TRAITEMENT BIOLOGIQUES DES EAUX USEES

BIOLOGICAL TREATMENT OF WASTEWATER

Description

CA 02247871 1998-09-23
BIOLOGICAL TREATMENT OF WASTEWATER
FIELD OF THE INVENTION
The present invention relates to the treatment of
wastewater and more particularly, the biological treatment
thereof and an apparatus for carrying out the method.
BACKGROUND OF THE INVENTION
The treatment of wastewater is a well known art and
systems for the treatment of wastewater are readily
available. The systems and associated methods range from a
septic tank and drainage field for residential use to high
volume units for urban areas and industrial plants. The
methods may include mechanical operations, chemical
treatment, biological treatment, etc. as well as various
combinations thereof. The present invention is primarily
concerned with the biological treatment although the same
may be combined with others.
In the biological treatment of wastewater, it is
desirable to provide for effective treatment which reduces
the pollutants in the wastewater and particularly nitrogen
and phosphorus compounds. It is also desirable to provide
for treatment wherein process parameters are maximized and
treatment times are minimized.
According to the present invention, there is
provided a method of treatment wherein means are provided
for adding microbial material to the treatment process and
wherein the microbes or bacteria are activated prior to
their addition to the process.
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CA 02247871 1998-09-23
In conventional use, the bacteria are available in a
liquid preparation or a dehydrated powder. They are
provided as such for storage purposes. In such a state, the
bacteria exists as a spore. Bacterial spores and are in a
resting state which permits them to survive for a long time
until conditions are provided where they become reactivated.
To do so, generally takes several hours during which they
pass through what is known as a latent phase before becoming
active. Also, during the process of drying, a number of the
bacteria are injured and are known as heat injured cells.
As a result, these bacteria require a longer time to
reactivate and are generally weaker.
In the present invention, one ferments the bacteria
and injects the ferment into the used water. In doing so,
one can choose the appropriate conditions for each situation
and one can produce in an economical manner large quantities
of bacterial cultures which are capable of immediately
working without any reactivation period.
If the bacteria are not utilized immediately, the
culture may be cooled rapidly and used within a certain
period of time, generally within 48 hours.
The method may be used in any convention biological
wastewater treatment. Such treatments will include those
where in the wastewater is passed through a plurality of
treatment cells known as trickle filter cells. It may also
be used in those types of systems using rotating biological
contacting members such as are known in the art.
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Having thus generally described the invention,
reference will be made to the accompanying drawings
illustrating an embodiment thereof, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view, in schematic
form, of a wastewater treatment system according to the
present invention; and
Figure 2 is a graph showing the growth of the
bacteria prior to the addition of the wastewater treatment
system.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Referring to the drawing in greater detail and by
reference characters thereto, the illustrated system
includes a first sedimentation or decantation tank generally
designated by reference numeral 10. Basin 10 includes a
wastewater inlet 12 and an interior dividing wall 14
separating the basin into first and second sessions 16 and
' 18 respectively. From second section 18, an overflow
conduit 20 permits passage of fluid to an aeration basin
which is generally designated by reference numeral 24. A
gas outlet conduit 22 extends from the upper portion of
basin 10 for reasons which will be discussed hereinbelow.
At aerator basin 24, there is provided a basin
having a submersed aerator 26 in order to provide maximum
oxygenation to the wastewater and to help maintain the
suspended solids in suspension. A pump 28 pumps the
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CA 02247871 1998-09-23
wastewater through a fluid outlet conduit 27. A gas
outlet conduit 29 is also provided from the upper portion
of basin 24.
The invention utilizes a treatment station which is
generally designated by reference numeral 30. Treatment
station 30 includes a first cell 32 having a basin 34
therebelow. Mounted within basin 34 is a pump 36 to pump
the wastewater received from conduit 37 up through conduit
38 to the top of cell 32. Mounted within cell 32 are media
(not shown) to provide for the growth of bacteria as the
wastewater trickles down therethrough (a trickle filter).
Basin 34 includes an overflow conduit 40.
Overflow conduit 40 communicates with a second basin
44 of a second cell 41. In a manner similar to that of
first cell 32, there is provided a pump 46 in a basin 44 to
pump the wastewater fluid to the top of cell 42. Again,
cell 42 is a trickle filter having a plurality of media
therein.
An overflow conduit 50 is in fluid communication
with a third basin 54 forming a part of a third cell 52. As
was the case with the first two cells, there is provided a
pump 56 to pump the wastewater up conduit 58 to the top of
third cell 52. Third cell 52 also contains a media as has
previously been described.
From basin 54 of third cell 52, there is provided an
overflow conduit 60 which is preferably gravity fed and
wherein the wastewater flows in the direction as indicated
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CA 02247871 1998-09-23
by arrow 61 to a denitrification basin 62. Within
basin 62 there is provided a pump 64 which is adapted to
pump solids therefrom from a conduit 66 to an anaerobic
dephosphorization treatment basin generally designated by
reference numeral 68. Water flows by gravity from overflow
conduit 70 between basins 62 and 68.
Basins 62 and 68 are sized to have a capacity
roughly equivalent to 1 1/2 hours of fluid treatment. A
pump 72 in basin 68 is adapted to pump solids or the sludge
to conduit 74 to a solids storage container 76.
It will be noted that container 76 has a gas outlet
78 associated therewith. In a similar manner, there are
provided gas outlets 80 and 82 associated with basins 62 and
68 respectively. Gas outlets 22, 29, 78, 80 and 82 are
adapted to feed gases emanating from their respective basins
or containers to a gas inlet conduit 84 associated with
first cell 32. By so doing, gases from these containers are
released therein and tend to be dissolved within the action
of first cell 32.
From anaerobic basin 68, fluid is pumped by means of
a pump (not shown) through a conduit 86. In turn, a
portion, (preferably in the area of 10% - 25%) of the liquid
from conduit 26 is fed through a conduit 88 which is in
fluid communication with aerator basin 24. The remaining
portion (approximately 75% - 90%) is fed through conduit 90
to a basin 94 associated with a fourth cell 92. Fourth cell
92 is a trickle filter also contains a plurality of media;
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liquid is pumped from cell 94 by means of pump 96 through a
conduit 98 to the top of the cell.
An overflow conduit 100, in the illustrated
embodiment, is in fluid communication with a basin 104 of a
i fifth cell 102. Fifth cell 102 is preferably filled with a
I
peat moss. As shown, a pump 106 pumps fluid through
conduit 108 to the top portion of cell 102 from where the
wastewater may filter therethrough.
At the bottom of cell 102, there is provided a
discharge conduit 110 in fluid communication with a final
treatment station 112. Station 112 is a UV treatment
station; from there, the treated wastewater is discharged
through conduit 114.
The invention comprises the use of a fermenter 120
which has an outlet conduit 122 leading to a pump 124. From
pump 124, a conduit 126 provides for recirculation of the
material into fermenter 120.
In operation, the mother stock of the microbes is
introduced into fermenter 120 where suitable conditions are
provided for multiplication of the microbes - i.e. a
suitable nutritive material along with appropriate pH and
temperatures. The solution is recycled to maximize the
increase in the microbes.
As shown in Figure 2, the microbial population
initially goes through a lag phase (prior to line A-A)
followed by an expenditial increase in the microbial
population at which point it maximizes as shown by line B-B.
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Preferably at this point in time, or soon thereafter, the
microbial population is pumped from pump 124 through conduit
128 to one of the cells or treatment tanks.
It will be understood that a multiplicity of such
fermenters may be employed that each such fermenter may
include a specific bacteria or a bacteria mix appropriate
for a suitable phase of treatment.
It will be understood that the above described
embodiment is for purposes of illustration only and that
changes and modifications may be made thereto without
departing from the spirit and scope of the invention.

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