Bioaerosols – Sources and control measures

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Abstract

In every field of activity where organic material is being handled, emissions of dust, gases, odor as well as bioaerosols are bound to arise. For this reason, waste management facilities or else agricultural enterprises are potential emission sources of bioaerosols. The dispersion of bioaerosols from waste treatment facilities and their health impacts continue to be the subject of numerous discussions. This article addresses organizational and engineering measures for the mitigation of bioaerosol emissions. The required scale of emission reduction and the choice of microbiological parameters have to be assessed with respect to location and facility type.

Introduction

Over the past 15 years, biological treatment has found broad application in the waste management sector. Biological treatment is achieved by creating an environment that enhances the metabolic activity of naturally occurring microorganisms. While biological processes offer the advantage of using the waste constituents as substrate and energy source in natural cycles, controlled biological degradation may, however, also imply the release of bioaerosols into the direct plant surroundings. This issue has been much publicized by the media without bothering for a differentiated discussion of the measurement methodology, sampling procedures, other bioaerosol sources, etc. and considering such factors in the overall assessment, thus heightening anxieties among facility neighbors. Compounding the situation is that professional studies as well have arrived at different assessments. The German Council of Experts on Environmental Matters addressed the issue in the Environmental Report 2004 (Deutscher Bundestag, 2004) (SRU, 2004), pointing out the potential health risks and demanding an effective reduction of bioaerosol emissions. Both the German Federal Immission Control Act and the German Technical Instructions on Municipal Waste provide a basis for addressing bioaerosol emissions within the scope of the requisite permitting procedures.

Bioaerosols – that is bacteria, fungi and their metabolic products (e.g., endotoxins) – are part of the biosphere of humans and ubiquitous in the ambient air. Sources of bioaerosols are the microbial decomposition of organic material in all naturally occurring processes and/or the atmospheric dispersion of bioaerosols. In addition, a multitude of processes associated with human activities lead to elevated bioaerosol emissions. The following list gives an overview over potential facility-related bioaerosol sources:

  • Waste disposal facilities

    • Biological waste treatment facilities

    • Residual waste pre-treatment facilities (MBT)

    • Materials recovery and transfer stations

    • Landfills

    • Waste water treatment plants

  • Agriculture

    • Crop and livestock production

  • Food production

  • Other areas

    • Paper and wood processing

    • Horticulture facilities

    • Refrigeration plants

The German Waste Avoidance, Recycling and Disposal Act 1994 marked a step change in waste management from a pure disposal to a recycling and reuse strategy. The act is being implemented into practice by increased source separation of recyclables (post-use paper, biowaste, post-use wood, electrical scrap (see “Abfallmengenbilanz, 1995–2004” for instance), the reprocessing of recyclables by means of optimized treatment processes and their subsequent reuse. Against this backdrop, biowaste composting and mechanical–biological waste treatment have become key elements of waste management.

In waste treatment facilities, microbial decomposition of organic material occurs under intensified conditions. This is the reason why bioaerosol emissions from waste treatment facilities are an issue from both occupational health and safety as well as environmental hygiene aspects, even though these facilities account for only a small fragment of the broad spectrum of potential emission sources (see above list).

Section snippets

Standardization work

In order to obtain representative and comparable data, it is imperative that measurements be performed on the basis of standardized procedures or conventions. While there are numerous published data from bioaerosol emission and ambient air bioaerosol measurements, work on establishing binding standards and/or guidelines has only just started. In 1999, the Standardizing Committee within the Commission on Air Pollution Prevention (KRdL) of VDI and DIN established a joint committee on Bioaerosols

Emission sources in biological waste treatment facilities

Biological waste treatment facilities vary greatly in their treatment concepts and type of construction. Basically, these facilities can be classified into:

  • Open facilities: composting is accomplished in open windrows, either aerated or non-aerated, covered or roofed-over.

  • Partially enclosed facilities: use of enclosed, aerated reactors for the main composting phase; curing carried out in open windrows.

  • Enclosed facilities: fully contained facilities from the receiving area through to the curing

Control mitigation

In principle, it can be assumed that all abatement measures generally deemed to be effective on dust and odor emissions will also contribute to a reduction in bioaerosol releases. Bioaerosol emissions from continuous sources can be reduced by thermal, biological and physical/chemical exhaust air treatment processes.

Comprehensive measurement results and literature data on different exhaust air cleaning technologies are presented in Guideline VDI 4255 Part 1. A final evaluation of all eligible

Permitting aspects

The assessment of bioaerosol emissions within the scope of the permitting procedure for biological waste treatment facilities is likewise to be based on the following central provision of the German Federal Immission Control Act (Section 5 (1) BimSchG, 2001):

Facilities subject to permitting shall be built and operated in such a way as to avoid harmful effects on the environment and any other hazards, significant disadvantages and significant nuisances to the general public and the neighborhood.

Summary

According to current knowledge, a great variety of control approaches, although primarily aimed at the control of dust emissions, is also applicable to mitigating bioaerosol releases. At the same time, some German states recommend minimum setback distances for the sitting of composting facilities and landfills. These recommendations are generally based on odor and dust emissions without expressly considering potential emissions of bioaerosols and their metabolic products.

However, there is still

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