Water Environment Federation (WEF)

Elucidation of Exopolysaccharide Isolated from a Dow Wastewater Treatment Facility


A UNOX wastewater treatment facility in a Dow Chemical site has experienced major operational challenges as a result of a microorganism producing copious amounts of slime in the activated sludge flocs believed to be involved in viscous bulking. Viscous bulking within the clarifying basin causes the rake arms to freeze due to high sheer stress, resulting from poor compaction and increased water retention in the waste sludge. In 2005, this resulted in limiting site production to maintain discharge compliance.

In order to elucidate the enriched biopolymer from the activated sludge at the UNOX waste water treatment facility several analytical methods were developed and implemented to determine the composition of the biopolymer. Four samples of enriched biopolymer from the activated sludge were analyzed to determine: protein content, deoxyribonucleic acid (DNA) content, and polysaccharide content and composition. Protein content was determined by a combination of Bradford protein assay and sodium dodecyl-sulfate polyacrylamide gelelectrophoresis (SDS-PAGE). Total protein content in the samples was estimated by Bradford assay to be between ~5 to 11% of total sample dry mass. DNA content was determined by a combination of UV spectroscopy and OliGreen fluorescent assay. Total DNA content was determined to be between ~2 to ~4% of total sample dry mass by UV absorption and OliGreen assays. Polysaccharide content and composition was determined by a combination of capillary electrophoresis - laser induced fluorescence (CE-LIF), gas chromatography mass spectrometry (GC-MS), and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). CE-LIF analysis resulted in estimated total monosaccharide content of ~60- 74% of total sample dry mass. In addition, CE-LIF revealed the presence of the following monosaccharides: Arabinose (Ara; 4.2%), Galactose (Gal; 2.0%), Glucose (Glc; 14.3%), Nacetyl- galactosamine (GalNAc; 23.3%), N-acetyl-glucosamine (GlcNAc; 5.2%), Glucuronic
acid (GlcUA; 24.2%), Mannose (Man; 2.4%), Rhamnose (Rha; 2.4%), Xylose (Xyl; 12.4%). The CE-LIF monosaccharide profiles for four samples were similar to each other, indicating a similar monosaccharide composition of the bacterial polysaccharide. Within the monosaccharide pool, GalNAc and GlcUA were predominant components. GC/MS and MALDI-TOF MS analysis on 447-1 sample corroborated the CE-LIF results. The summation of determined amounts of protein, DNA, and carbohydrate resulted in ~75-83% total sample mass coverage.

Polysaccharide, viscous bulking, monosaccharide

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