 28 by line 36 and mixed liquor solids are recycled .

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from the second reactor 28 to the first reactor 24 by line 38.
The treated water in line 34 is contactëd with alum fed by line 40 in a chemical treatment tank 42 to cause deposition of phosphate. The chemical treatment tank 42 may take the form described in U.S. Patent No. 4,008,159. As described in this U.S. Patent, chemical treatment to remove phosphorus is effected by feeding a mixture of water containing phosphorus materials and alum into a rotating fluidized bed of chemical sludge, chemically coagulating the phosphorus material within the fluidized bed, recycling liquor from the fluidized bed to the feed mixture to maintain the fluidized bed and separating treated liquid from the fluidized bed.
In this procedure, the amount of alum added and the recycle ratio are dependent on one another. Optimum phosphate removal has been found to occur with a recycle ratio between about 1:1 and 1:3 and an alum feed of about 180 to 200 mg/l.
Any excess sludge formed in the treatment unit 20 is allowed to overflow from the sludge separator 32 with the liquor in line 34 into the chemical treatment tank 42 and is collected therein along with the chemical sludge produced from the alum treatment.
The sludge collected in the chemical treatment tank 42 is periodically or ntinuously removed by line 44 into a sludge thickener 46. Liquor separated from the sludge thi~kener 46 may be cycled to the treatment unit 20 by line 4~, particularly to the first reactor 24. Alternatively, the separated liquor may be passed by line 49 to the sludge separator 32, the choice of feed by line 48 or line 49 depending on the water quality of the liquor. Waste sludge 1 30 is removed by line 50 for disposal.
The chemically treated liquor is passed by line 51 ~ _ 4 _ . ~ . .

to an ozone treatment column 52 to which ozone is fed by line 54 for~removal of further contaminants before passage by line 56 to a filtration bed 58 for removal of suspended solids.

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' ~ . .' ' :. ' ~ , The filtration bed may he backwashed from time to time to remove accumulated solids.
The backwash effluent may be stored and forwarded to the chemical treatment tank 42 during operation of the waste treatment plant 10.
Purified liquid from the carbon filter bed 58 may be passed to storage or by line 60 to a disinfection tank 62 to which ozone is fed by line 64, before discharge of the effluent by line 66.
Turning now to consideration of Figure 2, which illustrates in more detail the treatment unit 20, each of the tanks, namely the first reactor 24, the second reactor 28 and the sludge separator 32, is in the form of an upright cylindrical tank having a frusto-conical insert at the lower portion thereof to avoid the accumu-lation of sludge in thebottom corners of each tank.
The first reactor tank 24 has an inverted funnel 110 located therein separating the tank 24 into a first zone 112 located between the inner wall of tank 24 and the outer surface of the inverted funnel 110 and a second zone 114 located within the funnel 110 and communicating with the first zone 112 only at the lower end of the funnel 110.
A liquor flow path through the first reaction tank 24, therefore, is established downwardly through the first zone 112 from thescreened raw sewage inlet 18 and upwardly through the second zone 114 to the discharge pipe 26 communi-cating with the neck 116 of the inverted funnel 110.
A pipe 118 extends axially of the inverted funnel 110 through the neck 116 and the second zone 114 to a loca-tion adjacent the bottom of the tank 24.

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~ ' , - ' ' ' ' '' ' A pair of arms 120, 122 extend radially-of the . reaction tank 24 from the upper end of the pipe 118 to a location adjacent the inner wall of the tank 24 where they communicate with discharge pipes 124, 126 located adjacent the intended liquid level in the first zone 112.
The pipe 118, arms 120, 122 and discharge pipes 124, 126 establish a flow path from the lower end of the tank 24 to the upper portion of the first zone 112 out of fluid flow communication with the second zone 114 other than at the lower end of the pipe 118.and allows internal recycle of the mixed liquor in the tank 24.
A second axial pipe 128 extends through the pipe 118 to the lower end thereof and is used to convey air or another oxygen-containing gas into the tank 24 at the lower end of the pipe 118 to maintain the internal liquor recycle. - .
The second reactor tank 28 has a cylindrical sleeve 130 extending axially of the tank 28 defining a first zone 132 located between the inner wall of the tank 28 and the outer surface of the sleeve 130.
A liquor flow path through-the second reaction tank 28, therefore, is established downwardly through the first zone 132 from the inlet pipe 26 to the discharge pipe 30 which extends to the lower end of the sleeve l30~Liquor flow through the combination of the two reactor tanks 24 and 28 therefore passes downwardly from the sewage entrance pipe 18 around the outside of the inverted funnel 110, upwardly to the discharge pipe 26 inside the inverted funnel 110, and downwardly from the entrance pipe 26 around the outside of the sleeve 130 to the discharge pipe 30 inside the sleeve 130.

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If desired, the second reaction tank 28 may be provided with an inverted funnel identically to the tank 24 with the discharge pipe 30 communicating with the upper end of the inverted funnel.
A pipe 136 extends axially of the sleeve 130 from the top thereo~ through the internal zone 13~ of ~ sleeve 130 to adjacent the bottom of the tank 28. A pair of arms 138 and 140 extend radially of the reaction tank 28 from the upper end of the pipe 136 to a location adjacent the inner wall of the tank 28 where they communicate with discharge pipes 142 and 144 located adjacent the intended liquid level in the first zone 132.
The pipe 136, arms 138, 140 and discharge pipes 142, 144 establish a flow path between the lower end of the tank 28 to the upper portion of the first zone 132 out of fluid flow communication with the internal zone 134 other - than at the lower end of the pipe 136 and allows internal recycle of mixed li~uor in the tank 28.
A second axial pipe 146 extends through the pipe 136 to the lower end thereof and is used to convey air or other molecular oxygen-containing gas into the tank 28 at the lower end of the pipe 136 to maintain the internal liquor recycle.
; A third pipe 148 extends downwardly internally of the sleeve 130 in parallel fashion to the pipe 136 to a location adjacent the lower end of the tank 28 and communicates at its other end with recycle pipe 38 exten~
ding to the first tank 24. The third pipe 148 and the pipe 38 establish a flow path from the lower end of the -30 second tank 28 to the upper portion of the first zone 112 in the first tank 24 for recycle of mixed liquor from the second tank 28 to the first tank 24.
A fourth pipe 150 extends axially of the pipe .
, . . :: - . , 148 to adjacent the lower end thereof to feed air into the pipe 148 to achieve an air lift of mixed liquor along the recycle flow path from the second tank 28 to the first tank 24.
The slu~ge separator tank 32 has an inverted funnel 152 located therein separating the clarifier into zones to establish a flow path of liquor from the inlet pipe 30 first downwardly between the outer wall of the inverted funnel 152 and the inner wall of the tank 32 and then upwardly internally of the inverted funnel to the outlet pipe 34.
A pipe 154 extends axially of the inverted funnel 152 through the neck 156 to a location adjacent the bottom of the sludge separator tanlc 32. The pipe 154 communicates at its upper end with recycle pipe 36, so that pipes 154 and 36 establish a flow path between the lower end of the tank 32 and the upper portion of the first zone 132 in the : second reaction tank 28 for the recycle of settled sludge to the second reaction tank 28.
A second axial pipe 158 extends internally of the .
, pipe 154 to a location adjacent the lower end thereof to , feed air into the pipe 154 to air lift settled sludge along , the recycle flow path from the clarifier tank 32 to the second reaction tank 28.
. The sludge which passes through the treatment unit 20 is a bulking sludge which is a combination of filamentous organisms and nitrogen gas bubbles contained ~ :within the mixed liquor. It was found that gentle stirring of the mixed liquor enhanced settling by producing coagula-tion of sludge particles to a heavier mass. It is preferred :
,' to provide the inflowing liquor to the sludge separator tank 32 .`

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, as a slowly rotating mass outside the inverted cone 152 to improve flocculation of the sludge around the inverted cone 152 and in~rease the settleability of the sludge. A
typical rotation speed is about 1.5 rpm.
As may be seen from the plan view of Figure 3, rotation of the liquor within the clarifier tank 32 may be achieved by separating the incoming feed in line 30 into three separate streams 160, 162 and 164 which are discharged around the outside of the cone 156 in approxi-mately tangential manner.
While the construction and operation of the slu~geseparator tank 32 as described above has particular utility for handling bulking sludge in the two-tank treatment opera-tions of tanks 24 and 28, such a sludge separator tank 32 operation may be used to aid in the settling of bulking sludge obtained from any biological treatment procedure, for example that described in U.S.Patent No.3,980,556, especially in the absence of added activated carbon.
In the operation of the treatment unit 20, sewage or other waste water fed by line 18 to the first reaction tank 24 is mixed with recycled mixed liquor from the second tank 28 and with internally recycled oxygenated mixed liquor. The recirculation rate of mixed liquor within the tank 24 is sufficient to màintain sludge mainly in suspension within the tank 24.
The recirculation rate of mixed liquor from the second tank 28 is greater than the rate of flow of external liquor into the tank 24 by lines 18 and 48 to ensure that all the introduced liquor passes through the two tanks and is subjected to treatment.
The dissolved oxygen in the liquor at the top of the zone 112 and oxygen picked up by the splashing of g ~;

the recycle streams into the liquor in the first tank 112 to provide a momentarily higher dissolved oxygen content, is sufficient initially to sustain aerobic reactions, including conversion of ammoniacal nitrogen to nitrate and/
or nitrite, nitrogen and conversion of carbonaceous material to carbon dioxide. Typically, the dissolved oxygen concentration value at the top of the zone 112 is about 0.5 mg/l.
As the liquor moves downwardly through zone 112, the oxygen available for aerobic reactions rapidly is diminished and anaerobic conversion of nitrate and/or nitrite nitrogen to nitrogen gas with consequent consump-tion of dissolved carbon co~mences, resulting in a typical -dissolved oxygen concentration at the lower end of the tank of less than 0.1 mg/l.
Anaerobic reactions predominate in the reaction tank 24 and these reactions combined with cell growth deplete the carbonaceous material content of the incoming sewage substantially completely. Cell growth also accounts for some nitrogen and phosphorus removal. Some mixed liquor is recycled within the tank 24 by pipe 118 and this re-cycled mixed liquor is oxygenated during the recycle to provide the required dissolved oxygen in the mixed liquor and mixing of the mixed liquor. Gases formed in the first j reaction tank 24 are vented.
Mixed llquor overflowing from the tank 24 to the second tank 28 having a low dissolved carbonaceous material content but still containing the bulk of the ammoniacal nitrogen of the initial sewage, is mixed with recycled settled sludge from the sludge separator 32 and internally recycled oxygenated mixed liquor to form a mixed liquor ; having a high dissolved oxygen concentration at the top of the zone 132.
-- 1 0 -- ' , The rate of return of sludge from the sludge separator 32 is determined by the hydraulic flow to the sludge separator 32 required to maintain the slow rotation in the tank 32 to achieve flocculation.
The rate of recycle of mixed liquor within the reaction tanX 28 is considerably higher than that within the tank 24 owing to a higher dissolved oxygen concentration requirement in the tank 28 and serves to maintain the sludge in suspension within the tank 28.
In the tank 28, the dissolved oxygen concentra-tion of the mixed liquor at the top of zone 132 should be sufficient to establish mainly aerobic conditions with zone 132. Typically, the dissolved oxygen concentration i8 in excess of 2 mg/l.
The aerobic conditions predominating in tank 28 result in conversion of the ammoniacal nitrogen to nitrate and/or nitrite nitrogen until the oxygen level is in-sufficient to sustain aerobic conditions and anaerobic reac-tions occur. The dissolved oxygen concentration of the mixed liquor recycled by pipe 38 to the first reaction tank 24 preferably is approximately that of the mixed liquor at the top of the zone 112 in tank 24, typically about 0.5 mg/l.
In the two reaction tank system used in the illustrated embodiment of the invention, the contaminants in the incoming sewage are subjected to a symbiotic process with a single sludge in which the contaminants are subjected first to aerobic reactions for a short period and then to anaerobic reactions in the tank 24 and second to aerobic con-ditions for a long period and then to anaerobic conditions in tank 28, with recycling from tank 28 to tank 24 to deplete nitrate and/or nitrite nitrogen. In this way, in combination with sludge cell growth, carbonaceous material and nitrogenous material contaminants are depleted.
Phosphate material also is removed by sludge cell growth.
The mixed liquor from the second reaction tank 28 overflows into the sludge separator 32 wherein settling of sludge occurs allowing a supernatant clear effluent to be removed by line 34. Periodic wasting of sludge from the system is necessary and this is achieved by allowing sludge to overflow with the effluent in line 34 to the chemical treatment tank 42 from which it is removed with chemical sludge by line 44 to the sludge thickener 46.
Alternatively, sludge may be wasted from the sludge separator tank 32 by using a sludge pump operably connected to the tank 32 or recycle line 36.
The mixed liquor concentration throughout the system of the first and second reaction tanks 24 and 28 is substan-tially uniform and varies from about 3000 to 7000 mg/l, preferably in the range of about 4000 to 5000 mg/l. The corresponding MLVSS values are 2500 to 6000 mg/l and pre-ferably 3400 to 4500 mg/l.
The treatment unit 20 removes about 0.006 to about 0.057 lb of ammoniacal nitrogen from sewage per lb MLVSS per day, preferably about 0.02 lb NH3-N/lb/MLVSS/day, about 0.011 to about 0.054 lb of total nitrogen per lb MLVSS per day, preferably about 0.031 lb TN/lb MLVSS/day, and about 0.017 to about 0.112 lb SOC/lb MLVSS/day, preferably about 0.040 lb SOC/lb MLVSS/day.
- - The treatment unit 20 operates effectively in the absence of added activated carbon and it has been found that the presence of added activated carbon has little or no effect on the removal of contaminants, although such activated carbon presence may improve the settleability of the sludge.

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': . :. ' -Exam~le I
A waste treatment system as illustrated in Figure 1 was operated continuously under pilot plant conditions over a period of sixteen weeks treating domestic sewage from an adjacent housing subdivision. No activated carbon was added to the system. The dimensions of the units of the system are set forth in the following Table I:
TABLE I

Vnit Height ~ft) Diameter Effective Total Effective (ft) 3volume ft USG
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Reactor 24 10.0 9.5 6.5 2742050 Reactor 28 10.0 9.5 6.5 2742050 Separator 32 10.0 9.5 6.5 132987 Chemicaltrea ~ nt 42 10.0 8.8 6.5 265 1984 Ozone col.52 15.0 15.0 0.3 3 22 Filter 56 10.0 6.0 2.0 32236 Disinfection 62 15.015.0 2.0 47353 Thickener 46 10.6 9.7 4.0 122912 Flow rates of liquor through the system and air flows are set forth in the following Table II:

TABLE II

Flow Rate Air ` (USGPM) (SCFM2 Raw sewage line 12 7.5 Internal Recycle Reactor 24 60.0 5.0 I Reactor 28 to Reactor 24 I line 38 12.0 0.5 Sludge Thickener liquor in line 48 or llne 49 - 2.0 0.25 Line 26 21.5 Internal Recycle Reactor 28 240.0 25.0 Separator 32 to Reactor 28 line 36 22.0 2.0 , .
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, TABLE II (Continued) Flow Rate Air (USGPM) (SCFM) Line 30 31.5 Line 34 9-5 Input to chemical treatment 42 17.0 0~5 Chemical treatment 42 recycle 7.5 Line 51 7.5 Line 44 2.0 Line 56 7~5 Line 60 7.5 Line 66 . 7 5 .
During the test period, the water quality of incoming sewage and final effluent were determined for samples taken every 15 minutes for 24 hours a day.
Weekly means values for the various contaminants were determined. These results appear in the following Table .

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, 106~380 Based on the data appearing in Tahle III, efficiencies of removal of nitrogen, carbon and phosphorus by the system were determined and the results appear in the following Table IV:

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,,, The mean3 removal efficiencies of 82.3~ for nitrogen, 93.9~ for total organic carbon, 98.4~ for BOD5 and 97.7% for phosphorus represent very satisfactory results.
Example II
During the period of the test results reproduced in Example I, grab samples at twice weekly intervals also were taken at the input in line 18, at the effluent from the sludge separator in line 34, at the effluent from the chemical clarifier in line 51 and at the final effluent in line 66. During the same period, random determinations were made in the two reaction tanks 24 and 28 of the volatile suspended solids (MLVSS) concentrations, oxygen uptake rates (OUR) and specific uptake rates (SUR).
The following Table V gives the volatile suspended solids concentrations and uptake rates and Table VI gives the weekly mean values for contaminants in the grab samples at the various locations.
TABLE V
. _ Determina- MLVSS OUR SURReactor.28 .l:

. tion No. MLVSS~r . O~lb -:
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1 4620 600.013 3800 60 0.016 .

2 3390 600.018 3390 60 0.018

3 3600 780.022 4580 72 0.016 . 4 3150 660.021 3080 60 0.019 ; .... 5 289060 0.021 3130 64 0.020 .',.,~ j, ' .. . . . . . .
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The results reproduced in this Example illustrate the effect that the carbon and nitrogen treatment unit 20 and the chemical treatment have in the overall sewage treatment system of ~igure 1, the detailed results of which appear in Example I.
EXAMPLE III
During the test period of Examples I and II, random spot determinations of ammoniacal nitrogen, nitrate nitrogen and soluble organic carbon were made at various locations in the treatment unit 20. The following Table VII
reproduces these results:

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, The resulis of the above Table VII illustrate the effect of the various components of the unit 20 on the in-coming sewage.
Example IV
The procedure of Example I was repeated with addit--ions of various quantities of activated carbon. Contaminants were tested using,the continuous sampling (i.e. every 15 minutes) technique described in Example I and removal efficiencies were determined. Mixed liquor concentrations and uptake rates were also randomly determined.
The following Tables VIII and IX reproduce the data obtained:

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3 ~ ~ r m , TABLE IX

Det~n~nation Reactor 24 Reactor 28 mg/l mg/l/hr Ib OJlb mg/l m~/l/hr lb O~/lb MLVSS/hr MLVS~/hr 1 3270 90 0.028 3770 72 0.019 2 3260 93 0.029 3530 84 0.024 3 3850 102 0.026 3290 94 0.029 . -

4 3580 100 0.028 3700 98 0.026 4510 105 0.023 4320 83 0.019 .
6 3090 32 0.009 3560 68 0.019 _ 7 6680 57 0.009 ~380 15 0.003 Noke: Deb~n~nations Ncs.l bo S were made in weeks 1 an~ 2, debc~ration:
No. 6 was made inw~ek 3 and ~ebe~bnotion No.7 was ma~e inweek 5.
The mean removal efficiencies of 80.2% for nitrogen, 93.3% for total organic carbon, 98.5% for BOD5 and 98.9% for phosphorus represent very satisfactory results but do not differ significantly from the results set forth in Example I in the absence of added activated ca~bon.
Example V
Based on the data contained in the above Examples, design parameters for the process of this invention can be compared with those of conventional activated sludge process as set forth in the standard textbook by Metcalf and Eddy, 1972. The comparison appears in the following T ble X:

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The present invention, therefore, provides a waste water treatment system in which two fluidly-interconnected tanks and a single sludge are used to achieve symbiotic anaerobic and aerobic operations to remove nitrogenous and carbonaceous materials. Modifica-tions are possible within the scope of the invention.

Claims (14)

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

1. A method for the treatment of waste water containing contaminants including dissolved biodegradable carbonaceous material and nitrogenous material mainly in non-nitrate and/or non-nitrite form by biological consumption and conversion to gases using a single mixed microbial sludge, which consists essentially of:
establishing a first reaction zone consisting of a first upright reaction tank containing liquor, a second reaction zone physically separate from but fluidly inter-connected with said first reaction zone and consisting of a second upright reaction tank containing liquor, and a sludge separation zone physically separate from both said first and second reaction zones but fluidly interconnected with said second reaction zone and consisting of an upright sludge separator tank containing liquor, feeding the waste water to said first reaction zone and passing the waste water as mixed liquor in association with said single mixed microbial sludge successively through said first and second reaction zones and said sludge separation zone along a first flow path which extends from an inlet communicating with the level of liquor in said first reaction tank, downwardly within said first reaction tank into communication with an outlet from said first reaction tank, from said first reaction tank outlet to an inlet communicating with the level of liquor in said second reaction tank, downwardly within said second reaction tank into communication with an outlet from said second reaction tank, from said second reaction tank outlet to an inlet communicating with the level of liquor in said sludge separa-tion tank, and downwardly within said sludge separation tank into communication with a clarified liquor outlet from said sludge separation tank, recycling said mixed liquor at a suspended solids concentration in each of said reaction zones of about 3000 to about 7000 mg/1 within each reaction zone to maintain said mixed liquor substantially in suspension in each of said first and second reaction zones, establishing and maintaining mainly anaerobic conditions in said first reaction zone for conversion of nitrate and/or nitrite nitrogen to nitrogen gas and consumption of carbonaceous material in said conversion, establishing and maintaining mainly aerobic conditions in said second reaction zone for conversion of nitrogenous material to nitrate and/or nitrite nitrogen and oxidation of carbonaceous material, said latter steps of internal recycling and establishing said anaerobic and aerobic conditions in said respective reaction zones being effected by:
establishing a second flow path within each of said reaction tanks from the bottom of the respective reaction tank to above the liquid level therein, passing a molecular oxygen containing gas into said second flow path in each of said reaction zones adjacent the lower end thereof at a rate at least sufficient to convey mixed liquor upwardly along said second flow path and maintain said mixed liquor in suspension in each of said tanks, controlling said rate of flow of said gas into said second flow path of said first reaction tank to provide a dissolved oxygen concentration in said waste liquor at the upstream end of said first flow path which is less than about 0.5 mg/1 and is capable of sustaining aerobic reactions only for an initial and short portion of said first flow path through said first reaction tank, and controlling said rate of flow of said gas into said second flow path of said second reaction tank to provide a dissolved oxygen concentration in said waste liquor at the upstream end of said first flow path within said second reaction tank which is at least about 2 mg/1 and capable of sustaining aerobic reactions for the major portion of said first flow path through said second reaction tank, recycling mixed liquor directly from said second reaction zone to said first reaction zone at a flow rate greater than the flow rate of waste water to said first reaction zone by:
establishing a third flow path directly from the bottom of said second reaction tank to above the liquor level in said first reaction tank, and passing a molecular oxygen containing gas into said third flow path adjacent the lower end thereof at a rate sufficient to convey said mixed liquor from said second reaction tank to said first reaction tank at a flow rate greater than the flow rate of waste liquor into said first reaction tank, controlling the dissolved oxygen concentrations in said first and second reaction zones to provide a dissolved oxygen concentration in the mixed liquor entering said third flow path for recycle from said second reaction tank to said first reaction tank which is approximately the same as the dissolved oxygen concentration in the mixed liquor at the upstream end of said first flow path in said first reaction tank and a dissolved oxygen concentration in the mixed liquor at the downstream end of said first flow path in said first reaction zone which is less than about 0.1 mg/1, venting gases formed in said first and second reaction zones, at least partially flocculating, separating and settling suspended sludge from treated waste water in said sludge separator tank during passage thereof along said first flow path within said sludge separation tank, recycling settled sludge from said sludge separator tank directly to said second reaction zone at a flow rate greater than the flow rate of waste water to said first reaction zone and at a rate at least sufficient to prevent anaerobic decomposition of the sludge in the sludge separation zone by:
establishing a fifth flow path directly from the bottom of said sludge separator tank to above the liquor level in said second reaction tank, and passing a molecular oxygen containing gas into said fifth flow path adjacent the lower end thereof at a rate sufficient to draw said settled sludge into said fifth flow path and convey the same to said second reaction tank at a flow rate greater than the flow rate of waste liquor into said first reaction tank, and removing clarified treated liquor from said sludge separation zone at a rate which is the same as the rate of feed of waste water to said first reaction zone.

2. The method of claim 1 wherein the mixed liquor solids concentration in each of said second reaction zones is about 4000 to about 5000 mg/1.

3. The method of claim 1 carried out in the absence of activated carbon.

4. The method of claim 1 wherein said aerobic and anoxic conversions and sludge growth are controlled to remove from said water about 0.006 to about 0.057 lb. of said non-nitrate and/or non-nitrite nitrogenous material per lb. MLVSS per day, about 0.011 lb. to about 0.054 lb.
of total nitrogen per lb. of MLVSS per day and about 0.017 to about 0.112 lb. of dissolved carbonaceous material per lb. MLVSS per day.

5. The method of claim 1, wherein said sludge separa-tion tank contains an inverted funnel-like member coaxially arranged with the tank and establishing said first flow path through the tank, the mixed liquor is fed to said sludge separation tank inlet to form a rotating mass of liquor in the zone external of the funnel-like member which has a rotation rate sufficient to assist in gas separation from the sludge and assist in flocculation of filamentous organisms in the sludge.

6. The method of claim 5, wherein said mixed liquor is discharged into said external zone at the upper end thereof in a plurality of circumferentially spaced separate discharges each generally tangential to the liquor in said external zone to achieve and maintain the rotation of the mass of liquor.

7. The method of claim 1, 4 or 5 including wasting excess sludge by allowing the same to discharge from said sludge separation zone with the treated liquor and subse-quently removing excess sludge from the treated liquor.

8. The method of claim 1, 4 or 5 including chemically treating the treated liquor from the sludge separation zone to remove phosphorus contaminants from the treated liquor as precipitated phosphorus compounds by:
mixing about 180 to about 200 mg/1 of alum with the treated liquor, feeding the mixture into a rotating fluidized bed of chemical sludge com-prising precipitated phosphorus compounds, coagulating the dissolved phosphorus contamiants in a fluidized bed, removing treated liquid and chemical sludge from the fluidized bed, separating the treated liquid from the chemical sludge and removing the treated liquor, and recycling liquor from the fluidized bed to the feed mixture at a ratio of recycled liquor to feed of about 1:1 to about 1:3 to maintain the fluidized bed.

9. An apparatus for the treatment of waste water containing contaminants including dissolved biodegradable carbonaceous material and nitrogenous materials mainly in non-nitrate and/or non-nitrite form by biological consumption and conversion to gases using a single mixed microbial sludge, which comprises:
a first reaction tank;
a first inlet to said first reaction tank for the inlet of waste water to said first reaction tank;
an outlet from said first reaction tank connected to a first inlet of a second reaction tank for feed of liquor to said second reaction tank from said first reaction tank;
a first outlet from said second reaction tank connected to an inlet of a sludge separator tank for feed of liquor from said second reaction tank to said sludge separator tank, a first outlet from said sludge separator tank for the discharge of treated waste water, a second outlet from said sludge separator tank connected to a second inlet of said second reaction tank for recycle of flocculated sludge from the sludge separator tank to said second reaction tank and first means for effecting said recycle, a second outlet from said second reaction tank connected to a second inlet of said first reaction tank for recycle of mixed liquor from said second reaction tank to said first reaction tank and second means for effecting said latter recycle, means for recycling mixed liquor within said first reaction tank, means for recycling mixed liquor within said second reaction tank, means for feeding controlled quantities of oxygen to said first reaction tank to establish and maintain predominantly anaerobic conditions therein, and means for feeding controlled quantities of oxygen to said second reaction tank to establish and maintain predominantly aerobic conditions therein.

10. The apparatus of claim 9, wherein said first reaction tank comprises a cylindrical upright tank and an inverted funnel-like member coaxially arranged with the tank and extending from the upper end of said tank towards the lower end thereof separating said tank into a first zone between the outer surface of said inverted funnel-like member and the inner surface of said tank and a second zone internally of said inverted funnel-like member;
said first and second inlets for said first reaction tank communicate with the upper end of said first zone;
said outlet from said first reaction tank commun-icates with the upper end of said second zone; and said means for recycling mixed liquor within said first reaction tank and feeding controlled quantities of oxygen to said first reaction tank comprise:
a riser tube extending from the lower end of said tank upwardly through said second zone axially of the tank and terminating at its upper end externally of said second zone in a cross-arm member extending radially of the tank, outlet pipes integral with each end of said cross-arm members for discharge of liquor into said first zone, and a molecular oxygen-containing gas feed tube extending from exteriorally of the tank through said riser tube and terminating adjacent the lower end thereof.

11. The apparatus of claim 9, wherein said second reaction tank comprises a cylindrical upright tank and a sleeve extending axially of the tank from the upper end of the tank towards the lower end thereof separating said tank into a first zone between the outer surface of said sleeve and the inner surface of the tank and a second zone internally of said sleeve;
said first and second inlets for said second reaction tank communicate with the upper end of said first zone;
said first outlet from said second reaction tank communicates with said second zone;
said means for recycling mixed liquor within said second reaction tank and feeding controlled quantities of oxygen to said second reaction tank comprise:
a riser tube extending from the lower end of said tank upwardly through said second zone axially of the tank and terminating at its upper end externally of said second zone in a cross-arm member extending radially of the tank;
outlet pipes integral with each end of said cross-arm member for discharge of liquor into said first zone, and a molecular oxygen-containing gas feed tube extending from exteriorally of the tank through said riser tube and terminating adjacent the lower end thereof; and said connection of said second outlet from said second reaction tank to said second inlet of said first reaction tank and said second recycle means is achieved by:
conduit means extending from adjacent the lower end of said second reaction tank upwardly through said second zone generally parallel to said riser tube and out of said second reaction tank to said first reaction tank, and a molecular oxygen-containing gas feed tube extending from exteriorally of said second reaction tank through said conduit means and terminating adjacent the lower end thereof in said second reaction tank.

12. The apparatus of claim 9, wherein said sludge separator tank comprises a cylindrical upright tank and an inverted funnel-like member coaxially arranged with the tank and extending from the upper end of said tank towards the lower end thereof separating said tank into a first zone between the outer surface of said inverted funnel-like member and the inner surface of said tank and a second zone internally of said inverted funnel-like member;
said inlet for said sludge separator tank communicates with the upper end of said first zone;
said first outlet from said sludge separator tank communicates with the upper end of said second zone; and said connection of said second outlet from said second reaction tank to said second inlet of said second reac-tion tank and said first recycle means is achieved by:
conduit means extending from adjacent the lower end of said sludge separator tank upwardly through said second zone generally axially of the sludge separator tank and out of the sludge separator tank to said second reaction tank, and a gas feed tube extending from exteriorally of said sludge separator tank through said conduit means and terminating adjacent the lower end thereof in said sludge separator tank.

13. The apparatus of claim 12, including a plurality of discharge pipes at the upper end of said first zone each communicating with said inlet to said sludge separator tank for discharge of mixed liquor at a plurality of circumfer-entially-spaced locations at the upper end of said first zone.

14. The apparatus of claim 9, wherein said first reaction tank comprises a first cylindrical upright tank and a first inverted funnel-like member coaxially arranged with said first tank and extending from the upper end of said first tank towards the lower end thereof separating said tank into a first zone between the outer surface of said first inverted funnel-like member and the inner surface of said first tank and a second zone internally of said first inverted funnel-like member;
said second reaction tank comprises a second cylindrical upright tank and a sleeve extending axially of the second tank from the upper end of the second tank towards the lower end thereof separating said second tank into a first zone between the outer surface of said sleeve and the inner surface of said second tank and a second zone internally of said sleeve;
said sludge separator tank comprises a third cylindrical upright tank and a second inverted funnel-like member coaxially arranged with the tank and extending from the upper end of said tank towards the lower end thereof separating said tank into a first zone between the outer surface of said second inverted funnel-like member and the inner surface of said third tank and a second zone internally of said second inverted funnel-like member;
said inlets for each of said tanks communicating with the upper end of the respective first zone of said tank;
said outlets for each of said tanks communicating with the respective second zone of said tank;

said means for recycling mixed liquor within each of said first and second reaction tanks and feeding con-trolled quantities of oxygen to each of said first and second reaction tanks for each of said first and second reaction tanks comprise:
a riser tube extending from the lower end of said tank upwardly through said second zone axially of the respective tank and terminating at the upper end externally of the respective second zone in a cross-arm member extending radially of the respective tanks, outlet pipes integral with each of said cross-arm members for discharge of liquor into the respective first zone, and a molecular oxygen-containing gas feed pipe extending from exteriorally of the respective tank through said riser tube and terminating adjacent the lower end thereof; and said connection of said second outlet from said second reaction tank to said second inlet of said first reaction tank and said connection of said second outlet from said sludge separator tank to said second inlet of said second reaction tank and their associated recycle means are achieved in each instance by:
conduit means extending from adjacent the lower end of the respective tank upwardly through the respective second zone and out of the respective tank to the respective second inlet, a molecular oxygen-containing gas feed tube extending from exteriorally of said respective tank through said conduit means and terminating adjacent the lower end thereof in the respective tank.