Cleaning fouled membranes using sludge enzymes
- Melamane, Xolisa L, Pletschke, Brett I, Leukes, Winston D, Whiteley, Chris G
- Authors: Melamane, Xolisa L , Pletschke, Brett I , Leukes, Winston D , Whiteley, Chris G
- Date: 2003
- Language: English
- Type: text
- Identifier: vital:6480 , http://hdl.handle.net/10962/d1006242
- Description: Maintenance of membrane performance requires inevitable cleaning or "defouling" of fouled membranes. Membrane cleaning using sludge enzymes, was investigated by first characterising ostrich abattoir effluent for potential foulants, such as lipids, proteins and polysaccharides. Static fouling of polysulphone membranes using abattoir effluent was also performed. Biochemical analysis was performed using quantitative and qualitative methods for detection of proteins on fouled and defouled membranes. The ability of sulphidogenic proteases to remove proteins adsorbed on polysulphone membranes and capillary ultrafiltration membranes after static fouling, and ability to restore permeate fluxes and transmembrane pressure after dynamic fouling was also investigated. Permeate volumes were analysed for protein and amino acids concentrations. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Static fouled membranes removed 23.4percent of proteins. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 h. Sulphidogenic protease activity was 2.1 U/ml and Flux Recovery (FR percent) was 64 percent.
- Full Text:
- Date Issued: 2003
- Authors: Melamane, Xolisa L , Pletschke, Brett I , Leukes, Winston D , Whiteley, Chris G
- Date: 2003
- Language: English
- Type: text
- Identifier: vital:6480 , http://hdl.handle.net/10962/d1006242
- Description: Maintenance of membrane performance requires inevitable cleaning or "defouling" of fouled membranes. Membrane cleaning using sludge enzymes, was investigated by first characterising ostrich abattoir effluent for potential foulants, such as lipids, proteins and polysaccharides. Static fouling of polysulphone membranes using abattoir effluent was also performed. Biochemical analysis was performed using quantitative and qualitative methods for detection of proteins on fouled and defouled membranes. The ability of sulphidogenic proteases to remove proteins adsorbed on polysulphone membranes and capillary ultrafiltration membranes after static fouling, and ability to restore permeate fluxes and transmembrane pressure after dynamic fouling was also investigated. Permeate volumes were analysed for protein and amino acids concentrations. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Static fouled membranes removed 23.4percent of proteins. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 h. Sulphidogenic protease activity was 2.1 U/ml and Flux Recovery (FR percent) was 64 percent.
- Full Text:
- Date Issued: 2003
Accelerated sludge solubilisation under sulphate reducing conditions: the effect of hydrolytic enzymes on sludge floc size distribution and EPS composition
- Akhurst, P, Rose, Peter D, Whiteley, Chris G, Pletschke, Brett I
- Authors: Akhurst, P , Rose, Peter D , Whiteley, Chris G , Pletschke, Brett I
- Date: 2002
- Language: English
- Type: Conference paper
- Identifier: vital:6455 , http://hdl.handle.net/10962/d1010430
- Description: Extracellular polymeric substances (EPS) are the construction materials for microbial aggregates such as biofilms, flocs and sludge, and greatly contribute to the structural integrity of sludge flocs in wastewater treatment processes. The loss of integrity of the sewage sludge floc is believed to be due to enhanced hydrolysis of important structural components such as lignin, protein and cellulose in the sludge floc matrix. The mechanism of enhanced sludge floc fracture, due to the action of enzymes hydrolysing these structural components, remains a key element in our understanding of how the floc integrity in systems utilising a sulphate reducing system is compromised. A range of relatively non-specific exogenous enzymes (ß-glucosidase, cellulase, proteases: trypsin, pronase E and chymotrypsin) were added to a sulphidogenic bioreactor- (containing both sulphate reducing bacteria (SRB) and a methanogenic bacterial system) and a (control) methanogenic bioreactor sample, and the effect of these enzymes on sludge floc size (diameter) distribution and EPS composition was investigated. Sludge samples from the bioreactors were examined under bright field and differential interference contrast light microscopy. Proteolytic and glucohydrolytic activity of the enzymes were monitored using standard enzyme assaying techniques, and Bradford, Somogyi-Nelson, and total carbohydrate assays were performed to establish the composition of the EPS (after extraction with 3% (v/v) glutaraldehyde and Sephacryl S-400 size exclusion chromatography). Sludge flocs present in the sulphidogenic environment of the sulphidogenic bioreactor were found to have smaller diameters than their counterparts present in the methanogenic bioreactor. The addition of hydrolytic (i.e. proteolytic and glycohydrolytic) enzymes resulted in an increased rate of matrix hydrolysis, leading to increased rates of floc fracture and deflocculation. The presence of ß-glucosidase, cellulase, and proteases naturally residing within the sludge floc was confirmed. We propose that the addition of commercially available enzymes may be prohibitively costly on a large scale, and that the activity of the enzymes naturally residing within the floc matrix be optimised or enhanced. As the bulk of the EPS was shown to be composed of mainly polysaccharides, we propose that by increasing the activity of the naturally occurring ß-glucosidases residing within the floc matrix, the process of deflocculation may be enhanced. As sulphide has been shown to increase the activity of this very important key enzyme, we propose that this is one of the contributing factors why sludge solubilisation is accelerated under sulphate reducing conditions.
- Full Text:
- Date Issued: 2002
- Authors: Akhurst, P , Rose, Peter D , Whiteley, Chris G , Pletschke, Brett I
- Date: 2002
- Language: English
- Type: Conference paper
- Identifier: vital:6455 , http://hdl.handle.net/10962/d1010430
- Description: Extracellular polymeric substances (EPS) are the construction materials for microbial aggregates such as biofilms, flocs and sludge, and greatly contribute to the structural integrity of sludge flocs in wastewater treatment processes. The loss of integrity of the sewage sludge floc is believed to be due to enhanced hydrolysis of important structural components such as lignin, protein and cellulose in the sludge floc matrix. The mechanism of enhanced sludge floc fracture, due to the action of enzymes hydrolysing these structural components, remains a key element in our understanding of how the floc integrity in systems utilising a sulphate reducing system is compromised. A range of relatively non-specific exogenous enzymes (ß-glucosidase, cellulase, proteases: trypsin, pronase E and chymotrypsin) were added to a sulphidogenic bioreactor- (containing both sulphate reducing bacteria (SRB) and a methanogenic bacterial system) and a (control) methanogenic bioreactor sample, and the effect of these enzymes on sludge floc size (diameter) distribution and EPS composition was investigated. Sludge samples from the bioreactors were examined under bright field and differential interference contrast light microscopy. Proteolytic and glucohydrolytic activity of the enzymes were monitored using standard enzyme assaying techniques, and Bradford, Somogyi-Nelson, and total carbohydrate assays were performed to establish the composition of the EPS (after extraction with 3% (v/v) glutaraldehyde and Sephacryl S-400 size exclusion chromatography). Sludge flocs present in the sulphidogenic environment of the sulphidogenic bioreactor were found to have smaller diameters than their counterparts present in the methanogenic bioreactor. The addition of hydrolytic (i.e. proteolytic and glycohydrolytic) enzymes resulted in an increased rate of matrix hydrolysis, leading to increased rates of floc fracture and deflocculation. The presence of ß-glucosidase, cellulase, and proteases naturally residing within the sludge floc was confirmed. We propose that the addition of commercially available enzymes may be prohibitively costly on a large scale, and that the activity of the enzymes naturally residing within the floc matrix be optimised or enhanced. As the bulk of the EPS was shown to be composed of mainly polysaccharides, we propose that by increasing the activity of the naturally occurring ß-glucosidases residing within the floc matrix, the process of deflocculation may be enhanced. As sulphide has been shown to increase the activity of this very important key enzyme, we propose that this is one of the contributing factors why sludge solubilisation is accelerated under sulphate reducing conditions.
- Full Text:
- Date Issued: 2002
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