Method and apparatus for removing oily materials and floating matters in general from the surface of bodies of water

Removal from the surface of bodies of water of oily and floating matters is conducted by preliminarily increasing the concentration of the oily and floating matters in the upper water layers by separating a liquid surface layer sufficiently thick to contain substantially all of the oily and floating matters, simultaneously giving the separated layer a relative speed so as to forward it to subsequent treatment steps with a minimum of or no turbulence, and introducing the separated layer into a basin having a horizontal size relative to the cross-section where the initial separation occurred such as to substantially reduce the relative velocity of the liquid flow, where the level of the liquid in the basin is kept near to the average level of the body of water outside the basin. The water in the basin is caused to have a downward flow direction by sucking from the bottom of the basin, leaving the already separated oil at the surface, thereby increasing its concentration. An upper liquid layer is then withdrawn from the basin surface. The upper liquid layer is forwarded to further decantation treatment where the liquids withdrawn from the surface layers are passed at low speed through an array of communicating tanks from which the water deposited at the bottom is sucked out and discharged while the oil is withdrawn and sent to store. An apparatus facilitating the method and the present invention is also disclosed.

FIELD OF THE INVENTION 
This invention concerns a method for removing oily materials, and floating 
matters in general, from the surface of bodies of water, as well as an 
apparatus whereby said method can be put into practical use; both method 
and apparatus being particularly suitable to operation even on rough sea. 
BACKGROUND OF THE INVENTION 
A large number of methods and apparatus are known for removing oily and 
floating waste (which in the following disclosure will be simply 
designated in general as "oil") from the surface of bodies of water, and 
in particular from the surface of the sea, of lakes and rivers. For 
exemplary purposes, reference if made to the method and apparatus 
described in GB-A-1 206 794, DE-A-2 931 795 and U.S. Pat. Nos. 4,119,541 
and 3,684,095. However, said methods and apparatus already known in the 
art, have considerable drawbacks, and particularly the following: 
a) a very low collecting efficiency, further remarkably reduced if an even 
slight wave motion is present; 
b) the oily floating waste is obliged, since already the first step of the 
process, to pass through a level drop from the sheet of water containing 
the floating matter to be removed, to the fluid surface within the 
apparatus performing the process (see U.S. Pat. No. 4,119,541). As a 
consequence emulsifying and stirring actions are produced between oily 
matter and water, being previously perfectly separate, one floating over 
the other, and the effects of these actions have to be subsequently 
reduced or counteracted thus negatively affecting the efficiency and 
adding to the structural complexity of the apparatus. For example 
according to the above-mentioned U.S. patent it is necessary not only to 
provide anti-emulsion plates 5, 5a, but also to cause water running zigzag 
with a longer path and to adopt both baffles 14 for maintaining a 
quiescent region and densitometers for detecting a possible content of oil 
carried by water beyond the filter. In order to improve separation and 
stratification of oily matter from water an array of the above-mentioned 
plates 5, 5a is used, the plates being parallel, slanting suitably spaced 
apart and provided with tiny holes; 
c) those methods and related apparatus based on the principle of enrichment 
in oil of the floating matter with water being discharged from the bottom 
and the concentrated oil recovered at the upper layers, such as in U.S. 
Pat. Nos. 4,119,541 and 3,684,095, require a very complex instrumentation 
system to control the level differences with respect to the outside, 
thickness of the concentrated oily layer and percentage of oil in the 
discharged water. Furthermore these instrumentation systems show some 
problems in their setup for operating in a smooth body of water and even 
cannot be used at all when such a body of water becomes slightly rough; 
d) all these known processes accomplish their effect in a single operative 
step, not to be repeated, by subjecting all the fluid under treatment to 
only one type of process without dividing it into successive steps, each 
relating to a different physical treatment specifically required to that 
particular step of the process, thus resulting in a low operational 
flexibility of the overall process. Therefore the known apparatus only 
seldom perform in the best operating conditions; e) remarkable 
transportation problems due to the large size of the apparatus, when they 
have to work in an even slightly rough sea, and the fact that they cannot 
be easily disassembled in order to make their transportation easier; 
f) a high operation complexity which makes absolutely compulsory a 
continuous attendance on board of personnel whose safety often puts a 
constraint to the use of such apparatus, which are further burdened by the 
logistics of said personnel; 
g) unsatisfactory seaworthiness as far as maneuvering and wave motion 
resistance, especially at sea, even when only slightly rough. 
It is an object of the present invention to provide a method and an 
apparatus for removing oily and in general floating waste matter from 
bodies of water, which overcome the above-mentioned drawbacks known in the 
art. 
One of the basic features of the present invention resides in the fact that 
the oily matter floating on the water is concentrated and at the same time 
separated from the greatest quantity of water as possible still before 
having to flow through any passage or level drop device which may cause 
therein some emulsifying and/or stirring action. 
Another basic feature of the present invention is that, contrary to the 
prior art according to which a single, simple process is applied to all 
the fluid under treatment (see point d) above), a complex process is 
applied consisting in a combination of various processes, each of which 
forms systematically part of the global one, is dimensioned according to 
the quantity of fluid to be treated and is provided with the required 
auxiliary equipments which are specifically required. 
A further basic feature of this invention is the fact oily matter removal 
may be performed with a constantly high separating efficiency, even in 
rough sea conditions, and by means of an apparatus whose weight and 
dimensions are relatively limited, at least compared to similar apparatus 
already known in the art. That is possible owing to the fact that, on the 
one hand the collection of the whole amount of oil involved is guaranteed, 
and on the other hand the amount of water subjected with the oil to the 
process is the least possible. A further important aspect of this 
invention, which improves the oil removal efficiency, is the fact that the 
various phases of preliminary separation and surface concentration of the 
oil are performed not only without resorting to the use of differential 
levels or other situations which could produce stirring and/or emulsifying 
in the liquid body, but also providing mechanical means for setting in 
motion the various liquid flows to be passed through by these flows only 
downstream of their final separation, and means adapted to reduce the 
effect of the turbulence induced by the wave motion on the liquid flows 
being treated, in addition to special design features and devices. 
A further feature of this invention is the possibility to be readily 
disassembled in order to make it easily transportable along roads, and 
then assembled again near the usage location. 
Still according to this invention, the process is such that it can be 
followed through automatic and/or radio-controls to the operating 
components of the apparatus wherein it is performed, whereby continuous 
attendance of personnel on board may not be required. In this way it has 
been made possible, on the one hand to provide the apparatus with 
qualities of further reduced weight, and on the other hand to enable the 
apparatus to be used in very rough sea conditions, when the apparatus 
already known would not be able to operate for personnel safety reasons. 
A further feature of this invention is the fact that the oil transfer 
operation to the stocking facilities can be performed simultaneously to 
the forward motion of the apparatus, or while the latter is at a 
standstill, without having to interrupt the collecting operations. 
A further particular advantage of this invention relative to the state of 
the art resides in the possibility to adjust the plurality of operating 
parameters to the variable conditions associated with each particular 
pollution reducing operation, such as the roughness of the sea, the 
density and thickness of the oil layer, the removal velocity, the 
allowable residual pollution, and so on, in order to attain an optimum 
operation flexibility. Finally, the apparatus is highly seaworthy, in 
terms of ability to maneuver and of sea resistance. 
The method according to the present invention is characterized by the 
features recited in claim 1 and the apparatus for putting in practice the 
same is characterized according to claim 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The apparatus according to the invention is comprised of a floating 
structure including substantially five structural bodies among which there 
are two side hulls A of the assembly, located symmetrically relative to 
the longitudinal symmetry plane of the apparatus, which plane is shown in 
chain lines in FIG. 1, said hulls having a substantially elongated and 
narrow parallelepipedal shape, suitably tapered at the front and rear ends 
thereof. It should be noted that in the following description, the 
direction of the apparatus indicated herein towards the left side of the 
figure by arrow F, will be defined "navigation direction", for 
non-operating transfer trips of the apparatus, while the opposite one, 
towards the right side of the figure, shown by arrow F', will be defined 
"collecting direction" and the apparatus moves "astern" in the latter 
direction. 
Between side hulls A there are located three central bodies, and among the 
latter a body shown at B, or basin, being shaped as a generally 
parallelepiped tank with no lid, connected to adjacent bodies A in a non 
rigid, but in a vertically sliding fashion, by means of special guide 
means, with the possibility of being fastened in a particular position. 
FIGS. 3 and 4 schematically show two examples of different trims taken by 
the apparatus, with body B located at two different levels relative to the 
floating line LG, during navigation and during a collecting operation 
respectively. 
Body C, or central hull, is located between the pair of side hulls A, in 
the region towards the navigation direction, and it forms the bow part 
during the transfer operation according to arrow F, while, together with 
said hulls A to which it is rigidly connected by means of disassemblable 
connecting means, known per se (not shown), it also forms the main frame 
of the apparatus which is driven by the pair of propellers shown at D in 
FIGS. 1 and 2. 
Eventually, body M, which substantially accomodates machinery, controls, 
instrumentation, and so on, is connected to the other parts A and C of the 
hull, preferably in a raised position relative to the latter. 
The five parts mentioned above may be disassembled from each other, and 
each one of them is so sized as to make the same normally transportable 
along roads. Bodies A are shaped in such a way as to create a minimum 
disturbance on the fluid flow ahead of basin B, i.e. in the collecting 
channel K. As it is shown in FIG. 2, both bodies A extend vertically below 
the floating line in a lesser measure compared to body C, in order to 
contribute to a wide floating figure with relatively reduced thrust. The 
weights of the apparatus are kept to a minimum and in particular those of 
the side tanks A are concentrated towards the center of gravity, in order 
to reduce the weight moment of inertia, while the floating surface is very 
much extended, in order to increase the geometrical moment of inertia. In 
this way, it is enhanced the ready adaptability of the structure to the 
wave profile so that, especially for the highest waves, the structure 
follows readily the movement, by reducing the difference of level between 
the instant height of the wave and the inlet edge (L.sub.2) of the stream 
into the apparatus. Reducing such a difference (conjointly with the 
reduction that may be obtained through an interlocking relationship of the 
basin height with respect to the wave profile, better explained later) 
involves a reduction of the difference between the average level (L.sub.3) 
of liquid in the basin and the instant one (L.sub.1) of the outside 
surface, varying with the waves, so that if such a difference could be 
zero at each instant no stirring or emulsifying action could occur, 
contrary to an apparatus of the type which, like the one disclosed in U.S. 
Pat. No. 4,119,541, provides for a constant difference of level between 
inside and outside of the basin, even in absence of waves. 
As clearly shown in FIGS. 1, 2, 3 the floating figure is extended ahead 
(according to the direction of arrow F') whereby its center of gravity is 
displaced in the forward direction in order to reduce the radius of the 
rotation the blades 5 or bulkhead P.sub.m would be subjected to by the 
structure oscillation relative to the waves, thereby reducing the 
immersion stroke that higher waves would produce thereon due to the 
rotation of the entire structure. Such an arrangement intends to achieve 
the same result of increasing the readiness of the above-mentioned 
rotation, thus contributing to keep as lowest as possible the difference 
of liquid level between the inside and the outside of the basin (the 
latter according to the wave). 
The space wherein basin B is received is enclosed on the sides and in the 
navigation direction by the walls defining bodies A and C, which extend 
also above the floating line. In order to limit the internal wave motion, 
the basin is divided in a plurality of cells extending for the whole depth 
thereof, and defined by vertical transverse bulkheads P.sub.1, P.sub.2 , . 
. . and longitudinal bulkheads 14 (see FIG. 8) the latter ones of which 
extend also above the floating line, while the transverse ones, except for 
the (outer) one towards F, end below said line, and preferably at a height 
close to that of bulkhead P defining the basin in the working direction. 
Basin B is made vertically movable by known type actuators (not shown) 
whereby it may be positioned either at the two different positions of oil 
transfer or collection, as it is shown in FIGS. 3 and 4, or also, if the 
actuators are controlled by a suitable sensor, that the basin is 
positioned in a continuously variable position in order to follow the 
incoming wave profile. 
Referring now to FIG. 5, concerning the first simplified version of basin 
B, which is shown in longitudinal section therein, there is shown on the 
right the first of a plurality of transverse bulkheads, shown at P, whose 
upper edge is positioned at level L.sub.2 which varies according to the 
vertical motion of a slidable part P.sub.m, or sluice gate belonging to 
said bulkhead P. 
A sensor positioned outside and ahead of the basin, senses suitably in 
advance the variable height L.sub.1 of the incoming outer liquid, and 
adjusts, by means of automatically controlled actuators, the level L.sub.2 
of P.sub.m, whereby the difference L.sub.1 -L.sub.2 is as much as possible 
constant, having a value which can be determined each time by the 
operator. 
The layer of liquid having a thickness L.sub.1 -L.sub.2, which flows over 
sluice gate P.sub.m arrives inside basin B wherein there is maintained an 
average level L.sub.3, lower than L.sub.2 and desirably equal to the 
average level at the outside, from which intakes a high flowrate pump G 
(shown in FIG. 7) through possibly adjustable suction ports F, located 
close to the bottom of the basin. Thereby water withdrawal is obtained 
only from the lower layers, with consequent oil enrichment in the surface 
layer immediately below level L.sub.3. It should be noted that there will 
be provided at least a suction port F in each of the chambers formed 
within basin B by transverse bulkheads P.sub.1, P.sub.2, and so on, in 
communication with each other in the upper region through openings E. In 
this way, in each of the chambers in which the bulkheads P.sub.1, P.sub.2, 
P.sub.3, etc. divide the basin, while the liquid of the upper layers flows 
over said bulkheads the water of the lowest layers is discharged from the 
bottom of the various chambers, water that has reached such layers by 
lowering due to the pump sucking and leaving at the surface the oil from 
which was already separated, as this was stratified in the upper layer and 
concentrated therein. All this without the need for water or oil of 
passing through stirring or turbulence regions, or at the presence of 
means which may cause the two fluids to mix together, thus negatively 
affecting the pre-existing separation. In the passage mentioned above, the 
liquid turbulence, or the motions thereof, are dampened by a device that, 
while not providing a relevant obstacle to the liquid flow directed 
towards the left, above the threshold, substantially prevents a possible, 
even transient backward flow in the opposite direction, in the meantime 
adding to the dampening effect of the wave motion inside the basin. As it 
is shown in FIG. 6, said device is preferably comprised of a rectangular 
sheet or "curtain" 0, extending along the whole threshold width, and 
preferably divided into a plurality of sections, both breadthwise and 
heightwise, which besides covering the whole threshold depth, extends also 
above the average floating level, preferably to a maximum level which can 
be reached by the liquid, in operation, above the threshold. Each one of 
the parts comprising said sheet is made of a very flexible, preferably 
thin and resilient material, substantially sealingly connected along one 
of the horizontal sides thereof, to a member R parallel to the threshold 
edge, and fixedly positioned relative to the structure, whereby sheet 0, 
or the entire assembly of flexible members comprising the latter and 
fixedly connected to points of the structure, when pushed by the flow 
overflowing the threshold to flex at right angles thereto, yields opposing 
only a negligible resistance (see FIG. 6) and when it is pushed, for 
instance by a wave motion internal to the basin, in the opposite 
direction, it is brought first to close the fluid passage above the 
threshold and then, once said position has been reached, it remains 
constrained thereto until there is a push in said direction, by means of 
suitable stops N provided for said purpose. Said stops will be such as to 
give anough strength and rigidity to flexible sheet 0 resting against the 
same, while not introducing any disturbance in the flow above the 
threshold, being for instance under the form of a plurality of stop 
abutments or of a stiff net having suitable wire and mesh size. 
In the latter chamber on the left there is provided a further transverse 
element illustrated as a bulkhead of a variable height by means of sluice 
gate P.sub.n manually or automatically settable in order to maintain the 
upper edge thereof at a level L.sub.4, lower than the average level 
L.sub.3 of the surrounding liquid by an entity determined by the operator. 
The automatic variation may take place through a motion coordinated in 
order to follow continuously and immediately the liquid level 
instantaneously present in the last basin chamber, in order to eliminate 
or to strongly reduce the variations in the threshold immersion depth 
provided by the upper edge of sluice gate P.sub.n for intake in a chamber 
I relative to the instant level in that region of the basin, and 
consequently the variations in the flowrate of the liquid overflowing from 
P.sub.n into I, for admission to the subsequent treatment. In that way, in 
chamber I called also "header" possibly divided in the transverse 
direction, there sets up an incoming flow of an oil/water mixture, very 
rich in oil. 
The liquid entering header I is withdrawn through ports H, under a variable 
flowrate, in order to keep the surface between the levels L.sub.5 and 
L.sub.6, maximum and minimum respectively, at a level suitably selected 
and such that, relative to level L.sub.4 it is lower by a preferably small 
amount, in order to reduce to a minimum the unavoidable, slight turbulence 
induced by the overflowing, but in the meantime large enough to prevent 
substantial backflows of liquid from the header to the basin, caused for 
instance by motions of the structure, or by a wave motion possibly taking 
place within the basin. 
There is provided at least two ports H, one on the right and one on the 
left of header I, and each of them is connected by means of suitable 
diameter hoses to the respective flange, shown at X (FIG. 9) of the first 
tank included in said plurality of tanks U, located on the same side, and 
inside each one of the side hulls A. In the drawings, an array of twelve 
tanks has been shown to indicate that therein not merely a "storing" 
operation is provided but an actual treatment as described in the 
following. Each one of said tanks U, for both arrays, is in communication 
with the following one through passage slots located at the top and at the 
bottom, shown at Q and S respectively, as it is illustrated in FIG. 10. In 
the last tank of each array, a suitable intensity of vacuum is provided in 
order to obtain total filling to the top of the twelve tanks with the 
liquid withdrawn from header I through ports H. The last tank of each 
array is provided with a raised dome, shown at Z in FIG. 9, on top of 
which there are provided pipes for oil and air suction, the automatic 
vacuum control mechanisms, and the liquid surface level indicators, all of 
them being already known. While the vacuum is maintained, also a total 
filling of the twelve tanks U with an oil/water mixture is maintained. 
This is only a small fraction of the total mass of liquid entering the 
basin B over the separating element P.sub.m, whereby it has a very small 
flowrate and due to the long, slow, non turbulent crossing through the 
array of tanks, enables only oil to concentrate at the top, and only water 
to concentrate at the bottom. If water is withdrawn from the lower part of 
the last tanks U, through flanges Y (FIG. 9), the top portion of the same 
tanks will fill up with oil. The separation surface between water and oil 
will actuate, at a predetermined minimum position, the start and suction 
from dome Z, of an oil transfer pump, while the pump stop will be 
controlled by a signal derived from the maximum predetermined level of 
said surface. In fact, since the tanks communicate with each other also at 
the top, the oil/water separation surface comes to the same level in all 
the tanks U, and since only a single withdrawal position is sufficient for 
the suction of the collected oil, it will be possible to transfer the oil 
from the tanks even without interrupting the collecting operations. In 
addition, the fact that all the tanks are full of liquids, results in 
preventing both trim variations and reduction in stability which could 
reduce the speed with which the structure adjusts to the tallest waves, 
besides possible turbulence and shocks within said tanks, what would 
hinder the separation water/oil. 
Oil withdrawal through tank Z can be performed by connecting the top 
portion of the tanks, by means of lines of pipe, with a small sump, 
preferably provided at a lower level compared to the water level 
maintained within header I, whereby the oil can flow thereto even only 
under the action of gravity. From said sump the oil is withdrawn by means 
of a pump, controlled according to known techniques, by two level 
indicators in order to control oil transfer towards the final oil stocking 
containers, so that, when the amount of oil contained in tanks U goes over 
a certain value, one of the sensors actuates the transfer start, and when 
said amount falls below another predetermined value, the second sensor 
controls the transfer stop. It should also be clear that, by decreasing 
the pressure within the system of tanks with respect to the atmosphere 
weighing on the basin, the level of the liquids contained therein can be 
made to rise above the one previously indicated, and possibly even above 
the basin level, being then possible to increase the useful height of the 
tanks mainly in order to increase the decanting and stocking capacity 
thereof. The purpose of this vacuum is clearly different from that used in 
DE-A-2 931 795, wherein air intake is only for sucking air collected in 
the chamber 40 and the suction therein has only the aim of causing the 
fluids to flow without passing through a pump or another device which 
could stir or whirl the mixture. In practice, in said raised dome Z on top 
of the last tank of each array in both hulls A, there is provided both the 
air suction outlet necessary to maintain said vacuum, and underneath the 
latter the collected oil withdrawal pipe, as well as the fittings for the 
level indicators and controllers. Furthermore, dome Z is also a 
liquid-filled volume which, like a plenum or a reservoir, compensates the 
level variations caused by changes in the incoming flow from header I, and 
by changes in water outgoing flow through bottom flange Y. 
Referring now to FIGS. 7 and 8, there is shown in more detail therein a 
preferred embodiment as an example of the simplified and more general form 
of basin B shown in FIG. 5. P is still the front wall enclosing basin B on 
the front side, while the internal transverse walls are shown as 8. On the 
upper edge of P there slides an arc-shaped gate 1, substantially like a 
portion of a cylinder surface, extending all the way towards the floating 
surface. Gate 1 is hingedly connected to a stationary transverse shaft 2 
by means of arms 3, radially converging toward the latter. At the upper 
end of movable gate 1 there is pivoted, along a shaft 4 parallel to shaft 
2, a blade-like or blade member 5 facing out from the basin, and in 
particular towards the region shown at K in FIG. 1. In addition, blade 5 
is rigidly connected to a system of floats 6 (and of springs not shown in 
detail), which keep the floats submerged on the average for about one half 
of the volume thereof. In that way, blade 5 is kept in a horizontal 
position, at a determined level L.sub. 2 &lt;L.sub.1, which can be set in 
advance by known means, already mentioned above, while describing the 
embodiment of FIG. 5, with ample possibility to move vertically, as 
allowed by the hinged connection relative to shaft 2, below floating 
surface L.sub.1. In such a way, the average thickness of the liquid layer 
L.sub.1 -L.sub.2 above blade 5 is kept relatively constant, independent of 
the wave profile. Any vertical translation impressed to blade 5 causes 
therefore a corresponding motion of wall 1 which slides tangentially and 
substantially sealingly along the upper edge of first wall or bulkhead P. 
Therefore, on the one hand blade 5 is able to freely follow the wave 
motion while on the other hand a relative sliding is provided between wall 
1 and the edge of the vertical gate, in a substantially scaled fashion, 
and without any relevant friction. 
The blade 5 and gate 1 assembly corresponds to the sluice gate P.sub.m of 
FIG. 5. Blade 5 is a member effecting a first separation of the liquid 
layer to be admitted to the basin, and it must remain substantially 
horizontal, while being able to perform vertical traverse motions, at 
right angles to the plane thereof, along part of an almost vertical 
circular path required by rotation of the rear supporting body comprising 
gate 1. Stationary wall P shields the lower portion of member 1 from the 
dynamic pressure of the water in that the upper edge is located at a very 
short radial distance from the cylindrical surface of said member, in 
order to ensure a good sealing against the entrance in the basin of water 
passing between the movable member 1 and the stationary part P. 
It should be noted that the separating member, or blade 5, can be supported 
by a rear member 1 which, instead of having the shape of a cylindrical 
surface, has a substantially flat vertical shape, as shown schematically 
at P.sub.m in FIG. 5, constrained to slide in a parallel direction along 
stationary part P, with a minimum clearance, possibly providing known type 
seals, in order to improve the sealing action, and preferably a 
servomechanism of known type for actuating the whole system, so that the 
position of blade 5 readily follows, with little deviation, the varying 
wave level. 
According to a further embodiment, the motion of blade 5 may be different 
from the substantially vertical one permitted by float 6. In fact, said 
blade may be pivoted directly on the stationary structure, by means of a 
horizontal shaft transversely arranged relative to the liquid flow, along 
a side thereof, or along an internal axis which does not need to pass by 
the center of gravity in order to reduce to a minimum the unbalance 
induced thereon by the dynamical force deriving from the relative motion 
of the water. The depth of the pivot connection will be equal or close to 
the average separation distance required for the surface liquid layer and 
a known type connection will be provided to a control system adapted to 
swing the blade front edge according to the wave profile variations. 
Flexible and water-proof connections will be further provided between the 
pivot shaft and the frame, located in such a way as not to interfere with 
the blade swinging motion. 
In the embodiment of the invention shown in FIG. 7, basin B is divided in 
four regions 7a-7d, by means of substantially vertical and transversely 
arranged bulkheads 8 which extend from the basin bottom up to openings E 
in order to maintain continuity in the surface layer, with a simultaneous 
partitioning of the mass of water contained within basin B in order to 
reduce a possible turbulence or wave motion propagation. Close to the 
upper horizontal edge of bulkheads 8 there are provided substantially 
horizontal hinged flaps 9 which extend in such a way as to cover almost 
the entire width and almost a half of the length of the central regions 7b 
and 7c of basin B. Said flaps 9 are connected to known type damper means 
10, such as piston dampers, in order to be able to oscillate at a 
predetermined average depth to dampen wave motions, while allowing the oil 
rich surface layers to pass thereabove. Damper means 10 absorb and 
dissipate part of the wave energy thus damping the wave motion. Each flap 
9 is arc-shaped whereby, even at a position different from rest, they do 
not have substantially any influence on the motions of the overlying 
layers, while they hinder wave motions in the surrounding areas, and 
turbulence component coming from underlying layers. 
The anti-backflowing or unidirectional openings E provided at the top of 
each bulkhead 8 have already been described in detail referring to FIG. 5 
and, concerning the flexible "small curtains" 0, with reference to FIG. 6. 
Basin B, further provided with already described longitudinal bulkheads 14, 
in order to reduce to a minimum possible transverse wave motions, is 
provided with a bottom duct 11, laid across said basin in the longitudinal 
direction, and having a front inlet 12 and a rear outlet 13 provided on 
the rear wall or on the basin bottom. Close to duct oulet 13 there is 
provided a pump means G performing liquid suction both from outside 
through intake 12, and from inside regions 7a-7d through transverse 
headers F connected to duct 11 and provided on the bottom of chambers 
7a-7d. Headers F and intake 12 may be suitably choked by known means, in 
order to control, according to need, the amount of water sucked from 
outside or from the various chambers of basin B. To allow oil collecting 
operations to be performed either when the structure is at a standstill or 
proceeding at low speed, removable devices may be provided, each one being 
preferably in the form of a length of elbow duct to be attached to the 
outlet 13, in order to subject the disharged water iet to the proper 
amount of deviation, preferably in opposition among the jets, or 
downwards, so that the propulsion thrust action on the structure, due to 
the jet exhausted by pump G through oulet 13, is neutralized. 
Within chamber 7d, where a higher concentration of oil has taken place, 
there is provided a flexible and waterproof hose 15 whose cross section is 
kept constant by means of a number of stiff horizontal rings wherein the 
one ring closest to the surface, shown at 15a in FIG. 7, is connected both 
to a vertically slidable positioning member (not shown in the drawing) 
preventing a ring overturning from the horizontal plane, and to a float 
system 16 provided to keep the hose intake at a predetermined and 
adjustable level underneath the free surface of the basin, whereby the 
liquid contained in area 7d continuously overflows into hose 15. Through 
the latter, under the action of gravity, the liquid reaches header I 
whereby it is subsequently subjected to the process previously described 
referring to FIGS. 5, 9 and 10. 
It should be pointed out that the above processing operations may be 
repeated sequentially, by performing liquid separation and withdrawal from 
the uppermost layers, while the lower ones are rejected, no longer on 
substantially undisturbed water, but on that portion containing the oil 
layer which has already been subjected to preliminary concentration during 
the first or the following sequential treatment operations, and 
introducing the withdrawn pre-concentrated liquid again in one or more 
subsequent basins, for slowing-down and separation, wherein further 
operations are possibly carried out comprising slowing-down, water 
ejection from below, and surface withdrawal of liquid having an increased 
oil concentration. 
As it was mentioned above, central basin B is connected to the structure by 
non-integral means, but through known type guides for a vertical sliding 
motion, in particular relative to the pair of side hulls A. Said motion 
may be provided through known power control means, both directed by the 
operator or by a signal taken from a dedicated sensor, whereby the 
vertical distance relative to the wave profile is not rigidly dependent 
upon the floating structure motion relative to the same profile, but may 
be adjusted continuously in order to reduce changes of said distance to a 
minimum. Said changes then substantially coincide, still referring to the 
wave profile, with those of that structure portion to which said blade or 
separating member 5 is connected. Displacements of the latter will then be 
controlled only to eliminate or to reduce those variations in the 
thickness (L.sub.1 -L.sub.2) of the liquid layer admitted to B caused by 
the minor wave motions and by that part of the major wave motion which has 
not been compensated by displacing the basin or rotating the floating 
structure. 
The consequence is that the instant differences of level between inside and 
outside of the basin are almost completely compensated by the structure 
rotation and the basin shift and for the remaining portion, extremely 
reduced, the relevant effects on the water layer thickness, thereby the 
flowrate entering the basin, are counteracted by the movement of blade 5. 
The vertical and longitudinal size of the basin is determined as a 
function of the water flowrate withdrawn from the bottom of the various 
chambers (in total, together with the flowrate entering the side tanks, 
corresponding to the flowrate running into the basin over the blade 5) so 
as to neutralize the stirring effect due to the turbulence produced by 
said residual fraction of instant difference of level with respect to the 
wave profile. 
It should eventually be noted that the apparatus of the invention is shaped 
and arranged in such a way as to be able to navigate and to maneouver, 
during transfer trips wherein no oil collection is performed, in a 
direction opposite to that of the oil collecting operations, whereby the 
member that during said operations performs the first separation between 
the surface layers of the surrounding body of water, i.e. blade 5, during 
said transfer navigation, is located substantially astern of said floating 
structure. On the ether hand, the opposite end of body C, which during 
navigation comprises the bow, will be preferably shaped in such a way as 
to optimize the navigation qualities of the assembly concerning in 
particular speed and ability to manoeuver. At the same time, since the 
basin is vertically movable, it may be kept at the height position which 
better suits said navigation qualities, and possibly completely or 
partially emptied of water.