[Composting facilities. 2. Aerogenic microorganism content at different working areas of composting facilities]

At two composting facilities (plants D and E), contamination of the air with total bacteria and mould fungi, and in addition with gram-negative bacteria (only at plant D) was analyzed at different indoor sites and outdoor in the vicinity. Statistical validity of the determination of contents of microorganisms in air samples was guaranteed by the collection and analysis of 30 parallel samples. At plant D, total bacteria concentrations in outdoor air ranged from 106 to 15,618 CFU/m3 air (median: 495 CFU/m3 air), gram-negative bacteria concentrations ranged up to 71 CFU/m3 air (median: below the detection limit of 35 CFU/m3 air), and mould fungi reached 7,138 CFU/m3 air (median: 141 CFU/m3 air). Highest concentrations of total bacteria above the upper detection limit (> 84,806 CFU/m3 air, sample volume: 28.3 l) and of mould fungi (38,940 CFU/m3 air) occurred at the place where three months old compost was mixed, highest concentrations of gram-negative bacteria (14,134 CFU/m3 air) were measured during mixing of fresh compost (younger than 8 days). Maximum and median values of the examined microorganisms ranged so high that special protective means for personnel working directly beneath the mixing process seem to be necessary under hygienic aspects. Raw and clean air at the composting filter at plant D showed highly significant differences concerning air concentration of gram-negative bacteria and mould fungi, indicating a good separation efficiency for these types of microorganisms. Maximum and median values of gram-negative bacteria and mould fungi concentrations (all < 1,000 CFU/m3 air) measured in clean air behind the composting filter lie in the range of normal outdoor air. Merely total bacteria show statistical significant differences to outdoor air with median values of clean air of 1,979 CFU/m3 air (edge of filter) resp. 3,110 CFU/m3 air (upside the filter) and with maximum values of above 30,000 CFU/m3 air in each case. In the outdoor air at plant E, total bacteria concentrations ranged from 362 to 7,633 CFU/m3 air (median: 1,312 CFU/m3 air), mould fungi ranged from 115 to 4,072 CFU/m3 air (median: 345 CFU/m3 air). Highest concentrations of total bacteria and mould fungi (all analyses above the upper detection limit of 21,201 CFU/m3 air; sample volume: 113,2 l) occurred during shredding of a mixture of kitchen and green wastes and of shrubs. During experimental shredding of separately collected panty diapers air concentrations of total bacteria ranged from about 19,000 CFU/m3 air to > 21,201 CFU/m3 air.(ABSTRACT TRUNCATED AT 400 WORDS)