Wastewater treatment system

Abstract

The wastewater treatment system of the present invention is adapted to remove COD and nitrogenous compounds from wastewater. The system includes a carbon-removing anaerobic fluidized bed reactor and a nitrogen-removing fluidized bed reactor. The carbon-removing anaerobic fluidized bed reactor is mainly adapted to transfer most of the COD in the wastewater into methane through hydrolysis, acedogenesis and methanogenosis reactions. The nitrogen-removing fluidized bed reactor is adapted to transfer ammonium nitrogen and residual COD in the wastewater into nitrogen gas through partial nitrification, anammox and denitrification reactions.

What is claimed is: 
     
         1 . A wastewater treatment system, for at least partially removing COD and nitrogenous compounds from wastewater, the nitrogenous compounds including ammonium nitrogen, the wastewater treatment system comprising:
 a carbon-removing anaerobic fluidized bed reactor, including a first cylinder, a plurality of first granular carriers, a first sedimentation tank, a first fluidized means, first microorganisms and extracellular enzymes; the first cylinder defining therein a first fluidized chamber, the first cylinder having a first upper opening and a first lower opening, the first upper and lower openings both being communicated with the first fluidized chamber; the first fluidized chamber being locally filled by the first granular carriers; the first sedimentation tank having a first bottom opening and a first outfall locationally higher than the first bottom opening, the first bottom opening being communicated with the first upper opening; the first fluidized means being for guiding the wastewater into the first fluidized chamber through the first lower opening and for suspending the first granular carriers in first fluidized chamber; a part of the COD performing hydrolysis reaction with said extracellular enzymes to decompose organic compounds of the COD into at least one of amino acids, carbohydrates and fatty acids, at least one part of said first microorganisms being attached to the first granular carriers, said first microorganisms including acidogenic bacteria and methanogens, wherein the acidogenic bacteria perform acedogenesis reaction to transfer said at least one of amino acids, carbohydrates and fatty acids into fatty acids having 4 or fewer carbons on their backbone chains, hydrogen gas and carbon dioxide, and the methanogens perform methanogenesis reaction to transfer the fatty acids having 4 or fewer carbons on their backbone chains, hydrogen gas and carbon dioxide into methane and carbon dioxide, said first fluidized chamber having an oxidation-reduction potential therein smaller than −400 mv; the first outfall allowing the wastewater to be drained from the carbon-removing anaerobic fluidized bed reactor; and   a nitrogen-removing fluidized bed reactor, including a second cylinder, a plurality of second granular carriers, a second sedimentation tank, a second fluidized means and second microorganisms; the second cylinder defining therein a second fluidized chamber, the second cylinder having a second upper opening and a second lower opening, the second upper and lower openings both being communicated with the second fluidized chamber, the second lower opening serving to introduce the wastewater that has been processed in the carbon-removing anaerobic fluidized bed reactor; the second fluidized chamber being locally filled by the second granular carriers; the second sedimentation tank having a second bottom opening and a second outfall locationally higher than the second bottom opening, the second bottom opening being communicated with the second upper opening; the second fluidized means being for guiding the wastewater into the second fluidized chamber through the second lower opening, and for suspending the second granular carriers in the second fluidized chamber; at least one part of said second microorganisms being attached to the second granular carriers, said second microorganisms including nitrifying bacteria, anammox bacteria and heterotrophic denitrifying bacteria, the nitrifying bacteria performing partial nitrification reaction to oxidize ammonium nitrogen into nitrite nitrogen, the anammox bacteria performing anammox reaction to transfer ammonium nitrogen and nitrite nitrogen into nitrogen gas and nitrate nitrogen, the heterotrophic denitrifying bacteria performing denitrification reaction to transfer nitrate nitrogen and at least a part of the residual COD into nitrogen gas.   
     
     
         2 . A wastewater treatment system, for at least partially removing COD and nitrogenous compounds from wastewater, nitrogenous compounds includes ammonium nitrogen, the wastewater treatment system comprising:
 a carbon-removing anaerobic fluidized bed reactor, including a first cylinder, a plurality of first granular carriers, a first sedimentation tank, a first fluidized means, first microorganisms and extracellular enzymes; the first cylinder defining therein a first fluidized chamber, the first cylinder having a first upper opening and a first lower opening, the first upper and lower openings both being communicated with the first fluidized chamber; the first fluidized chamber being locally filled by the first granular carriers; the first sedimentation tank having a first bottom opening and a first outfall locationally higher than the first bottom opening, the first bottom opening being communicated with the first upper opening; the first fluidized means being for guiding the wastewater into the first fluidized chamber through the first lower opening and for suspending the first granular carriers in first fluidized chamber; a part of the COD performing hydrolysis reaction with said extracellular enzymes to decompose organic compounds forming the COD into at least one of amino acids, carbohydrates and fatty acids, at least one part of said first microorganisms being attached to the first granular carriers, said first microorganisms including acidogenic bacteria and methanogens, wherein the acidogenic bacteria perform acedogenesis reaction to transfer said at least one of amino acids, carbohydrates and fatty acids into fatty acids having 4 or fewer carbons on their backbone chains, hydrogen gas and carbon dioxide, and the methanogens perform methanogenesis reaction to transfer the fatty acids having 4 or fewer carbons on their backbone chains, hydrogen gas and carbon dioxide into methane and carbon dioxide, said first fluidized chamber having an oxidation-reduction potential therein smaller than −400 mv; the first outfall serving to drain the wastewater that has been processed through hydrolysis reaction, acedogenesis reaction and methanogenesis reaction;   an anaerobic fluidized membrane reactor, including a third cylinder, a plurality of third granular carriers, a third sedimentation tank, a third fluidized means and at least one tubular membrane, the third cylinder defining therein a third fluidized chamber, the third cylinder having a third upper opening and a third lower opening, the third upper and lower openings both being communicated with the third fluidized chamber, the third lower opening serving to introduce the wastewater that has been processed in the carbon-removing anaerobic fluidized bed reactor; the third fluidized chamber being locally filled by the third granular carriers; the third sedimentation tank having a third outfall, the third sedimentation tank is provided atop the third cylinder, the third sedimentation tank being communicated with the third fluidized chamber through the tubular membrane, the tubular membrane extending form the third sedimentation tank into the third fluidized chamber, the tubular membrane being defined by a porous wall, the third fluidized means being for guiding the wastewater into the third fluidized chamber through the third lower opening and for suspending the third granular carriers in the third fluidized chamber; the third outfall serving to drain the wastewater from the anaerobic fluidized membrane reactor; and   a nitrogen-removing fluidized bed reactor, including a second cylinder, a plurality of second granular carriers, a second sedimentation tank, a second fluidized means and second microorganisms; the second cylinder defining therein a second fluidized chamber, the second cylinder having a second upper opening and a second lower opening, the second upper and lower openings both being communicated with the second fluidized chamber, said second lower opening serving to introduce the wastewater that has been processed in the anaerobic fluidized membrane reactor; the second fluidized chamber being locally filled by the second granular carriers; the second sedimentation tank having a second bottom opening and a second outfall locationally higher than the second bottom opening, the second bottom opening being communicated with the second upper opening; the second fluidized means being for guiding the wastewater into the second fluidized chamber through the second lower opening, and for suspending the second granular carriers in the second fluidized chamber; at least one part of said second microorganisms being attached to the second granular carriers, said second microorganisms including nitrifying bacteria, anammox bacteria and heterotrophic denitrifying bacteria, the nitrifying bacteria performing partial nitrification reaction to oxidize ammonium nitrogen into nitrite nitrogen, the anammox bacteria performing anammox reaction to transfer ammonium nitrogen and nitrite nitrogen into nitrogen gas and nitrate nitrogen, the heterotrophic denitrifying bacteria performing denitrification reaction to transfer nitrate nitrogen and at least a part of the residual COD into nitrogen gas.   
     
     
         3 . The wastewater treatment system of  claim 1 , wherein a dissolved oxygen concentration in the second fluidized chamber is 0.1-0.5 mg/L. 
     
     
         4 . The wastewater treatment system of  claim 2 , wherein a dissolved oxygen concentration in the second fluidized chamber is 0.1-0.5 mg/L. 
     
     
         5 . The wastewater treatment system of  claim 1 , wherein the first sedimentation tank is atop provided with a methane vent. 
     
     
         6 . The wastewater treatment system of  claim 2 , wherein the first sedimentation tank is atop provided with a methane vent.