Assessment of the pollution potential of mercury contaminated biosolids

Biosolids from Melbourne Water's Western Treatment Plant (WTP) in Australia contain elevated levels of mercury. Consequently, monitoring programs are crucial in order to assess localised impacts to the environment and on humans immediately surrounding the boundaries of the WTP. Dry biosolids were surveyed for Hg, other heavy metals, cations, soluble anions, sulfur and phosphorus. Mercury concentrations were found to vary between 3.5 and 8.4 mg kg(-1) Hg, indicating that biosolids from some locations were above the safety level (5mg kg(-1) Hg) for land applications. High concentrations of soluble anions and cations revealed elevated salinity levels. The biosolids with the highest Hg concentration were further studied to assess their potential for Hg remediation. The results obtained by a sequential extraction procedure showed that 59.01% of the total mercury was complexed with organic ligands. In addition, the influence of air temperature, water content and irradiation on the emission of gaseous elemental mercury from biosolids was studied. Light exposure and water addition were the main factors affecting this emission with flux values up to 132 ng m(-2) h(-1).