Resource recovery in wastewater management: After appropriate treatment and drying, what is a common beneficial use of dried sewage (biosolids)?

Introduction / Context:
Modern sanitation emphasizes circular economy principles where treated wastewater and solids can be beneficially reused. Dried, stabilized sewage sludge (biosolids) can return organic matter and nutrients to soils when processed to meet safety standards.

Given Data / Assumptions:

• Biosolids are properly stabilized (e.g., anaerobic digestion), dewatered, and dried.
• Pathogen reduction and vector attraction reduction meet local regulations.
• Land application aligns with agronomic nutrient rates and soil needs.

Concept / Approach:

Biosolids contain nitrogen, phosphorus, potassium, and organic carbon that improve soil fertility and structure. When processed, they can be applied as fertilizer/soil conditioner for agriculture, landscaping, and land reclamation, replacing a portion of synthetic fertilizers.

Step-by-Step Solution:

Verification / Alternative check:

Soil and tissue testing verifies nutrient uptake and confirms no exceedance of metal limits; audit application records and environmental monitoring.

Why Other Options Are Wrong:

(b) Structural building materials require different mechanical properties and certification; (c) biosolids are not dosing chemicals for BOD control; (d) paints/coatings do not use biosolids as base material.

Common Pitfalls:

Applying without nutrient management planning; using unstabilized sludge; ignoring local regulations and public acceptance.

Final Answer:

Fertilizer for soil conditioning and nutrient return