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Controlling Organic Dust and Bioaerosols at a Biosolids Composting Facility

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The City of Longmont, Colorado owns and operates an 8.5 dry tons per day aerated static pile Biosolids composting facility. The composting facility consists of a totally enclosed missing building and a separate, totally enclosed composting/curing screening building.

Since the Longmont composting facility began operating in 1991, moisture control throughout the process was very difficult. As a result of the low humidity and extremely dry conditions, the amount of organic dust generated by normal operations has become a concern for worker health and safety.

In 1994, the National Institute for Occupational Safety and Health (NIOSH) issued a warning of the dangers of organic dust and the need for prevention. The health effects from organic dust exposure include inflammation, allergy, and infection.

In an effort to reduce dust and airborne contaminants at the composting facility, the City of Longmont commissioned a study to assess dust aerospore concentrations at the facility and to determine both operational and facility modifications. Air monitoring was conducted at the facility for total dust, respirable dust, endotoxin, and Aspergillus fumigatus. Samples for dust were taken in the facility and directly on personnel during activities.

The highest concentration of total dust was measured during pile teardown and screening The concentrations measured were below the Occupational Safety and Health Administration (OSHA) standard of 15 mg/m3 for airborne particulate matter. Respirable dust concentrations were also below the OSHA exposure standard. Operator measurements showed that exposure was greatest in the mixing area. Endotoxing levels in the facility ranged from <0.5ng/m3 to .640 mg/m3. The higher levels could result in mucous membrane irritation and bronchial constriction. There was a direct correlation between total and endotoxin concentrations.

Based on these results, the City of Longmont implemented a series of mitigation measures that were recommended. These included a dust collection system in the screening area and a high-pressure wash-water truck in the composting building and the high traffic areas. Operational measures to reduce potential dust emissions were also implemented.

This paper will discuss the following

Results of the study

Worker health implications

Mitigation measures implemented

Application to other biosolids composting and management facilities

Document Type: Research Article


Publication date: January 1, 2002

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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