Identification of correlation relationships and establishment of regression models among multiple microbial indicators in reclaimed waters

Zhuo Chen; Qi Shi; Han Yan; Banghao Huang; Keying Song; Kefan Cao; Yun Lu; Hong-Ying Hu

doi:10.1016/j.envres.2025.120896

Identification of correlation relationships and establishment of regression models among multiple microbial indicators in reclaimed waters

Environ Res. 2025 Jan 17:120896. doi: 10.1016/j.envres.2025.120896. Online ahead of print.

Authors

Zhuo Chen¹, Qi Shi², Han Yan³, Banghao Huang², Keying Song⁴, Kefan Cao², Yun Lu¹, Hong-Ying Hu⁵

Affiliations

¹ Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, PR China; Beijing Laboratory for Environmental Frontier Technologies, Beijing 100084, PR China.
² Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, PR China.
³ Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, PR China. Electronic address: [email protected].
⁴ Basic Education School, Beijing Information Technology College, Beijing 100070, China.
⁵ Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, PR China; Beijing Laboratory for Environmental Frontier Technologies, Beijing 100084, PR China; Research Institute for Environmental Innovation (Suzhou), Tsinghua, Jiangsu, Suzhou, 215163, PR China.

PMID: 39828189
DOI: 10.1016/j.envres.2025.120896

Abstract

Monitoring and controlling microbial water quality is crucial for ensuring water reuse safety. In particular, existing water reuse guidelines and regulations normally prescribed coliform bacteria as microbial indicators. However, the use of non-unified coliform groups may bring difficulties to compare and optimize the conformity efforts on microbial surveillance. This study has identified the correlation relationships in each pair of four microbial indicators in reclaimed waters, namely the heterotrophic plate counts (HPCs), total coliforms (TC), fecal coliforms (FC) and E. coli (r=0.861-0.987). Ultimately, the built regression model for internal conversion is expressed as: log₁₀HPC (MPN/mL)= 0.737×log₁₀TC (MPN/L)= 0.830×log₁₀FC (MPN/L)= 0.872×log₁₀E. coli (MPN/L) with further verification and validation. The developed model can be used to help water reuse regulators and practitioners improve the efficiency in universal microbial risk detection and management. Besides, the resistant microbes in HPCs (e.g. disinfection resistant bacteria and pathogens) after reclaimed water treatment and disinfection also call for future attention.

Keywords: Coliform indicators; Correlation relationships; Heterotrophic plate counts; Reclaimed water; Regression models.