Extraction, characterization, and biosurfactant properties of extracellular polymeric substance from textile wastewater activated sludge

Textilewastewater treatment generates sludge that needs to be disposed of safely. The cost of sludge management is 50% of the total treatment cost of thewastewater. To reduce the expense, the sludge can be repurposed as a valuable resource by extracting extracellular polymeric substance (EPS). EPS contains polysaccharides, proteins, and humic substances, which are surface-active substances that act as potential biosurfactants. In this study, we investigated sludges (sludge 1 and sludge 2) from two different textile industries for EPS production. The results showed a maximum EPS yield of 179 mg/gactivated sludge from the wastewater from sludge 2. The EPS from textile wastewater activated sludge had a protein/ carbohydrate ratio of 0.27e0.56, lower than that of municipal activated sludge. This difference is due to variations in nitrogen/carbon ratio in these wastewaters. Based on the biosurfactant activity test, EPS from both textilewastewaters could lower the water surface tension to around 60 mN/m and emulsify olive oil better than Tween 20 and 80. However, only EPS from sludge 2 showed better xylene emulsification than EPS from sludge 1 due to the difference in humic acid content.