No abstract

An assessment of the fugitive release of bioaerosols from static compost piles was conducted at a green waste composting facility in South East England; this representing the initial stage of a programme of research into the influence of process parameters on bioaerosol emission flux. Wind tunnel experiments conducted on the surface of static windrows generated specific bioaerosol emission rates (SBER2s) at ground level of between 13 and 22 x 10(3) cfu/m2/s for mesophilic actinomycetes and between 8 and 11 x 10(3)cfu/m2/s for Aspergillus fumigatus. Air dispersion modelling of these emissions using the SCREEN3 air dispersion model in area source term mode was used to generate source depletion curves downwind of the facility for comparative purposes.

We present source term data from both passive and active sources, and compare emissions from compost aged at 1, 2, 4, 6, 8, 12 and 16 weeks. The results reveal that the age of compost has little effect on the concentrations emitted. The bioaerosol emissions from passive sources were in the range of 10 3-10 4 cfu/m 3 , with releases from active sources usually 1-log higher. We propose further improvements to current risk assessment methodologies by examining the differences between two air dispersion models for the prediction of downwind bioaerosol concentrations of off-site points of exposure. Our results show that SCREEN3 provides a conservative estimate of the source depletion curves of bioaerosol emissions in comparison to ADMS 3.3. However, the results from both models

Actinomycetes are the dominant bacteria isolated from bioaerosols sampled at composting facilities. Here, a novel method for the isolation of actinomycetes is reported, overcoming masking of conventional agar plates, as well as reducing analysis time and costs. Repeatable and reliable actinomycetes growth was best achieved using a soil compost media at an incubation temperature of 44ºC and 7 days' incubation. The results are of particular value to waste management operators and their advisors undertaking regulatory risk assessments that support environmental approvals for compost facilities.

A study was conducted in the Beirut, Lebanon, Water Treatment Plant to determine the dose of chlorine lethal to algae which were causing operational difficulties in the Plant. In laboratory experiments, it was found that a single dose of 1.8 mg/1 of chlorine was sufficient to kill all the algal taxa growing in the plant. If the chlorine dose was regenerated to the original concentration every 24 hours, then a dose of 1.2 mg/1 was sufficient. In field studies, continuous dosing of chlorine to maintain a residual chlorine level of 0.8 mg/1 was found lethal to the algal taxa. Prechlorination is therefore recommended as an effective method for the control of algal growth in conventional water treatment plants.