Sewage sludge composting: quality assessment for agricultural application

Area of Science:

• Environmental Science
• Agronomy
• Soil Science

Background:

• Sewage sludge (SS) utilization in agriculture requires quality assessment for safe application.
• Composted SS can serve as a valuable fertilizer and soil amendment, particularly in semi-arid environments.

Purpose of the Study:

• To evaluate the quality and agronomic value of composted SS mixed with plant waste.
• To determine optimal SS to plant waste ratios for effective composting and safe agricultural use.

Main Methods:

• Composting anaerobically digested SS with green and dry plant waste in 1:1, 1:2, and 1:3 (v/v) ratios.
• Analysis of compost quality parameters: pH, electrical conductivity, organic matter, C/N ratio, phytotoxicity, microbial load, and heavy metals.

Main Results:

• Composts from 1:2 and 1:3 SS/plant waste mixtures exhibited high organic matter degradation and low heavy metal content.
• These mixtures resulted in a high germination index and significant pathogen reduction.
• pH and electrical conductivity levels were within permissible agricultural standards.

Conclusions:

• Composted SS and plant waste at 1:2 and 1:3 proportions are suitable for agricultural use and land restoration.
• These composts pose no threat to soil or plant quality when applied according to international standards.
• The study highlights the potential of SS composts as a sustainable resource in semi-arid agriculture.