CA1046662A - Biological waste treatment system - Google Patents

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.

Description

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 ;,~i `~ 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 .; ' 1 ' ~ ' ' . . . .
.~ , 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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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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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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Claims (5)

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 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.