Extracellular polymeric substances and bound water drastically affect bioleached sludge dewaterability at low...

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• Bioleaching using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans enhances sludge dewaterability at ambient temperatures.
• Limited data exists on the impact of low temperatures on bioleaching efficiency for sludge dewatering.

Purpose of the Study:

• To investigate the optimal sludge retention time for bioleaching at low (10°C) and normal (28°C) temperatures.
• To elucidate the mechanisms behind dewaterability enhancement in bioleached sludge at different temperatures.

Main Methods:

• Two bioleaching systems were operated at 10°C and 28°C.
• Sludge capillary suction time (CST), pH, extracellular polymeric substances (EPS), and bound water content were measured.
• Statistical analysis correlated CST with sludge properties.

Main Results:

• Acidithiobacillus bacteria remained active at 10°C, reducing CST in the initial 3 days.
• Dewaterability enhancement was significantly lower at 10°C compared to 28°C.
• Higher sludge pH, EPS, and bound water content at 10°C limited dewatering improvement.

Conclusions:

• Low temperatures reduce the effectiveness of bioleaching for sludge dewatering.
• Sludge pH, EPS, and bound water are key factors influencing dewaterability.
• Pre-treatment methods like reducing pH or removing EPS and bound water could enhance low-temperature sludge dewatering.