Environmental pollution and health risk related to metals in the solid fraction and effluent from waste water treatment.

摘要

This study determined the potential risk to animals, the environment and human health of reusing solid fractions produced by waste water treatment plants (WWTPs) in the Slovak Republic treating animal slurry and sewage. The quality of effluents from the WWTPs was also investigated in terms of Cd, Pb, Cu and Zn content. A relatively high removal (80.3-98.9%) of the observed heavy metals was reached in both WWTPs. A higher concentration of metals was present in the influent to the WWTP treating animal slurry, which was reflected also in the quality of the effluent. The effluent from the WWTP treating sewage complied with the acceptable limits for Cd, Pb and Zn in surface water only. The levels of the investigated metals in both sludges were below the accepted limits in the Slovak Republic except for Cd, which was the main element of concern and exceeded the limit in three samples of sludge from the WWTP treating animal slurry (12.5, 15.2 and 11.8 mg/kg) and 2 from the WWTP treating sewage (10.4 and 12.4 mg/kg). The concentration of the investigated metals in the effluent from the sewage WWTP presents no significant risk to surface- and groundwater. Higher levels of Cd and Pb and potentially also of Cu and Zn from the pig slurry WWTP may be a subject of concern in periods with low flow rates in the recipient..