Phosphorus availability for beneficial use in biosolids products

It has become necessary to identify accurately the availability of phosphorus in biosolids products applied to land. The fertiliser value of these products must be quantified not only to satisfy the customer but also to ensure the best use of phosphorus when considering the need to avoid excess concentrations in the wider environment. With the advent of chemical phosphorus removal at more wastewater treatment works, the impact of iron and phosphate availability is particularly important. Existing research has indicated that there is a correlation between phosphate availability, and factors such as biosolids pH and iron concentration. However, it has not yet been possible to draw any firm conclusions, which can be used as a tool to manage the availability of phosphate in practice. Through a joint research programme for Anglian Water, involving literature investigation, laboratory tests on biosolid/soil interactions, and benchmarking phosphate availability over time, the study uses the best available input and output data to indicate the parts of the land bank most at risk from over-enrichment.