Session- Bioaerosols
Monitoring the Release of Bioaerosols From Composting Facilities in the Uk: Interpretation, Modelling and Appraisal of Mitigation Measures
E JANE GILBERT (1), Adrian Kelsey (2), Jon D Karnon (2), Jillian RM Swan (2) and Brian Crook (2)
(1) The Composting Association, Avon House, Tithe Barn Road, Wellingborough, NN8 1DH, UK (2) Health and Safety Laboratory, Broad Lane, Sheffield, S3 7HQ, UK, UK
The identification and quantification of airborne micro-organisms and their constituent parts (bioaerosols) formed at composting facilities has been well documented. Inhalation of large concentrations of bioaerosols has been shown to elicit allergic and immunotoxic respiratory diseases and occasionally respiratory infection. As these hazardous substances can be dispersed from facilities by wind currents, neighbouring populations may be affected adversely. In response, concentrations of culturable mesophilic bacteria and the fungus Aspergillus fumigatus were determined in duplicate at distances downwind from two open-air turned-windrow composting facilities in the UK using single stage Andersen samplers. Atmospheric conditions were monitored during the sampling period. Concentrations were plotted on a semi-logarithmic (log10) scale against distance from source. The data were used to estimate the source strength, the decimal reduction distance (D value) and the distance to reach background concentrations. Weather data were used to derive the atmospheric stability class. Concentrations decreased approximately exponentially with distance from the source, with background concentrations attained within 200 m of the source activities. The D values, however, did not provide any indication of the range of applicability of the results, or the mechanisms involved in the reduction. The data were thus used in dispersion models. As the source term could not be measured directly this was estimated from the best fit curve. Interpretation and range of applicability of these values was an issue; possible approaches to calculation of source terms will be discussed. Mitigation measures may be established surrounding sites to reduce the potential impact on neighbours. This paper will present an appraisal of possible site infrastructure measures coupled with a cost-benefit analysis.
A Systematic Analysis of Bioaerosols From Composting Facilities
Peter Kämpfer, Rita Schäefer, Andreas Albrecht
Institut für Angewandte Mikrobiologie, Justus-Liebig-Universitaet, Giessen, Germany
Microorganism and odor emissions from composting plants often lead to acceptance problems, especially for people living close to such plants. Both parameters were studied in a 3-year systematic approach under specific local climate conditions at nine different composting plants in Germany with the emphasis on microorganisms. Both emission- and immisio9n measurements are performed under "normal case" and "real worst case" conditions, ie. conditions which are typical for the specific locations (local climate conditions, working activities on the plants), and those for which a clear spread of bioaerosols from the composting facility into the surrounding enviironment can be documented. Airborne microorganisms are sampled using filitration and impingement and the subsequent cultivation on four differnet culture media (fungi on DG18 aty 25 C, "total plate counts" on CaSO-agar at 36 C, thermophilic fungi on malt-extract agar at 45 C, thermophilic actinomyucetes on glycol-arginine agar at 50 C) allows quantification and also partly qualification. In addition to the cultivation-based techniques, microorganisms (thermophilic actinomycetes) are detected by using 16S rRNA targeted oligonucleotide probes. The detailed sampling strategy and results will be presented. A generalized statement about the emission of microorganisms from compostign plants is not possible. The site specific meteorological situations must be considered carefully in any sampling and hence siting strategy. Especially drainage flow situations can lead to high microorganism concentrations (>104-105 CFU m-3 of thermophilic actinomycetes and thermophilic fungi in the surroundings of composting plants. Thermophilic fungi and actinomycetes can serve as indicator organism groups.
Aspergillus Fumigatus Control at Composting Plants Through the Use of Biofilters
SANCHEZ-MONEDERO, MIGUEL A., Stentiford, Ed I.
School of Civil Engineering. Leeds University. Leeds LS2 9JT. United Kingdom, UK
Bioaerosols are a key issue when a new composting site is being planned because of the potential risk to health. One possible way of limiting their impact is through the use of biofilters, which are normally used for odour control. This study evaluated the effectiveness of biofilter systems for reducing bioaerosol release. Aspergillus Fumigatus (AF) concentrations were measured in the air stream before and after passing through the biofilter systems at several commercial composting plants. The composting facilities were chosen because of their different operating conditions relating to the air supply for the composting pile, the wastes used for composting and the different biofilter designs. Results showed that, in most cases, biofiltration achieved an average reduction higher than 90% in the AF concentration when compared to the untreated air. In a typical case incoming values of 1.2x104 spores/m3 were reduced to 1.6x102 spores/m3 after passing through the biofilter. Biofilters appear to be a promising way for AF reduction, but further investigations are needed to study their effectiveness in removing of a wider range of airborne microorganisms.
Airborne fungi in compost plants: a neglected environmental and health hazard
Giovanna C VARESE (1), Valeria Prigione (1), Antonella Anastasi (1), Leonardo Casieri (1), Samuele Voyron (1) and Valeria Filipello Marchisio (1)
(1) Dept. of Palnt Biology, University of Turin, Italy
Composting is a microbiological process that generates airborne biological contaminants, particularly bacteria and fungi. The risk of forming unacceptably health-threatening atmospheric concentrations of these contaminants is very high in compost plants. This work describes the analysis of airborne fungi in three municipal compost plants in Piedmont (Italy). The samples were collected in critical steps of the composting process and outside the plant, upwind and downwind. A single stage volumetric sieve sampler was used. The collection media were: PDA and DRBC for the total load (CFUm-3) (incubation temperature 24 C), PDA plus cycloheximide for the selective isolation of Aspergillus fumigatus (incubation temperature 37 C), AFPA for the isolation of Aspergillus flavus, Aspergillus parasiticus and related species (incubation temperature 30 C). At each site 2,4 m-3 were aspirated. The complete quali and quantitative analysis of the airborne mycoflora has been studied only for one plant; in the other two plants the total load (CFUm-3) and the quali and quantitative airborne composition of Aspergilli (recognised as markers of environmental pollution) were evaluated. In most of the samplings the total load of airborne fungi was well above the range of the instrument (> 40.000 CFUm-3). In the upwind samples the load was many times less than the loads inside the plants (ratio in/out up to 97). The percentage of Aspergillus spp. ranged from 13% to 100%. A. fumigatus was sampled in most of the sites, often with high load. This alarming situation underlines the need of obligatory controls and of legislative standards for the bioaerosol fungal component.