Biosolids microbes pose manageable risk to workers

Oct 27, 2008

Class B biosolids are sewage sludges that have been treated to contain fewer than 2.0 x 106 fecal coliforms/dry gram. The USEPA estimates that 6.3 million tonnes of Class B biosolids are generated in the United States each year, and that by 2010, the amount generated per year will increase to 7.4 million tonnes. Biosolids produced during municipal sewage treatment are most commonly applied to land as a fertilizer at agricultural sites throughout the United States. Class B biosolids, which are the principal type of biosolids applied to land, contain a variety of enteric pathogens.

Land application of biosolids has received national attention due to the potential for off-site transport of disease-causing microorganisms through soil, water, and air. Workers face greater exposure to bioaerosols from biosolids than those not associated with the operation. A new study published in the November–December issue of Journal of Environmental Quality investigated levels of microorganisms in air immediately downwind of land application operations and estimated occupational risks from aerosolized microorganisms.

The authors report that risks of aerosol-borne infection for biosolids workers are generally low, at less than 1 or 2% per year. Overall, occupational exposure to bioaerosols from biosolids appears to be less risky than similar exposures among wastewater treatment workers.

In all, more than 300 air samples were collected downwind of biosolids application sites at various locations within the United States. Coliform bacteria, coliphages, and heterotrophic plate count (HPC) bacteria were enumerated from air and biosolids at each site. Concentrations of coliforms relative to Salmonella and concentrations of coliphage relative to enteroviruses in biosolids were used, in conjunction with levels of coliforms and coliphages measured in air during this study, to estimate exposure to Salmonella and enteroviruses in air.

The HPC bacteria were ubiquitous in air near land application sites whether or not biosolids were being applied, and concentrations were positively correlated to windspeed. Coliform bacteria were detected only when biosolids were being applied to land or loaded into land applicators. Risks from aerosolized microorganisms at biosolids land application sites appear to be lower than those at wastewater treatment plants, based on previously reported literature.

Source: Soil Science Society of America

Explore further: Oil from Russian trawler wreck reaches Canaries' beaches

Related Stories

Ears, grips and fists take on mobile phone user ID

16 hours ago

A research project has been under way to explore a biometric authentication system dubbed Bodyprint, with interesting test results. Bodyprint has been designed to detect users' biometric features using the ...

More than 2,200 confirmed dead in Nepal earthquake

16 hours ago

A powerful aftershock shook Nepal on Sunday, making buildings sway and sending panicked Kathmandu residents running into the streets a day after a massive earthquake left more than 2,200 people dead.

Nepal quake: Nearly 1,400 dead, Everest shaken (Update)

Apr 25, 2015

Tens of thousands of people were spending the night in the open under a chilly and thunderous sky after a powerful earthquake devastated Nepal on Saturday, killing nearly 1,400, collapsing modern houses and ...

Recommended for you

Holistic soil to boost productivity

Apr 24, 2015

Western Australia has launched Soil Constraints – West, a flagship initiative bringing together research on a range of farming problems that limit agricultural production.

Heat still on despite warming slowdown

Apr 23, 2015

The recent slowdown in the rise of global average air temperatures will make no difference to how much the planet will warm by 2100, a new study has found.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.