Hygienisatie van organisch afval tijdens biologische verwerkingsprocessen

Despite economic and population growth in the European Union is limited, amounts of waste are still increasing, causing unnecessary loss of materials and energy, environmental damage and negative effects on health and the quality of life. The long-term goal of the European Union is to prevent waste and to promote re-use, recycling and recovery among which biological treatment of waste (such as composting and anaerobic digestion) in order to reduce the negative environmental impact of waste. The end-product of the biological treatment of waste is used on land as crop fertilizer or for the production of potting media. Consequently, it is of great importance that pathogens and weed seeds are sufficiently reduced. Although there is an extensive literature on the survival of human and animal pathogens in farm animal and human sewage wastes, less information is available on the survival of these pathogens during green waste and vegetable, fruit and garden waste composting. Moreover, limited research has been done concerning the sanitation capacity of pre- and post-treatment processes of anaerobic digestion. Therefore, the objectives of this study were (i) recording the minimal requirements that are necessary for the inactivation of Salmonella Senftenberg W775 during green waste and vfg-waste composting and (ii) providing policy supporting advice concerning the biosafety of anaerobic digestion and the pre- and post-treatment processes. To determine the hygienic safety of composting processes, the indicator organism Salmonella enterica ssp. enterica serotype Senftenberg strain W775 was artificially inoculated on a meat carrier and monitored subsequently. Different types of composting processes, i.e. composting in enclosed facilities, in open-air and in-vessel composting, were investigated. The waste materials used in this work were either vegetable, fruit and garden wastes or green wastes. The impact of temperature, moisture content and the presence of an indigenous microflora on the eradication of W775 was determined. The temperature was found to be the most important parameter to eradicate W775 from compost. When the temperature of the compost heap was 60°C and the moisture content varied between 60 65%, W775 (108 cfu g-1) was below the detection limit within 10 hours of composting. The moisture content was, beside temperature, a second parameter that influenced the survival of W775. When the water content of the composting materials or meat carriers was reduced, a higher survival rate of W775 was observed (survival rate increased 0.5 log10 unit when there was a reduction of 5% in moisture content (from 65.8 to 60.6%)). In addition, other parameters (such as microbial antagonism, toxic compounds, etc.) had an influence on the survival of W775 as well. All types of tested composting processes were sufficient to eradicate W775 providing that they are well managed in terms of temperature and moisture content. To elucidate the influence of temperature, moisture content and microbial competition on the inactivation of Salmonella Senftenberg W775, several lab-scale experiments were set up, since parameters can be controlled in a better way in these circumstances. Pieces of meat inoculated with Salmonella Senftenberg W775 were exposed to different temperatures and moisture contents. To determine the influence of indigenous microflora on the survival of Salmonella Senftenberg W775, autoclaved as well as nonautoclaved W775-infested meat samples were used. Longer survival times were observed at lower temperatures and at lower moisture contents. However, the latter seemed to be temperature-dependent, as the effect of a low moisture content changed from being sensitive to protective at a temperature between 45 and 55°C. Besides temperature and moisture content, other parameters, like microbial competition, seemed to influence the survival of Salmonella Senftenberg W775 in samples containing meat. The time-temperature relationship of different pathogens and seeds was investigated during mesophilic anaerobic digestion in lab experiments. The percentage of viable tomato seeds was below 2% (guide value according to the Ordinance on Biowastes, BioAbfV, 1998) after 2 weeks of mesophilic digestion at 36°C, while for Salmonella Senftenberg W775 a 5 log10 reduction could be reached after 7 days in the same circumstances. On the contrary, the most heat sensitive pathogen that was tested during mesophilic digestion at 36°C, i.e. Ralstonia solanacearum, was completely eliminated within 5 hours. Moreover, the hygienisation capacity of different post-treatment processes was determined at lab- as well as full-scale. A pasteurization step of 1 hour at 70°C seemed to be very efficient in the inactivation of pathogens and seeds. Both, Salmonella Senftenberg W775 and tomato seeds were already completely inactivated within 5 minutes at a temperature of 70°C. In addition, the biothermal drying process seemed to be an efficient way to inactivate Salmonella Senftenberg W775 and tomato seeds. The conveyer drying process on the contrary, was - despite the high air temperatures - not efficient in the elimination of Salmonella Senftenberg W775 or tomato seeds, as no influence could be observed in a full-scale experiment. Furthermore, it was demonstrated that the required reductions of Salmonella Senftenberg W775, Enterococcus faecalis and bovine parvovirus can be reached within the minimal guaranteed retention time during thermophilic digestion, indicating the possible use of thermophilic anaerobic digestion as an alternative process for the mandatory pasteurization step in recycling category 3 material and manure. Moreover, the minimal guaranteed retention time can be easily determined with the aid of a chemical tracer and it seemed that the tracer bromide was the most appropriate in this kind of research. The results of these experiments can only be extrapolated to other installations if they operate at least within the same temperature regime, nevertheless when bovine parvovirus is concerned extra attentiveness is recommended. On the other hand, the minimal guaranteed retention time has to be determined for each digestion installation individually. The tool BioSafety@Digestion was developed which can be used to check whether pathogens and weed seeds are eliminated in a sufficient way. For this purpose, certain conditions have to be fulfilled. On the one hand, based on the operation temperature and the minimal retention time of a certain process, it can be verified if certain pathogens and weed seeds will be inactivated. On the other hand, when a waste stream contains certain pathogens, one can determine with the aid of this tool which rise in temperature and/or prolongation of the retention time is necessary to obtain a safe end-product. In conclusion, this thesis demonstrated the hygienisation capacity of composting processes providing that they are well managed in terms of temperature and moisture content. Especially at low temperatures, the impact of moisture content and indigenous microflora enlarges. Also anaerobic digestion and post-treatment processes provide a sufficient pathogen reduction when the hydraulic retention time is long enough. Nevertheless, attention must be paid to dry heating processes because low water activity increases the heat resistance of micro-organisms.status: publishe

Effect of Arbuscular Mycorrhizal Fungi on Pratylenchus penetrans Infestation in Apple Seedlings under Greenhouse Conditions

A major problem in fruit cultivation in Flanders is replant disease due to a lack of uncultivated soils available for new plantings. Replant disease can cause poor growth and affect time to full production, however Arbuscular Mycorrhizal Fungi (AMF) can prove their usefulness with regard to these problems. To further investigate the effect of AMF on nematodes, different AMF species were amended to potted apple seedlings in the presence of the nematode Pratylenchus penetrans. Generally, apple seedlings grew better in the presence of nematodes when mycorrhiza were inoculated into the soil. Moreover, a positive correlation (R2 ≥ 0.88) was found between the percentage root length colonization of the roots of apple seedlings, by AMF species, and nematode reduction in the soil of the seedlings. Indigenous AMF could colonize the roots of apple seedlings the most efficiently, resulting in a higher biocontrol effect. Besides, a synergistic effect was observed when two AMF strains were applied together leading to a significant growth response of the seedlings

A rapid monitoring assay for the detection of Salmonella spp. and Salmonella Senftenberg strain W775 in composts

Aims: The composting process needs to be validated for its hygienic status in order to ensure that it is free of pathogens. Generally, this is evaluated through temperature monitoring, or additionally through active inoculation and monitoring of indicator organisms. We aimed to develop a monitoring method for the heat-resistant indicator organism Salmonella enterica ssp. enterica serovar Senftenberg strain W775 for detection in composting biowastes. Methods and Results: The method development is comprised of: (i) optimization of molecular detection of bacteria belonging to the genus Salmonella; (ii) identification of a DNA marker for Salmonella strain W775; and (iii) development of a multiplex polymerase chain reaction (PCR)-based on both DNA markers. Subsequently, Salmonella strain W775 was inoculated and monitored during composting of biowastes in an industrial composting facility. Conclusions: A highly sensitive and specific detection of viable cells was obtained by enriching the compost sample prior to multiplex PCR analysis. Complete inactivation of Salmonella strain W775 was obtained within 4 days in an industrial composting facility at temperatures ranging between 41 and 57C. Significance and Impact of the Study: We describe a monitoring method for the simultaneous detection of naturally occurring Salmonella strains and artificially introduced Salmonella strain W775 in composting biowastes that can be applied in routine analysisstatus: publishe

Decrease in diversity and changes in community composition of arbuscular mycorrhizal fungi in roots of apple trees with increasing orchard management intensity across a regional scale

Understanding which factors drive the diversity and community composition of arbuscular mycorrhizal fungi (AMF) is important due to the role of these soil micro-organisms in ecosystem functioning and current environmental threats to AMF biodiversity. Additionally, in agro-ecosystems, this knowledge may help to evaluate their use in making agriculture more sustainable. Here, we used 454-pyrosequencing of small subunit rRNA gene amplicons to quantify AMF diversity and community composition in the roots of cultivated apple trees across 24 orchards in central Belgium. We aimed at identifying the factors (soil chemical variables, organic vs. conventional farming, and geographical location) that affect AMF diversity and community composition. In total, 110 AMF OTUs were detected, of which the majority belonged to the Glomeraceae (73%) and the Claroideoglomeraceae (19%). We show that soil characteristics and farming system, rather than the geographical location of the orchards, shape AMF communities on apple trees. Particularly, plant-available P content of the soil was associated with lower AMF diversity. In orchards with a lower plant-available P content of the soil (P < 100 mg/kg soil), we also found a significantly higher AMF diversity in organically managed orchards as compared to conventionally managed orchards. Finally, the degree of nestedness of the AMF communities was related to plant-available P and N content of the soil, pointing at a progressive loss of AMF taxa with increasing fertilization. Overall, we conclude that a combination of organic orchard management and moderate fertilization may preserve diverse AMF communities on apple trees and that AMF in the roots of apple trees appear not to be dispersal limited at the scale of central Belgium.status: publishe

Inactivation of Salmonella Senftenberg strain W 775 during composting of biowastes and garden wastes

Aims:  Determination of the minimum requirements (time–temperature relationship and moisture content) that are needed for a sufficient eradication of an indicator organism. Methods and Results:  To determine the hygienic safety of composting processes, the indicator organism Salmonella enterica ssp. enterica serotype Senftenberg strain W 775 (further abbreviated as W 775) was artificially inoculated on a meat carrier and monitored subsequently. Different types of composting processes, e.g. composting in enclosed facilities, in open-air and in-vessel composting, were investigated. The waste feedstocks used in this work were either biowastes (i.e. vegetable, fruit and garden wastes; also called source-separated household wastes) or pure garden wastes. Beside these large-scale trials, we also conducted some lab experiments in order to determine the impact of temperature, moisture content and the presence of an indigenous microflora on the eradication of W 775. We found the temperature to be the most important parameter to eradicate W 775 from compost. When the temperature of the compost heap is 60°C and the moisture content varies between 60–65%, W 775 (108 CFU g−1) will be inactivated within 10 h of composting. The moisture content is, beside temperature, a second parameter that influences the survival of W 775. When the water content of the composting materials or meat carriers is reduced, a higher survival rate of W 775 was observed (survival rate increases 0·5 log10 unit when there is a reduction of 5% in moisture content). In addition, other parameters (such as microbial antagonism, toxic compounds, etc.) have an influence on the survival of W 775 as well. Conclusions:  Our study demonstrates that all types of composting processes tested in this work were sufficient to eradicate W 775 providing that they are well managed in terms of temperature and moisture content. Significance and Impact of the Study:  To give a better view on the parameters of importance for the eradication of W 775 during composting.auteursgegevens; zie erratum https://lirias.kuleuven.be/handle/123456789/142799status: publishe

Venturia inaequalis trapped: molecular quantification of airborne inoculum using volumetric and rotating arm samplers

status: Published onlin