Abstract
In this study, extracellular polymeric substances (EPSs) producing strain was isolated from municipal wastewater sludge (MWWS). Growth profile and the EPS production by Cloacibacterium normanense using wastewater sludge as raw material in shake flask fermentation for 96 h were investigated. The highest concentration of S-EPS (13.0 ± 0.8 g/L) and C-EPS (0.3 ± 0.1 g/L) were attained at 48 h of fermentation. S-EPS revealed higher flocculation activity (94.2%) and dewaterability (59.9%) than other types of EPS in kaolin suspension. The dewaterability of MWWS with 2 g suspended solids (SS)/L was improved by 37.6% using 0.02 ± 0.01 g/L of S-EPS and 600 mg/L of Al2(SO4)3. The study showed a promising approach of new isolated strain to produce high concentration EPS in sludge with high flocculation activity as well as good settling.
Highlights
Sludge settling and dewatering are the most important steps of wastewater treatment and sludge management
The research of More et al [2] investigated the effect of fermentation time on Extracellular Polymeric Substances (EPS) production in activated sludge and found that the EPS content was proportional to the bacterial growth
A decrease in Broth EPS (B-EPS) concentration was observed between 48 and 96 h. This decrease could be due to the fact that the bacteria may have consumed EPS when carbon limitation occurred in the medium
Summary
Sludge settling and dewatering are the most important steps of wastewater treatment and sludge management. The microbial EPS plays an important role in bioflocculation by interacting with the sludge solids [3]. Many physical and chemical properties of microbial EPSs have led to a wide range of field applications, e.g., adhesion, chelation of heavy metals, coagulation and flocculation, detoxification of toxic compounds, nutrient sequestration, protection against osmotic shock, stabilizers, thickeners, gelling, film-forming and water-retention capability (in detergents, textiles, adhesives, paper, paint, food and beverage industries), oil recovery, mining industry and petroleum industries [2]. There has been growing interest in the isolation and characterization of microbial EPS owing to their practical importance. Different microorganisms produce various types of EPS with diverse characteristics and concentration. The present study aimed at: i) isolation and identification of high concentration EPS producing bacteria, ii) chemical and physical characterization of the EPS produced by the strain and iii) to evaluate the potential of produced EPS with respect to flocculation activity and dewaterability
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