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<p>This study assesses the bacterial pathogen load in secondary sludge from a sewage treatment plant that co-processes fecal sludge with municipal wastewater over 1&#xa0;year. It also examines how anaerobic digestion and temperature treatment affect pathogens (including bacteria and nematodes) and antibiotic-resistance genes in secondary sludge. Furthermore, it assesses the impact of bacterial pathogen survival during co-digestion of secondary sludge with food waste, bakery waste, and flower waste. A fluctuating viable pathogenic bacterial count with no consistent trend was observed during the 1-year period. <i>Staphylococcus </i>spp. remained consistently abundant with log values of 6.2–7.4&#xa0;CFU/g TS. Meanwhile, <i>E. coli</i> and <i>Salmonella </i>spp. ranged from 1.3 to 4.6 and 2.7 to 4.6 log CFU/g TS, respectively, significantly exceeding the Class A biosolid limits. Mesophilic anaerobic digestion for 21&#xa0;days showed limited pathogen removal, requiring 55&#xa0;days for complete elimination of Gram-negative bacteria, while <i>Staphylococcus </i>spp. exhibited only a 0.4-log reduction. Treatment at 70&#xa0;°C for 60&#xa0;min reduced 2–4 log units (<i>p</i> &lt; 0.05) of all Gram-negative bacteria tested, whereas 100&#xa0;°C for 30&#xa0;min was required to eliminate <i>Staphylococcus </i>spp. Complete eradication was not achieved for ARGs or nematodes after anaerobic digestion or treatment at 100&#xa0;°C for up to 90&#xa0;min. Co-digestion of secondary sludge with food, bakery, and flower waste over 21&#xa0;days effectively eliminated most bacterial pathogens, achieving complete removal (up to 100%) of <i>Salmonella </i>spp.,<i> E. coli</i>,<i> Vibrio </i>spp., and <i>Klebsiella </i>spp. Meanwhile, <i>Staphylococcus </i>spp. persisted during co-digestion, where the extent of reduction varied with the co-substrate used.</p>

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Effects of thermal treatment and anaerobic digestion on pathogen and ARG removal in bio-solids from a co-treatment plant for sewage and fecal sludge

  • 期刊论文

  • 发表日期：

    2025年4月8日

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  • K. Haritha,
  • M. K. Akhina,
  • B. Krishnakumar

摘要

This study assesses the bacterial pathogen load in secondary sludge from a sewage treatment plant that co-processes fecal sludge with municipal wastewater over 1 year. It also examines how anaerobic digestion and temperature treatment affect pathogens (including bacteria and nematodes) and antibiotic-resistance genes in secondary sludge. Furthermore, it assesses the impact of bacterial pathogen survival during co-digestion of secondary sludge with food waste, bakery waste, and flower waste. A fluctuating viable pathogenic bacterial count with no consistent trend was observed during the 1-year period. Staphylococcus spp. remained consistently abundant with log values of 6.2–7.4 CFU/g TS. Meanwhile, E. coli and Salmonella spp. ranged from 1.3 to 4.6 and 2.7 to 4.6 log CFU/g TS, respectively, significantly exceeding the Class A biosolid limits. Mesophilic anaerobic digestion for 21 days showed limited pathogen removal, requiring 55 days for complete elimination of Gram-negative bacteria, while Staphylococcus spp. exhibited only a 0.4-log reduction. Treatment at 70 °C for 60 min reduced 2–4 log units (p < 0.05) of all Gram-negative bacteria tested, whereas 100 °C for 30 min was required to eliminate Staphylococcus spp. Complete eradication was not achieved for ARGs or nematodes after anaerobic digestion or treatment at 100 °C for up to 90 min. Co-digestion of secondary sludge with food, bakery, and flower waste over 21 days effectively eliminated most bacterial pathogens, achieving complete removal (up to 100%) of Salmonella spp., E. coli, Vibrio spp., and Klebsiella spp. Meanwhile, Staphylococcus spp. persisted during co-digestion, where the extent of reduction varied with the co-substrate used.