BIOLOGICAL WASTE TREATMENT SYSTEM

SYSTEME DE TRAITEMENT BIOLOGIQUE DE DECHETS

English Abstract

SLUDGE RECYCLE SYSTEM
Abstract of the Invention
An extended aeration system includes a clarifier and
an aeration basin adjacent to the clarifier. Waste inlet means
supply waste to the aeration basin. Outlet means on the
aeration basin supply aerated waste from the aeration basin
to the clarifier. Clarified liquid outlet means remove the
treated water from the clarifier. Concentrated sludge outlet
means on the clarifier are connected to concentrated sludge
inlet means on the aeration basin for recirculating concen-
trated sludge settling from the aerated waste in the clarifier.
A rotary shaft in the aeration basin has an aeration impeller
on it adjacent the top of the aeration basin and a turbine on
it adjacent the concentrated sludge inlet means for pumping
said concentrated sludge from the clarifier to the aeration
basin and for mixing the concentrated sludge with waste in the
basin.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:-
1. An extended aeration system comprising a clarifier;
an aeration basin adjacent said clarifier;
waste inlet means for supplying waste to said
aeration basin;
outlet means on said aeration basin for supplying
aerated waste from said aeration basin to said clarifier;
clarified liquid outlet means for removing the
treated water from the clarifier;
concentrated sludge outlet means on said clarifier
connected to concentrated sludge inlet means on said aeration
basin for recirculating concentrated sludge settling from
said aerated waste in said clarifier;
a rotary shaft in said aeration basin;
an aeration impeller on said shaft adjacent the top
of said aeration basin; and
turbine means on said shaft adjacent said concen-
trated sludge inlet means for pumping said concentrated sludge
from said clarifier to said aeration basin and for mixing said
concentrated sludge with waste in said basin.
2. A treatment system according to Claim 1, wherein
the turbine means comprises an open turbine wheel capable of
creating a low pressure area below its blades.
3. A treatment system according to Claim 2, wherein
said clarifier outlet means is provided with a by-pass to allow
sludge to pass to a drying bed.
4. A process for the biological treatment of waste
material comprising the steps of aerating the waste material
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passing the waste material to a clarifier, running off clarified
effluent to discharge, and pumping the concentrated sludge from
the clarifier to the aeration basin by means of a turbine pump
located in the aeration basin.
5. A process according to Claim 4, wherein part of
the concentrated sludge is by-passed from the clarifier to a
drying bed.
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Description

104666Z
SLUDGE RECYCLE SYSTEM ..
1- sackground and summary of the Invention
This invention relates to biological waste treatment
systems and in particular relates to high rate biological
waste treatment systems.
Biological waste treatment systems envisaged by the
present invention are utilized to treat waste matter having a
demand for oxygen, such as sewerage and industrial effluents,
and destroy the biologically active material in the waste,
which if not so treated would consume natural oxygen in the
10. rivers or streams into which these wastes normally discharge.
! Conventional systems basically consist of a collect-
ing basin, such as a lagoon or a tank, having a bacteria growth
therein which consumes the biological material, and a mechanical
;I aérator which functions to dissolve the quantity of oxygen
necessary to support biological growth and provide mixing to
disperse the dissolved oxygen and to suspend the solids during
aeration. These known systems may have a surface aerator, a
submerged aerator or a combination of both.
¦ Material from the aeration basin passes to a settling
20- tank or clarifier where purified water is allowed to overflow
¦ therefrom and the floc, a conglomeration of bacteria which has
been growing in the aeration basin, is recovered from the
~ bottom of the clarifier in sludge form.
-¦ In what is known as a high rate system some or all of
j the sludge is returned to the aeration basin, whereas in a low
rate system all sludge recovered from the clarifier is pumped
I to waste such as a drying bed. When all of the sludge is -~ - .
returned to the aeration basin this is known as an extended
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`~ aeration system and when some of the sludge is pumped to waste
30. this is known as a standard activated sludge system.
In known systems where some or all of the sludge is
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104~6~2
1. returned to the aeration ~asin this has been accomplished by
providing a separate pumping installation with an inlet to
the aeration basin at or adjacent to the inlet of the waste
material. In systems where compressed air is used for aeration
some of this pressure air has been bled off to an air lift
pump or injector.
It is an object of the present invention to provide
a high rate biological waste treatment system wherein a sepa-
rately driven return sludge pumping installation is eliminated
10. and a common dri~e is utilized for both the aerator and pump,
thus providing a simplified, less expensive apparatus.
According to the invention there is provided a high
rate biological treatment system comprising: a clarifier; an
aeration basin adjacent said clarifier; waste inlet means for
supplying waste to said aeration basin; outlet means on said
aeration basin for supplying aerated waste from said aeration
basin to said clarifier; clarified liquid outlet means for
removing the treated water from the clarifier; concentrated
sludge outlet means on said clarifier connected to concentrated
20. sludge inlet means on said aeration basin for recirculating
concentrated sludge settling from said aerated waste in said
clarifier; a rotary shaft in said aeration basin; and aeration
impeller on said shaft adjacent the top of said aeration basin;
and turbine means on said shaft adjacent said concentrated
sludge inlet means for pumping said concentrated sludge from
said clarifier to said aeration basin and for mixing said con-
;l .
centrated sludge with waste in said basin.
The turbine means may comprise an open turbine wheel
~ capable of creating a law pressure area below its blades so as
;1~ 30. to pump the sludge from the clarifier to the aeration basin.
,1 The outlet means on the clarifier may be provided
with a controllable by-pass to a drying bed if all sludge is
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104~6~Z
1. not to be returned to the aeration basin.
Description of the Preferred Embodiment
In order that the invention and its manner of per-
formance may be more fully described, reference is now made
to an embodiment of the invention as illustrated in the
accompanying drawing.
The drawing is a flow chart wherein waste inlet 10
leads to an aeration basin 12 in which there is an impeller 14
and a turbine pump 16 driven by a common shaft 18 by a motor
10. 20. In aeration basin 12 there is a bacteria growth as is
known.
Material from aeration basin 12 passes through line
22 to a clarifier 24 wherein the purified effluent passes
through line 26 to discharge. The concentrated sludge or floc
is pumped through line 28 to aeration basin 12 by turbine 16.
Turbine 16 also functions to circulate and mix the waste in
aeration basin 12. ,
If desired, the sludge can be by-passed through by-
pas~ line 30 through valve 32 and drying bed 34.
20. It will, therefore, be appreciated that the mounting
of turbine 16 on extended shaft 18 provides a simplified, less
expensive system.
For purposes of example, a two horsepower electric -~
motor rotated a two inch diameter carbon steel shaft at about
seventy revolutions per minute in an aeration basin approxi-
~ mately 168 inches in diameter The impeller consisted of four
J axial flow blades thirty-eight inches in diameter and the tur-
i ., .
bine pump consisted of six lifter turbine blades approximately
twenty inche~ in ~iameter. The mixture in the tank was approxi-
; . . . .
30. mately 120 inches deep with the impeller blades being adjacent
. .'
the top surface of the mixture and the turbine blades being
about one inch aboYe a six inch lip at the base.
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10~66~Z
1. While there has been described what is at present
considered to be the preferred embodiment of the invention,
it will be obvious to those skilled in the art that various
changes and modifications may be made therein without depart- -
ing from the invention, and it is, therefore, aimed in the
appended claims to cover all such changes and modifications
as fall within the true spirit and scope of the invention.
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