Improvements in or relating to the recovery of effluent

Abstract

 Apparatus for and a method of recovering light effluent from water in a collection pool (5), flowing the effluent and some water over the upper edge of a wall of a catchment tank (6) located in the collection pool (5), and removing the effluent and water from the catchment tank (6). At least the upper edge (7) of said wall of the catchment tank (6) may be adjustable vertically.

Description

[0001] This invention relates to the recovery of effluent and more particularly the recovery of light effluent such as oil which has a density less than and is immiscible with water from contaminated waste water outlets from industrial plant such as for example a steel plant.

[0002] It is environmentally desirable and frequently required that surface or process water from industrial or similar plant areas should carry little or no oil when leaving the plant and entering natural waterways. This requirement presents serious difficulties with a number of industrial plants such as steel mills involving the use or production of considerable quantities of oil in association with subsequently discharged water. This is particularly true in the case of steel works, from coke ovens and rolling mills.

[0003] Previous proposals for the removal and indeed the recovery of oil from water have included amongst other things, filtration, chemical treatment and oil skimmers.

[0004] However, such arrangements have proved unsatisfactory because of'remnant constituents in the effluence, such as benzene and suspended solids, for example. In addition recovery rates have been found to be unsatisfactorily low and indeed have tended to be so low as to be useless.

[0005] An alternative proposal has been the use of a bowser or gulley suckel arrangement for removing oil contaminated water from the upper portion of a container or conduit of water. However such an arrangement provides an output which can typically include 90% water creating in itself significant further containment and separation problems.

[0006] It is an object of the present invention to overcome or at least substantially reduce these problems.

[0007] In accordance with the invention there is provided apparatus for the recovery of light effluent from a flow of contaminated water and effluent collection pool located in a side/channel from a flowing water channel, a surface boom located at the entrance to the side channel so as in use to direct effluent into the pool and retain it therewithin, a catchment tank located within the pool having a wall upper edge level with or immediately below the lower level of the effluent, a bowser or suction pipe connecting the inside of the tank with a settlement tank hydraulically separate from the channel and the pool, and separate drainage outlets from the settlement tank at different levels whereby the separated effluent and water may be removed therefrom.

[0008] According to another aspect of the invention there is provided a method of recovering and separating light effluent from water comprising the steps of flowing effluent from water along a channel diverting the effluent by means of a surface boom into a side channel to a pool whereat the effluent is caused to flow over the edge of a wall of a catchment tank and from which it is removed by means of a suction pipe to a separation tank, the effluent and water being withdrawn separately from the separation tank.

[0009] In order that the invention may be more readily understood one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a schematic plan view of apparatus for the recovery of oil from contaminated water according to the invention;

Figure 2 is a schematic end sectional elevation of the apparatus of Figure 1; and

Figure 3 is a schematic pictorial representation of the catchment tank of Figure 1.

[0010] In the drawings there is illustrated a drainage channel 1 which in normal usage may be used to transmit water into a river estuary or the sea, from a steel plant. A concrete lined side-channel slipstream arrangement 2 is constructed parallel to the channel 1 such as to receive effluent which may be present on the water from the channel. A steel boom 4 is placed diagonally across the channel so as to direct oil at the upper surface into the slipstream.

[0011] The slipstream 2 connects with a collection pool 5 within which is located a catchment tank 6 comprising a rectangular steel container having an open top, the upper walls 7 of the catchment tank 6 being just below the surface 8 of the oil/water level in the pool 5. Control of the level of the catchment tank is by means of a screw threaded supporting rod 9 controlled by a handle 10 and passing through appropriately threaded bores in an overhead support frame 11.

[0012] A suction pipe (not shown) is arranged to transfer oil and water from the catchment tank to a separating tank 12 located adjacent thereto. The separating tank 12 is provided with an outlet 13 for oil and an outlet 14 for water, the outlet for water draining into a return channel 15 to the pool, the pool itself being provided with a return pipe 16 to the channel downstream of a level changing weir 17 in the channel so as to ensure flow.

[0013] In practice oil contaminated water flows down the channel 1. The upper portion of the water together with its oil coating is deflected by the steel boom 4 into the slipstream 2 and adjacent pool 5. In the pool the oil and a slight upper part of the water flows into the catchment tank 6 and is then transferred via the suction pipe to the separating tank 12 whereat the oil and water are gravity separated, the water being returned to the pool whilst the oil is collected in separate tanks for cleaning and recycling in the Plant concerned.

[0014] The invention provides a simple effective and environmentally safe method of recovering oil or other effluent with a specific gravity of less than 1 and which is immiscible with water.

Claims

1. Apparatus .for the recovery of light effluent from contaminated water comprising a water and effluent collection pool, a catchment tank located within the pool having the upper edge of a wall level with or immediately below the lower level of the effluent within the pool, and means for removing from the catchment tank effluent and water flowing over said upper edge of the wall into the catchment tank.

2. Apparatus according to claim 1 wherein the upper edge of the wall of the catchment tank is adjustable vertically.

3. Apparatus according to claim 2 wherein the catchment tank itself is adjustable vertically.

4. Apparatus according to any one of the preceding claims wherein the means for removing effluent and water from the catchment tank comprises a bowser or suction pipe.

5. Apparatus according to any one of the preceding claims including a settlement tank to which effluent and water removed from the catchment tank is delivered, the settlement tank having separate drainage outlets at different levels whereby the separated effluent and water may be removed therefrom.

6. Apparatus according to any one of the preceding claims wherein the collection pool is arranged to carry static or slow moving water and effluent.

7. Apparatus according to claim 6 wherein the collection pool is located in a side channel from a flowing water channel, and a surface boom is located at the entrance to the side channel so as to direct, in use, effluent into the pool and retain it therewithin.

8. A method of recovering light effluent from water comprising the steps of collecting effluent and water in a collection pool, flowing the effluent with some water over the upper edge of a wall of a catchment tank located in the collection pool, and removing the effluent and water from the catchment tank.

9. A method according to claim 8 wherein the level of the upper edge of the wall of the catchment tank is adjustable.

10. A method according to claim 8 or 9 wherein the effluent is recovered from moving water, in which the effluent contaminated water is passed along a channel, and the upper portion thereof including the effluent is diverted by means of a surface boom into a side channel to said collection pool.

11. A method according to claim 8, 9 or 10 wherein the water and effluent in the collection pool is static or slow moving.

12. A method according to claim 8, 9, 10 or 11 wherein the effluent and the water is removed from the catchment tank by means of a suction pipe to a separation tank, the effluent and water being withdrawn separately from the separation tank.

Drawing