This paper reviews the effect of the wastewater and sludge treatment on …

• Abstract
• Introduction
• Effects of treatment on microorganisms
• Recent developments
• Quality management systems
• Conclusions
• References
• Tables

Biology Articles » Miscellaneous » Processes for Managing Pathogens » Tables

Tables

- Processes for Managing Pathogens

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Table 1. Removal of bacteria by physical treatment processes.

Data from Metcalf and Eddy, Inc. (1991).

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Table 2. Removal or destruction of bacteria and viruses by different treatment processes.

Removal Process Fecal coliform Salmonellae Enteric viruses % Primary sedimentation 50–90   50–90    0–30 Trickling filter 90–95   90–95   90–95 Activated sludge 90–99   90–99   90–99 Oxidation ditch 90–99   90–99   90–99 Waste stabilization pond  4–7 log 99.99–100 99.99–100 Lagoon  2–6 log   99–100   99–100

Three cells, 25-d minimum total retention. Data from Feacham et al. (1980).

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Table 3. Summary of pathogen reduction during sludge treatment.

Data from Ward et al. (1984), Ponugoti et al. (1997), and United Kingdom Water Industry Research (2002).

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Table 4. Effect of sludge treatment processes on numbers of Escherichia coli.

Log reduction in E. coli Log number of E. coli in treated sludge (100 g–1 dry wt.) Treatment n 25th percentile Mean 95th percentile 25th percentile Mean 95th percentile Lagooning  36 1.47 2.65 6.00 5.08 5.93 8.32 MAD, liquid 208 1.04 1.39 2.36 7.10 7.41 8.27 MAD, cake  93 1.76 2.29 3.64 6.27 6.65 7.46 Vermiculture  14 4.2 5.12 6.54 3.20 4.50 5.07 Composting  31 5.75 6.71 9.10 1.05 2.43 4.70 Lime addition  32 5.70 7.10 9.05 0 1.45 3.00 Thermal drying  70 6.52 7.14 8.90 0.33 1.67 3.56

Mesophilic anaerobic digestion. Data from United Kingdom Water Industry Research (1999).

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Table 5. End product microbiological standards for Class A and B sludges (USEPA, 1993).

Standard Class A Class B Fecal coliforms, g–1 dry solids Salmonellae, 4 g–1 dry solids Enteroviruses, pfu 4 g–1 dry solids Parasite ova , 4 g–1 dry solids

Geometric mean of seven samples.

For processes unable to satisfy specific operational requirements.

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Table 6. Proposed UK standards for treated and enhanced treated sludge.

Sludge category Reduction in numbers of E. coli across sludge treatment process Number of E. coli in final product Number of salmonellae in final product Treated 2 log10 105 g–1 dry solids no standard Enhanced treated 6 log10 103 g–1 dry solids absent from 2 g dry solids

To be achieved on 90th percentile basis for first 2 yr following introduction of the regulations with a maximum allowable concentration of 10⁷ g^–1 dry solids; thereafter maximum allowable concentration of 10⁵ g^–1 dry solids.

It is expected that well-controlled sludge treatment is likely to consistently produce a sludge containing less than 10² g^–1 dry solids. Should routine sampling indicate that the product quality was poorer than this, then the operation of the plant must be checked, even though the batch quality was within the final product standard.

In five random samples, each containing 2 g dry solids, with less frequent samples if consistently absent over 6 mo.

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