AU715076B2 - Improvements in separators for waste water and other liquids - Google Patents

Description

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: S.

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Complete Specification-Lodged: Accepted: Lapsed: Published: Priority 'pN9040 Related Art: Name of Applicant: TO BE COMPLETED BY APPLICANT SEPA Waste Water Treatment Pty. Imi ted (ACN 002 596 509) 13 Cawarra Road, CARINGBAH NSW 2229 Roger Andrew MiLnshull Address of Applicant: Actual Inventor: Addaress for ~Service: ANDERSON-TAYLOR ASSCIATES, Registered Patent Attorneys of 10 Harrison Avenue BONNET BAY N.S.W. 2226 Complete Specification for the invention entitled: IMPROVEMENTS IN SEPARATORS FOR WASTE WATER AND OTHER LIQUIDS The following statement is a full description of this invention, including the best method of performing it known to me: -1- This invention relates to separators for use with mixtures of liquids and/or suspended solids in liquids. More particularly although not exclusively it discloses an improved apparatus for separating out oil and/or suspended solids from waste water.

Existing apparatus of this kind and in particular large volume oil separators commonly use a tilted plate cross flow arrangement. The oil water mixture is passed horizontally in laminar flow between plates whereby the droplets coalesce and rise at right angles to the flow and the solids fall out in the opposite direction. While such configuration works satisfactorily in large scale installations small scale separators having flow volumes of less than about 10 litres per second when constructed in this form become unduly complex and expensive for the performance obtained. While it is known to use less complex tilted plate configurations having either downflow or upflow operation each of these has distinct disadvantages stemming from the inhibiting effects of a unitary flow direction on the separation process of the oil and solids.

It is therefore an object on this invention to ameliorate the aforementioned disadvantages and accordingly there is disclosed an apparatus for separating out a first liquid from a mixture formed with a second heavier liquid, said apparatus including a plurality of plates arranged within a tank at an acute angle to the vertical, means for introducing from an inlet a substantially laminar flow of said mixture downward between respective ones of a first substantially parallel series of said plates and upwards between respective ones of a second substantially parallel series of said plates whereby in operation of said apparatus the plates are submerged and during flow between the plates said first liquid substantially separates out toward a location above said plates, first and second weir means for subsequent drainage and separate discharge of said first and second liquids from said tank and means for collecting any solids separating out from said mixture.

Preferably said plates are disposed within the tank at an angle of from about 30 degrees to about 60 degrees to the *e vertical.

*0.o0 It is further preferred that the height of said second weir is chosen so that the liquid level in the tank is above said plates.

It is further preferred that the second weir is adjacent a blocking plate extending down into the tank whereby said second liquid has to flow downwardly and under said blocking plate to reach said second weir.

The currently preferred form of this invention will now be described with reference to the attached drawings in which: Figure 1 Figure 2 Figure 3 Figure 4 is a schematic cross-sectional side view of an oil water separator according to this concept, is an end elevation view of the separator from the direction A in figure 1, is an end elevation view of the separator from the direction B in figure 1, and is a plan view of the separator.

oooo a Referring first to figure 1 the separator may comprise a tank 1 of welded steel, stainless steel, aluminium or plastic (such as FRP) construction. Although the invention is not limited to any specific size, with this embodiment the tank is about 450 mm in width, 1100 mm in length and 400 mm in depth. The upper portion of the tank has mounted therein a plurality of parallel plates 2 which are aligned at about 30 degrees to the vertical and divided by a partition 2A. The invention however is not limited to this particular slope and other angles may be used with advantage. The plates extend completely across the interior of the tank and may attach by any suitable means to opposite side walls 3. To further support the plates within the tank a pair of parallel combs 4 (only one being shown in figure 1) extend transversely across the bottom edges thereof. The untreated oil water inlet 5 to the separator is located adjacent the top at one end of the -4tank and empties first into a flow averaging and grit separation box 6. The oil water mixture then spills over plate 7 where it passes in laminar flow down between the first series of plates designated C. During this passage between the plates some of the oil colloidal particles coalesce into larger droplets and rise to the liquid surface 8 adjacent the top of the tank. The suspended solids such as sand and grit also fall out from the liquid as the flow subsequently passes through the collection hopper 9 (see arrow 9A) at the base of the tank before passing back upward in laminar flow through the second series of plates designated D. During this passage the remaining small suspended oil droplets coalesce to larger droplets on the underside of the plates and then rise with the flow to collect in a layer 10 on top of the liquid surface 8. The treated substantially oil free water below 00 *0 "the surface 8 then flows over plate 11, beneath the oil blocking plate 12 and out the exit weir 13. Preferably this exit weir 13 includes a threaded collar 14 which is adjustable so that the height of the water surface 8 is sufficient to cause the top layer of oil 10 in the right hand sections of the tank (as shown in figures 1 and 4) which has accumulated from both series of plates 2 to spill out through a common exit weir Preferably the hopper 9 also has an outlet 16 to empty accumulated sediment from the bottom of the tank.

It has been found that by combining both downflow and upflow of a liquid mixture between separation plates together with a common oil collection weir a relatively small high performance oil separator can be produced at a much lower cost than prior art devices. Clearly however the example described is only the currently preferred form of this invention and a wide variety of modifications may be made which would be apparent to a person skilled in the art. For example the shape of the tank, the angle and number of the plates as well as the materials of construction may all be changed according to application .or design preference.

For the purposes of this specification expressions such as "downward", "upward", "above", "below', "bottom", "top" and "vertical" etc. refer to the apparatus in a position of use as illustrated in figure 1 for example and are not to be read as necessarily limiting.

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Claims (12)

1. An apparatus for separating out a first liquid from a mixture formed with a second heavier liquid, said apparatus including a plurality of plates arranged within a tank at an acute angle to the vertical, means for introducing from an inlet a substantially laminar flow of said mixture downward between respective ones of a first substantially parallel series of said plates and upwards :between respective ones of a second substantially parallel series of said plates whereby in operation of the apparatus said plates are submerged and during said flow between the plates said first liquid substantially separates out toward a location above said plates, first and second weir means for subsequent drainage and separate discharge of said first and second liquids from said tank a. a. °o°0 and means for collecting any solids separating out from said mixture.

2. The apparatus as claimed in claim 1 wherein said means for collecting any solids comprise a hopper located below said plates so that the mixture flows through said hopper during passage from the first to the second series of said plates.

3. The apparatus as claimed in claim 2 wherein said plates are disposed within said tank at an angle of from about degrees to about 60 degrees from the vertical.

4. The apparatus as claimed in claim 3 wherein said first weir is located above said plates.

The apparatus as claimed in claim 4 wherein said second weir is located to one side of said plates and adjacent a blocking plate extending down into the tank whereby said second liquid has to flow downwardly and under said blocking plate to reach said second weir.

6. The apparatus as claimed in claim 5 whereas said second weir is adjustable to vary the level of liquid in said .tank. ee e

7. The apparatus as claimed in claim 6 wherein said means for introducing a substantially laminar flow comprise a flow averaging box immediately downstream of said inlet.

8. The apparatus as claimed in claim 7 wherein the first series of said plates is parallel to the second series of said plates and is divided therefrom by a partition.

9. The apparatus as claimed in claim 8 wherein said plates extend across the internal width of said tank and attach to the sides thereof.

The apparatus as claimed in claim 9 wherein said plates are further supported by a comb means which extends transversely across the bottom edges thereof.

11. The apparatus as claimed in any one of claims 1 to wherein said first liquid is oil and said second liquid is water.

12. An apparatus for separating out a first liquid from a mixture formed with a second heavier liquid, said apparatus being substantially as described herein with reference to the drawings. Dated this Z7 day of 7A-49 1997 U SEPA WASTE WATER TREATMENT PTY. LIMITED By Our Patent Attorney MICHAEL ANDERSON-TAYLOR U U U U*