Sequential polymer dosing for effective dewatering of ATAD sludges

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Biotechnology

Background:

• Sludge dewatering presents significant challenges in wastewater treatment, leading to high operational costs.
• Autothermal thermophilic aerobic digestion (ATAD) produces sludge that is difficult to dewater, requiring substantial chemical conditioning.
• Existing chemical conditioners are often ineffective at acceptable doses for ATAD sludge.

Purpose of the Study:

• To investigate methods for improving the dewaterability of sludge generated from autothermal thermophilic aerobic digestion (ATAD).
• To identify cost-effective chemical conditioning strategies for ATAD sludge dewatering.
• To understand the role of chemical precipitation and colloidal properties in ATAD sludge dewatering.

Main Methods:

• Analysis of chemical precipitation during the ATAD process.
• Zeta potential measurements to characterize ATAD sludge colloids.
• Sequential polymer dosing experiments, including iron salts, cationic polymers, and anionic polymers.

Main Results:

• Chemical precipitation of divalent cations was observed during ATAD.
• Positive zeta potential of some ATAD sludge colloids was attributed to precipitated divalent cations.
• Sequential dosing with cationic and anionic polymers significantly improved sludge dewatering.
• Anionic polymer was found to be essential for effective dewatering, enabling reduced doses of cationic agents.

Conclusions:

• Sequential polymer dosing, particularly with an initial cationic agent followed by an anionic polymer, is an effective strategy for ATAD sludge dewatering.
• The use of anionic polymers is crucial for enhancing dewatering efficiency and reducing the required amounts of more expensive cationic polymers or iron salts.
• This approach offers a more economical solution for managing ATAD sludge, potentially increasing the process's overall viability.