Parametric and kinetic studies of activated sludge dewatering by cationic chitosan-like bioflocculant BF01314 produced from Citrobacter youngae

• Published in: Environmental research 2023-05, Vol.224, p.115527-115527, Article 115527
• Main Authors: Mohamed Hatta, Nur Syahirah, Lau, Shiew Wei, Chua, Han Bing, Takeo, Masahiro, Sen, Tushar Kanti, Mubarak, Nabisab Mujawar, Khalid, Mohammad, Zairin, Danial Aminin
• Format: Article
• Language: English
• Subjects: Biopolymer; Chitosan; Citrobacter; Filtration; Flocculation; Flocculation kinetics; Kinetics; Polymers; Sewage; Sludge conditioning; Waste Disposal, Fluid; Water
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.115527

Bacterial strains belonging to Citrobacter spp. were reported to produce polysaccharides consisting of N-acetylglucosamine and glucosamine like chitosan, with high flocculation activity. In this work, the flocculation dewatering performance of activated sludge conditioned by a novel cationic chitosan-like bioflocculant (BF) named BF01314, produced from Citrobacter youngae GTC 01314, was evaluated under the influences of flocculant dosage, pH, and temperature. At BF dosage as low as 0.5 kg/t DS, the sludge dewaterability was significantly enhanced in comparison to the raw (untreated) sludge, featuring well-flocculated characteristic (reduction in CST from 22.0 s to 9.4 s) and good sludge filterability with reduced resistance (reduction in SRF by one order from 7.42 × 1011 to 9.59 × 1010 m/kg) and increased compactness of sludge (increase in CSC from 15.2 to 23.2%). Besides, the BF demonstrated comparable high sludge dewatering performance within the pH range between 2 and 8, and temperature range between 25 °C and 80 °C. Comparison between the BF, the pristine chitosan and the commercial cationic copolymer MF 7861 demonstrated equivalent performance with enhanced dewaterability at the dosage between 2.0 and 3.0 kg/t DS. Besides, the BF demonstrated strong flocculation activity (>99%) when added to the sludge suspension using moderate to high flocculation speeds (100–200 rpm) with at least 3-min mixing time. The BF's reaction in sludge flocculation was best fitted with a pseudo first-order kinetic model. Electrostatic charge patching and polymer bridging mechanisms are believed to be the dominant mechanistic phenomena during the BF's sludge conditioning process (coagulation-flocculation). •BF01314 performs equivalent to commercial biopolymers in sludge dewatering.•Excellent dewatering performance between pH 2–8 and temperature 25–80 °C.•Sludge flocculation reaction was best fitted with pseudo first–order kinetic model.•Flocculation by BF01314 is preceded by electrostatic charge patching.