In general, water purifiers are classified into a hollow fiber membrane type water purifier and a reverse osmosis membrane type water purifier according to a water purification method employed therein.
Among them, the reverse osmosis (RO) membrane type water purifier has been known to be superior to other types of water purifying methods developed to date in terms of removing contaminants.
The reverse osmosis membrane type water purifier may be configured to include a sediment filter, a fine 5 micron filter, for removing dust, residue (or dregs), various floating matter from raw water supplied from a faucet, or the like, a pre-carbon filter for removing chemical substances, such as carcinogens (or a cancer causing agents), synthetic detergents, insecticides, or the like, harmful to a human body, residual chlorine, and the like, by using an active carbon absorption method, an RO membrane filter configured as an 0.001 micron RO membrane to filter sodium, various germs, and the like, as well as heavy metals such as lead, arsenic (As), and the like, and discharging condensed water through a drain pipe, and a post-carbon filter for removing an unpleasant taste or smell, a coloring matter, or the like, included in water which has passed through the RO membrane filter.
The hollow fiber membrane type water purifier employs a hollow fiber membrane filter (ultrafiltration filter (UF)) instead of the RO membrane filter. The hollow fiber membrane filter, a porous filter with pores, tens to hundreds of nanometers (nm) in size, removes contaminants from water through numerous fine pores distributed on the membrane surface.
The RO membrane type water purifier or the hollow fiber membrane type water purifier may use the four filters as mentioned above, may further include an antifungal filter or a functional filter in addition, or may include a complex filter configured to have the multiple functions of various filters. For example, the functions of the sediment filter and the pre-carbon filter may be implemented in a single complex filter.
However, in the water purifier, the post-carbon filter, or the like, may be easily contaminated by germs and since germs may thereby be introduced into the storage tank, microbes (or microorganisms) may grow in the storage tank. In addition, germs or microbes may infiltrate into and propagate in purified water stored in the storage tank or algae (or slime) may be formed on an inner wall of the storage tank.
Thus, in order to sterilize the germs or microbes to keep them from growing or propagating in the storage tank, a technique of supplying sterilization chemicals from the outside to sterilize the storage tank and a discharge flow path of purified water has been proposed.
However, the sterilization chemicals supply method is disadvantageous in that a user or a water purifier manager must carry out a sterilization chemicals supply operation, such that the sterilization operation may be cumbersome and sterilization management ineffective. Namely, when the sterilization chemicals are applied, an automatic supply of the sterilization chemicals is impossible, and if ever, the sterilization chemicals must be periodically applied, making the operation cumbersome.
In addition, when the sterilization chemicals are applied, the concentration of the sterilization chemicals may be higher than necessary, according to circumstances, and the sterilization chemicals may be applied in smaller or larger amounts, according to the user or the manager, leading to a possibility in which the sterilization chemicals remain in the interior of the water purifier after a cleansing operation (or washing operation). Thus, a rinsing operation must necessarily be performed several times after the cleansing operation, and in this case, if the rinsing operation is not perfect, supplied water might be harmful to a human body and the smell of remaining sterilization chemicals could increase user dissatisfaction.
In addition, since the water purifier manager must perform the sterilization chemical supply operation, incurring costs for sterilization, the user may feel burdened by the cost for the service.
In particular, in most cases, the water purifier is cleansed by a service superintendent, rather than being sterilized and cleansed by itself, inevitably making the operation onerous, which leads to a degradation of the water purifier.
Also, the conditions for dissolving or eluting the sterilization chemicals differ according to water purifier operation conditions (e.g., raw water pressure, flow rate, etc.). For example, when the flow rate is low, sterilization density may relatively increase, and when the flow rate is high, sterilization density may decrease, causing difficulty in controlling sterilization. Thus, if the density of the sterilization chemicals is high, the purified water will possibly smell bad.
In addition, the sterilization material generated by the sterilization chemicals is mainly an OCl− material having either a very low or very high pH, emitting an offensive odor, and since the sterilization performance of the sterilization material is merely about 1/70 that of HOCl, a larger amount of sterilization material is required to sterilize a tank having the same capacity. Thus, sterilization efficiency is drastically degraded as compared with a case in which a sterilization material is formed of a mixed oxide including the HOCl material as a main ingredient by using an electrolytic cell (to be described).
Thus, in an effort to solve the problem of the water purifier sterilized by using the sterilization chemicals, a method for automatically sterilizing the storage tank by using an electrolytic cell has been proposed. FIG. 1 illustrates a water treatment apparatus disclosed in Korean Laid Open Publication No. 2009-0128785.
As shown in FIG. 1, the related art water treatment apparatus 10 filters raw water supplied from a raw water supply unit such as a waterworks (or a water supply system) 15 by means of a water purification filter 14 and stores it in a water tank 13. When the user requests water, the related art water treatment apparatus 10 supplies purified water through a dispenser 17. Here, when it is detected that the purified water accommodated or housed in the interior of the water tank 13 has been contaminated by a contamination level sensor 13a provided in the water tank 13, or when a certain period of time has elapsed, hypochlorous acid is generated by using a chloride supply device 11 and an electrolysis device 12 and supplied to the water tank 13. A cleansing operation of the water tank 13 disclosed in the publication will now be described in detail.
First, when it is detected that the water tank 13 is required to be cleansed by the contamination level sensor 13a, or the like, water accommodated in the water tank 13 is completely drained (or water is mostly drained to have a low level or to be close to the bottom of the water tank 13) by using an extraction pipe (G) and a dispenser 17 or through a drain pipe (F) to sewage 16. When the drainage of water accommodated in the water tank 13 is terminated, a valve (Vg or Vf) is shut off. The chloride supply device 11 supplies chloride such as sodium chloride (NaCl), potassium chloride (KCl), or the like, to the electrolysis device 12, and in order to generate a chloride aqueous solution, raw water (tap water), which has not passed through the water purification filter 14, may be supplied through a raw water supply pipe (B), or purified water which has been filtered by the water purification filter 14 may be supplied through a purified water supply pipe (C) at a rear stage of the water purification filter 14. In this case, after the chloride and raw water (tap water) or purified water is supplied to the interior of the electrolysis device 12, power is applied to an electrode 12a of the electrolysis device 12 after a lapse of a time sufficient for dissolving the chloride, to produce an aqueous solution including hypochlorous acid through electrolysis (an oxidation-reduction reaction) of the chloride aqueous solution. The water tank 13 is filled with the hypochlorous acid aqueous solution produced thereby, until such time as the water tank 13 has a high water level, and this state is maintained for a certain period of time required for sufficiently sterilizing and cleansing the water tank 13. When a certain period of time has lapsed, the hypochlorous acid aqueous solution is discharged to the outside of the water tank 13. In this case, in order to remove the hypochlorous acid aqueous solution, water, which has passed through the water purification filter 14, is supplied to the water tank 13 through the purified water supply pipe (D) or tap water, which has not passed through the water purification filter 14, is supplied to the water tank 13 through a rinsing pipe (H) until such time as the water tank has a high water level, and thereafter, when a certain period of time has lapsed, the rinsing water accommodated in the water tank 13 is drained. These operations are performed several times to complete the cleansing operation of the water tank 13. Thereafter, raw water is filtered through the water purification filter 14 and the purified water is supplied to the water tank 13 so as to be supplied to a user.
However, the related art water treatment apparatus 10 having the foregoing configuration has the following problems.
First, since sterilization water such as the hypochlorous acid aqueous solution is required to be generated to sterilize and cleanse the water tank 13, the chloride supply device 11 is a requisite.
Namely, the related art water treatment device supplies chloride in the form of sodium chloride (NaCl), potassium chloride (KCl), or the like, to the electrolysis device 12 through the chloride supply device 11, and the electrolysis device 12 electrolyzes the chloride aqueous solution to generate the hypochlorous acid aqueous solution.
However, the supply of the chloride to the electrolysis device 12 requires time for the chloride to be completely, or at least mostly, dissolved to generate the chloride aqueous solution, lengthening the cleansing time, and in this case, if a time for dissolving the chloride is intended to be reduced, a stirrer is required.
In addition, a space for installing the chloride supply device 11 is required, and in order to supply a certain amount of chloride to the electrolysis device 12, the structure and controlling of the chloride supply device 11 is complicated.
Second, since the hypochlorous acid aqueous solution is generated through the chloride supply device 11 and the electrolysis device 12, the hypochlorous acid aqueous solution having strong sterilizing power and a strong smell must be completely (or at least mostly) drained from the water tank 13 and a rinsing operation is required to be performed several times. In particular, since the hypochlorous acid aqueous solution having a strong smell may not be sufficiently removed through a single rinsing operation, the user may experience unpleasantness, and, since the rinsing operation must be performed several times, a great deal of time is required for the rinsing operation and a large quantity of water may be consumed.
Third, in the related art water treatment apparatus 10, when raw water (tap water) is supplied through the raw water supply pipe (B), without passing through the water purification filter 14, to the electrolysis device 12, the life span and performance of the electrode are drastically degraded.
Namely, when unfiltered raw water (tap water) is supplied to the electrolysis device 12, various foreign materials are supplied to the electrolysis device 12 to shorten the life span of the electrode 12a, reduce the area in which the electrolysis reaction occurs, generating air or an overcurrent, or the like.
Meanwhile, in the related art water treatment apparatus 10, when water, which has passed through the water purification filter 14, is supplied to the electrolysis device 12 through the purified water supply pipe (C), the amount of total dissolved solids (TDS) may be significantly reduced and fail to supply a sufficient amount of electrolytes to the electrolysis device 12, and thus, without the chloride supply device 11, a mixed oxidant (MO) (a sterilizing material) having a certain concentration or higher required for exhibiting the sterilizing performance cannot be generated. Namely, as mentioned above, the water purification filter 14 includes a plurality of filters such as the RO membrane filter, so when water passes through all of the filters, such as the RO membrane filter, the amount of TDS is considerably reduced, failing to generate the mixed oxidant required for implementing the sterilizing performance with only the purified water.
Also, in the related art water treatment apparatus 10 illustrated in FIG. 1, water, which has passed through the water purification filter 14, moves to the water tank 13 or the electrolysis device 12. Thus, in this related art, the flow path is merely changed to allow water, which is to flow to the water tank 13, to flow to the electrolysis device 12 (namely, the flow path (C) is diverged from the flow path (D), so the flow rate of water introduced to the electrolysis device 12 cannot be controlled. Namely, in the related art, the flow rate cannot be controlled over the electrolysis device 12, causing a problem in which the concentration (or density) of the sterilizing material generated in the electrolysis device 12 is not uniform.
Fourth, in the related art water treatment apparatus 10, purified water accommodated in the water tank 13 is completely (or at least mostly, to have a low water level or to be close to the bottom) drained before the hypochlorous acid aqueous solution is supplied to the water tank 13 to cleanse the water tank 13, and to this end, excessive time may be required to drain water and a large amount of water may be wasted (i.e., water wastage is severe).
In particular, in the related art water treatment apparatus 10, the large capacity water tank 13 is completely (or mostly) emptied and the interior of the water tank 13 is filled with the hypochlorous acid aqueous solution, an operation time of the electrolysis device 12 for supplying the hypochlorous acid aqueous solution is lengthened, consuming excessive power, shortening the life span of the electrode 12a, and requiring a lengthy period of time to supply the hypochlorous acid aqueous solution.
Fifth, in the related art water treatment apparatus 10, natural drainage is employed to empty the water tank 13 in the draining operation before the hypochlorous acid aqueous solution is supplied, in the draining operation of the hypochlorous acid aqueous solution, and in the draining operation of a rinsing solution. This requires a large amount of time for drainage, and as a result, a relatively large amount of time is required to sterilize and cleanse the water tank 13.
In particular, as mentioned above, the requirement of a lot of time for sterilizing and cleansing the water tank is quite burdensome to the user or the water purifier manager, and although the sterilizing and cleansing processes are performed at nighttime when a user does not frequently use the water purifier, a user cannot use the water purifier while the water tank is being sterilized and cleansed and noise generated by the sterilizing and cleansing operation is maintained for a long period of time, causing user inconvenience.
Sixth, in the related art water treatment apparatus 10 illustrated in FIG. 1, a dispenser (cock) 17 can be sterilized and cleansed by discharging the hypochlorous acid aqueous solution through the dispenser (cock) 17. In this case, however, a waterspout member is required to receive the discharged sterilizing and washing water. In particular, considering that the water tank 13 has a large capacity, there is a limitation in automatic drainage.