The roles and interactions of cations, proteins, and polysaccharides in the settling and dewatering of activated sludge
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Results from the full-scale activated sludge plants correlated well with results from laboratory activated sludge systems and demonstrated the cation content in these systems had a direct impact on the settling and dewatering properties. Field trials in which divalent cations were added to activated sludge systems resulted in dramatic improvements in the settling properties of these systems. Characterization of the exocellular protein extracted from laboratory, industrial and municipal activated sludges revealed the presence of a single protein, which appears to be a lectin. The molecular weight of the protein measured by SDS PAGE was approximately 16,000 Daltons with similar amino acid composition as microbial lectins. Also, amino acid sequencing analysis indicated the N-terminal sequence of the protein was consistent with those of microbial lectins. In addition, the activated sludge cultures exhibited lectin activity as demonstrated by binding site inhibition experiments. A model of bioflocculation that includes the role of protein was proposed.
- Doctoral Dissertations