Optimization of Sewage Sludge Thickening Using Straw Pellets

Straw pellets are an effective, natural material supporting the sludge thickening process. They improve dewatering efficiency, lower transport costs, and enhance working conditions in wastewater treatment plants.

Why straw pellets improve sludge thickening

• High absorbency – rapid absorption of free water.
• Improved structure – better porosity and solid–liquid separation.
• Natural composition – fully biodegradable.
• Balanced C:N ratio – important for composting or anaerobic digestion.

Application guidelines

• Dosage: 5–15% of sludge mass.
• Dosing point: before mechanical thickening section.
• Contact time: at least several minutes.
• Pellet size: 6 mm or 8 mm.

Benefits for wastewater treatment plants

• Sludge volume reduction by 20–30%.
• Lower transport and disposal costs.
• Better performance of dewatering equipment.
• Reduced odors and leakage.

Integration with downstream processes

After dewatering, sludge with added pellets is more easily digested anaerobically, composts faster, and can be used for soil remediation after meeting sanitary requirements.

Case study

In a 20,000 PE municipal plant, a 10% pellet dosage reduced dewatering time by 15%, cut sludge mass by 26%, and lowered transport costs by 18% annually.

Common mistakes

• Excessive pellet dosage.
• Dosing at the wrong stage.
• Uneven mixing of pellets.