A study of the potential release of bioaerosols from containers as a result of reduced frequency residual waste collections.

Microorganisms have the potential to grow within waste containers if waste is stored for longer periods as a result of an extended residual waste collection cycle. Release of microorganisms as bioaerosols during waste collection and processing may be an occupational risk to workers within the industry. There may be many constituents of the bioaerosol that may be of concern, however, there are currently only workplace exposure limits proposed for endotoxin (90EUm-3). A field-scale trial was established to determine the concentration of mesophilic bacteria, Gram-negative bacteria, Listeria monocytogenes, thermotolerant fungi, Aspergillus fumigatus, and endotoxin and (1→3)-ß-d-glucan in air within bins containing either bagged or loose residual waste, in warm (23°C) or cold (7°C) conditions, to simulate an extended collection cycle. Fresh waste was added during the first four weeks, with an additional 'missed collection' phase of a further four weeks where no more waste was added. A second trial examined the microbiological components of bioaerosols associated with 'tipping' the bins, simulating the moment when bins are emptied into waste collection vehicles. The majority of mesophilic bacteria, fungi and A. fumigatus concentrations were recorded when fresh material was added to the bins, with only mesophilic bacteria recorded up to week 6 during the 'missed collection' phase. (1→3)-ß-D-glucan concentrations were variable throughout the first trial, (geometric mean range 0.4-13.8ngm-3). Perhaps the bioaerosol component of most interest was endotoxin (geometric mean range 0.52-1288EUm-3). Elevated endotoxin concentrations were recorded during the 'missed collection' phase of the extended collection cycle and during 'tipping'. This data demonstrates significant concentrations of bioaerosols and particularly endotoxin can be generated during prolonged residual waste storage and collection. As endotoxin is a bioaerosol component of concern it can be concluded there is the potential for workplace exposure hence identifying key areas for risk assessment.

Abundance and Distribution of Enteric Bacteria and Viruses in Coastal and Estuarine Sediments-a Review.

The long term survival of fecal indicator organisms (FIOs) and human pathogenic microorganisms in sediments is important from a water quality, human health and ecological perspective. Typically, both bacteria and viruses strongly associate with particulate matter present in freshwater, estuarine and marine environments. This association tends to be stronger in finer textured sediments and is strongly influenced by the type and quantity of clay minerals and organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the environment by offering physical and chemical protection from biotic and abiotic stresses. How bacterial and viral viability and pathogenicity is influenced by surface attachment requires further study. Typically, long-term association with surfaces including sediments induces bacteria to enter a viable-but-non-culturable (VBNC) state. Inherent methodological challenges of quantifying VBNC bacteria may lead to the frequent under-reporting of their abundance in sediments. The implications of this in a quantitative risk assessment context remain unclear. Similarly, sediments can harbor significant amounts of enteric viruses, however, the factors regulating their persistence remains poorly understood. Quantification of viruses in sediment remains problematic due to our poor ability to recover intact viral particles from sediment surfaces (typically <10%), our inability to distinguish between infective and damaged (non-infective) viral particles, aggregation of viral particles, and inhibition during qPCR. This suggests that the true viral titre in sediments may be being vastly underestimated. In turn, this is limiting our ability to understand the fate and transport of viruses in sediments. Model systems (e.g., human cell culture) are also lacking for some key viruses, preventing our ability to evaluate the infectivity of viruses recovered from sediments (e.g., norovirus). The release of particle-bound bacteria and viruses into the water column during sediment resuspension also represents a risk to water quality. In conclusion, our poor process level understanding of viral/bacterial-sediment interactions combined with methodological challenges is limiting the accurate source apportionment and quantitative microbial risk assessment for pathogenic organisms associated with sediments in aquatic environments.

Changes in the physicochemical properties and enzymatic activity of waste during bioreduction of pig carcasses.

Bioreduction is a novel method for the on-farm storage of fallen stock in a vessel containing water that is heated and aerated, prior to disposal. The combination of a mesophilic temperature and high bacterial population leads to rapid degradation of carcasses due to microbial and enzymatic breakdown of protein material; and ultimately the reduction in volume of waste to be disposed. The system could, however, be improved if more was known about the changes that occur during a bioreduction cycle. Pig carcasses were placed within two commercial-scale bioreduction vessels (BVs) (6.5 m3 capacity) and the changes in physicochemical parameters, enzymatic activity, gas emissions and microbial communities were analysed over 56 days. Analyses showed that each vessel displayed different physicochemical parameters. The microbial communities within both vessels were also distinct, though they converged between days 28 and 42 before again diverging. Of the enzymes assayed, acetylesterases showed the highest activity during initial stages, with a subsequent increase in lipase towards the end. All other enzymes showed little activity in comparison. Despite active aeration of the vessels, conditions were redox-constrained, leading to the emission of gases associated with anaerobic conditions, namely NH3 and H2S. It was concluded that no single parameter governed the biochemical processes and that each BV will have its own unique microbial population and hence rate of decomposition. Further work is needed to increase the rate of bioreduction through bioaugmentation or developing enzyme additives.

Bioreduction of sheep carcasses effectively contains and reduces pathogen levels under operational and simulated breakdown conditions.

Options for the storage and disposal of animal carcasses are extremely limited in the EU after the introduction of the EU Animal By-products Regulations (ABPR; EC/1774/2002), leading to animosity within the livestock sector and the call for alternative methods to be validated. Novel storage technologies such as bioreduction may be approved under the ABPR provided that they can be shown to prevent pathogen proliferation. We studied the survival of Enterococcus faecalis, Salmonella spp., E. coli O157 and porcine parvovirus in bioreduction vessels containing sheep carcasses for approximately 4 months. The vessels were operated under two different scenarios: (A) where the water within was aerated and heated to 40 °C, and (B) with no aeration or heating, to simulate vessel failure. Microbial analysis verified that pathogens were contained within the bioreduction vessel and indeed reduced in numbers with time under both scenarios. This study shows that bioreduction can provide an effective and safe on-farm storage system for livestock carcasses prior to ultimate disposal. The findings support a review of the current regulatory framework so that bioreduction is considered for approval for industry use within the EU.

Fate of pathogens in a simulated bioreduction system for livestock carcasses.

The EU Animal By-Products Regulations generated the need for novel methods of storage and disposal of dead livestock. Bioreduction prior to rendering or incineration has been proposed as a practical and potentially cost-effective method; however, its biosecurity characteristics need to be elucidated. To address this, Salmonella enterica (serovars Senftenberg and Poona), Enterococcus faecalis, Campylobacter jejuni, Campylobacter coli and a lux-marked strain of Escherichia coli O157 were inoculated into laboratory-scale bioreduction vessels containing sheep carcass constituents. Numbers of all pathogens and the metabolic activity of E. coli O157 decreased significantly within the liquor waste over time, and only E. faecalis remained detectable after 3months. Only very low numbers of Salmonella spp. and E. faecalis were detected in bioaerosols, and only at initial stages of the trial. These results further indicate that bioreduction represents a suitable method of storing and reducing the volume of livestock carcasses prior to ultimate disposal.

The environmental and biosecurity characteristics of livestock carcass disposal methods: A review.

Livestock mortalities represent a major waste stream within agriculture. Many different methods are used throughout the world to dispose of these mortalities; however within the European Union (EU) disposal options are limited by stringent legislation. The legal disposal options currently available to EU farmers (primarily rendering and incineration) are frequently negatively perceived on both practical and economic grounds. In this review, we assess the potential environment impacts and biosecurity risks associated with each of the main options used for disposal of livestock mortalities in the world and critically evaluate the justification for current EU regulations. Overall, we conclude that while current legislation intends to minimise the potential for on-farm pollution and the spread of infectious diseases (e.g. transmissible spongiform encephalopathies, bacterial pathogens), alternative technologies (e.g. bioreduction, anaerobic digestion) may provide a more cost-effective, practical and biosecure mechanism for carcass disposal as well as having a lower environmental footprint. Further social, environmental and economic research is therefore warranted to assess the holistic benefits of alternative approaches for carcass disposal in Europe, with an aim to provide policy-makers with robust knowledge to make informed decisions on future legislation.