Water-extractable phosphorus in biosolids: implications for land-based recycling

Area of Science:

• Environmental Science
• Agricultural Science
• Soil Science

Background:

• Phosphorus (P) management is crucial for land application of biosolids to prevent agricultural runoff.
• Water-extractable phosphorus (WEP) in livestock manures indicates P loss risk in watersheds.
• Evaluating WEP in biosolids is essential for effective nutrient management.

Purpose of the Study:

• To assess the utility of water-extractable phosphorus percentage (PWEP) as an indicator for biosolids.
• To compare PWEP in biosolids from various treatment processes with manures and fertilizers.
• To understand how biosolids composition and processing influence phosphorus (P) migration potential.

Main Methods:

• Analyzed PWEP in 41 biosolids samples representing diverse treatment processes.
• Compared biosolids PWEP to dairy manure, poultry manure, and triple superphosphate fertilizer.
• Investigated the impact of pathogen reduction processes on biosolids PWEP.

Main Results:

• Mean PWEP for conventionally treated biosolids (2.4%) was significantly lower than fertilizer (85%), dairy manure (52%), and poultry manure (21%).
• Elevated aluminum and iron content in biosolids, from chemical additions, contributed to low PWEP.
• Biological phosphorus removal processes resulted in higher PWEP (approx. 14%), while heat-drying yielded the lowest (<0.5%).
• Pathogen reduction processes generally decreased biosolids PWEP.

Conclusions:

• Biosolids PWEP varies widely based on composition and processing, influencing P migration risk.
• Nutrient management policies for land-applied biosolids must consider this variability to mitigate phosphorus loss.
• Understanding PWEP is vital for sustainable land-based recycling of biosolids.