Apparatus and method for treating wastewater containing nitrogen-containing dyes

Abstract

To provide a wastewater treatment apparatus capable of easily decolorizing and decomposing, at a low cost, a persistent nitrogen-containing dye such as azo compound in wastewater containing a nitrogen-containing dye, being compact, having excellent durability and high processing power and ensuring long-term stable operation. A wastewater treatment apparatus for decolorization and denitrification of wastewater containing a nitrogen-containing dye, which comprises an obligatory anaerobic tank for bringing the wastewater containing a nitrogen-containing dye into contact with sulfate-reducing bacteria under obligatory anaerobic conditions, a nitrification tank for bringing the wastewater into contact with nitrifying bacteria under aerobic conditions and a denitrification tank for bringing the wastewater into contact with the denitrifying bacteria under anaerobic conditions.

1 . A wastewater treatment apparatus comprising an obligatory anaerobic tank for bringing wastewater containing a nitrogen-containing dye into contact with sulfate-reducing bacteria under obligatory anaerobic conditions, a nitrification tank for bringing the wastewater into contact with nitrifying bacteria under aerobic conditions and a denitrification tank for bringing the wastewater into contact with the denitrifying bacteria under anaerobic conditions.  
     
     
         2 . A wastewater treatment apparatus of  claim 1 , wherein the obligatory anaerobic tank, the denitrification tank and the nitrification tank are disposed in the order of mention and a portion of the treated water discharged from the nitrification tank is caused to return and circulate to the denitrification tank.  
     
     
         3 . A wastewater treatment apparatus of  claim 1 , wherein the obligatory anaerobic tank, the nitrification tank and the denitrification tank are disposed in the order of mention and a re-aeration tank for bringing BOD decomposing bacteria into contact with the wastewater under aerobic conditions is disposed downstream of the denitrification tank.  
     
     
         4 . A wastewater treatment apparatus, wherein a denitrification tank for bringing wastewater containing a nitrogen-containing dye into contact with sulfate reducing bacteria and denitrifying bacteria under obligatory anaerobic conditions and a nitrification tank for bringing the wastewater into contact with nitrifying bacteria under aerobic conditions are disposed in the order of mention, whereby a portion of the treated water discharged from the nitrification tank is caused to return and circulate to the denitrification tank.  
     
     
         5 . A wastewater treatment apparatus of  claim 1 , wherein the bacteria have been immobilized by a microorganism immobilization support in at least one tank selected from the obligatory anaerobic tank, the nitrification tank and the denitrification tank.  
     
     
         6 . A wastewater treatment apparatus of  claim 3 , wherein the bacteria have been immobilized by a microorganism immobilization support in at least one tank selected from the obligatory anaerobic tank, the nitrification tank, the denitrification tank and the re-aeration tank.  
     
     
         7 . A wastewater treatment apparatus of  claim 4 , wherein the bacteria have been immobilized by a microorganism immobilization support in at least one tank selected from the nitrification tank and the denitrification tank.  
     
     
         8 . A wastewater treatment apparatus of  claim 5 , wherein the microorganism immobilization support is at least one support selected from gelled support, plastic support and fibrous support.  
     
     
         9 . A wastewater treatment apparatus of  claim 8 , wherein the gelled support is a polyvinyl alcohol hydrogel.  
     
     
         10 . A method of treating wastewater containing a nitrogen-containing dye, which comprise the following steps (1) to (3): 
 (1) an obligatory anaerobic step for bringing the wastewater containing a nitrogen-containing dye into contact with sulfate reducing bacteria under obligatory anaerobic conditions;    (2) a nitrification step for bringing the wastewater into contact with nitrifying bacteria under aerobic conditions; and    (3) a denitrification step for bringing the wastewater into contact with denitrifying bacteria under anaerobic conditions.