TECHNICAL FIELD

This invention relates to a floating filter system, inter alia*, a crossflow filter system and its application for the removal of algae in open lakes or ponds.

BACKGROUND ART

Algae are of vital importance in the formation and maintaining of present atmosphere. They are also of vital importance in supplying food to living things. However, they may also be harmful when bloom and cause water body hypoxic. The root cause of algae bloom is the excess nutrients in the water body. Living algae are actually cleaners of the nutrients, but when they die and decay, they return the nutrients back to the water body. In most of the cases, algae bloom once started will last until the weather cools. To remove the excess algae from the water body directly may be one of the most direct and quickest measures to tackle the harmful algae bloom.

Existing art of removing algae in practice as happening in Taihu Lake in Wuxi andDianchi Lake in Kunming, China is to suck the surface 50mm algae-containing water and treat the water by flocculation and then sedimentation/filtration. It is only carried out in leeward or downstream bays or shores where severe algae scum has formed. There is other technique to separate algae from water. Direct filtration, for instance, is disclosed by Dodd in 1981 in USP No. 4255261 and by Willuweit in 2013 in USP No. 8496120.

The premise of the application of above arts is that all the influent to be treated must be fed to the devices. Algae are tiny cyanobacteria and very dilute in natural water bodies in terms of weight even when they bloom. It is hardly affordable to pump only the surface 50mm water of a lake.

SUMMARY OF DISCLOSURE

One objective of our invention is to provide a filter system and method capable but not limited to concentrate algae in- situ a water body without pumping vast volume of the water to be treated;

Another objective of our invention is to provide a device and method capable but not limited to collect and remove algae;

Another objective of this invention is to provide an application method of crossflow filter to tackle the fouling problem by organisms like algae;

Another objective of this invention is to provide a device and method to remove most of the dilute algae in large water bodies;

Another objective of this invention is to provide a device and method to Harvest high purity fresh algae in large lakes by separating coarser contaminants from algae simultaneously;

Yet another objective of this invention is to provide a device and' method to disturb least other living creatures and their living environment when removing most of the algae from the water bodies;

Still another objective of this invention is to provide a high efficiency and low energy consuming device and method to remove most of the dilute algae in large water bodies;

Still another objective of this invention is to provide a device and method to concentrate and remove most of the algae in large water bodies without addition of any chemicals;

Yet another objective of this invention is to provide a device and method that is also capable to remove most of the algae when diverting the algae from entering a protected water body.

In the first preferred embodiment of our invention as illustrated in Fig 1, it is provided a floating filter system comprising a chain of floats (1) , a filter medium (2) hanged on said floats along its upper edge, a collection slot (3) disposed in the middle of said chain of floats and filter medium and sealed to them with its front edges, a chain of rigid bars (4) hanging alone the lower edge of said filter medium (2) , bands (5) equipped at each joint point of said floats (1) and said bars (4), buoy ^~ (7) with a hook ring hanging below water surface, and towirig ropes (6) connecting said bands and said ring under said buoy (7) , forming a funnel plan view. Preferably said floats are polymer made long airbags, being able to stretch and stand straight when pumped with air. Preferably said filter medium (2) has a smooth surface, being strong, less elastic and not biodegradable, permissive to water but retentive to most of algae colonies. Preferably the filter medium is lined on its backside with durable cloth or net material to form soft tubes, along its upper edge and lower edge suitable for insertion of said floats and weight bars. Preferably said collection slot (3) is made of fibre-reinforced-product and is equipped with electric scrapers. Preferably said ropes (6) have their overall specific gravity equal or very close to 1. '

In the second preferred embodiment of out invention as illustrated in Fig 2, it is provided a floating filter system assembly with the addition of a coarser floating filter system in front of the first embodiment. Preferably the front filter medium (8) is of bigger mesh that permits algae and water to pass freely, but rejects most of the coarser floating debris. The front and rear floating filters are linked with towing ropes (6) tied at the bands (5) to form illustrated plan view in Fig 2.

In the third preferred embodiment of out invention as illustrated in Fig 6 derived from the first embodiment, the number and length of floats on both sides of the collection slot are not equal.

Preferably the floats (1) are properly sized and the hanging bars (4) are properly weighted in all embodiments hence the filter medium (2) and (8) is under enough tension to be flat or near flat in the water all the

Preferably two airbags (9) and (10) are attached to said collection slot (3) underneath in the front and rear respectively, enable user to adjust the draft of the mouth and the tail of the collection slot through pumping in or release the air in the airbags . Preferably said collection slot is equipped with a scraper (11) enable to load the algae slurry concentrated at the mouth of the collection slot to a collection bag or boat attached to tail.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood with reference to the accompanying drawings or figures, and the detailed description that follows hereinafter wherein specific embodiments are described as non-limiting examples or illustrations, in which;

Fig 1 is a conceptual plan view of the general embodiment of a floating filter system.

Fig 2 is a schematic plan view of. a floating filter system assembly.

Fig 3 is a schematic side view of the collection slot.

Fig 4 is a schematic section view of the first embodiment of the- invention. Fig 5 is a schematic section view of the second embodiment of the invention.

Fig 6 is a schematic plan view of the third embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the first preferred embodiment of our invention as illustrated in Fig 1 and Fig 4, when the floating filter system is towed and the ropes (6) are in tension, the filter medium surface is facing up and center forward. When the filter assembly moves forward, most of the water will pass the filter medium while most of the algae colonies will be retained and form algae concentrate in front of the filter medium surface. As there is an angle between the moving direction and filter medium facing direction, the retained algae Concentrate will form a crossflow along the filter medium surface and flow towards the collection slot (3) at the bottom of the filter funnel. Preferably the upper forward ^■ inclination of the filter medium surface (2) is greater than centre forward inclination, which helps to prevent or reduce the algae concentrate from escaping around the lower edge of the, filter medium. Typically the floating filter system can be as long as a hundred meters if the water body condition allows, while only less than a meter deep. Typically the floating filter system moves forward slowly so that the pressure differential across the filter medium is small to minimize the fouling of filter medium by algae and the like. In the second preferred embodiment of the invention illustrated in Fig 2 and Fig 5 , when the floating filter assembly is towed forward in the open water, the visible floating debris will be caught by the front filter medium (8) , while water and algae will pass freely and reach the rear filter medium (2) . Most of the algae will be retained and form algae concentrate and crossflow towards the collection slot (3) . Thus harvested algae are purer and more valuable for further beneficial process.

In the third preferred embodiment of the invention as illustrated in Fig 6, the floating filter system is anchored with its two ends of to the bank if possible or through said buoy (7) across a water course forming an angle with the wind or water flow direction. The filter medium surface shall always incline up-forward towards upstream or the moving direction of algae. The collection slot if not in the centre of the filter system shall be located at the downstream wing of the system. Compared to common oil boom, the floating filter system of this invention not only prevents or reduces the algae from entering the downstream or leeward water area, but also enables easy removal of accumulated algae from the water body by collecting concentrated algae slurry at the collection slot .

In all above preferred embodiments, the concentration of the algae concentrate is a joint result of the filter medium facing angle against the water flow direction, the moving speed, the wind direction and speed, the draft of the collection slot, etc. It is always preferred to tow the floating filter system windward.