Benefits and risks of long-term recycling of pharmaceutical sewage sludge on agricultural soil.

European policy is direct towards increasing the agricultural reuse of sludge on soil for improving the fertility; however, the effects of long-term pharmaceutical sewage sludge (PSS) application on soil properties are still unknown. Thus, the aim of this work was to evaluate the agronomic and environmental effects on soil after 17 years of organic amendment with PSS derived from daptomycin production. Five different doses of PSS were spread on lands located in Anagni, Central Italy. Physico-chemical soil properties were investigated, as well as total and bioavailable heavy metals, changes in the soil organic matter quality and biochemical functioning. PSS application showed a positive agronomic potential, improving SOM quality, increasing soil humified organic matter and raising plant nutrients. SOM dynamic was different at low and high PSS supplies, as confirmed by the chemical and biochemical analysis (e.g. C biomass, FDA hydrolysis activity, basal respiration, dehydrogenase, urease and phosphatase activities). However, in a long-term agricultural reuse, environmental risks of PSS recycling were related to the increase of some heavy metals (Hg, Zn and Cu) and exchangeable Na.