Flocculant in wastewater affects dynamics of inorganic N and accelerates removal of phenanthrene and anthracene in soil

Recycling of municipal wastewater requires treatment with flocculants, such as polyacrylamide. It is unknown how polyacrylamide in sludge affects removal of polycyclic aromatic hydrocarbons (PAH) from soil. An alkaline-saline soil and an agricultural soil were contaminated with phenanthrene and anthracene. Sludge with or without polyacrylamide was added while emission of CO₂ and concentrations of NH₄⁺, NO₃⁻, NO₂⁻, phenanthrene and anthracene were monitored in an aerobic incubation experiment. Polyacrylamide in the sludge had no effect on the production of CO₂, but it reduced the concentration of NH₄⁺, increased the concentration of NO₃⁻ in the Acolman soil and NO₂⁻ in the Texcoco soil, and increased N mineralization compared to the soil amended with sludge without polyacrylamide. After 112 d, polyacrylamide accelerated the removal of anthracene from both soils and that of phenanthrene in the Acolman soil. It was found that polyacrylamide accelerated removal of phenanthrene and anthracene from soil.