Methods for Enhancing the Dewaterability of Sludge with Alpha-Amylase Treatment

Abstract

The present invention relates to enhancing sludge dewaterability by adding an alpha-amylase to the sludge prior to conventional conditioning and dewatering operations.

1 . A method for enhancing the dewaterability of sludge comprising adding an alpha-amylase to the sludge prior to mechanical dewatering equipment. 
     
     
         2 . The method of  claim 1 , wherein the alpha-amylase is derived from a strain of  Geobacillus stearothermophilus.    
     
     
         3 . The method according to  claim 1 , wherein the alpha-amylase has at least 80% identity to the alpha-amylase shown in SEQ ID NO: 1 as determined using the Clustal method (Higgins, 1989, CABIOS 5: 151-153) using the LASERGENE™ MEGALIGN™ software (DNASTAR, Inc., Madison, Wis.) with an identity table and the following multiple alignment parameters: Gap penalty of 10 and gap length penalty of 10. Pairwise alignment parameters are Ktuple=1, gap penalty=3, windows=5, and diagonals=5. 
     
     
         4 . The method according to  claim 1 , wherein the alpha-amylase has at least 80% identity to a  Geobacillus stearothermophilus  alpha-amylase as determined using the Clustal method (Higgins, 1989, CABIOS 5: 151-153) using the LASERGENE™ MEGALIGN™ software (DNASTAR, Inc., Madison, Wis.) with an identity table and the following multiple alignment parameters: Gap penalty of 10 and gap length penalty of 10. Pairwise alignment parameters are Ktuple=1, gap penalty=3, windows=5; and diagonals=5. 
     
     
         5 . The method according to  claim 1 , wherein the dose of alpha-amylase is between 2 and 140 g per dry ton of total suspended solids. 
     
     
         6 . The method according to  claim 1 , wherein the dose of alpha-amylase is between 2 and 70 g per dry ton of total suspended solids. 
     
     
         7 . The method according to  claim 1 , wherein the dose of alpha-amylase is between 2 and 35 g per dry ton of total suspended solids. 
     
     
         8 . The method according to  claim 1 , wherein the dose of alpha-amylase is between 2 and 8 g per dry ton of total suspended solids. 
     
     
         9 . The method according to  claim 1 , wherein the dose of alpha-amylase is between 2 and 5 g per dry ton of total suspended solids. 
     
     
         10 . The method according to  claim 1 , wherein the enzyme is allowed to incubate with the sludge for 1 minute to 24 hours. 
     
     
         11 . The method according to  claim 1 , wherein the enzyme is allowed to incubate with the sludge for 30 minutes to 12 hours. 
     
     
         12 . The method according to  claim 1 , wherein the enzyme is allowed to incubate with the sludge for 1 hour to 2 hours. 
     
     
         13 . The method according to  claim 1 , wherein the sludge is generated during conventional municipal and industrial wastewater treatment operations. 
     
     
         14 . The method according to  claim 5 , wherein the sludge is selected from the group consisting of primary sludge from primary clarifiers, waste activated sludge, return activated sludge, anaerobically digested sludge and aerobically digested sludge. 
     
     
         15 . The method according to  claim 2 , wherein the alpha-amylase is added in combination with one or more proteases, lipases, cellulases, a hemicellulases, oxidoreductases, laccases, glycosyl hydrolases and/or an esterases. 
     
     
         16 . A method for enhancing the dewaterability of sludge comprising adding an alpha-amylase to the sludge prior to mechanical dewatering equipment, wherein the alpha-amylase is derived from a strain of  Geobacillus stearothermophilus  or is an alpha-amylase having an amino acid sequence which has at least 80% identity to the alpha-amylase shown in SEQ ID NO: 1. 
     
     
         17 . The method according to  claim 16 , wherein the alpha-amylase is derived from a strain of  Geobacillus stearothermophilus.    
     
     
         18 . The method according the  claim 16 , wherein the alpha-amylase is an alpha-amylase having an amino acid sequence which has at least 80% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 85% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 90% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 95% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 96% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 97% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 98% identity to the alpha-amylase shown in SEQ ID NO: 1, at least 99% identity to the alpha-amylase shown in SEQ ID NO: 1. 
     
     
         19 . The method according to  claim 16 , wherein the alpha-amylase has the amino acid sequence of SEQ ID NO: 1.