Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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EQUALIZATION BASl[N-REACTOR SYSTEM
BACKGROUND OF THE INVENTION
5 1. Field of the Invention
This invention relates to treatment of aqueous materials, particularly,
wastewater, and wastewater sludges, and is related to single stage and multistage
equalization basin-reactor systems treating variable influent flows.
10 2. Description of the Prior Art
Many water, wastewater, and other treatment systems have variable influent
flows and concentrations. Process controls also produce variable flows and
concentrations, for example, through recirculation of various process streams, di lution
with the treated streams, by feeding the reagents, and by other control actions. The
15 treatment efficiency depends on the ability of the treatment system to handle the
variable characteristics of the influent flows. First, flow and concentration variations
are reduced in the treatment system via equalization effects, which are related to the
flow patterns and degree of mixing in equalization basins and reactors. Second, the
concentration variations are also reduced due to the physical, chemical, physical-
20 chemical, or biological matter transformations. High treatment efficiency and stability,and low capital and operating costs can be provided by utilizing appropriate
combinations of flow and concentration equalization basins and reactors. Functions of
flow and concentration equalization and materials transforrnation can be perforrned in
separate flow equalization basins, usually, single or multiple tanks with variable
25 volume of the liquid being treated, concentration equalization basins, single or multiple
tanks with a variety of flow and mixing patterns, and in reactors of one or another type.
Systems with multiple tank are usually arranged into multi-stage systems. The
equalization and transforrnation fimctions can also be perfonned in a single flow-
through tank.
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For example, a single tank system known under trade name Biolac (U.S. Patent
Nos. 4,287,062, 4,448,689, 4,797,212) combines flow equalization and treatment
functions is a single aerobic reactor with a clarifier having a floating weir or a floating
clarifier for collecting the clarified water. The weir flow is equal to or greater than the
5 average design flow. Accordingly, the single reactor provides complete flow
equalization. Such a reactor can be divided into sequential process zones (U.S. Patent
5,472,611). However, with a single level floating weir or clarifier at the effluent
discharge, this reactor functions as a single tank flow equalization basin. Single flow-
through tanks with a single level discharge line and floating clarifiers or weirs handle
10 flow variations in a small to moderate range well. For example, these tanks are used for
equalizing variations of municipal wastewater flows within a day and industrial
wastewater flows within a production shift or a day. However, the required volume of
these tanks becomes very large when combined storrn and municipal, or industrial,
flows need to be equalized. In systems with variable flow recirculations, for example,
15 for diluting or neutralizing the influent, the capacity of single level clarifiers installed
for h~ndling minimum to average flows is inadequate. Adding more clarifiers
discharging at the same level causes problems with water distribution among clarifiers,
or among collection means (such as weirs) in these clarifiers.
If another reactor is added downstream of the single tank equalization basin-
reactor, the system becomes a multistage reactor. The downstream reactor will beoperated at the constant (equalized) flow rate. The volume of the downstream reactor
will stay constant, and it cannot be used for flow equalization. Corresponding depths
(liquid level) fluctuations in the first reactor must accomrnodate all equalization
requirements, and will be substantial.
An ~ltern~tive treatment system for highly variable wastewater flows and
concentrations is the sequencing batch reactor (SBR). In this system, usually, two or
more single-tank reactors are installed and operated in the periodic mode: filling the
wastewater influent, treatment, settling of the sludge, and dec~nting the wastewater
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effluent. SBR combines the functions of flow equalization, treatrnent, and sludge
separation in one tank. However, in contrast to multistage systems, it is difficult or
impossible to accommodate various process stages, like nitrification and denitrification.
With influents having variable flows and concentrations, the end of the treatment
period, or a functional treatment step (for example, nitrification) in the sequence of
operations is difficult to detect. Accordingly, SBRs are often operated on a time clock
set based on a worst case scenario. This results in grossly overdesigned SBR reactors.
The main objective of the present invention is to improve single stage and
10 multi-stage treatment systems, by combining equalization and treatment of wastewater
in at least two stages of the multiple stage treatment process. Thus improved systems
retain all advantages of multistage systems when treating influents with variable llows
and compositions and use more than one reactor for flow equalization. Other
advantages will become apparent from the ensuing description of the invention.
SUMMARY OF THE INVENTION
This invention is a single stage or a multi-stage apparatus for treatment and
equalization of variable flows of an influent material, wherein said influent material is
processed in a plurality of sequential reactors cont~ining liquid and having influent,
20 reactor connecting, and at least two effluent lines. The improvement to a single stage
apparatus comprises:
(1) at least one equalization basin-reactor providing means for flow
equalization,
(2) a lower elevation connecting line connecting first floating flow transfer
means within the said equalization basin-reactor to the first of the said
at least two effluent lines, wherein the said first effluent line is a lower
elevation effluent line, and
(3) at least one higher elevation connecting line connecting second iloating
transfer means within the said at least one equalization basin-reactor to
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the second of the said at least two effluent lines, wherein the said second
effluent line is a higher elevation effluent line.
The improvement to a multi-stage apparatus comprises:
(l) at least two reactors for flow equalization, the said two reactors are
selected from the said sequential reactors,
(2) providing the lower elevation flow transfer means attached to the said
reactor connecting and effluent lines in the said selected reactors,
(3) providing at least one higher elevation flow transfer means attached to
the said reactor connecting and effluent lines in at least one of the said at
l 0 least two selected reactors for the flow equalization, the said at least one
of the said at least two selected reactors precedes the said other selected
reactors in the sequential connection of reactors.
The flow transfer means is selected from a group comprising floating weirs and
l 5 floating clarifiers, which can be connected to the said reactor connecting and discharge
lines by flexible connections. Several reactor connecting lines per reactor can be
provided at the same or at different elevations. Floating weirs and clarifiers can be
made at least in part from a flexible material, for example, soft plastics. Floating
clarifiers are selected from a group comprising Imhoff clarifier, vertical flow clarifiers,
horizontal flow rectangular clarifiers, clarifiers with suspended sludge blanket, or other
solid liquid separation means. Imhoff clarifiers do not need specific means for sludge
evacuation. In other clarifier types, airlifts (or gaslifts), pumps, or other means can be
used for sludge evacuation.
This apparatus further includes the means for directing said influent material to
more than one of the said stages simultaneously. The influent can be split into equal or
unequal flows and each of these flows can be directed to more than one of the said
stages simultaneously via floating cut off weirs with flexible lines leading to the
downstream reactors. Floating cut offweirs is convenient means for controlling the
delivery of the influent to downstream reactors because they descend in the first reactor
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during low flow periods and cut offthe flow to the downstream, and when tlle ilo~
increases they rise and transfer part of the higher flow rate to the downstream reactors.
The apparatus further includes the means for transferring at least one flow of the
liquid contained in at least one reactor into the same or at least one different reactor in
5 the said plurality of reactors. The said means can be a floating weir, including a cut off
floating weir.
The stages in the present apparatus include anaerobic, facultative, anoxic,
aerobic and polishing reactors for biological processes. These sequential reactors can
10 comprise alternating anaerobic (or facultative nonaerated) and aerobic reactors. The
apparatus also includes alternating reactors selected from the group consisting of
anaerobic and aerobic zones, and alternating aerobic and anaerobic conditions in the
same reaction vessel. Additionally, a special reactor stage can be provided for exposing
said influent material and intermediate metabolic products to both anaerobic and15 aerobic biomass simultaneously (U.S. Patent Nos. 5,514,277 and 5,514,278)
The improved apparatus further includes at least one sludge conditioning zone
in at least one reactor in the said plurality of sequential reactors. The sludgeconditioning zones can be aerobic and anaerobic zones. Sludge conditioning zones can
20 be provided with means for recycling the conditioned sludge from the said sludge
conditioning zone in at least one reactor, any reactor, in the said plurality of sequential
reactors. The means for transferring the conditioned sludge from the said at least one
sludge conditioning zone in at least one other reactor in the said plurality of sequential
reactors is also provided.
The present apparatus further includes the means for adding powdered activated
carbon in at least one reactor in the said plurality of sequential reactors.
BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a plan view of a multistage system showing the basic arrangemel1t of
the present invention;
Fig. 2 is a cross-sectional view taken along lines I-I in Fig. l;
Fig. 3 is a cross-sectional view taken along lines II-II in Fig. l;
Fig. 4 is a view similar to Fig. 2 and showing the first anaerobic reactor with a
sludge conditioner and a mixer;
Fig. 5 is a view similar to Fig. 3 but showing additionally a cut off wcir for
transferring at least part of the influent to the second reactor, a liquid transfer weir, and
a cut off weir;
Fig. 6 is a view similar to Fig. 2 and showing a flow splitter and a cut off weir
for the influent flow;
Fig. 7 is a view similar to Fig. 2 also showing a flow transfer weir;
Fig. 8 is a view similar to Fig. 2 and showing a cut off weir;
Fig. 9 is a cross-sectional view of a floating Imhoffclarifier made of lle,Yiblematerial;
Fig. 10 is plan view ofthe clarifier shown in Fig.9;
Fig. 11 is plan view of the flow splitter and cut offtransfer weir for tlle innuent;
Fig. 12 is a view along lines I-I in Fig. 1 1; and
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Fig. 1 3 is a view along lines II-II in Fig. 11.
DETA~LED DESCRIPTION OF THE EMBODrMENTS
The basic system as shown in Figs. 1, 2, and 3 comprises two consecutive
stages of biological reaction 1 and 2. More than two reactors can be included in the
plurality of reactors in the multistage system. Stage 1 has an intake line 3 (a pipe or a
channel), at least one lower elevation flow transfer means 7 (for example, a floating
clarifier, or a floating weir, or a combination of the two) having an intake opening (for
example, at the bottom as in Irnhoff clarifier as shown later) and a discharge line 8.
For a floating flow transfer means, line 8 can be a flexible line. Line 8 is connected to
a reactor connecting line 4 at a fixed vertical position in the wall (or walls, if these
reactors are made of separate vessels) between reactor stages 1 and 2. At least one flow
transfer means 9 with a flexible line 10 connected to a line 5 is provided in the stage l .
Line 5 is higher than the line 4. For example, means 9 can be another floating clarifier,
or a weir, or a combination of a clarifier and a weir. Stage 1 can be used separately
from stage 2 as an independent single-tank equalization basin-reactor system. In the
stage 2, at least one flow transfer means 11 with a discharge line 12 attached to the
effluent line 6 is provided. In case the means 11 is a floating clarifier or a weir, the line
12 can be a flexible line. Flexible lines 8, 10, and 12 can be made, for example, of
metal or rigid plastic pipes with movable joints, or of flexible hoses. Additionally
referring now to Figs. 9 and 10, there is shown an exarnple of a floating clarifier made
of flexible plastic. It is supported by six floats 66, which hold a rigid frame made of
three beams 67 and two water collection troughs 68a and 68b. Hooks 70 are secured to
the bearns 67. Two flexible plastic side walls 81 and 82 with eyeloops at the top and at
the bottom are provided. Bars 72 are inserted in the upper eyeloops and placed on the
hooks 70. Strips 73 are inserted in the lower eyeloops. The side walls 81 and 82 are
connected to the plastic front and back walls 64 and 65 which are also secured to the
rigid frame by hooks 70. Three vertical bars 70 with top nuts 71 and bottom spacers 75
and 76 pass through the holes in the bearns 67 and the strips 73 and support the side
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walls 81 and 82 at the bottom and fix the bottom opening between these walls. Pipes
69a and 69b are attached to the collection troughs 68a and 68b. Pipes 69a and 69b can
be joined and than attached to lines ~ and 4 (or 10 and 5), or one of this lines can be
attached to the lines 8 and 4, while the other is attached to the lines 10 and 5. Multiple
5 clarifiers can be used. More than two collection troughs in a single clarifier can be
used. These troughs can be attached to the reactor connecting lines at differentelevations. The clarifier of Figs. 9 and 10 can be used as items 7, 9, and 1 1 in Figs I, 2,
and 3. Additional weirs can be attached to the clarifier outside for transferring mixed
liquor.
Referring now to Figs. 1, 2, and 3, the multistage treatment process is opcratedas follows.
The influent is fed in the reactor 1 via influent line 3, where it is treated and at
15 least partially partially equalized. The treated and partially equalized flow is collected
and discharged (when the reactor 1 is used independently), or transferred to the reactor
2 by using the flow transfer means 7 and 9 via flexible lines 8 and 10 and the
connecting lines 4 and 5. Thus transferred liquid is additionally treated and equalized
in the reactor 2 and is discharged by using the flow transfer means 11 via lines 12 and
20 6. Various chemical, biological, and other processes known to the skillful in art can be
performed in an independent reactor 1, or in reactors 1 and 2. The equalization occurs
as follows. At a certain moment after sustained low flows of the influent the flow
transfer means 7 and 9 are at their lower elevation which is determined by the elevation
of the line 4, the lower of lines 4 and 5. For as long as the influent flow does not
25 exceed the capacity of the flow transfer means 7, both means 7 and 9 remain at the
lowest position. When the influent flow through line 3 increases above the capacity of
the flow transfer means 7, liquid in the reactor 1 accumulates. Respectively, both
means 7 and 9 rise. During the rise up to the higher elevation reactor connecting line 5,
only the means 7 transfers the liquid to the reactor 2. At liquid elevations above the
30 line 5, means 7 and 9 transfer liquid downstream. If the influent flow is greater than the
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combined capacity of these two means, the liquid level in the reactor 1 rises till the
influent flow declines below the transfer means capacity. Two flow transfer means
provide a so called step-wise flow control: the flow transferred to the reactor 2 equals
either the capacity of one (lower) transfer means, or the total capacity of tlle two
transfer means. More than two flow transfer means can be used at more than two
elevations. Additionally, an overflow passage at a preset maximum allowable liquid
level in the reactor l can be provided. A step-wise control provides partial llow
equalization. Partial flow equalization requires less volume than the complete
equalization. Changes in the liquid level in the reactor l and the required reactor
l 0 volume are also smaller as compared to a case of complete equali~ation. A partially
equalized flow enters the reactor 2 and is further equalized. If multiple flow tr~nsfer
means in the reactor 2 are attached to effluent lines 6 of the same elevation, the
complete flow equalization will result, except for the sustained minimum flow when the
flow transfer means will be at the lower position and will discharge the flow below
their total capacity. For complete equalization, the total capaci~y of the flow transfer
means should be found as a conservative estim~te of the average flow rate of theinfluent. The required equalization volume in the reactor 2 for the flow alreadypartially equalized is smaller than that needed for the nonequalized influent.
Accordingly, a smaller depth increment is assigned for the flow equalization. More
than two reactors in sequence can be provided with the flow transfer means activated at
preset liquid elevations in the reactors. The use of floating clarifiers as the flow transfer
means offers a specific advantage over the conventional fixed clarifiers because it
permits a simple gravity flow across the multistage treatrnent train for the variablc
influent flow.
Referring now to Figs. 1, 2, and 3, a single independent reactor I can be used as
acombined system for treatment of storm water and municipal (or industrial)
wastewater. During dry weather, lower level floating clarifiers will be used, and both,
lower and upper level floating clarifiers will be used in wet weather.
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Referring now to Figs. 9 and 10, the floating clarifier is operated as follows. It
rises and descends with the liquid level fluctuations in reactors 1 and 2. Additionally,
the mixed liquor enters the clarifier through the bottom opening between the side walls
8 l and 82 and flows upward. The suspended biomass flocculates, settles down, and
S passes back in the reactor via the said bottom opening. The clarified water is collected
in the troughs 68a and 68b, and is discharged via pipes 69a and 69b followed with the
pipes 8 and 4, and/or l0 and 5, and 12 and 6. This discharge occurs when tlle said
troughs in the clarifier are lifted above the level of the respective connecting and
effluent pipes and above the level of the liquid in the subsequent reactor into ~hich tlle
10 liquid is discharged.
Referring now to Fig. 4, there is shown an example of an anaerobic-aerobic
system for wastewater treatment. This is a cross-section of the apparatus simi lar to that
shown in Figs. 1,2, and 3, and descriptions of the same elements will not be repeated
15 Anaerobic reactor l is divided by a baffle 34 into a reaction zone 27 and a sludge
conditioning zone 28. A line 25 and a pump 26 are provided for the conditioned sl~ldge
feed from the sludge conditioner 28 to the reaction zone 27. A mixer 20 is installed for
mixing the liquor in the reaction zone 27. The aerobic reactor 2 is divided by a baffle
35 into an aeration zone 29 and a sludge conditioner zone 30, optionally, zone 30 can
20 be an anaerobic zone. The aeration zone 29 is provided with diffilsed air floating
aerators 3 l connected to floats 32 by braces 33. Altematively, floating mechanical
aerators can be used. A line 23 with a pump 24 is provided for the sludge feed from the
conditioner 30 to the reaction zone 29. A line 21 with a pump 22 is provided for the
sludge feed from the conditioner 30 to the reaction zone 27 in the reactor 1. Optionally,
25 various combinations of lines with pumps can be provided between zones 27,28, 29,
and 30. The apparatus of Fig. 4 is operated as follows. The flow equalization
occurs as previously described for the Figs. l, 2, and 3. The anaerobic degradation of
the influf~nt con~tit lents occurs in the section 27 by the microorganisms grown in this
section and transferred from the section 28 to the section 27 via line 25 by a pump 26.
30 The anaerobically treated liquid enters the floating clarifier 7, for example, Imhoff
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clarifier, where the sludge is separated and settled down in the zone 28, while tlle
clarified liquid is transferred to the reactor 2, aerated zone 29. The settled anaerobic
sludge is conditioned as known to the skillful in art. The anaerobically treated liq~lid is
further treated in zone 32 by a mixed liquor substantially made of aerobic and
5 facultative organi.cn~.~. This mixed liquor enters the floating clarifier 11, for example,
Imhoffclarifier, where the sludge is separated and settled down in the zone 30, while
the clarified and treated liquid is discharged from the system via effluent line 6. In
zone 30, the sludge is conditioned, for example under anaerobic conditions. Thissludge can be transferred to reaction zones 29 and/or 27, or to an anaerobic sludge
10 conditioner 28 (not shown). Part ofthe anaerobic mixed liquor from zone 27 can be
transferred to the aerobic reaction zone 29 using the previously described floating weir,
and/or part of the conditioned sludge from zone 28 can be transferred to zone 29 by
pumping (not shown). The excess sludge can be discharged, preferably, from the
sludge conditioning zones 28 and 30.
Referring now to Fig. 4, tank 2 can be used separately from the tank 1, for
example, as an aerobic treatment system for combined municipal (or industrial) and
storm influents. Tank 2 can be additionally provided with the upper level floating
clarifiers (not shown, but analogous to the reactor 1), wherein the lower level clarifiers
20 would be used in dry weather, and the lower and upper level clarifiers will be used
during wet weather. Optionally, airli~s, or other lifting or mixing means can beprovided for scouring the sludge from the bottom and/or transporting it to the higher
elevations in the reactor in addition to the floating aerators when the water stage in the
tank 2 rises to a level at which aerators cannot sufficiently suspend the sludge.
Referring now to Fig. 5, this is a plan of the system similar to that shown in Fig.
1, but additionally having a floating means 41 for splitting the influent flow between
reactors 1 and 2, a floating flow transfer weir 55, and a floating cut off weir 51.
Additionally referring now to Figs. 6, 11, 12, and 13, there is shown a floating flow
30 splitting means 41 comprising an influent flow splitter compartment 42 with a flow
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control weir 44 (in the side wall) discharging to the reactor l and a flow cut off weir ~5
(in the wall 60) discharging in a compartment 43. Compartrnents 42 and 43 are
provided with flexible connections 46 and 47 to the influent line 3 and a pipe 48 and a
connection line 49 leading to the reactor 2. Additionally, referring now to Fig. 7, there
5 is shown a floating flow transfer means 55 with a weir 58, the said means is connected
to the reactor connecting line 56 via flexible line 57. The elevation of the weir 58 is
below the liquid level in the reactor l. Additionally, referring now to Fig. 8, there is
shown a floating flow cut off means 5 l with a weir 59, the said means is connected to
the recycle cut off line 53 via flexible line 52. Lines 21 with a pump 22 and a flexible
10 line 54 connect the reactor 2 with the floating cut off mealls 5 l . The elevation of the
weir 59 is above the liquid level in the reactor l. Floats for the floating means
described herein are not shown to avoid trivial details. Skilled artisans can provide
such floats.
lS The floating flow splitting means 41 is operated as follows. The influent is fed
in the compartment 42. If lines 48 and 49 are above the elevation of the weir 45, the
entire influent flow is fed in the reactor 1 via discharge weir 44. At greater intluent
flows, when the floating means 41 rises and the weir 45 is above the level of lines 48
and 49, part of the influent flow is split to the reactor 2. Now, skilled artisans can
20 easily design this device for splitting the flow to more than one downstream reactor. It
is easy to split the flow in equal or desired unequal portions. Simplicity, versatility and
ease of operation are the advantages of the floating means for flow splitting.
The floating flow transfer means 55 is operated as follows. When liquid level in25 the reactor l is below the line 56, there is no flow via the floating weir 55. With the
influent flow to the reactor l increasing, the liquid level rises and the floating means 55
is lifted above the line 56, the liquid from the reactor l flows over the weir 58 into the
means 55 and via lines 57 and 56 in the reactor 2.
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The floating flow cut offmeans 51 is operated as follows. The pump ~
continuously delivers a flow of the recycled liquid from the reactor 2 to the reactor 1.
This liquid can be mixed liquor, or separated sludge, or conditioned sludge. At low
liquid levels in the reactor 2, the recycled flow is discharged via weir 59 in the reactor
5 1. When the liquid level in the reactor 1 rises and the floating cut off means 51 is lifted
above the line 53, the flow delivered by the pump 22 is returned to the reactor 2 (or,
optionally, any desired section of a downstream reactor).
The floating flow splitting means 41, the floating flow transfer means 55, and
10 the floating flow cut off means 51 help to equalize flows and transfer the in~luent and
biomass in multistage reactor system by transferring the maximum influent flows and
the liquid from the upstream reactors in the less hydraulically loaded downstream
reactors, and by reducing the hydraulic loading due to flow recycling in the upstream
reactors in the periods of higher influent flows. Accordingly, the required equalization
l S volumes are better allocated among the reactors, and the needed throughput capacities
of the clarifiers in particular treatment stages are reduced.
The embodiments of Figs. 1 to 13 show many arrangements forproducing
unexpected useful effects in the simultaneous equalization and chemical, physical-
20 chemical, and biological treatment of influent materials. It will therefore be understoodby the skilled in the art that the particular embodiments of the invention here presented
are by way of illustration only, and are meant to be in no way restrictive; therefore,
numerous changes and modifications may be made, and the full use of equivalents
resorted to, without departing from the spirit or scope of the invention as outlined in the
25 appended claims.
