This application claims priority from Taiwanese Application No. 96139012, filed on Oct. 18, 2007.
1. Field of the Invention
The invention relates to a diffuser for an aeration system, and more particularly to a diffuser which allows gas introduced in the aeration system to form small and fine bubbles, so as to increase the concentration of a gas, such as oxygen, that is dissolved in a water pool equipped with the aeration system.
2. Description of the Related Art
In order to establish an aerobic condition commonly used in the treatment of wastewater or sewage, or in the cultivation of biological materials in water pools, an aeration system is employed to increase the oxygen concentration in water.
An aeration system includes a plurality of diffusers adapted to be provided on the bottom of a water pool, conduits connected to the plurality of diffusers, and a blower forcing air to flow into the conduits and to pass through the slits provided in the diffusers, so as form a plurality of bubbles in the water pool.
As shown in
The commercially available membrane diffuser for aeration systems is generally made from an elastomeric material of a synthetic rubber, such as ethylene-propylene-diene monomer rubber (EPDM) rubber and a thermoplastic elastomer (TPE), the slits of which are generally millimeter-sized.
An object of the present invention is to provide a diffuser for an aeration system which overcomes the disadvantages encountered with the aforesaid prior art.
Another object of the present invention is to provide a diffuser for an aeration system that increases the dissolved gas concentration in a water pool.
According to one aspect, the present invention provides a diffuser for an aeration system, comprising
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:
The first embodiment of a diffuser 1 for an aeration system is illustrated in
The valve member 4 is configured to close the inlet 214. To be specific, the valve member 4 comprises a head portion 41 and a stem portion 42 which extends along the central line X and can close the inlet 214 by engaging with the valve seat 215. The diaphragm 3 is placed between the head portion 41 and the stem portion 42 and is pressed therebetween. Preferably, the valve member 4 is made of a waterproof elastomeric material, such as polyurethane, so that the valve member 4 can be adhered to the diaphragm 3. The diaphragm 3 of the diffuser 1 of the first embodiment of this invention includes a central portion 33, a peripheral portion 31 and a surrounding web segment 32. The central portion 33 is disposed to carry the valve member 4 to place the diaphragm 3 in a non-aerating position when the inlet 214 is closed. The peripheral portion 31 surrounds the central portion 33, and is secured to the periphery 211 to form upstream and downstream sides separated by the diaphragm 3 such that, when the back pressure at the upstream side is higher than an ambient pressure at the downstream side, the valve member 4 is forced to move away from the valve seat 215 to place the diaphragm 3 in an aerating position.
The surrounding web segment 32, which is interposed between the central portion 33 and the peripheral portion 31, is configured to stay in abutment with the outer major surface 212 in the non-aerating position. The surrounding web segment 32 includes a plurality of fibrous filaments which are arranged to form a textured structure with a plurality of pores of a dimension such that, in the aerating position, the introduced aerating gas can be bubbled through the plurality of pores, and such that the abutment of the surrounding web segment 32 with the outer major surface 212 can sufficiently institute a barrier to guard against a back flow through each one of the pores immediately after the back pressure is set to drop below the ambient pressure.
The fibrous filaments of the surrounding web segment 32 have a diameter in the range of 0.005 μm to 5 μm, and the formed textured structure is a non-woven structure which has a basis density in the range of 20-150 g/cm2, and which has said plurality of pores with a mean size ranging from 1 to 20 μm, preferably ranging from ranging from 5 to 12 μm.
In a preferred embodiment, the diffuser 1 further comprises a reinforcement layer 8 which is disposed to shield the diaphragm 3 from the back pressure. The reinforcement layer 8 has an auxiliary web segment 82 that is configured to be superimposed upon the surrounding web segment 32 and that includes a plurality of macro-pores of such a dimension as not to interfere with the bubbling of the introduced aerating gas through the plurality of pores of the surrounding web segment 32. The surrounding web segment 32 and the auxiliary web segment 82 are made of fibers with different diameters. The auxiliary web segment 82 of the reinforcement layer 8 is made from a non-woven fabric which has a basis density in the range of 20-150 g/cm2, and which has said plurality of macro-pores with a mean size ranging from 8 to 100 μm, preferably ranging from 10 to 30 μm. The non-woven fabric is made of a fiber having a diameter in the range of 10 μm to 200 μm. Due to the specific arrangement of the surrounding web segment 32 and the auxiliary web segment 82, the radial diffusion of the aerating air from the central portion of the base 2 can be enhanced, and the formation of the fine air bubbles and the air dissolved in water can be increased.
The surrounding web segment 32 may be a non-woven fabric made from any suitable material, including, but not limited to, polyester, polyproprylene and polyethylene. Furthermore, the non-woven fabric may be formed of a single-layered or multilayered structure.
The auxiliary web segment 82 of the reinforcement layer 8 has a tensile strength greater than that of the surrounding web segment 32, so as to shield the surrounding web segment 32 of the diaphragm 3 from the back pressure. The reinforcement layer 32 may be made of any material suitable for the formation of woven and non-woven fabrics, including, but not limited to, polyester, polyproprylene, and polyethylene. When a non-woven fabric is used as the reinforcement layer 82, the non-woven fabric is preferably a spunbonded fabric of a single-layered or multilayered structure.
It is preferable that the reinforcement layer 8, which is a spunbonded fabric in the first embodiment, is adhered to the diaphragm 3, which is a non-woven fabric made by melt-blowing in the first embodiment, by a thermopress process, and the peripheral portion 31 of the diaphragm 3 together with the reinforcement layer 8 are attached to the periphery 211 of the base 2 by an ultrasound process. Accordingly, the diffuser 1 of the first embodiment can be easily manufactured by thermopress and ultrasound processes.
With reference to
For each of the diffusers 1, when no air is supplied from the conduits 11, the valve member 4 is positioned in the non-aerating position and the valve member 4 is seated on the vale seat 215 to close the inlet 214. The surrounding web segment 32, which is in the non-aerating position, stays in abutment with the outer major surface 212, as shown in
As shown in
Experiment on Dissolved Oxygen Concentration
This experiment was carried out using the diffuser 1 of the first embodiment of this invention (“Example”). The diaphragm 3 was made from a non-woven fabric material made of a polypropylene fiber a diameter of 3±2 μm by melt blowing, and which had a basis weight of 60 g/m2 and an average pore size of 7.5 μm. The reinforcement layer 8 was made from a spunbonded non-woven fabric material made of a PET fiber having a diameter of 15±5 μm, and which had a basis weight of 220 g/m2 and an average pore size of 11 μm. The diaphragm 3 and the reinforcement layer 8 were bonded to each other by a thermopress process and then attached to the periphery 211 of the disk-shaped base 2 having a diameter of about 30 cm. Further, a diffuser of Model Disc-300, which is commercially available from Kai-Shing Incorporation, is made of EPDM rubber, and includes a disk-shaped base having a diameter of 30 cm, was employed in the Comparative example. The properties of the diffusers are set forth in the Table 1.
The diffuser 1 of the Example and the diffuser of the Comparative example were respectively attached to aeration systems in two test pools (Test 1 and Test 2), which had been filled with 100 liters of tap water. The two pools were aerated for 10 min at an air flow rate of 30 L/min by a blower. The ambient temperature during the experiment was 28.8° C. The oxygen concentrations in the water were detected before aeration and after aeration, respectively, and the results of such detection are set forth in Table 2.
Table 2 shows that, with the use of the diffuser 1 of the first embodiment of the present invention, the oxygen concentration in the test pool increases by 3.31 mg/L. In contrast thereto, use of the diffuser of the Comparative example resulted in an increase of the oxygen concentration in the test pool of only by 2.01 mg/L. Accordingly, the diffuser 1 of the present invention, when used in an aeration system, can significantly increase the dissolved oxygen concentration in water by 65%.
While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
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