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Fresh evidence

Fresh evidence The Washington dc-based National Research Council's committee on toxicants and pathogens in biosolids (solid organic matter recovered from sewage treatment) has recently come out with its report. The report, Biosolids applied to land: Advancing standards and practices, questions the very basis of the us Environmental Protection Agency's (epa) standards on application of sewage sludge to land.

It urges that epa standards, notified in 1993 under the Clean Water Act as the Code of Federal Regulations, Title 40 (Part 503), commonly known as the part 503 rule, need to be reviewed.

Thanks to the 1992 prohibition on disposal of sewage sludge in oceans, roughly 60 per cent of the 5.6 million dry tonnes of biosolids, high in organic content and plant nutrients, are diverted to farmlands as fertiliser.
Growing concern However, biosolids could contain pollutants from household, commercial and industrial wastewater with organic contaminants (such as pharmaceuticals), inorganic contaminants (metals and trace elements) and pathogens (bacteria, viruses and parasites). Worse still, after wastewater treatment concentration levels of some pollutants in the sludge increase. Depending on the extent of treatment, biosolids may be applied on areas with limited public exposure, such as farms, or with more treatment on public sites, such as parks, golf courses and lawns. Of late, public health concerns regarding the use of biosolids are growing, especially from citizens living near application sites.

Ellen Z Harrison of Ithaca-based Cornell Waste Management Institute points out (Land application of sewage sludges: an appraisal of the us regulations; International Journal of Environment and Pollution, Vol 11, No 1; 1999) that the current us federal regulations are not adequately protective of human health, agricultural productivity or ecological health.

The part 503 rule establishes minimum standards that must be met if sludge is to be land-applied. The regulation includes concentration limits for nine metals and pathogens, and requires that flies and rodents are not attracted to the site. Of its adequacy, the nrc report says, "

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