Liquid-solid circulating fluidized bed waste water treatment system for simultaneous carbon, nitrogen and phosphorus removal

Abstract

Biological nutrient removal (BNR) in wastewater treatment to remove carbonaceous substrates, nutrients and phosphorus, has recently become increasingly popular worldwide due to increasingly stringent regulations. Biological fluidized bed (BFB) technology, which could be potentially used for BNR processes, can provide some advantages such as high efficiency and compact structure. This present invention incorporates the fixed-film biological fluidized bed technology with the biological nutrient removal in a twin liquid-solid fluidized bed, which has achieved the simultaneous elimination of organic carbon, nitrogen and phosphorus, in a very efficient manner and with very compact space requirements. The BNR-LSFB has two fluidized beds, running as anoxic/anaerobic and aerobic processes to accomplish simultaneous nitrification and denitrification and to remove carbonaceous substrates, nutrients and phosphorus, with continuous liquid and solids recirculation through the anoxic/anaerobic bed and the aerobic bed. The new BNR-LSFB system is not only an excellent alternative for conventional activated sludge type BNR technologies but is also capable of processing much higher loadings and suitable for industrial applications.

1 .- 18 . (canceled) 
   
   
       19 . A twin liquid-solid fluidized bed system, comprising:
 solid particles having effective immobilized bacteria coated thereon,   a first fluidized bed having a first and second end, said first fluidized bed being a riser fluidized bed including an inlet at said second end for introducing a first fluidizing fluid into said first fluidized bed;   a second fluidized bed being a downer fluidized bed having a first end and a second end;   first connecting conduit connecting said second end of said first fluidized bed to said first end of said second fluidized bed, said first connecting means including means to feed said solid particles into said second fluidized bed;   second connecting conduit connecting said second end of said second fluidized bed to said first end of said first fluidized bed; and   means to feed said solid particles having effective immobilized bacteria coated thereon into said second fluidized bed through said first connecting conduit and to feed said solid particles into said first fluidized bed through said second connecting conduit, wherein said solid particles and said second fluidizing fluid flow in counter flow relationship in said second fluidized bed and wherein said solid particles and said first fluidizing fluid flow co-currently in said first fluidizing column.   
   
   
       20 . The twin liquid-solid fluidized bed system according to  claim 19  configured for biological nutrient removal from raw wastewater feed stream to remove carbon, nitrogen and phosphorus therefrom, the raw wastewater feed stream being fed into the first fluidized column through a wastewater feed stream inlet, which may or may not be the same as the inlet for the inlet at said second end of said first fluidized column, including gas injection means connected to said second fluidized bed, and wherein said second fluidized bed includes an aerobic zone for biodegrading wastewater predominately by the immobilized bacteria in the presence of oxygen, and wherein said first fluidized bed includes an anoxic zone for denitrification, and an anaerobic zone for phosphorus release. 
   
   
       21 . The twin liquid-solid fluidized bed system according to  claim 20  wherein said first fluidized bed is configured such that a liquid velocity of the first fluidizing fluid is lower than a transition velocity from a particulate fluidization regime to a fast fluidization regime. 
   
   
       22 . The twin liquid-solid fluidized bed system according to  claim 20  wherein said first fluidized bed is configured such that a liquid velocity of the first fluidizing fluid is higher than a transition velocity from a particulate fluidization regime to a fast fluidization regime. 
   
   
       23 . The twin liquid-solid fluidized bed system according to  claim 20  wherein said first fluidized bed further includes a fluid-solid separator means located at the second end thereof for separating solid particles from fluid and exhausting such separated fluid to provide separated solid particles which are fed by the means for feeding from the fluid-solid separator means to the second fluidizing bed, and wherein said first fluid circulating means circulates the separated fluid to the first end of the first fluidizing bed, and including a clarifier means located at the first end of said second fluidized bed for separating solid particles from fluid and withdrawing such separated fluid as treated effluent to provide separated solid particles which settle back into the second fluidized bed in order to minimize loss of particles through the effluent, wherein said clarifier means includes sludge withdrawal means for exhausting sloughed sludge formed during the process, and wherein said second fluid circulating means circulates some of the treated effluent to the second end of the second fluidizing bed as the second fluidizing fluid. 
   
   
       24 . The twin liquid-solid fluidized bed system according to  claim 20  wherein said first and second connecting conduits include any one of a pump and propeller for assisting in moving fluid and solid particles between said first and second fluidized beds. 
   
   
       25 . The twin liquid-solid fluidized bed system according to  claim 20  including a third conduit extending from said second conduit into a pre-selected location in said second fluidized bed for extracting solid particles from said pre-selected location in said second fluidized bed and circulating them to said first fluidized bed, and including a fourth conduit extending from said first conduit to a pre-selected location in said first fluidized bed for extracting solid particles from said pre-selected location in said first fluidized bed and circulating them to said second fluidized bed.