AU622527B2

AU622527B2 - Aerobic effluent treatment

Info

Publication number: AU622527B2
Application number: AU51123/90A
Authority: AU
Inventors: Jeffrey Robert Diston
Original assignee: DISTON BUILDERS AND WATER PURI
Current assignee: Diston Builders & Water Purification Pty Ltd
Priority date: 1987-04-13
Filing date: 1990-03-07
Publication date: 1992-04-09
Anticipated expiration: 2008-04-13
Also published as: AU5112390A

Description

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AUSTRALI A PATENTS ACT 0 7 COMPLETE SPECIFICATION

ORIGINAL

(FOR OFFICE USE) Class Int Class Application Number: Lodged: Complete Specification Lodged: Accepted: *o o o *I oPubl ished: 04040 Priority: t Related Art: 0 t C oo a f o I Name of Appl icant(s) P.I.S. T.Q BU.I.L.DP ER.S WATER .PURI.F.I.CAT 1.N P.TY..LTD 9 a It Address of Applicant(s) F.ac.tor.y. t yswater, ictor a, Actual Inventor(s) JEFFREY ROBERT pD Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade, Box Hill, Victoria 3128 Complete specification for the invention entitled: AEROBIC EFFLUENT TREATMENT The following statement is a full description of this invention, including the best method of performing it known to AEROBIC EFFLUENT TREATMENT This invention relates to treatment of effluent and particularly although not exclusively to treatment of sewage.

Domestic and small commercial sewage treatment presents unique engineering problems.

In aerobic treatment plant it is known to provide a rotary disc array which comprises a number of parallel discs on a rotary shaft, the discs being partially immersed in the effluent. As the discs rotate the biomass which develops on the aq oo e 0 discs is raised out of the effluent. Such a plant is shown in o0 1O 4 1, /4-SS 0 .0 o 0 Australian Patent Specification No. 40,15 445 5 in the name of o Scholes.

oooo 0 S o Conveying drive from the shaft to the discs requires a 00 0 secure support particularly since uneven loads on the discs develop.

o"aa* It is an object of the present invention to provide an 0- 00 0000 o°"o effluent treatment apparatus using rotary discs effectively.

0. o0 According to the present invention there is provided an 0 0 aerobic effluent treatment apparatus including a treatment vessel for receiving liquid effluent to be treated, a rotary oo 20 0 aerobic biomass support for providing a support for the growth of a biomass where aerobic treatment of the liquid effluent occurs, the biomass support being mounted to a rotary drive shaft which is substantially horizontal so that the biomass support is in use continually rotated so as to cause different portions of the biomass support to be successively immersed in and raised above the liquid effluent in the treatment vessel, drive means in use operatively coupled to the drive shaft so as to cause rotation of the drive shaft and hence of the biomass p i ii I 1_ _1 support, the biomass support comprising a plurality of substantially parallel discs spaced along the drive shaft, the drive shaft extending through the general centre of each of the discs, and disc support means mounted to the drive shaft and extending radially outwardly from the drive shaft at an end of the array of discs so as to support and transfer drive to the discs.

Preferably the support comprises radial arms extending radially outwardly from the drive shaft, the arms being provided S at spaced intervals around the drive shaft. There may be ,,10, :I t atsae nevl S provided four arms arranged at 900 angular increments around the anulrinreetsarud h drive shaft.

6 C 0 t, The arms may have radially inner ends mounted to a hub located on the drive shaft so that as the drive shaft rotates, 1 the hub and hence the arms rotate to rotate the discs.

o The discs may be substantially circular and made of Door ::te polypropylene.

Soo The effective surface area of each disc is preferably between two and three square metres.

The discs are immersed to a depth of generally half the depth of effluent within the vessel so that there is a substantial volume of liquid in the vessel below the lower edges of the discs in use.

Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawings. However it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. In the drawings: 3 k

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Fig. 1 is a side elevational cross sectional view of a treatment system according to a possible preferred embodiment of the present invention, Fig. 2 is a top plan view of the system of Fig. i, and 5 Fig. 3 is a view along the line A-A in Fig. 2.

The secondary treatment apparatus illustrated is for receiving effluent from a primary treatment apparatus (not shown) such as a conventional septic tank. The secondary treatment apparatus includes a flow regulating volume 11 for C C C C C I receiving influent from the primary treatment apparatus. The flow regulating volume 11 has a volume sufficiently large to IC C create a flow balancing or buffering effect even for above C average incoming flow rates. The secondary treatment apparatus C CC r c¢ further includes a main treatment volume 21 for continually 15 receiving liquid from the flow regulating volume 21 normally at a measured rate and an elevating means 15 operative to raise liquid from the bottom of the flow regulating volume 11 and to pass the liquid to the main treatment volume 21.

0 C The flow regulating volume 11 is in the form of a flow 20 regulating compartment having an inlet 12 in use receiving 20

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influent from the septic tank. This may be by gravity flow.

The flow regulating or buffer compartment 11 has a relatively large volume for providing the flow balancing effects and preferably has a volume in excess of a quarter and preferably between quarter and three quarters of the total average single day's flow with which the system is to be usable. Preferably the buffer compartment 11 has a volume equal to or greater than about one half of the total average day's flow. For example the buffer compartment 11 may have a capacity of say 500 600 4 L-4 i-L litres in a system for treating an average daily flow of a thousand litres.

Expressed in another way, the volume of the buffer compartment 11 is sufficient to store all major surge loadings from the primary treatment system (septic tank). This capacity includes taking account of the continuous steady removal rate, 1 litre per minute). With such a buffer compartment capacity, the effect of spreading the total daily Flow and all surge flows within the normal 12 to 16 hour period of household 09 00 water usage is achieved. No surge flows pass to the main o Soo o0: treatment compartment 21.

o In any event, the buffer compartment volume 11 is chosen so o 00 0 S0, that the flow from an average domestic sewage installation can oo be regulated so as to produce a substantially constant feed flow rate to the main treatment volume 21 regardless of normal .000 diurnal flow variations and reasonably expected extraordinary 0 flow variations. This will result in substantial immunity of 0 0 Sthe treatment system to surges in flow through the primary treatment system.

The main treatment volume 21 may be of any suitable construction and operation. For example, the main treatment volume 21 may be a single or compartmentalised tank 22 having for example a volume of say 1500 2000 litres and a retention 4,period of say forty hours. The tank 22 is provided with 25 rotating biological disc treatment apparatus 23. This comprises a series of substantially parallel circular polypropylene discs spaced along a substantially horizontal rotary shaft 24. The discs are arranged to be approximately half or a little less than half submerged in liquid in the main treatment tank 22.

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ki' i i i The discs are rotated by the means of a drive means 30 coupled to the shaft 24, the rotation being at a relatively slow rate to provide conditions for growth on the discs of a biomass active in aerobically treating the effluent and reducing its BOD. The effective surface area of each disc may be say 2 to 3 square 5 metres.

The drive to the discs is conveyed from the shaft 24 by the four radial arms 25aarranged at 900increments around the shaft.

The arms 25aare mounted at their inner ends to the hub 26aon the shaft 24. The arms 24atherefore support and drive the discs generally at their outer peripheries.

The main treatment tank 22 discharges into a settlement tank C c 35 where sludge is allowed to settle under quiescent conditions.

00* C The settlement tank 35 may have a volume of say 500 1000 litres. Supernatant liquid can be withdrawn through discharge 15 port 39 for discharge after chlorination if required. Sludge °o can be recycled via line 36 and return pump 37, say to the primary treatment apparatus, e.g. under timer control as is known in the art.

The elevating means 15 associated with the flow regulating o" volume 11 comprises an elevating pump 16 having an inlet 17 located at the bottom of the flow regulating volume 11 and an outlet 18 through which pumped liquid is discharged into the main treatment volume 21. The provision of a pump 16 will enable liquid to be lifted from any depth as may be required so that the preferred system of the present invention which is provided with an elevating pump 16 can be ultilised with deeper or shallower flow regulating volumes 11 as may be dictated by the installation requirements. These variations in possible depths of the flow regulating volume 11 need not be accompanied by other dimensional changes, particularly width changes as is necessary with a rotary bucket arrangement.

The elevating pump 11 is preferably a reciprocating pump.

For example the reciprocating pump 11 may comprise a piston movable within a cylinder, the piston being operable to draw H liquid into the cylinder through an intake valve during a suction stroke and to discharge taken up liquid through a discharge valve during a compression stroke. The cylinder 0 0 0 O o o within which the piston of the preferred embodiment is movable i is preferably provided with a relatively large bore diameter, 000000 0i 0 9 e.g. of the order of 100 150mm in order to provide the 0 V4 S 0, required effectiveness and enable simple operation and maintenance. The cylinder for example may be made of a plastics material such as PVC. The intake and discharge valves may be o° for example generally conventional PVC flap valves provided in 0000 o say 32 50mm diameter plastics tubes opening into the cylinder. These valves may be flap valves to provide for long 0 a life and resistance to clogging.

The reciprocating pump 11 may be driven from the same drive S means 30 which is operative to drive the shaft 24 on which the treatment discs are mounted. This shaft 24 for example may .1 rotate at say 2 3 rpm. The piston may be reciprocated by means of a connecting rod 25 extending from the piston to a 25 crank point 26 eccentrically located relative to the axis of rotation of the shaft 24 whereby as the shaft 24 rotates the connecting rod 25 causes the piston to reciprocate within the piston. The liquid may be pumped at a rate of say 1 litre per Sminute which will be sufficient to pump in excess of 1000 litres Iper day to the main treatment volume 21.

7 The drive means 30 may be of any convenient construction and operation. For example the drive means 30 may comprise an electric motor 31 mounted preferably above ground level so that flooding of the associated tank will not flood the electric motor. Drive from the electric motor 31 to the rotary shaft 24 may be conveyed say by means of a gearbox 32 and pulley or toothed belt 33 or other suitable drive arrangement.

Briefly the operation of the total system is as follows.

Raw sewage flows say by gravity into the primary septic tank 00 0 where the waste undergoes settlement and anaerobic digestion 0 before the effluent passes into the secondary treatment system.

1 o* In this system the rotating biological contact chamber 21 l e e provides discs which rotate through the effluent and through air 0*0 alternately. Biological stabilisation of the effluent then occurs by means of the biomass that grows on the disc surfaces.

The treated effluent and resulting sludge then passes into the settlement tank (humus tank) 35 where supernatant liquid is drawn off by means of a 100mm diameter P.V.C. junction. The t4 effluent is then discharged into the nearest stormwater drain.

Chlorination of the effluent can be carried out by an additional c s c contact tank and chlorinator device, if and when required by local health authorities. The settled sludge in the settlement tank 35 can be returned nightly to the primary sewage tank under timer control.

It will be seen that the preferred embodiment of the secondary effluent treatment system according to the invention as well as the overall treatment system can be relatively simple and robust in construction and effective in operation. The secondary treatment system provides for aerobic effluent 1i; 4 treatment using well supported and positively driven circular discs on which an aerobic biomass develops.

It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiment(s) of the invention as herein described without departing from the spirit and scope of the invention as defined in the appended claims.

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Claims

2. Treatment apparatus as claimed in Claim 1 wherein the oo support comprises radial arms extending radially outwardly from the drive shaft, the arms being provided at spaced intervals around the drive shaft.
3. Treatment apparatus as claimed in Claim 2 wherein there are 25 provided four arms arranged at 900 angular increments around the drive shaft.
4. Treatment apparatus as claimed in Claim 2 or 3 wherein the arms have radially inner ends mounted to a hub located on the drive shaft so that as the drive shaft rotates, the hub and Shence the arms rotate to rotate the discs. Treatment apparatus as claimed in any one of the preceding claims wherein the discs are substantially circular and made of polypropylene.
6. Treatment apparatus as claimed in any one of the preceding claims wherein the effective surface area of each disc is between two and three square metres.
7. Treatment apparatus as claimed in any one of the preceding claims wherein the discs are immersed to a depth of generally half the depth of effluent within the vessel so that there is a substantial volume of liquid in the vessel below the lower edges 00 of the discs in use. o00*
8. Treatment apparatus as claimed in any one of the preceding c claims and substantially as herein before described with particular reference to the accompanying drawings. 099 0 K a 0 2 t .4 cc r r t C t 9 c Dated this 6th day of March, 1990 PATENT ATTORNEY SERVICES Attorneys for DISTON BUILDERS WATER PURIFICATION PTY LTD