[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-225] Novel bacterial EPS-based biocoagulants for treating high turbidity and humic acid in raw water

Yueh-Syuan Li¹, Jung Chou¹, ○Yi-Tang Chang¹ (1. Department of Microbiology, Soochow University (Taiwan))

Keywords:

extracellular polymeric substances,biocoagulants,turbidity,humic acid,tightly bound EPS,loosely bound EPS

Bacterial extracellular polymeric substances (EPS), primarily composed of polysaccharides and proteins, play an important role in flocculation and aggregation. EPS-based biocoagulants are biodegradable and non-toxic, becoming an eco-friendly alternative to chemical coagulants. The performance of these biocoagulants for treatment is usually unstable, influenced by their molecular structure, functional groups, environmental conditions (e.g., pH, salinity), and the presence of cations. This study introduces hydrophobic or hydrophilic groups of OPEO onto bacterial EPS to generate novel biocoagulants for treating the high turbidity or humic acid (HA) in raw water. Apply tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) as biocoagulants, extracted from the bacterial mixed culture incubated by octylphenol polyethoxylate (OPEO) containing two different EO lengths- TX-45 (average 4.5 EO units in a more hydrophobic condition) and TX-165 (average 16.5 EO units in a more hydrophilic condition) as the sole carbon sources. A bacterial mixed culture can produce higher yields of TX-165-EPS, including 723.4±30.8 mg/L of TX-165-LB-EPS and 558.65±3.5 mg/L of TX-165-TB-EPS. The yields of TX-45-LB-EPS and TX-45-TB-EPS are 388.55±11.2 mg/L and 480.10±26.0 mg/L, respectively. The composition of all OPEO-EPS biocoagulants mainly includes polysaccharides and proteins. TX-165-EPS biocoagulants have higher contents of polysaccharide (20.05±2.12-11.58±3.30 mg/g) and protein (36.49±4.96-19.59±3.48 mg/g). TX-45-EPS biocoagulants have low content of polysaccharide (1.67±0.44-1.55±0.35 mg/g) and protein (1.57±0.04-0.44±0.03 mg/g). Functional groups of OPEO-EPS-based biocoagulants are identified as O-H (stretching vibrations of polysaccharides), C=O (Amide I, stretching vibrations of proteins), C-O-C (stretching vibrations of polysaccharides), and C-H (bending vibrations of OEPO). OPEO-EPS-based biocoagulants effectively remove kaolin turbidity in raw water. The highest removals at high 500 NTU turbidity with 4 g/L additive are 68% for TX-45-TB-EPS and 61% for TX-45-LB-EPS, respectively. The removals at the same kaolin turbidity with 2 g/L additive are 48% for TX-165-TB-EPS and 44% for TX-165-LB-EPS, respectively. Moreover, OPEO-EPS-based biocoagulants effectively remove HA in raw water. The highest removals at 10 mg/L HA with 2.5 g/L additive are 68% for TX-45-TB-EPS and 65% for TX-45-LB-EPS, respectively. The removals of 15 mg/L HA with 1.5 g/L additive are 85% for TX-165-TB-EPS and TX-165-LB-EPS, respectively. Overall, OPEO-EPS-based biocoagulants show high potential for treating high turbidity or HA in raw water. These biocoagulants can serve as practical coagulant aids to enhance flocculation for turbidity and remove dissolved organic matter in water supply engineering.