Note: Descriptions are shown in the official language in which they were submitted.
20681677
F I ELD OF THE I NVENT I 023
This invention relates to bioreactors used in the
treatment of domestic and industrial waste water, before release
to the environment.
5BACRGROUND OF T~E INVENTION
Bioreactors are used for microbiological treatment of
waste waters. Industrial or domestic waste waters usually support
organic and/or inorganic loads. These loads are often toxic to the
biota, sometimes even only in trace concentrations, and therefore
10it is desirable and indeed now required by several environmental
laws to remove from the waste water substantial portions of these
organic and inorganic loads, before release to the environment.
Patents issued during the year 1992 in this general field
include United States patents No 5,104,803 for a
15''Photobioreactor'', and No 5,106,496 for a ''Treatment of volatile
organic substances at waste water treatment plants''.
It is understood that the~se bioreactors will
progressively become clogged mostly with organic loads, but also
with some inorganic loads, which therefore need to be periodically
20removed from the bioreactor basin to continuously sustain the waste
water treatment operation. One of the key elements to take into
account in order to provide efficient operations of bioreactors in
waste water treatment, is to reduce to the minimum the downtime and
back wash water volume associated with this periodic washing of the
25bioreactor.
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OBJECTS OF THE INVENTION
The gist of the invention is to increase the afficiency
and total waste water treatment capacity of bioreactors.
A major object of the invention is having a bioreactor
which will provide a two step, graded, gravity-dependent waste
water treatment, namely: a first, mainly organic load reducing
step, and a second step for suspended (particulate matter) solid
retention.
A further object oE the invention is that the above-noted
bioreactor also provides some inorganic load degradation, at said
first step, and some organic as well as inorganic load reduction,
at said second step.
An important object of the invention is to provide means
for periodic washing of said bioreactor media and packings, and for
lS dirt-loaded wash water discharge frorn the reactor basin, either by
way of an overflow technique, under siphoning action, or by way of
a vacuum pumping device.
A corollary object of the invention is to provide an
above-noted bioreactor wash means, which will address the need for
substantially reducing the downtirne and~or bac~wash water volume
associated with periodic washing of the bioreactors.
SU~ R~l OF THE I~iVENTION
In accordance with the objects of the invention, there
is disclosed a bioreactor for waste water treatment, comprising:
(a) a basin, for enclosing waste water, and defining a bottom
flooring member; (b) a first layer of a plurality of packings,
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each of relative density smaller than one, for mainly organic load
reduction; (c) a second layer of a plurality of media, each of
relative density greater than one, for mainly suspended solid
retentlon in the waste water; wherein said pac~ings and media are
both to be submerged in waste water; said second media located at
a lo'wer portion of said basin, said first packings located at an
upper portion of said basin; said waste water to be fed into said
basin about an upstream raw waste watsr end corresponding to said
basin upper portion, and to reach said basin lower portion through
said packings and media, by gravity; wherein each packing has a
high void space ratio and supports and anchors colonies of micro-
organisms, said micro-organisms capable of organic load degradation
and also having some inorganic material degradation capability; and
(d) means for discharge outside of said basin of the treated waste
water, the latter means having a treated water outlet means located
about said basin flooring member.
Preferably, the bioreactor further includes means for
periodic washing of said media and pack:ings, said washing means
including: (a) kinetic force means, for shaking said media and
packings in view of frictionally dislodging organic material
adhering thereon; (b) wash water feed means, for liquid-washing
said media; and ~c) wash water removing means, said wash water
removing means drawing the dirt-loaded wash water outside of said
basin, by gravity.
The invention is also directed to a method for periodic
washing of this bioreactor, the latter being provided with forced
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compress air means being fed into said media. This washing method
would then comprise the following steps: a. stopping waste water
feed; b. stopping forced process air flow into said basin; c.
allowlng the waste water level in the basin to lower down to a
first, intermediate, set level; d. closing the basin bottom water
outlet, e. triggering pressurized air flow through said flooring
member, into said basin; f. triggering wash water flow through
said bottom water outlet, into said basin concurrently with said
pressurized air flow; g. allowing the media to become agitated
under the combined action of said wash water and pressurized air
flows, wherein accumulated matter is dislodged from the media and
from the packings; h. allowing the wash water level in the basin
to raise up to and including a second set level, above said first
set level; i. allowing dirt-loaded wash water from the basin to
escape therefrom through escape means, j. restarting waste water
treatment operation.
BRIEF DESCRIPTION OF THE DRAWING5
Figure 1 is a vertical section of a preferred embodiment of paclced
bioreactor for waste water treatment in accordance with the
teachinys of the invention;
Figures 2 and 3 are views similar to figure 1, but for two
alternate embodiments of packed bioreactors; and
Figures 4 and 5 are vertical sections, orthogonal to one another,
of a fourth embodiment of packed bioreactor.
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DETAILED DESCRIPTION OF THE INVENTION
The bioreactor of figure 1, at 10, consists of a large
basin 12 having vertical side walls 14, a flooring 16 and a top
open mouth 18. Basin 12 is destined to be loaded with waste water.
A partition wall or false floor, 20, is mounted to side walls 14,
spacedly proximate flooring 16. False floor 20 is pierced by a
plurality of through-bores 22, for free outflow passage of treated
waste water and inilow of backwash air and water.
At least two layers of bio-media are loaded into the
basin 12 above horizontal false floor 20: a first layer of non-
buoyant ''media'', 24, destined to abut directly against false
floor 2Q, and a second layer of buoyant ''packings'', 26, destined
in a liquid medium to float freely above the non-buoyant media 24.
Each layer 24, 26 consists of a plurality oE vertically stacked,
generally horizontal rows of biomedia. Tha number of biomedia units
in a given layer 24 or 26 will vary accordingly with the
qualitative as well as quantitative characteristics of the
contaminants in the waste water to be treated. Said media is to
be completely submerged in waste water, while most of said packings
are to be completely submerged.
The non-buoyant media 24 is made from a material
consisting preferably of expanded shale, having a large surface to
volume ratio (i.e., the so-called ''void ratio''), and also have
a good abrasion resistance. The buoyant packings 26 have relative
density of less than one, and are preferably larger than the non-
buoyant packings 24. The overall dimensions of each buoyant
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packings 26 may vary from 5 to 200 mm, and most preferably from 15
to 100 mm, so as to prevent plugging thereof even with high biomass
loading. Each media 24 and packing 26 may have a variety of
shapes, e.g. spherical or cylindroid.
The packings 26 are preferably made from an injection-
moldable plastic material, for example polypropylene or low density
polyeithylene, with a void space percentage of for example 77 to
98~, for example the plastic biopackings sold by the FABCO company
or the NORTON company.
It is understood that these packings and media act as
substrates for supporting the growth of colonial microorganisms.
Preferably, the height of the layer of media 24 ranges
between 0,5 and 2 meters.
Waste water is to be gravity-fed into basin 12, from the
top of baqin 12, onto buoyant packings 26, to seep through and
around these packings 26 and then through media 24. This upstream
waste water thereiore comes in contact with the bacterial colonies,
which, during their metabolic activity, substantially reduce
organic (carbon-based substances) pollution therein, for example,
feces or urine. Some retention of solid suspension particles (e.g.
macroparticles of non soluble matter) in the waste water occurs at
the level of buoyant biopackings 26, although it is mainly organic
pollution reduction by the colonial microorganisms which occurs,
at a percentage which ranges preferably from 60 to 95 % relative
to the original (upstream) organic load.
Moreover, it is envisioned to be well within the scope
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of the invention that inorganic ~substances lacking any carbon
element) loads be also at least partly treated, i.e. screened and
retained by the buoyant biopackings 26. For example, phosphorous
and nitrogen, which are often released to the environment by the
waste water, would be treated by the packings and media, to prevent
their release with the treated waste water.
To increase the organic matter degradation capability of the
aerobian bacteria anchored to their packing substrate 26, air feed
means 28 are provided to oxygenate the waste water column in basin
12. Water oxygenation means 28 consists of an air pipe 30,
e~tending through a side wall 14 spacedly closely above partition
20, and provided with a plurality of air outlet ports 32 for air
escape into basin 12. Pressuri~ed air means (not shown) feed pipe
30. Air pipe 30 extends through the single- or multi-layer non-
buoyant media 24.
The waste water, by gravity, seeps through the upper
layer of buoyant packings 26, and engages the media 24. Because
of water discharge ports 22, upstream waste water is biased by
hydrostatic forces to also seep through the lower layers of media
24, to eventually escape through these clischarge ports 22 located
in false floor 20. The seeping of waste wat0r through the lower
media single- or multi-layer 24 provides screening mainly by
particulate material suspension retention, although some biological
degradation is still performed by the colonial microorganisms
growing within the media 24 to complete the biological degradation
that initially occurred at said upper layer of packings 26.
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To prevent pluggi.ng by media 24 of false floor discharge
ports 22, a screen or grid 34 is mounted on the upstream (top) end
of each port 22, with the grid mesh apertures being smaller than
the med1a 24. Each grid 34 may be made integral to an elongated
tube 36, extending through and downwardly beyond false floor 20 but
stopping short of Elooring 16. The filtered water discharged
through nozzles 36 flows into a treated water chamber 40, formed
by walls 14, 16 and false floor 20, and escapes from chamber 40
through treated water e~cape pipe 38.
Pipe 38 is connected to an upwardly extending column,
not shown in figurP 1 but shown as reference 74 in figure 5. As
wash water level raises in this latter water column, some relative
hydrostatic pressure balancing occurs between the water in basin
12 and the water in the upright column at the exterior of basin 12.
Periodic cleaning of the bioreactor is re~uired, usually
once a day, to remove the recurrent crust of organic and inorganic
matter microparticles that builds with time on the media 24 and
packings 26. In accordance with the hereinbelow described methods
of wash cleaning, the whole bioreactor washing operation can be
completed in less than half an hour. The cleaning means of the
bioreactor includes a second pressurized air feed inlet pipe 42,
extending through side wall 14 and into bottom chamber 40, and
clean water feed inlet pipe 44, also extending through side wall
14 and into bottom chamber 40. The water used for the back washing
with pipe 44 of the bioreactor may come for example from a treated
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water holding tank, not shown. A known water valve 46 is to seal
water discharge pipe 38, after upstream waste water fsed has been
interrupted, to enable proceeding with the bioreactor washing
operation.
A notch 48 is made about the top rim portion of one of
the side walls 14, at 14a, of basin 12, and opens into a channel
member 50 depending from the outer face of that latter side wall
14a. An inwardly-upwardly-inclined flat grid plate 52 projects
inwardly from side wall 14a, in register with notch 48, to prevent
buoyant packings 26 - but not the wash water - from escaping by
overflow through notch 48 into channel 50, as the water column
inside basin 12 raises, as will now be seen.
Alternative overflow systems are also envisioned, e.g.
a gutter system extending transversely through the basin top mouth
18, at a height lower than the top rim 14a of basin 12, so that as
the wash water level raises in basin 12, it eventually overflows
into the gutter before reaching the top rim level. The gutter
would drain into a discharge channel similar to channel 50.
The method of periodic cleaning oE the bioreactor 10
includes the following steps:
1. stopping waste water feed.
; 2. stopping ~orced process air flow into basin 12 about
oxygenating pipe 30;
3. allowing the waste water level in basin 12 to lower down around
static level (by ''static'' is meant the level at which the
hydrostatic pressure of the waste water in basin 12 balances that
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of the upright water column downstream of discharge pipe 38).
4. closing the valve in bottom water discharge outlet 38.
5. triggering pressurized air flow through air pipe 42 into
chamber 40, downstream through passages 36 into basin 12;
6. allowing the media 24 to become shaken under the combined
action of the fluids from pipes 42 and 44, wherein accumulated
matter is dislodged from the media and from the packings; this step
preferably lasting from 60 to 120 seconds.
7. triggering wash water flow through pipe 44 into chamber 40,
through tubes 36 and into basin 12;
8. allowing the back wash water level in basin 12 to raise up to
and including the level of notch 48;
9. allowing wash water from basin 12 to overflow through notch
48, into escape channel 50 (for example, for a new cyclic sludge
treatment).
10. preventing packings 26 from escaping with the overflowing
water, thanks to retaining grid de~lector plate 52.
The embodiment of ~igure 2 i5 similar to that of figure
; 1, but for a wash water discharge siphon member 60. Siphon member
is joined to a collecting device, for example a tubular
horizontal leg 62, extending through the width of tank 12 slightly
over the media 24, and a U-shape part defining two vertical legs
64, 66 and a web 68. Inner vertical leg 64 merges ~ith horizontal
leg 62 about an elbow 64a. Arcuate web 68 engages sealingly into
and is supported by a shaped aperture 49 made at the upper portion
of the basin side wall 14a'. Outer vertical leg 66 defines a mouth
- .
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66a at its bottom end, located spacedly pro~imate the flooring 50a'
of channel member 50'. There is no notch 48 in wall 14a'.
Accordingly, packings deflector grid 52' is raised to fit the top
rim of basin 12', above the siphon web 68, to prevent escape of
packings 26 during backwash cycle.
An operative requirement for siphon member 60 to function
properly is that its downstream outlet end, 66a, be located at a
height lower than that of the apertures 652a at its upstream
horizontal leg 62. Indeed, the siphon horizontal device 62 could
consist for example of a tube including one or more lengthwise
slits 62a, preferably located on the oottom portion of the tube 62.
This preferred location of the slits 62a is suggested in order to
prevent media from plugging same during temporization (outgazing),
and to further prevent water line sludge settling onto the tube 62.
Each slit 62a will have a width which would preferably range
between 5 to 25 mm, and with overall length for the combined slits
62a ranging advantageously from 0,2 to 0,8 m\m2 of filtering area.
The filtering area corresponds to the horizontal inner section of
basin 12. The slits 62a must have a width smaller than the buoyant
packings 26, but not necessarily smaller than media 24.
The method of cleaning the bioreactor with this second
embodiment differs from the first method as detailed in the
following series of steps:
1. to 7. : same as in first method steps 1 to 7;
8. allowing the wash water level in basin 12' to raise slightly
short of the siphon top U-part web 68, with the height of the
11
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siphon U-part 64-68 preferably ranging between one and two meters
- the longer this U-part 64-68, the smaller the number of cleaning
cycles required for complete cleaning of the bioreactor.
9. stopping air flow in pipe 42' and wash water flow in pipe 44',
for outgazing, preferably for a period from 30 to 90 seconds long.
10. injecting wash water (for example, treated water from another
basin 12) from pipe 44', through chamber 40', into the basin 12',
in order to trigger the siphoning action.
11. draining under siphoning action the dirt-loaded wash water
from basin 12', through pipes 62-68 and outlet 66a, and evacuating
same through channel 50'.
12. if required ~due to hardened, embedded media clogging),
repeating successively the above listed steps (5) to (11), at least
o~ce, and preferably three to four times, before resuming
additional waste water treatment.
In the third embodiment of bio-reactor, shown in figure
3, an L-shape overflow system 60''' is provided, comprising a main
leg 62''', e~tending generally horizontally through basin 12 and
engaging through and outwardly beyond a side wall of basin 12, and
; 20 an upright leg 65, verticàlly extending Erom the outer end of tube
6~''' (exteriorly o~ basin 12'''). Tubes 62''', 65 are in fluid
communication with each other and define wash water intake slits
or ports 62a''', along the lower portion of tube 62''', and a water
outlet port 63a'' at the top end of vertical tube 65. Tube 65
extends into channel 50''', so that overflow of wash water from
overflow system 60''' through outlet 63a'' will fall into this wash
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water discharge channel 50'''. As in the Eirst embodiments, the
wash water 50''' is envisioned to be reused in the waste water
treatment plant, for suitable purposes, in order to address the
need to concentrate the sludges to the maximum before dumping.
It is understood that waste water will escape into
channel 50''', once the hydrostatic pressure of waste water column
inside basin 12, above the main horizontal leg 62''', biases the
waste~water to flow through tube 62''' upwardly of tube 65, and to
esc~pe through the top mouth 63a''' of the vertical leg 65, into
channel 50'''. This will occur when the height of wash water
column in basin 12''' reaches a level higher than the height of the
pipe top mouth 63a'''.
The wash method for the embodiment of figure 3 is
basically the same as in the method for the embodiment of figure
1.
The fourth embodiment of washing means for bioreactor
12'''' is shown in figures 4-5, and is somewhat different from the
first three embodiments detailed hereinabove. In this bioreactor,
the perio&ic washing means of the media :24 and packings 26 inside
the basin 14'''' includes a movable vacuum pump device 70 for
suction of backwash water. The suction device 70 is carried by a
wheel carriage 72 rollingly mounted by wheels 73 to the top rim 75a
of an upright pair of spaced parallel walls 75. A basin 74
encloses one bioreactor 12'i~' with a plurality of bottom
compartments 14'''' mounted side by side. The side walls 74b of
basin 74 are not as high as walls 75~ but are much higher than
13
2~68~7~
those of compartmellts 14''''.
Compartrnents 14'''' house so:Lely non-buoyant media 24,
which fill almost all the inner volume of the compartment while
basin 74 houses above the compartments 14'''' the buoyant packings
26. Bottom nozzle outlets 36~''' of all the compartments 14''''
open into a single common chamber 40'''', beneath compartments 12.
A treated water outlet port 74c is made in wall 74b of basin 74,
and opens into chamber 40'''' for treated water discharge to the
environment through suitable channel means 77.
Suction device 70 includes a suction pump power means
76, integral to the overlying carriage 72, a hood 78 and a
flexible hose 80 operatively interconnecting the hood to the
suction pump means 76. The size and shape of the suction device
hood 7~ corresponds to that of the top rim of any given compartment
14'''', so as to fit and seal snugly thereon. The
hood 78 includes a peripheral ~preferably elastomeric) sealing
cushion mem~er, 78a, for ensuring releasable fluid tight engagement
with the selected top rim of compartment:s 14'''', during backwash
water operation.
For bioreactor washing, it is understood that, instead
of discharging the wash water from the bioreactor basin by an
overflowing techni~ue ~emhodiments of figures 1 or 3) ~r hy
siphoning action (embodiment of figure 2), here, the backwash water
is sucked in by the suction device hood 78, against gravity forces,
so that the wash water i5 lifted from the selected compartment
14'''', exclusively of the media proper 24, and pulled inside the
14
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suction device hose 80 and upwardly thereof, and discharged thr~ugh
a discharge outlet pipe 82 (figure 4) into an outlet channel member
84 that outwardly depends from the side wall 75.
Hence, the washing by wash water is made only for the
media 24, in this last embodiment, about which solid suspension
retention occurs and thus where macroparticulate material adherence
is most likely, instead of both the media 24 and the buoyant
packings 26, since the latter is not directed as such to
macroparticle retention, mainly because the packings are buoyant
hut also because of the relatively large size of the packings 26.
By ''relatively large size'' for the packings 26, we mean relative
to the dimensions of the macroparticles present in the waste water
to be treated by the bioreactor. With this last ernbodiment, the
wash water volume required for periodic bioreactor upkeep is kept
to a strict minimum, in view of irnproved efficiency.
