Sewage sludge treatment

Abstract

An apparatus and method for treating organic waste sludge such as sewage sludge is disclosed wherein the sludge is first dewatered, moved to a day hopper for storage, and then successively passed through first and second reactors. As the sludge is passed through the first reactor, in a continuous fashion, the sludge and acid are thoroughly mixed and has the pH thereof substantially lowered due to the addition of acid in the first reactor. The sludge is then moved through the second reactor where the sludge is subjected to a base material to substantially raise the pH thereof. The treated sludge is then pumped from the second reactor to a pugmill and then to a dryer which dries the material. The dried material is then suitable for use as a fertilizer.

1 . A reactor for use in treating organic waste sludge, comprising: 
 an elongated, generally horizontally disposed reactor body having opposite ends and a selectively closable open upper end;    at least first and second horizontally spaced-apart shafts rotatably mounted in said reactor body;    each of said shafts having a plurality of spaced-apart mixing paddles mounted thereon which extend therefrom;    an inlet means in communication with said body for introducing organic waste sludge and either an acid or a base material thereinto;    an outlet means adjacent one end of said body permitting the mixture to be discharged from said body.    
     
     
         2 . The reactor of  claim 1  wherein right-hand paddles are mounted on said first shaft and left-hand paddles are mounted on said second shaft.  
     
     
         3 . The reactor of  claim 1  wherein right-hand and left-hand paddles are mounted on said first and second shafts.  
     
     
         4 . An apparatus for disinfecting organic waste sludge so that it may be used as a fertilizer, comprising: 
 means for dewatering sludge;    a first acid reactor including an elongated, non-pressurized mixing body having opposite ends and having at least two rotatable shafts therein which have mixing paddles mounted thereon for rotation therewith;    means for supplying the dewatered sludge to said first acid reactor adjacent one end thereof;    means for introducing acid to said mixing body of said first acid reactor adjacent one end thereof;    means for rotating said shafts so that the dewatered sludge will be mixed with the acid whereby the pH of the dewatered sludge will be reduced to a level to kill substantially all the bacteria therein;    a second base material reactor;    means for delivering the acidized sludge from said first acid reactor to said second base material reactor so that the acidized sludge is passed through said second reactor;    means for drying the treated sludge after passing through said second reactor.    
     
     
         5 . The apparatus of  claim 4  wherein the paddles on said shafts are right-handed and left-handed and may interchanged with one another to produce intermittent reverse flow of the dewatered sludge in said mixing body of said first acid reactor.