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<p>This study gives an in-depth analysis of the physico-chemical and microbiological characteristics of sludge samples (dewatered or digested) collected from 7 sewage treatment plants (STPs) across Tamil Nadu, India, comprising Sequencing Batch Reactor, Moving Bed Biofilm Reactor and Activated Sludge Process. The findings revealed that the moisture content exceeded the 15–25% threshold set by the Fertilizer Compost Order (FCO) standard, raising concerns about its compostability. Additionally, while pH and EC levels were slightly above regulatory limits in some STPs. Heavy metal concentrations were generally low compared to international standards, with the exception of Ni (0.25 – 66.20&#xa0;mg/kg). Despite these promising results, pathogen levels particularly <i>Salmonella</i> sp. and helminth eggs (more than 1 Egg/ 4&#xa0;g TS) exceeded the permissible limits of FCO, United States Environmental Protection Agency and Central Public Health and Environmental Engineering Organisation necessitating heat treatment to reduce these harmful microbes. Multivariate analysis revealed key relationships between moisture content, electrical conductivity and nutrient availability, highlighting the interdependence of sludge properties across STPs. Pollution indices (pollution load index, geoaccumulation index and contamination factor) highlighted elevated levels of Cd, Ni and Cu in the sludge. Overall, the findings emphasize that untreated sludge is unsafe for agriculture reuse due to pathogen and contaminant risks. Key actions for safe valorization include applying pre-treatment methods to reduce pathogens, nutrient enrichment, heavy metal removal and optimized composting to improve nutrient availability. Implementing these strategies enables the safe reuse of sewage sludge as a valuable resource in agriculture, promoting soil health and nutrient recycling.</p>

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Physico-chemical, nutrient and contaminant profile of sewage sludge from sewage treatment plants in Tamil Nadu, India: implications for agricultural reuse

  • 期刊论文

  • 发表日期：

    2025年10月23日

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  • Anjali Kumari Shaw Birendar,
  • Saranya Kuppusamy,
  • Kanmani Sellappa,
  • Ganesh Kumar Pandian

摘要

This study gives an in-depth analysis of the physico-chemical and microbiological characteristics of sludge samples (dewatered or digested) collected from 7 sewage treatment plants (STPs) across Tamil Nadu, India, comprising Sequencing Batch Reactor, Moving Bed Biofilm Reactor and Activated Sludge Process. The findings revealed that the moisture content exceeded the 15–25% threshold set by the Fertilizer Compost Order (FCO) standard, raising concerns about its compostability. Additionally, while pH and EC levels were slightly above regulatory limits in some STPs. Heavy metal concentrations were generally low compared to international standards, with the exception of Ni (0.25 – 66.20 mg/kg). Despite these promising results, pathogen levels particularly Salmonella sp. and helminth eggs (more than 1 Egg/ 4 g TS) exceeded the permissible limits of FCO, United States Environmental Protection Agency and Central Public Health and Environmental Engineering Organisation necessitating heat treatment to reduce these harmful microbes. Multivariate analysis revealed key relationships between moisture content, electrical conductivity and nutrient availability, highlighting the interdependence of sludge properties across STPs. Pollution indices (pollution load index, geoaccumulation index and contamination factor) highlighted elevated levels of Cd, Ni and Cu in the sludge. Overall, the findings emphasize that untreated sludge is unsafe for agriculture reuse due to pathogen and contaminant risks. Key actions for safe valorization include applying pre-treatment methods to reduce pathogens, nutrient enrichment, heavy metal removal and optimized composting to improve nutrient availability. Implementing these strategies enables the safe reuse of sewage sludge as a valuable resource in agriculture, promoting soil health and nutrient recycling.