Water purification apparatusTechnical Field
The present invention relates to water purification apparatus and methods, and in particular to water purification apparatus which can be used as a gravity feed system or adapted for connection to a mains water supply.
The invention has been developed primarily for use in drinking water applications and will be described hereinafter with reference thereto. It will be clear, however, that the invention is not limited to this particular field of application.
Background and Prior Art
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
A large number of people in the world live in countries with a severe shortage of sanitary drinking water. People have to rely directly on ground water sources such as wells, ponds and rivers. These water sources are often contaminated with sewage, industrial waste water, and agricultural by-products such as pesticide residues. Water is microbiologically safe and WHO recommends 6log bacterial removal, 4log viral removal and 3log cyst removal. Although bacteria and viruses can be removed to the desired degree by using chemical disinfection (e.g., by contact with halogens) or radiation-based disinfection (e.g., by exposure to ultraviolet radiation), these disinfection methods do not achieve 3log cyst removal.
Gravity feed devices are available that can use filtration in combination with biocide action to achieve 6log bacterial removal, 4log viral removal and 3log cyst removal. Gravity feed devices can operate without pressurized and flowing water.
WO2005095284(Unilever, 2005) discloses a gravity fed water purification system comprising: a filtration unit suitable for separating particulates and solubles from the influent, in the form of a carbon block, and typically with an additional non-woven fabric filter; the system further comprises a chemical dispensing unit such that the effluent flow rate of the filtration unit is regulated by a flow control device before the water contacts the biocide dispensed by the chemical dispensing unit; the water is then retained in the retention chamber for a predetermined period of time before being discharged from the water purification system through a scavenger means adapted to separate the dispensed biocide and its by-products from the effluent. The device is quite complex with a large number of replaceable parts.
WO07000238(Unilever, 2007) discloses a water purification device comprising an upper chamber and a lower chamber, wherein the lower chamber comprises an outlet means for collecting purified water and a filter medium for removing suspended particles and dissolved organics. The biocide system with which it is integrated is a device that can dispense a unit dose of biocide and can feed water into a chamber in which the biocide can be dispensed. The device is designed for solid biocides only and is not suitable for liquid biocides. A disadvantage of solid biocides is that they degrade when exposed to air.
WO08083896(Unilever, 2008) discloses a gravity fed water purification device that can incorporate (controlled) dosing (dosing) of liquid biocides. The apparatus uses a feed channel comprising a venturi, wherein the upper chamber is in fluid communication with the lower chamber and water can flow from the upper chamber to the lower chamber. The water in the system must flow at a high flow rate and the dosing rate is dependent on the flow rate of the water. The dosing of the biocide is caused by a negative (suction) pressure at the discharge end of the liquid dosing pipe, which is caused by the water flowing through a venturi connected in a gas-tight manner to the discharge end of the liquid dosing pipe. In this case, the air pressure within the compartment containing the liquid biocide is at atmospheric pressure, and the liquid biocide is "sucked" out of the compartment by the negative pressure at the discharge end of the compartment containing the biocide. In practice, venturi-based dosing systems are very sensitive to physical dimensions and the control of the dosage is more difficult. The construction of this system requires many materials and is therefore expensive.
EP2184263(Unilever) discloses a gravity-fed water purification device in which a reduction in the concentration of biocide or by-products thereof in downstream water and a relatively longer life of the scavenger medium is achieved by the feature that the outlet is located and the reservoir is separated in combination with the wall height of the scavenger unit. The device comprises a biocide unit in fluid communication with a reservoir separated by a wall from an eraser unit with an eraser medium, the eraser unit being in fluid communication with the dispenser chamber through an outlet located on a partition separating the eraser unit from the dispenser chamber. To achieve this, it is necessary that at least 10wt% of the medium (M) is located below the lowest level of the outlet (O) and that the wall (W) extends above the highest level of the medium and above the lowest level of the outlet. This document does not disclose or discuss how to dose the biocide nor does it disclose a liquid biocide dosing system.
The inventors of the present invention have devised a liquid biocide dosing system and arrangement for delaying the contact of water, in which biocide has been dispensed, with a filter-cum-biocide-scavenger device and making it suitable for use in gravity-fed water purification equipment.
WO04074182A (Unilever) discloses a flow control device for controlling the leaching of solid biocides, wherein the leaching control is achieved by controlling the water flow into a solid biocide dispensing unit. It discloses a flow control device that provides a constant flow through the chemical dispensing unit, thereby leaching a uniform amount of solid biocide without being affected by the water intake head in the upper chamber. The dosing of the biocide into the water is achieved by the solid biocide tablet being contacted with the water so as to gradually erode, the water flow being controlled by means of a flow regulator, which in turn controls the erosion of the biocide tablet. It does not disclose how to control dosing of liquid biocides.
US4093551(IFUO AB) discloses an apparatus for purifying water in a small sewer piping system comprising means for automatically adding a chemically active liquid to the water flowing through the apparatus. The invention eliminates the need for any moving parts by using two siphons to control the liquid supply. The sewage passes through one of the siphons and the corresponding flow creates a suction force by which the chemically active liquid is transported through the other siphon. This discloses a liquid disinfectant dosing system in which the liquid is dosed by means of a "suction" or negative pressure created in the water as it flows through the siphon tube. The other siphon has one end immersed in the liquid biocide bath and a discharge end disposed within the first siphon. Thus, as water flows through the first siphon, liquid biocide is "sucked" into both siphons. The two siphons used thus constitute a liquid dosing system.
The inventors of the present invention have designed two siphons to provide a means for delaying the introduction of biocide-added water to the biocide removal section, and these siphons do not control the dosing of liquid biocide. The two siphons are not physically connected, but simply provide residence time for the biocide to act on the microorganisms, while liquid disinfectant dosing is achieved by positive pressure generated by air pockets.
The inventors of the present invention have thus devised a novel liquid dosing apparatus which is controlled by the positive pressure generated by the hydrostatic head of the water and the provision of two siphons arranged in a manner which can provide additional residence time to enhance the interaction of the biocide with the water to be purified.
Our co-pending indian patent application 2126/MUM/2009 describes a water purification plant in which the required level of microbial kill is achieved by a liquid biocide dosing system. An important feature of the device is a filling cup, the filling of which enables the dosing system to dose the required amount of biocide into the water purification chamber. Without the fill cup, the device would not work properly. One drawback with having a fill cup is that the device is difficult to miniaturize.
The inventors of the present invention have devised a novel biocide dosing system by using impulse lines and a siphon discharge mechanism. The relative position of the siphon discharge mechanism and the pressure guide pipe enables the purification equipment to work normally. Furthermore, the geometry of the impulse pipe and its length of submersion controls the biocide dosing. The apparatus of the present invention does not contain a fill cup and is therefore easily miniaturized.
In view of the above, it is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art.
The object of the present invention is to provide a water purification device which is simpler and thus more economical in its construction.
It is another object of the present invention to provide a water purification device that is suitable for use with both solid and liquid biocides.
It is a further object of the present invention to provide a water purification apparatus that can be used as a gravity feed apparatus and that is suitable for use in an on-line system.
It is a further object of the present invention to provide residence time means within the water purification apparatus to ensure that even the first drops of water flowing from the water purification apparatus are completely free of any harmful microorganisms.
Disclosure of Invention
According to one aspect of the present invention, there is provided a water purification apparatus comprising a water purification chamber, comprising:
a biocide dispensing cartridge in fluid communication with the biocide storage compartment and the biocide dispensing port, wherein the biocide dispensing cartridge is connected to the impulse tube and the free end of the tube extends down into the water purification chamber; the water purification chamber is in fluid communication with the filter chamber through an inverted 'U' shaped inflow siphon discharge mechanism of unequal leg lengths; wherein the opening of the small pin of the inflow siphon discharge mechanism is positioned above the bottom of the water purification chamber; the long pipe foot extends into the filter chamber, and the top end of the inverted 'U' -shaped inflow siphon pipe discharge mechanism is higher than the free end of the pressure guide pipe.
According to another preferred aspect of the present invention there is provided a water purification apparatus according to the present invention, wherein the inflow siphon discharge is in fluid communication with the filter chamber via a dwell time chamber and then with the outflow siphon discharge, wherein the outflow siphon discharge is housed in the dwell time chamber.
The term "comprising" is intended to be non-limiting with respect to any subsequently stated elements, but rather to encompass non-explicitly stated elements of greater or lesser functional importance. In other words, the listed steps, elements or options need not be exhaustive. When the words "comprising" or "having" are used, they are intended to have the same meaning as "comprising" above.
Drawings
Fig. 1 is an embodiment of a water purification apparatus according to the present invention.
Fig. 2 is another preferred embodiment of the water purification apparatus according to the present invention with residence time providing means.
Fig. 3 is another embodiment of a water purification apparatus according to the present invention, wherein a biocide dispensing unit is housed within the water purification chamber.
Detailed description of the invention:
accordingly, the present invention provides a water purification apparatus comprising a water purification chamber, comprising:
a biocide dispensing cartridge in fluid communication with the biocide storage compartment and the biocide dispensing port, wherein the biocide dispensing cartridge is connected to the impulse tube and the free end of the tube extends down into the water purification chamber; the water purification chamber is in fluid communication with the filter chamber via an inverted 'U' shaped inflow siphon discharge mechanism of unequal leg lengths; wherein the opening of the small pin of the inflow siphon discharge mechanism is positioned above the bottom of the water purification chamber; the long pipe foot extends into the filter chamber, and the top end of the inverted 'U' -shaped inflow siphon pipe discharge mechanism is higher than the free end of the pressure guide pipe.
The impulse pipes may have different shapes and sizes and may have different cross-sections. The cross-section of the tube may be rectangular, circular, polygonal, oval or various other geometric shapes. The tube may be fully or partially tapered in any direction.
The apparatus of the present invention can be made in different capacities and sizes, for example 1, 2, 3, 5 liters or more.
The biocide may be provided in solid or liquid form. When in solid form, the apparatus is designed to dissolve an appropriate amount of the solid to provide the correct amount of liquid biocide in the biocide dispensing cartridge. The biocide is preferably selected from any halogen-releasing compound and preferably chlorine-releasing biocide including chlorinated trisodium phosphate, sodium or potassium hypochlorite or calcium hypochlorite, various N-chlorinated compounds known in the art which release active chlorine, such as sodium or potassium dichloroisocyanurate, trichlorocyanuric acid, monochloramine, dichloramine, [ (monotrichloro) -tetrakis (monopotassium dichloro) ] pentaisocyanurate, 1,3-dichloro-5, 5-dimethylhydantoin (1,3-dichloro-5, 5-dimethyllidatone), chloramine T, p-toluenesulfonyldichloride, trichloromelamine, N-chloramine, N-chlorosuccinimide, N' -dichloroazodicarboxamide, N-chloroacetylurea, N-dichloroazodicarboxamide, N-chloroacetyl urea, N-dichlorobiuret (N, N-dichlorobiuril), dicyandiamide chloride, hydrogen peroxide or its derivatives, peroxyacetic acid.
Suitable liquid biocides that can be used in the apparatus of the present invention include aqueous solutions of sodium hypochlorite, sodium dichloroisocyanurate, iodine, quaternary ammonium compounds or glutaraldehyde. The most preferred liquid biocide is an aqueous solution of sodium hypochlorite. When sodium hypochlorite is the liquid biocide used, it is added to the biocide storage compartment at a concentration in water in the range of 0.01-50wt%, more preferably 1-20 wt%. By means of the device of the invention, the concentration of biocide in the water purification chamber can be made in the range of 0.5-100ppm by weight, more preferably 1-50ppm by weight in the water.
According to a preferred aspect of the invention, the filter may be integrated with a biocide scavenger. The filter cum biocide scavenger preferably comprises an activated carbon block filter medium. Activated carbon block filter media includes Powdered Activated Carbon (PAC) and a binder, which are thoroughly mixed and briquetted by pressure and heat treatment. PACs are preferably selected from bituminous coal, coconut shell/charcoal, petroleum tar. Preferably, the PAC used has a dimensional uniformity coefficient of less than 2, more preferably less than 1.5, and a carbon tetrachloride value of greater than 50%, more preferably greater than 60%.
The filter-cum-biocide scavenger is also provided with a particulate filter which is a single-or multi-layer non-woven fibrous-fabric filter, wherein the outermost layer is pleated. Alternatively, the filter may comprise a combination of pleated and spiral wound fabric filters.
Particularly preferred carbon block filter media are those disclosed in GB2390987, more preferably those disclosed in our co-pending application 320/MUM/2004. This co-pending application describes a carbon block filter medium for a gravity feed filter comprising Powdered Activated Carbon (PAC) and a binder material having a Melt Flow Rate (MFR) of less than 5, wherein the PAC has a particle size such that 95wt% of the particles pass through a 50 mesh screen and no more than 12% of the particles pass through a 200 mesh screen. Further preferred carbon block filter media have 55-80wt% PAC particles in the 100-200 mesh size range in the lower 50vol% of the carbon block filter media.
The discharge mechanism may be a faucet or bellows activated hand pump as discussed later.
The invention will be illustrated below by means of a specific non-limiting example of a water purification device according to the invention shown in figures 1-3.
The drawings illustrate in detail:
fig. 1 is an embodiment of a water purification apparatus according to the present invention. The device has a water purification chamber (1) with a lid (6), opening the lid (6) exposing a water inlet enabling a user to pour water into the water purification chamber. The water purification chamber comprises a biocide dispensing cartridge (3) in fluid communication with a biocide storage compartment (5) and a biocide dispensing port (4). The biocide dispensing box is connected to a pressure pipe (2) and the pipe extends down into the water purification chamber. The tube is in fluid communication with the biocide dispensing cartridge. The water purification chamber is in fluid communication with a filter chamber (10) having a filter-cum-biocide-scavenger (7) via an inverted 'U' -shaped inflow siphon discharge (13). The opening of the small pin of the inflow siphon discharge is located above the bottom of the water purification chamber. The filter is located on a partition wall that partitions the water purification chamber and the purified water discharge chamber. An inflow siphon discharge is provided for operatively connecting the water purification chamber and the filter chamber such that water from the water purification chamber flows into the filter chamber only via the inflow siphon discharge. An exhaust port (12) provided on the filter chamber operates the inflow siphon discharge mechanism by allowing an upwardly directed passage for air to exit the filter chamber. The discharge of water from the filter chamber is via the filter-cum-biocide scavenger, while the entry of water into the filter chamber takes place via the inflow siphon discharge mechanism. The top end of the inverted 'U' shaped inflow siphon discharge is located above the free end of the impulse pipe to ensure that no water flows through the siphon discharge without the addition of the required amount of biocide. A watertight cover (11) provided at the filter chamber ensures that water enters the filter chamber only via the inflow siphon discharge. When the water purification chamber (1) fills the top of the inflow siphon discharge, the inflow siphon discharge starts to discharge water into the filter chamber. When the water with biocide fills the filter chamber, the water flows through the filter-cum-biocide scavenger, which removes colloidal impurities and residual biocide from the water and discharges the water into the clean water discharge chamber (8), from which clean water free of biocide can be obtained by a dispensing device such as a tap (9).
When water flows into the water purification chamber via the water inlet of the water purification chamber and fills it, the water level in the water purification chamber generates air pressure in the impulse pipe, so that the biocide can be discharged from the biocide dispensing cartridge into the water purification chamber via the biocide dispensing opening.
Fig. 2 is another embodiment of the water purification apparatus according to the present invention with residence time providing means. Fig. 2 shows a water purification chamber (1) which is provided in its bottom interior region with a filter chamber (10) surrounding a filter-cum-biocide-scavenger (7). The filter chamber is provided with a watertight cover (11) and an exhaust port (12). The biocide dispensing cartridge (3), the biocide dispensing port (4), the biocide storage compartment (5) and the impulse pipe (2) are located in their respective positions as shown in fig. 1. In fig. 2, a dwell time chamber (14) with an outflow siphon discharge mechanism (15) is provided. An outflow siphon discharge mechanism is disposed within the dwell time chamber. The residence time chamber has an exhaust (16). The vent provided at the dwell time chamber enables the outflow siphon discharge mechanism to operate by allowing an upwardly directed passage for air to exit the dwell time chamber. An inflow siphon discharge (13) is operatively connected to the residence time chamber. The inflow siphon discharge is in fluid communication with the filter chamber via the dwell time chamber and then in fluid communication with the outflow siphon discharge. The apparatus of fig. 2 is designed to ensure that even the first drop of water coming out of the clean water discharge chamber is free of any harmful microorganisms by means of a double residence time.
In use, filling of the water purification chamber creates air pressure in the impulse lines, which then conduct into the biocide dispensing box, resulting in dosing of biocide through the biocide dispensing port. After the water level in the water purification chamber reaches the highest level (level) of the inflow siphon discharge, the biocide-mixed water enters the residence time chamber via the inflow siphon discharge. After entering the residence time chamber, water begins to fill the residence time chamber. When the water level in the residence time chamber reaches the highest level of the outflow siphon discharge mechanism, the biocide-mixed water enters the filter chamber via the outflow siphon discharge mechanism, thereby providing a double residence time. After removal of residual biocide in the filter chamber and filtration of the water, the purified water can be discharged from the purified water discharge chamber by opening the tap.
Fig. 3 is another embodiment of a water purification apparatus according to the present invention. All features and characteristics of fig. 3 are the same as described for fig. 1. The only difference between the embodiments of fig. 1 and 3 is that in fig. 3 the biocide storage compartment (5), the biocide dispensing cartridge (3), the biocide dispensing port (4) are all housed within the water purification chamber.
Example (b):
effect of impulse pipe geometry and immersed pipe height on liquid biocide dosing:
in this embodiment, the submerged pipe height refers to the length of the impulse pipe immersed in the water purification chamber, i.e., the distance between the highest water level in the water purification chamber and the lowest point of the impulse pipe. In table 1, L1 and L2 refer to two different sides of a rectangle and a square.
Table 1 below describes the effect of impulse pipe geometry and submerged pipe height on biocide dosing.
TABLE 1
| Cross-sectional shape of pressure pipe | L1, mm | L2, mm | Immersed tube height, mm | Volume of charge, ml |
| Rectangle | 28 | 14 | 4 | 4 |
| Square shape | 13 | 13 | 5 | 3.5 |
| Square shape | 10 | 10 | 6 | 3.5 |
It is clear from the data in table 1 that the biocide dosing amount varies with changing impulse pipe geometry and immersed pipe height. The volume of biocide dosed can thus be accurately controlled according to the capacity of the water purification device.
The effect of the residence time chamber on increasing the contact time of the biocide with the raw water (influent):
using an apparatus configured as shown in fig. 1-3, the time it takes for water containing biocide dispensed from the biocide dispensing cartridge to flow through the filter is referred to as the contact time. The contact time is the duration of time that the biocide acts on the microorganisms in the influent water.
Table 2 summarizes the contact times with and without a residence time chamber.
TABLE 2
| Different embodiments of the water purification unit according to the invention | Time of contact of influent water with the filter chamber |
| FIG. 1 shows a schematic view of a | Less than 1 minute |
| FIG. 2 | 5 minutes or longer |
| FIG. 3 | Less than 1 minute |
As is clear from the data in table 2, by providing a residence time chamber as shown in the preferred embodiment of fig. 2, the contact time can be increased. This feature has been found to ensure that even the first drop of water coming out of the water purification device of the present invention does not contain any harmful microorganisms.