Abstract:
Process and apparatus to remove colloids and nitrogen compounds from contaminated water by coagulating the colloids and separating them from the water. The water is then continuously oxidized with chlorine electrolytically to destroy the nitrogen compounds.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Non-provisional application Ser. No. 13/449,255, filed on Apr. 17, 2012 which claims priority to and is a continuation of U.S. Non-provisional application Ser. No. 11/694,306, U.S. Pat. No. 8,157,984, filed on Mar. 30, 2007, both of which are incorporated by reference in their entirety. U.S. Non-provisional application Ser. No. 11/694,306 is a non-provisional of U.S. Provisional Application Ser. No. 60/787,907, filed on Mar. 31, 2006, and is also a non-provisional of U.S. Provisional Application Ser. No. 60/788,278, filed on Mar. 31, 2006, both of which are incorporated herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to a process for water purification and to an apparatus for carrying out the process. The invention further relates to the electrolytic chlorination of the purified water. 
     BACKGROUND 
     Economical and efficient methods and apparatus for purifying contaminated water, particularly water containing fatty acids, have long been sought. Contaminated water, e.g., waters containing soluble nitrogen compounds, suspended organic colloidal emulsions or suspensions such as effluents from meat processing plants, dairies, cheese processing plants, bakeries, chemical plants, paper plants and petroleum plants and effluents including raw sewage are of particular interest. 
     The colloids have a negative charge which prevents them from coalescing and makes filtration or separation practically impossible. Previous methods for water purification include combining the fatty acid contaminated water with metallic ions released from electrodes during electrolysis to form hydrophobic, metallic soaps. Bivalent or trivalent metal ions are released from electrodes during electrolysis and combine with the fatty acids to form an insoluble flocculant. The flocculant, in turn, entrains or absorbs other impurities present in the contaminated water. Thus, the flocculant serves as a transport medium to remove not only fatty acids, but also other impurities from the water. In order to ensure continuous production of ions, the electrodes were disposed in a moving bed of solid particles. The solid particles were kept in motion by the flow of process water through the electrolysis chamber in order to continuously abrade and clean the electrode surfaces. The flocculant and entrained impurities were directed to a flocculation/separation basin where the flocculant and entrained impurities were separated by flotation, leaving purified water for withdrawal from the basin. 
     Electrolytic water treating systems, including electro-flotation and electrocoagulation systems, while functional, have difficulties when their electrodes become covered with an insoluble layer that is not removable by merely changing the polarity of the electrodes. This is especially true when sewage water containing fatty acids is electrolyzed with metal electrodes which form an insoluble metal soap at the surface of the anode which is difficult to remove. 
     Current electrolytic water treating systems clean the electrodes by a moving bed of hard particles and introduces air before the electrolytic cell to move the bed and the water through the system. However, it has been found that bubbles before the electrolytic cells increase the electrical resistance between the electrodes thereby requiring higher voltages and inducing excess wear on electrodes, walls and parts of the cell. 
     After the majority of contaminants have been removed, remaining dissolved and suspended contaminating materials need to be removed and have been electrolytically treated with chlorine. Chlorine is normally made electrolytically, continuously introducing a concentrated salt solution (chloride ions) into the anode compartment of an electrolysis cell which is separated from the cathode compartment by a permeable diaphragm. Before the advent of ion exchange diaphragms the diaphragm were made of many plies of asbestos paper between anode and cathode to prevent as much as possible mixing of the caustic produced in the cathode compartment with the chlorine produced in the anode compartment. Currently, cationic ion exchange diaphragms that prevent the flow of anions and of solutions from one compartment to another are typically used. 
     Chlorine as sodium hypochlorite may be made by electrolyzing salt water without the use of diaphragms. This process is especially useful for swimming pool applications. This process has the disadvantage of using salt and the calcium and magnesium present in the water to form carbonates which deposit on the cathode eventually isolating it and preventing current flow between the electrodes. The cathode must then be cleaned with acid to remove the calcareous coating. 
     The standard electrolytical technique to chlorinate water in swimming-pools is to provide a separate cell containing a high concentration of common salt which upon electrolysis gives sodium hypochlorite or chlorine which is fed into the swimming-pool. Theoretically, it is possible to add sufficient common salt to the swimming-pool water and to electrolyze it directly. However, this technique has the disadvantage that the water tastes salty to the bathers and that the calcium contained in the water deposits onto the cathodes to such an extent that the flow of the current stops or is impaired. Changing of polarity to remove the calcium deposits on the cathodes has been found in practice to lead to corrosion of the cathode. 
     The water purification industry has continued to seek new and improved methods for removing fatty acids and other contaminants from water. Accordingly, there has been a long-felt but unfulfilled need for more economical, more efficient and more convenient methods for purifying water, particularly water contaminated with fatty acids and other contaminants and treating the purified for eventual discharge or use. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention describes a chlorination system is described as having one or more anodes, a porous diaphragm surrounding the anodes, a cathode surrounding the porous diaphragm, means for directing the flow of fluids towards the anode, and means for preventing the backflow of fluids out of the cell. Preferably, the porous diaphragm is permeable enough to allow laminar flow but tight enough to prevent turbulent flow. In some embodiments, the system also includes a non-conductive separator spaced between the anode and the porous diaphragm and surrounding the anodes. The anode may be made of carbon, titanium covered with platinum, titanium covered with ruthenium oxide, or other non corrodible elements. In some embodiments, the means for directing the flow of fluids towards the anode is a porous diaphragm having a non-permeable bottom and an open top. In some embodiments, the means for preventing the backflow of fluids is a check valve, ball valve, or gate valve. 
     In another embodiment of the invention, a water chlorination process is described as having the following steps: (a) flowing a water stream in an upward direction into an electrolytic cell comprising an anode compartment and a cathode compartment separated by a porous diaphragm; (b) concentrating chloride ions in the water in the anode compartment via electrodialysis, (c) accumulating hydrochloric acid in the anode compartment. In some embodiments, the process also includes intermittently diffusing the hydrochloric acid from the anode compartment to the cathode compartment through the porous diaphragm. 
     In another embodiment of the invention, an apparatus for the purification of contaminated waste having (a) an electrolytic cell, (b) an entry port below the electrolytic cell, (c) an upper section above the electrolytic cell including an air sparger and an outlet, (d) a closed draining space adjacent to the upper section comprising means for separating water and impurities, and (e) a re-circulating pump connecting the outlet to the entry port of the electrolytic cell. The electrodes of the electrolytic cell are preferably connected in series. The apparatus may also include an inclined bottom basin which slopes away from the upper section having a purified water outlet at the lower end of the inclined bottom opposite the upper section, a recirculating outlet located above the purified water outlet, and an exit port located above the recirculating outlet. The re-circulating outlet may be connected to the re-circulating pump. In alternate embodiments, the apparatus may also include a filter such as, but not limited to, a rotary vacuum filter, a filter press, conveyor belt vacuum filter, a sand filter or a centrifuge filter. In some embodiments, the upper section is conical in cross section and the electrodes may be iron, magnesium, aluminum and their alloys. In some embodiments, the polarity of the electrodes is cycled continuously and the frequency of cycling the polarity of the electrodes is between about 1 change per 1 second and about 1 change per 10 minutes. In some embodiments, a chlorinator is also included in the apparatus. 
     In another embodiment of the invention, a water purification process having the following steps is described; (a) passing contaminated water in a generally vertically upward direction through an electrolytic cell having a plurality of electrodes surrounded by a moving bed of solid, non-conductive particles to form a hydrophobic floc comprising purified water, water, impurities and suds; (b) directing the floc to a closed chamber directly connected to an upper end of the electrolysis chamber; (c) separating the impurities, suds and water from the purified water; (d) recirculating a portion of the water from the closed chamber to the electrolytic cell; (e) removing the impurities and suds from the closed chamber, and (f) removing the purified water from the closed chamber. In some embodiments, air is sparged above the electrolytic cell and the electrodes are connected in series with the polarity of the electrodes being changed continuously. In some embodiments, the upward velocity of the water is partially accomplished by re-circulating the water through the cell and the contaminated water is directed through the moving bed by pressure. The non-conductive particles are preferably granite and have a specific density greater than that of the contaminated water and their free falling velocity is greater than the upward velocity of the water. In some embodiments, the purified water is further chlorinated. In some embodiments, the polarity of the electrodes is being alternated by applying a direct current voltage and the frequency in change of polarity ranges from about 1 change per second to about 1 change per 10 minutes and the change of polarity has the same duration. In some embodiments, additional soap solution is added to the water to be purified and micro bubbles are produced utilizing the change in pressure due to a re-circulation pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an embodiment of a water purification apparatus and process in accordance with the present invention. 
         FIG. 2  shows an alternate embodiment of the apparatus and process for the purification of water in accordance with the present invention. 
         FIG. 3  shows a horizontal cross section of an embodiment of an electrolytic cell. 
         FIG. 4  shows a vertical cross section of the embodiment of  FIG. 3 . 
         FIG. 5  shows a horizontal cross section of an alternate embodiment of an electrolytic cell. 
         FIG. 6  shows a vertical cross section of the embodiment of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Contaminated water is treated electrolytically to produce highly positive compounds using corrodible electrodes to form with high molecular weight organic acids highly positive insoluble hydrophobic soaps which traps organic compounds and encapsulates some microbes. Contaminated water sources include, but are not limited to, water from meat processing plants, dairies, cheese processing plants, bakeries, chemical plants, paper mills, and petroleum plants and effluents including raw sewage. 
       FIG. 1  shows a preferred embodiment of a water purification apparatus. An inlet conduit  1  is connected to the bottom of an electrolytic cell  2 . At the top of the electrolytic cell  2  is an upper section  4  having an outlet passage  5 . The upper section  4  preferably includes a conical section  3  connected to the top of the electrolytic cell  2  and an outlet conduit  18 . The outlet passage  5  is located above the conical section  3 . Between the outlet passage  5  and the conical section  3 , the outlet conduit  18  exits the upper section. Outlet conduit  18  includes line  21  and is fed to the inlet of a re-circulating pump  13 . Air and additional soap may be introduced through line  21  into the system. The upper section  4  is preferably closed to the atmosphere. 
     Electrodes  6  are mounted in cell  2  in any suitable way (not shown in the drawing) and are connected in series to a direct current source which is changed in polarity continuously. The change in polarity of the current insures the equal corrosion of the end electrodes which are connected in series to the current source but enhances the cleaning action of the fluid bed. The frequency of change in polarity is preferably done at equal periods of time. In some embodiments, continuously, as referred to herein, refers to changing the polarity between about 1 change per 1 second to about 1 change per 10 minutes and is dependent upon the amount of contaminants in the water and the tendency of the contaminants to accumulate on the electrodes. 
     In some embodiments, the electrodes  6  are preferably corrodible and made of, but not limited to divalent or trivalent metals, such as, aluminum, iron, magnesium or their combination or alloys. The electrodes are connected in series to a direct current source whose polarity is changed during short, preferably, equal periods of time. The electrodes  6  are surrounded by a moving bed of solid non-conductive hard particles whose specific density is greater than that of the contaminated water. 
     In some embodiments of the invention, located at the top of the conical section  3 , above the point where the solid particles have settled, is an air sparger  7 . The air sparger  7  supplies additional bubbles besides those formed during electrolysis to the upper section  4 . The air sparger  7  may be connected to a compressed air supply  8 . The compressed air produces bubbles to float the flocs produced by the release of metallic soaps during the electrolysis of the water to be purified. In some embodiments, the air bubbles are introduced after the electrolytic cell. 
     Although a conical section  3  is shown, any cross-section may be used and preferably a cross-section which will decrease the upward moving velocity of the water to a value where the solid particles will settle down into the electrolytic cell is used. The solid particles free falling velocity in water should be higher than the upward moving velocity of the water. The flow through the flocculation basin should preferably be maintained to allow any solid particles which are carried away from the bed to return to the electrolysis chamber. 
     Outlet passage  5  is connected to basin  9 . Basin  9  also includes a draining space  15  that may have an inclined bottom  10 . A recirculating conduit  11  is near the upper edge of the basin and preferably opposite from the outlet passage  5 . The basin  9  is preferably closed to the atmosphere. A purified water outlet  12  is at the bottom of basin  9 , also preferably opposite from the outlet passage  5 . A suds outlet  16  is located opposite the outlet passage  5 , preferably some distance away to allow acceptable separation of the floc and the purified water. Recirculating conduit  11 , along with outlet conduit  18 , is fed to re-circulating pump  13  whose outlet  14  may be connected to the inlet conduit  1  below the electrolytic cell  2 . Basin  9  also includes a suds outlet  16  which is located above the draining space  15 . The location of the recirculating conduit  11  is preferably located near or below the layer of bubbles in order to catch any settling floc and recycling it to the electrolytic cell. This insures that all floc preferably exits through the suds outlet  16 . 
     Both upper section  4  and basin  9  are preferably closed to the atmosphere. In practice, it has been found that exposure to the atmosphere dries out and bursts the bubbles and the flocs tend to settle, making it difficult to obtain a pure water free of flocs. The closed environment protects the bubbles carrying the flocs against drying and bursting. The bubbles are also drained of excess water and delivered through the suds outlet  16  to the atmosphere. Basin  9  preferably has sufficient capacity to hold water being treated for approximately 15 minutes to obtain maximum separation of water and flocs. In alternate embodiments, the basin  30  is sized to hold water being treated for about 10 minutes, 20 minutes or whatever time necessary to allow separation of the flocs and water and allow the flocs to rise to the top. 
     During operation, contaminated water flows through inlet conduit  1  and upward into the electrolytic cell  2 . High molecular weight organic acids combine with metallic ions released from the electrodes forming highly positive insoluble hydrophobic soaps which trap organic compounds and encapsulates microbes. These highly positive compounds neutralize the negatively charged colloids permitting the colloids to coalesce, making filtration or separation possible. Floc is formed through the build-up of colloidal hydrated oxides of the separated metal ions. The floc binds, or absorbs, other impurities present in the contaminated water and serves as a transport medium to remove the impurities from water. 
     The solid non-conductive particles are moved at various speeds in various directions, by way of the water flow and gasses produced in the electrolytic cell, against and along the surfaces of the electrodes to insure cleaning of the electrodes. An additional electrode cleaning effect results from the return motion of those solid particles which have been carried along with water and which move past the electrodes as they settle downward. 
     The contaminated water is directed through the moving bed of particles in the electrolytic cell by the inlet water pressure. In some embodiments, the pressure is provided by the re-circulating pump  13 . In other embodiments, air is blown into the bed to intensify its motion. In alternate embodiments, additional air is provided by supplying air into the suction side of the re-circulating pump via line  21 . In a preferred embodiment, the contaminated water is generally directed through the moving bed in substantially vertically upward direction. 
     Water containing flocs and bubbles is led through passage  5  to basin  9  and the draining space  15 . Purified water leaves via purified water outlet  12  which is preferably at a level below that of the suds layer during operation. Recirculating conduit  11  and conduit  18  leads recirculating water with flocs through pump  13  and conduit  14  to intake conduit  1 . Conduit  18  recirculates the upper layer of water in the conical section of the electrolytic cell through the electrodes. 
     Some embodiments include valve  19  and valve  20  which may be used to control the re-circulation ratio. Soap solution and additional air is supplied to water outlet conduit  11  through line  21 . Additional soluble soaps may be introduced into the water in some embodiments, particularly where the amount of high molecular weight organic acids or esters are insufficient in the contaminated water to be treated to form the electrolytically highly positive metallic soaps required for coagulation. Due to the pressure supplied by the pump  13 , the air and soap added through line  21  will generally be compressed and dissolved into the water and will form very small micro-bubbles in the electrolytic cell. 
     Suds outlet  16  delivers drained suds  17  to the atmosphere. The drained suds contain substantially all of the impurities of the contaminated water feed. These hydrophobic flocs are easy to dry and handle. In some embodiments, flocs may be used as fertilizer after being sterilized. In alternate embodiments, the flocs are dried and may be used as fuel. 
       FIG. 2  shows an alternate embodiment of a water purification system. An inlet conduit  22  is connected to the bottom of an electrolytic cell  23 . At the top of the electrolytic cell  23  is an upper section  24  having a outlet passage  26 . The upper section  24  preferably includes a conical section connected to the top of the electrolytic cell  23  and a recirculating conduit  32 . The outlet passage  26  is located above the conical section. Between the outlet passage  26  and the conical section, the recirculating conduit  32  exits the upper section  24 . Recirculating conduit  32  includes line  33  and is fed to the inlet of a re-circulating pump  39 . Air and additional soap may be introduced through recirculating conduit  32  into the system. The upper section  24  is preferably closed to the atmosphere. 
     Electrodes  27  are mounted in cell  23  in any suitable way (not shown in the drawing) and connected in series to a direct current source which is changed in polarity continuously. The change in polarity of the current insures the equal corrosion of the end electrodes which are connected in series to the current source but enhances the cleaning action of the fluid bed. The frequency of change in polarity is preferably done at equal periods of time. In some embodiments, continuously, as referred to herein, refers to changing the polarity between about 1 change per 1 second to about 1 change per 10 minutes and is dependent upon the amount of contaminants in the water and the tendency of the contaminants to accumulate on the electrodes. 
     In some embodiments, the electrodes  27  are preferably corrodible and made of, but not limited to divalent or trivalent metals, such as, aluminum, iron, magnesium or their combination or alloys. The electrodes are connected in series to a direct current source whose polarity is changed during short, preferably, equal periods of time. The electrodes  27  are surrounded by a moving bed of solid non-conductive hard particles whose specific density is greater than that of the contaminated water. 
     In some embodiments of the invention, located at the top of the conical part of the upper section  24 , above the point where the solid particles have settled, is an air sparger  28 . The air sparger  28  supplies additional bubbles besides those formed during electrolysis to the upper section  24 . The air sparger  28  may be connected to a compressed air supply  29 . The compressed air produces bubbles to float the flocs produced by the release of metallic soaps during the electrolysis of the water to be purified. In some embodiments, the air bubbles are introduced after the electrolytic cell. 
     Although a conical section is shown, any cross-section may be used and preferably a cross-section which will decrease the upward moving velocity of the water to a value where the solid particles will settle down into the electrolytic cell is used. The solid particles free falling velocity in water should be higher than the upward moving velocity of the water. The flow through the flocculation basin should preferably be maintained to allow any solid particles which are carried away from the bed to return to the electrolysis chamber. 
     Outlet passage  26  is connected to basin  30 . Basin  30  also includes a draining space  37  that may have an inclined bottom. Opposite the outlet passage  26  is a filter  34 . In a preferred embodiment, the filter  34  is a rotating vacuum filter. In alternate embodiments, the filter may be filter press, a conveyor belt vacuum filter, a sand filter, a centrifuge filter, or any filter known to one skilled in the art. Basin  30  preferably has sufficient capacity to hold water being treated for approximately 15 minutes to allow flocks to grow before filtering. In alternate embodiments, the basin  30  is sized to hold water being treated for about 10 minutes, 20 minutes or whatever time necessary to allow flocks to grow before filtering. 
     Both upper section  24  and basin  30  are preferably closed to the atmosphere. In practice, it has been found that exposure to the atmosphere dries out and bursts the bubbles and the flocs tend to settle, making it difficult to obtain a pure water free of flocs. The closed environment protects the bubbles carrying the flocs against drying and bursting. The bubbles are delivered to the filter  34 . 
     During operation, contaminated water flows upwardly through inlet conduit  22  into electrolytic cell  23  and through the upper section  24 . Passage  26  delivers water and suds to basin  30 . After being filtered through filter  34 , filtered water is delivered through central pipe outlet  35  via vacuum pump (not shown) to atmospheric pressure. Filtered solids  36  are scraped from rotating filter  34  by scraper  38 . In some embodiments, the filtered water is passed through a chlorinator. In some embodiments, the filtered solids may be sterilized and used as fertilizer or dried and used as fuel. 
     After contaminated water has been treated to remove colloids, soluble nitrogen compounds may be reacted with chlorine. In one embodiment of the invention, chloride ions are introduced into a cathode compartment and transferred to an anode compartment by electro-dialysis. 
       FIG. 3  shows a horizontal cross section of one arrangement of an electrolytic cell of the invention.  FIG. 4  shows a vertical cross section of cell arrangement of  FIG. 3 . 
     Electrodes (anodes)  301  are surrounded by a non-conductive separator  302  which is further surrounded by a porous diaphragm  303  which is further surrounded by a metal cathode  304 . In a preferred embodiment, the electrodes are solid carbon. In alternate embodiments, the electrodes may be platinum, titanium covered with platinum or with ruthenium oxide. The non-conductive separator surrounds the electrodes  301  but provides sufficient free space  306  within the anode compartment to accumulate at least the necessary amount of hydrochloric acid to react with the calcareous deposits on the cathode. The non-conductive separator  302  is preferably a plastic grid. In alternate embodiments, the non-conductive separator  302  is glass. The non-conductive separator  302  is preferably thin. In some embodiments, the non-conductive separator is about 0.5 millimeters thick. The porous diaphragm  303  may be made of, but is not limited to, porous porcelain, porous PVC, poly-propylene felt, close-woven filter cloth and others. The porous diaphragm  303  preferably includes a non-permeable bottom and a permeable top. The non-conductive separator  302  preferably enhances the free flow of gases between the permeable diaphragm  303  and the electrodes  301 . The permeable diaphragm  303  is preferably a porous membrane which allows free laminar flow of solutions between the anode and cathode compartments, but close-woven or tight enough to prevent turbulent flow. In some embodiments, the cathode is made of stainless steel. 
     An outer surrounding pipe  307  encircles the cathode and conducts water  308  to be chlorinated in a substantially vertical upward flow. A valve  309  may be provided in the inlet line to prevent the backflow of fluids. Although a valve is shown, any valve or other mechanism that prevents the backflow of water may be used. In some embodiments, a check valve is used. 
     During the chlorination process, electricity and water may be simultaneously shut off to allow the accumulated hydrochloric acid in free space  306  and diffuse out through diaphragm  303  to react and dissolve any calcareous deposits on cathode  304 . 
       FIG. 5  shows another embodiment of the invention having an anode  411  surrounded by porous diaphragm  413  which is further surrounded by a metal cathode  414 . In a preferred embodiment, the anode  411  is made of expanded titanium covered with platinum or covered with ruthenium oxide or other non-corrodible elements. In alternate embodiments, the anode  411  may be made of graphite or other rust-proof alloy. The porous diaphragm  413  may be made of, but not limited to, porous porcelain, porous PVC, poly-propylene felt, close-woven filter cloth and others. The porous diaphragm  413  preferably includes a non-permeable bottom and an open top. The permeable diaphragm  413  is preferably a porous membrane which allows free laminar flow of solutions between the anode and cathode compartments, but close-woven or tight enough to prevent turbulent flow. 
     The distance between the anode  411  and the diameter of inner centered rod  415  provides sufficient free space  416  within the anode compartment to accumulate at least the necessary amount of hydrochloric acid to react with the calcareous deposits on the cathode. 
     Outer surrounding pipe  417  encircles the cathode and conducts water  418  to be chlorinated, in a substantially vertical upward flow. A valve  419  is provided in the inlet line to prevent the backflow of fluids. Although a valve is shown, any valve or mechanism that prevents the backflow of water may be used. 
     During the chlorination process, electricity and water are simultaneously shut off to allow hydrochloric acid to accumulate in free space  416  and diffuse out through diaphragm  413  to react and dissolve any calcareous deposits on cathode  414 . 
     Not shown in  FIGS. 3 ,  4  and  5  are the electrical connections to the anode or to the cathode which are respectively connected to the positive and to the negative pole of a direct current supply. 
     An example of the cell arrangement as shown in  FIG. 3 , has carbon electrodes measuring 1 inch in diameter by 10 inches in length, operating with water containing 40 parts per million of chlorides, will start producing chlorine in less than one minute. This is the time it takes for the chloride concentration to reach the level where chlorine is produced. 
     There are many other configurations possible, for instance flat expanded metal electrodes may be used with the free space required for the hydrochloric acid being formed behind the anode. 
       FIG. 6  shows another embodiment of the invention where an anode  519  is bent and surrounded with a diaphragm  520  to provide free space  522 . Also shown is a bent cathode  521  surrounding anode  519 . An impermeable wall  525  holds diaphragm  520  in place preventing diffusion through the flat portion of the diaphragm  520  facing the anode  519 . Outer surrounding pipe  523  conducts water  524  in a substantially vertical upward flow. The anode  519 , cathode  521 , and diaphragm  520  are as described for  FIG. 3  or  5 . 
     Embodiments of the chlorinator of the invention may be used in a wide variety of applications, including for example, in combination with the systems shown in  FIGS. 1 and 2 . However, embodiments of the chlorinator may be used apart from the systems shown in  FIGS. 1 and 2 , including for example, in swimming pools or to purify any aqueous stream containing soluble contaminants, such as urea and/or microbes. 
     The present invention and the embodiment(s) disclosed herein are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited is to be understood as referring to all equivalent elements or steps. The description is intended to cover the invention as broadly as legally possible in whatever forms it may be utilized.