Abstract
Aim of study: To investigate the content, contamination levels and potential sources of five heavy metals (Hg, Pb, Cd, Cr, As) in sewage sludge from eight wastewater treatment plants (W1 to W8).Area of study: Wuhu, located in southeastern Anhui Province, southeastern China.Material and methods: The sewage sludge pollution assessment employed the single-factor pollution index, Nemerow’s synthetic pollution index, monomial potential ecological risk coefficient and potential ecological risk index. The potential sources among the five heavy metals were determined using the Pearson’s correlation analysis and principal component analysis (PCA).Main results: The mean concentrations of the heavy metals were 0.27 mg/kg (Hg), 70.78 mg/kg (Pb), 3.48 mg/kg (Cd), 143.65 mg/kg (Cr) and 22.17 mg/kg (As). W1, W5 and W6 sewage sludge samples showed the highest levels of heavy metal contamination, and cadmium had the highest contamination level in the study area. Pearson’s correlation analysis and PCA revealed that Pb and Cd mainly derived from traffic emissions and the manufacturing industry and that As and Cr originated from agricultural discharges.Research highlights: The pollution of cadmium in Wuhu should be controlled preferentially. The heavy metal pollution of W1, W5 and W6 sewage treatment plants is relatively high, they should be key prevention targets.
Highlights
W1, W5 and W6 sewage sludge samples showed the highest levels of heavy metal contamination, and cadmium had the highest contamination level in the study area
Pearson’s correlation analysis and principal component analysis (PCA) revealed that Pb and Cd mainly derived from traffic emissions and the manufacturing industry and that As and Cr originated from agricultural discharges
Sewage sludge is generated during the process of treating municipal wastewater, and it is rapidly increasing (Dong et al, 2013)
Summary
Sewage sludge is generated during the process of treating municipal wastewater, and it is rapidly increasing (Dong et al, 2013). Sludge can be disposed in the form of soil conditioners or fertilizers, and improper disposal leads to a loss of organic matter and nutrient elements, representing a waste of resources. To evaluate the environmental risk and sources of heavy metals in sewage sludge, the geo-accumulation index (Igeo), single-factor pollution index (PI), Nemerow pollution index (PN), monomial potential ecological risk coefficient (Eri ) and potential ecological risk index (RI), together a multivariate statistical analysis have been widely applied (Abrahim & Parker, 2008; Shafie et al, 2013; Kowalska et al, 2016; Birch, 2017; Yang et al, 2017; Zhu et al, 2018)
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