Patent Publication Number: US-2021169053-A1

Title: Method for Neutralizing and Removing Ammonia from an Aqueous Solution

Description:
TECHNICAL FIELD 
     These claimed embodiments relate to a method for neutralizing for removing ammonia from an aqueous solution. 
     BACKGROUND OF THE INVENTION 
     A method and apparatus for neutralizing and removing ammonia from any aqueous solution is disclosed. 
     In an aquaculture application in which the finfish or shrimp are farmed in a self-contained aqueous solution in a closed loop environment, the waste from the shrimp generates toxic ammonia. High amounts of ammonia result in mortality events in the fish or shrimp. Bi-products of attempts to treat the solution and remove the ammonia have also killed the shrimp/fish. Many solutions to remove the bi-products have required costly filtration or chemicals being added to the aqueous solution. 
     Processes have used electrolytic cells to produce gases from reactions in the treatment of water in aquaculture applications. Other processes have used electrolytic cells to produce a chemical reaction while submerged in the treatment loop in aquaculture applications, this process is known to be very inefficient and not cost effective in the aquaculture application. Such systems also only work in saltwater species, as they depend on sodium chloride in the aquaculture medium to serve as a weak electrolyte. 
     Many prior processes are not very efficient and have not been cost effective in neutralizing the ammonia. Examples of prior processes and principles are described in “Ionization of ammonia and deuterated ammonia by electron impact from threshold up to 180 eV”, J. Chem. Phys. 67, 3795 (1977) by T. D. Mark, F. Egger, and M. Cheret, Synergy of Water and Ammonia Hydrogen Bonding in a Gas-Phase Reaction, Wen Chao, Cangtao Yin, Yu-Lin Li, Kaito Takahashi, Jim Jr-Min Lin, J. Phys. Chem. A 2019, 123, 7, 1337-1342, Jan. 25, 2019 of the American Chemical Society. 
     SUMMARY OF THE INVENTION 
     One general aspect includes a method for reducing the ammonia level of an aqueous solution in a tank. The method includes applying a positive electrically charged current into a brine solution in a first chamber. A negatively charged current is applied into a caustic solution in a second chamber separated from the first chamber by a membrane resulting in Hydrogen gas (H 2 ) being extracted from the caustic solution in the second chamber and chlorine gas being extracted from the brine solution in the first chamber. The extracted hydrogen gas is injected into the aqueous solution containing un-ionized ammonia to neutralize the un-ionized ammonia by converting the un-ionized ammonia to ammonium (ionized ammonia). Chlorine gas is injected into the ammonium to produce a chloramine byproduct. Byproducts produced from the injection are filtered to produce an ammonia free solution. The ammonia free solution is fed back in the aqueous tank. The chlorine gas or hydrogen gas may be injected into the ammonium at a rate based on ammonia concentration originating from the aqueous tank. The chlorine gas or hydrogen gas may be injected at a rate based on a concentration of bacteria and parasitic entities in the aqueous tank. The byproducts produced from the injection into the aqueous stream may be filtered using a catalytic carbon filter. 
     In another embodiment, a method of toxic ammonia compound removal from an aqueous solution includes injecting hydrogen and chlorine gases into a closed-loop aqueous tank containing the toxic ammonia compound to incite various chemical reactions. Bi-products resulting from the various chemical reactions may be removed with filtration and adsorption to effectively eliminate all of the toxic ammonia compounds. The aqueous solution may contain an aquatic species. 
     In a further implementation, a method of neutralizing the toxic action of un-ionized ammonia (NH 3 ) within a solution containing an aquatic species includes ionizing the un-ionized ammonia, originating from the solution containing the aquatic species, with electrolytically produced hydrogen gas (H 2 ) to form a neutralized ionized ammonia (NH 4 +). The neutralized ionized ammonia may be injected into the solution containing the aquatic species. A flow and volume of the un-ionized ammonia may be altered to increase contact time with the gases based on the concentration of bacteria in the solution containing the aquatic species. Chlorine gases may be injected into the neutralized ionized ammonia to produce chloramine byproducts. Byproducts produced from the injection of the chlorine gases into the neutralized ionized ammonia may be filtered to produce an ammonia free solution, and the ammonia free solution may be re-injected into the solution containing the aquatic species. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference number in different figures indicates similar or identical items. 
         FIG. 1  is a system diagram illustrating an operation of a membrane separation cell; 
         FIG. 2  is a system diagram illustrating an apparatus for producing chlorine and hydrogen gases using a chemical storage device, a dry electrolytic cell chamber, a gas delivery apparatus, and a membrane assembly; and 
         FIG. 3  is a flow diagram of a process for extracting ammonia from an aqueous solution using the apparatus shown in  FIGS. 1 and 2 . 
         FIG. 4  is a chart showing the effects of Ammonia concentrations in water on various aquatics species over a 48-hour period. 
         FIG. 5  is a chart showing a relationship between bacterial survival on chlorine concentration decay in a solution over a 30-minute time period. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  there is shown a membrane separation cell  100  using a chloralkali process. The most common chloralkali process involves the electrolysis of aqueous sodium chloride (a brine, a saline or an aqueous based solution) in a membrane cell. Cell  100  includes first chamber  102  coupled through Polytetrafluoroethylene membrane  104  to second chamber  106 . 
     First chamber  102  is coupled to a brine input  121 , a recycled exhausted brine output  122 , and a Cl 2  gas output  123 . Second chamber  106  is coupled to a water (H 2 O) input  130 , a NaOH recycle output  131 , and a Hydrogen (H 2 ) gas output  128 . An anode  125  is inserted into first chamber  102  to supply a positive charge to solution in chamber  102 , and a cathode  127  is inserted into second chamber  106  to supply a negative charge to solution in chamber  106 . Anode  125  and cathode  127  are connected to the positive and negative terminals respectively of a Distributed Current power source (not shown). 
     Saturated brine solution  124  is passed via brine input  121  into the first chamber  102  of the cell  100 , and water is passed into the second chamber via water input  130 . In first chamber  102  the chloride ions in the Brine solution are oxidized at the anode  125 , losing electrons to become chlorine gas using the equation: 
       2Cl−→Cl 2 +2 e− 
 
     At the cathode  127 , positive hydrogen ions pulled from water molecules are reduced to hydrogen gas by the electrons that are provided by the electrolytic current, thereby releasing hydroxide ions into the solution using the formula: 
       2H 2 O+2 e −→H 2 +2OH−
 
     The ion-permeable ion exchange membrane  104 , separating the first chamber  102  from the second chamber  106 , allows sodium ions (Na+) in brine solution  124  in the first chamber  102  to pass to the second chamber where they react with the hydroxide ions in water  129  in chamber  106  to produce a caustic soda. 
     The overall reaction for the electrolysis of brine is thus: 
       2NaCl+2H 2 O→Cl 2 +H 2 +2NaOH
 
     Thus membrane  104  prevents the reaction between the chlorine in the brine and hydroxide ions in water. If this reaction were to occur, the chlorine would disproportionately form chloride and hypochlorite ions using the equation: 
       Cl 2 +2OH−→Cl−+ClO−+H 2 O
 
     If the brine is heated to above 60° C., chlorate can be formed citing the equation: 
       3Cl 2 +6OH−→5Cl−+ClO 2 −+3H 2 O
 
     Due to the corrosive nature of chlorine production, the anode  125  (where the chlorine is formed) should be non-reactive and in one implementation made from platinum metal, graphite, or a mixed metal oxide clad titanium anode (also referred to as a dimensionally stable anode). Historically, magnetite, lead dioxide, manganese dioxide, and ferrosilicon have also been used as anodes. Unclad titanium cannot be used as an anode because it anodizes, forming a non-conductive oxide and passivates. 
     In one implementation, the cathode  127  (where hydroxide forms) is constructed from unalloyed titanium, graphite, or a more easily oxidized metal such as stainless steel or nickel. If current applied to Anode  125  and Cathode  127  is interrupted while cathode  127  is submerged, cathodes constructed from easily oxidized materials such as stainless steel could dissolve in an unpartitioned cell. 
     Referring to  FIG. 2 , there is shown a system diagram of a gas production device  200  that includes chemical storage device  240  coupled to gas delivery apparatus in chamber  242  via a membrane assembly  244 . Coupled to chemical storage device  240  and gas delivery apparatus in chamber  242  is dry cell chambers  246 . 
     Chemical storage device chamber  240  includes a Cl 2  gas out valve  201  a Cl 2  Off-Gas Bell  202 , a Cl 2  Delivery Riser Tube  203 , a Cl 2  Atmospheric Isolated Pressure Vessel  204 , a Submerged Brine Vessel Manifold  205 , a 26-28% Brine Solution (NaCl) tank  208 , a Float/Autofill/Shut-off Assembly  209  and a Fill Tube/Turbulator  210 . 
     Gas delivery apparatus  242  includes a Caustic Side Fresh H 2 0 Inlet  220 , a Float/Autofill/Shut-off Assembly  221 , a Fill Tube/Turbulator  222 , a Submerged Caustic Vessel Manifold  226 , a H 2  Gas Outlet  227 , a H 2  Off-Gas Bell  228 , a H 2  Delivery Riser Tube  229  and a H 2  Atmospheric Isolated Pressure Vessel  230 . 
     In one implementation the electrolytic solution vessels  204  and vessels  230  will be applied on a negative pressure application only. Water will be automatically filled through an assembly that responds to a float for fluid level controls. The assembly may contain an overfill emergency shutoff in case there is a blockage. 
     The tank  208  (filled with brine solution) and tank  232  (filled with a caustic solution) are separated atmospherically but manifolded below the water level. This allows a displacement in the event of a pressure build-up that will cause the main vessel waterline to rise, triggering a system shutdown. 
     Feeds  213  and  220  may consist of purified Reverse Osmosis water. The Brine side tank  208  will periodically require pure NaCl be inserted into the feed in the form of powder, granules, or crystalized rock salt. In the case of the latter, time will be needed to dissolve the NaCl before operation. 
     Membrane assembly  244 , includes a Polytetrafluoroethylene Membrane  215  coupled with a Membrane Isolation Valve Manifold  214 , a Membrane Isolation Drain  216  and a Membrane Isolation Maintenance Access  217 . 
     The Polytetrafluoroethylene membrane  215  could occasionally wear out and need to be replaced to prevent cross contamination of the two solutions. To change the membrane  215 , the isolation manifold  214  may need to be manipulated to separate a membrane chamber (the chamber where membrane  215  is held) from main vessels. A drain  216  at the bottom of the chamber will prevent the solutions from mixing during maintenance. 
     Access to the membrane  215  may be achieved through access panel  217  on the top of the vessel. Cartridge based membranes may be utilized to replace membrane  215  for ease of use. 
     Dry cell chambers  246  includes Power Converter/Pulse Width Modulation/Bridge Rectifier  218  coupled to a Brine Side Anode Dry Cell (Platinum/graphite/titanium)  207  and a Caustic Side Cathode Dry Cell  225  (with 316 Stainless Steel). Rectifier  218  receives AC (Alternating current) power  219  that is converted to DC (direct current) power that is supplied to Cell  207  and Cell  225 . Cell  207  receives brine in chamber  240  via Dry cell Brine delivery tube  211  using brine recirculation pump  212  and supplies positively charged brine to chamber  240  via Cl 2  Dry Cell Return Line  206 . Cell  225  receives water in chamber  242  via Dry cell caustic delivery tube  223  using caustic recirculation pump  224  and supplies negatively charged water to chamber  242  via H 2  Dry Cell Return Line  231 . 
     Electrolytic solution is passed through the dry cell chambers  246  with a recirculation pumps  224  to increase circulation and enable efficient cooling. In one implementation, the pumps generate a 7-10 GPM Flow rate. 
     In one implementation the plates within chambers  246  will be made of Platinum, Titanium, graphene, or some variation of graphite for the Cl 2 /brine side cell  207 , and  216  Stainless for the H 2 /Caustic Side cell  225 . 
     Referring to  FIG. 3 , there is shown a system  300  for extracting and neutralizing ammonia from an aquaculture container. System  300  includes a Water Column with Aquatic Species or any water tank  301 , coupled via Recirculation Pump  302 , and H 2  Venturi Injector  303  to H 2  Contact/Mixing Tank  304 . Tank  301  contains a solution that contains a concentration of ammonia (NH 3 ) and/or bacteria generated by aquaculture (e.g. shrimp, fin-fish, crustaceous). 
     Mixing tank  304  is coupled via Cl 2  venturi  307  to mixing tank  309 . Reducing Gas Venturi Injection  309  is coupled via catalytic carbon filter  310  to tank  301 . Gas production device  306  ( FIG. 1 and/or 2 ) is coupled to H 2  Venturi Injector  303  via H 2  Delivery Line  305  and is coupled to Cl 2  mixing tank  309  via Cl 2  Gas Delivery Line  308  and Cl 2  venturi  307 . Gas production device  306  may be connected to an external source of Cl 2  gas or electrolytically produced H 2  gas. 
     System  300  removes ammonia (NH 3 ) from a water tank  301  by manipulation of certain chemical reactions, induced by the apparatus and method in any recirculating water system  300 . 
     Water/solution is extracted from tank  301  at an appropriate pipe diameter with an appropriate recirculation pump  302  based on volume and flow. Next, electrolytically produced Hydrogen Gas H 2 , or Hydronium (also referred to herein as a “reducing gas”) is injected from the gas production device  306  (The embodiment in  FIG. 2  or from an external source) via a pressure differential venturi using injector  303 . From there, the water is passed through a baffled contact/mixing tank  304 . 
     In mixing tank  304  the reducing gas reacts to ionize any unionized ammonia (NH 3 ) into ionized ammonium (NH 4 +). In mixing tank  304  the reducing gas reacts to ionize any un-ionized ammonia (NH 3 ) into ionized ammonium (NH 4   + ). In solution, hydronium(H+) cations form in the presence of hydrogen atoms (H 2 ). The weak base NH 3  attracts a proton from the hydronium ions in solution. 
     The chemical reaction is as follows: 
       H + +NH 3   → NH 4   +   
     Four gallons(15 L) of aquaculture medium were added to a vessel. 20 early stage larval White Shrimp ( Penaeus vannamei ) were then added to bucket. The shrimp were fed the appropriate amounts of industry standard feed, and oxygen was added to the bucket. No water filtration methods were used. 
     A constant stream of Hydrogen gas was introduced into the bucket through aeration stone for the duration of the experiment. The species of shrimp used has a very low total ammonia nitrogen (TAN) tolerance (see  FIG. 4 ). These 20 shrimps in the bucket survived until the TAN levels were 90 ppm, over 72 hours later. Upon post-mortem examination of non-surviving shrimp, it was determined that the shrimp were killed by toxic levels of carbon dioxide, most likely a result of inadequate off gassing in the test vessel. In experiment 1, neutralized NH 4 + was the only constituent of TAN present in the treatment test medium. 
     All the ammonia in the water post mixing tank  304  was ionized ammonia. This reaction once H 2  was injected occurred in seconds. The mixing tank  304  ensured complete contact and conversion of the chemical species. 
     Upon water exiting mixing tank  304 , chlorine gas (Cl − ) is injected from gas production device  306  into the exiting water stream via Cl 2  Gas Delivery Line  308  and pressure-differential venturi  307 . Chlorine gas may be obtained from the embodiment in described in  FIG. 2  or from an external source. The rate of the chlorine gas injection may be a function of, and may be automatically adjusted in response to, changes in the bacteria or ammonia concentration of the solution in the aqueous tank  301  (using a feedback sensor in tank  301  and a controller—not shown). 
     Through combination static-mixer or baffle tank  309 , ionized ammonia reacts with chlorine gas to create several biproducts. 
     The chemical reaction(s) are as follows: 
       2NH 3 +CL 2 =2NH 2 Cl 
       NH 3 +3Cl 2 ═NCl 3 +3H + +3Cl − 
 
       NH 4   + +3Cl 2 ═NCl 3 +NCl 3 +4H + +3Cl − 
 
     A practical example of these reactions in use is at a municipal water treatment plant. The operators add these amines to produce inorganic chloramines that improve the disinfecting power, and control waterborne disease. The US EPA has accepted chloramine as a disinfectant and recognized its ability to control THM formation. In this embodiment, water is disinfected in the process loop. 
     When the water leaves the mixing tank  309 , only forms of chloramine and other haloform reaction bi-products remain. The pH and ammonia-chlorine equilibrium determine which types of Chloramines are formed. These bi-products are commonly known and accepted to be completely and easily removed by catalytic carbon filter  310  or other industry standard medias when the correct media volume and flowrate are applied. Catalytic carbon is an inert, porous support material, it can be used to apply chemicals on its large internal surface, thus making them accessible to reactants (chloramines in this case). 
     The chemical mechanism can be explained in two steps: 
       NH 2 Cl+H 2 O+C→NH 3 +H++Cl−+CO and,
 
       NH 2 Cl+CO→N 2 +2H++2Cl−+H 2 O+C
 
     The process will be appropriately sized, with twin-alternating pressure vessels containing proper media volume, 24-hour operation, and correct backwash settings. 
     Media sizing of the vessel may be most effective if applied in a manner consistent with 2.5 GPM flow rate per 1 cu/ft of media surface area. 
     In this experiment, the treated water then returns to the water column  301  with zero detectable ammonia. 
     Additional benefits are derived and manipulated from the contact time of various disinfectant properties of chemicals produced and applied through the process. 
     Both chloramine and chlorine compounds may be used as commonly accepted disinfecting agents for municipal water treatment. 
     In another implementation, the flowrate is slowed, or the mixing apparatus is made larger to induce longer disinfection contact time. (See  FIG. 5 ) The flowrate may be increased or slowed to change the concentration of ammonia or bacteria in the aqueous tank  301 . 
     The result would not affect the ammonia removal function, while imparting additional sterilization (of bacteria) action. Such sterilization may be a value-add in numerous applications. 
     While the above detailed description has shown, described and identified several novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions, substitutions and changes in the form and details of the described embodiments may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the scope of the invention should not be limited to the foregoing discussion but should be defined by the appended claims.