Abstract:
A method for cleaning a water area including dredging, via a dredging apparatus, waste from the water area through a suction pipe into a sedimentation basin, generating a flow of the dredged waste from the water area to the sedimentation basin via siphonage and variations in heights of the suction pipe relative to a bottom of the water area, and converting energy caused by the flow of the dredged waste in the suction pipe into energy for driving the dredging apparatus.

Description:
This application is a national phase of PCT International Application No. PCT/FI02/00639 filed on Jul. 17, 2002 under 35 U.S.C. § 371. This application also claims priority of Application No. 20011581 filed in Finland on Jul. 27, 2001 under 35 U.S.C. § 119. The entire contents of each of the above-identified applications are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a method for cleaning a water area, such as a lake, pond, river or a similar water basin. The invention also concerns an apparatus for cleaning a water area, such as a lake, pond, river or a similar water basin. 
     At present, dredging and cleaning of water basins are carried out using conventional machinery in which the drive engines are usually petrol-fuelled internal combustion engines. However, internal combustion engines consume fuel and pollute the air as well as water basins. Moreover, such engines are relatively noisy. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to eliminate the drawbacks of prior art and to achieve a completely new type of system for creating dredging and cleaning equipment and equivalent for use in water basins. 
     In the system of the invention, the sludge and other residuals produced in connection with dredging and water purification can be removed from the lake via the same suction tube, a so-called “single-pipe system”. 
     In the system of the invention, a dredging apparatus is used for cleaning the bottom of a lake to remove excessive humus and undesirable fine-grained sediment, which have been partly produced from waste water emissions in the course of decades. Reducing the amount of nutrients dissolved in the water contributes towards improving the natural oxygen situation in the water and promoting the well-being of the biological population. 
     The cleaning is implemented by utilizing an environmentally friendly and energy-economical dredging apparatus, by means of which the sludge is conveyed via a feeble-constructed plastic discharge pipe into a sedimentation basin. The water separated is finally filtered and passed via an open drain into a natural ditch. 
     The dredging apparatus is very energy-economical and almost completely nonpolluting as compared with current methods. A further advantage of the system can be seen in the fact that the lake side remains intact as the system does not disturb or damage the environment because the dredgings are passed into a sedimentation basin located at a distance from the lake side area. The cleaning of a lake can be performed even including the shallow coastal waters and grassy areas. Neither do depth variations in the water area impede the use of the equipment. The sedimentation basin is built in a chosen location by making use of natural banks so that no actual construction materials are needed, and the land area in question can be restored after use to its original form. 
     After final filtering, the water separated from the sedimentation basin is passed in a purified state into the inflow ditch. The humus and sludge carried into the sedimentation basin are composted within the basin area and dried and processed further, to be reused as fertilizer and soil conditioner. 
     By applying the invention, a very environmentally friendly and reliable system for use as a cleaning apparatus in a water area is achieved. The dredging of the material to be actually dredged is performed without mechanical loading and transportation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be described in greater detail by the aid of an example with reference to the attached drawings, wherein 
         FIG. 1  presents dredging equipment according to the invention, moving on a lake, 
         FIG. 2  presents the floating operating carriage of a dredging apparatus, 
         FIG. 3  presents a side view of the dredging apparatus of the invention, 
         FIG. 4  presents a suction turbine at the end of a suction pipe, and 
         FIG. 5  presents a more detailed view of the dredging apparatus, and 
         FIG. 6  presents another dredging apparatus according to the invention, moving on a river. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     EXAMPLE 1 
       FIG. 1  shows dredging systems according to the invention for dredging a lake  1 , which comprise a floating operating carriage  2  serving as a kind of ferry supporting the dredging apparatus, guide cables  3  for guiding it, a suction pipe  4  leading to an inflow ditch  7  of the lake or by some other route to a sedimentation area situated at a lower altitude, and coastal vessels  5  or control ferries  6 , by means of which the motion of the operating carriage is controlled. 
     According to the invention, the suction pipe  4  leads into the sedimentation basin  8  located at a lower level. The invention is used to remove the light nutrient organic layer of nutrients and humus from the area of the lake system. By means of the apparatus, light nutrient humus is taken away from the water area (lake) via the piping system  4  into the sedimentation basin  8  located at a lower level and clarified there by reducing the flow rate so that the flow in the discharge area of the pipe  4  in the sedimentation basin  8  is spread over an area (typically 10–50 times) wider than the suction area at the beginning of the pipe. In addition, the flow can be controlled by means of boom elements  9  provided in the basin  8 . The mass removed from the lake by suction is deposited, restoring its original form, and the purified water is passed via an exit ditch  10  back into the inflow ditch  7 . The end of the discharge pipe  4  is placed below the water surface in the mudflow basin or choked so that no air can enter into the pipe. 
     Some or all of the operating energy needed in the process is obtained from a suction turbine which is connected between the upper end of the suction pipe and the dredging apparatus and which utilizes the water flow occurring by siphonage in the suction pipe  4  and the movement of the mass mixed in it. It is also possible to use an external energy source. 
     The floating operating carriage presented in  FIG. 2  comprises cable guides  21 , counterweight supporting cables  22  and a water hydraulic motor  23  for cable drive. In addition, it may be provided with a reversing switch  24  for the water hydraulic motor and a control stopper  25  attached to the cable. 
     As shown in  FIG. 3 , the dredging apparatus comprises a supporting/lightening backstay wire rope  31  connected to a floating supporting/operating carriage and provided with a counterweight  32 , as well as operating wire cables  33  for steering right and left. The dredging apparatus moves along the bottom, and it comprises a suction turbine  34 , propulsion rollers  35  fitted on a frame and milling/feed rollers  36 . The suction pipe is supported by supporting floats  37 , and additionally stabilizing weights  38  are provided. 
     As shown in  FIG. 4 . the suction turbine  34  has a main drive shaft  41  and a turbine blade part  42 , both connected to the end of the suction pipe. Connected after the turbine is a water hydraulic pump  43  for operating the propulsion rollers and transfer cable etc. 
     As shown in  FIG. 5 , the actual dredging apparatus consists of a frame  51 , guide rollers  52  for the drive cable, a caterpillar drive roller  53 , and milling feed rollers  54  (front and rear) driven e.g. by means of a cogged rubber belt  55  by a main shaft  56 . Fitted in the frame are also the end of the suction pipe and the suction turbine. The suction inlet is provided with a limiter. The apparatus is inclined about the main shaft in the direction of motion through about 10–30° relative to the driving roller, so that the forward roller is milling while the rearward roller has a finishing function. The tilting is performed by the water hydraulic cylinders at the same time when the driving direction is changed. The direction of rotation of the feed rollers is not changed when the driving direction changes; instead, it remains the same regardless of the driving direction, only the inclination and the direction of the caterpillar drive are changed. The sludge is removed via the suction pipe. 
     The operating carriage may also be controlled electrically by means of an electronics unit, which may additionally be provided with e.g. a GPS positioning system for locating the operating carriage and directing it to the right direction of travel. The electric energy needed by the electronics etc. is produced by a water hydraulic generator included in the system. The apparatus can work even at a temperature below 0° C. when it is working under water, in which case it may be operated for long times, possibly round the year, e.g. under remote control or according to a predetermined program for a desired length of time, even under ice. The apparatus works independently of the depth of the lake and, being guided in vertical and horizontal directions by guide cables, it can pass over/under obstacles that can not be avoided using above-water guide equipment. 
     An extension can be connected to the discharge pipe during operation by using an extension float  11 , the pipes and the joint are under water and the flow continues without interruption. 
     EXAMPLE 2 
       FIG. 6  illustrates the operation of the apparatus in the case of cleaning a flowing river  61  in the direction of flow (as seen from the bottom of the river). In this case, the apparatus is used with a protective apron  62  fitted on it to protect the dredging area from the current of the river during the work. The apron may consist of two parts, in which case the dredging apparatus opens and closes the two halves in a zipper-like fashion as it is moving in the transverse direction of the river. Placed on the upper edge of the apron are additional weights  63  pressing the apron against the bottom to prevent excessive funneling of water under the protective apron, thus minimizing undesirable by-pass flow of water in the dredging area. Placed at the lower edge are supporting elements  64 , with the help of which the apron can move on when necessary without getting stuck on the bottom during work. 
     It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the examples described above, but that they may be varied within the scope of the claims presented below.