Integral evaluation of production safety and genotoxicity of recycling residual sludge for drinking water treatment plants

ABSTRACT

Recycling residual sludge in drinking water treatment plants (DWTPs) may release excessive heavy metals and organic matter, which are substances of concern because of their toxic and carcinogenic potential. The aim of this study was to investigate potential genotoxic, cytotoxic, and mutagenic effects of recycled residual sludge in terms of quality of water in potable water works. Genotoxic effects of reusing residual sludge were evaluated using: the Ames test, sperm abnormality test in mice, micronucleus assay, comet assay, and single-cell gel electrophoresis assay. The results of the Ames assay show that the disinfected water sample displays bacteriostasis at a dose of 7 L/dish regardless of treatment styles, but mutagenicity ratio (MR) < 2 can still be judged as negative. The micronucleus rates of conventional treatment were slightly genotoxic but only at 4 and 40 L/kg·bw, whereas micronucleus rates of filtered water and disinfectant from the recycling process were negative in all of the dose groups. The levels of DNA damage that are caused by different treatment processes were equivalent. Reusing residual sludge for DWTPs did not contribute to the release of genotoxic or mutagenic compounds, but it did have a remarkable effect on saving the drug dose and increasing drinking water yield. Thus, reusing residual sludge for DWTPs should be widely recommended.

GRAPHICAL ABSTRACT

KEYWORDS:

• Recycling residual sludge
• drinking water treatment plant
• gene mutation assay
• chromosomal aberration
• DNA damage

Acknowledgements

This work was supported by the Climbing Program of Guangdong Province, China (PDJH2020a1190). This work was also supported by the Science and Technology Project of Shenzhen Institute of Information Technology (SZIIT2020KJ001).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Science and Technology Project of Shenzhen Institute of Information Technology [grant number SZIIT2020KJ001]; Climbing Program of Guangdong Province, China [grant number PDJH2020a1190].