This paper describes the thermal properties (effective thermal conductivity and thermal diffusivity) of an organic waste used to model the composting process in relation to volumetric water content at 20°C. The organic waste was a mixture of fresh dairy cattle feces and sawdust with a ratio of one-to-one on a dry weight basis. The thermal probe method was used to determine the effective thermal conductivity and diffusivity. The effective thermal conductivities were found to increase with volumetric water content, and ranged from 0.0500 to 0.202 W m−1 K−1 at volumetric water contents of 0% and 44.2%, respectively. The thermal diffusivity was not affected by the volumetric water content, and was found to have a mean value of 1.08 × 10−7 m2 s−1. 相似文献
Wastewater treatment sludge and power boiler fly ash were combined and composted in mixed and static windrows 50 m long, 4 m high and 6 m wide. Moisture content was maintained above 50%. The final compost had a pH of 8.5, contained high concentrations of specific nutrients, and an average C:N ratio of 43:1. All metal, PCB, chlorophenol and PAH concentrations were below levels stipulated by local regulations. Over the first 8 weeks of the composting period dioxin concentration decreased by 45% to 41 pg/g TEQ. Leachate tests indicated minimal (<0.1 mg/l Cu and Pb; <50 mg/l Na, P, and SO4−2) leaching of contaminants from the composted material. Application of compost (8 cubic yards/acre) at a sod farm improved soil characteristics as measured by a number of parameters. The dioxin concentration in the final soil/compost mixture was 3 pg/g TEQ, allowing the soil/compost mixture to be classified as agricultural soil. It was concluded that composting produced an acceptable soil conditioner attractive for large volume users of inexpensive soil material (sod farms, golf courses, land reclamation sites). 相似文献
Both autoclaving and dry-heat treatments were applied to dairy manure-based compost to achieve target populations of indigenous microorganisms. A 3 strain-mixture of Escherichia coli O157:H7 of ca. 2 log CFU/g was inoculated into acclimated autoclaved compost (AAC) and dry heat-treated compost (DHTC) with different moistures, and stored at 8, 22, or 30 °C. Only selected groups of microorganisms grew in AAC during acclimation, whereas the relative ratio of each group of microorganisms was maintained in DHTC after heat treatment. E. coli O157:H7 grew more in AAC than DHTC in the presence of same level of indigenous mesophiles. However, control compost (no heat treatment) did not support E. coli O157:H7 growth. Our results revealed that both the type and population of indigenous microorganisms is critical for suppressing E. coli O157:H7 growth in compost, and dry-heat treatment can result in a compost product which resembles cured compost with different levels of indigenous microorganisms. 相似文献
Despite the numerous compost stability and maturity tests, no universally accepted compost stability or maturity index exists. The fluorescein di-acetate (FDA) enzymatic assay, originating from soil studies, is examined here as a potential new compost stability test, and is compared to microbial respiration and phytotoxicity indices. Thirteen composts were used in the study from different source materials. Static microbial respiration activity indices calculated were the cumulative O2 consumptions, O2 consumption rates, total C-CO2 production, the respiratory quotient and the bio C/N ratio. Compost phytotoxicity was quantified via a 7-day tomato seed germination assay. Results showed that the net fluorescein release rates correlated with all stability indices. The germination index marginally correlated with the fluorescein release rates, but not with any of the other stability indices. New limits to classify composts regarding their stability were proposed. 相似文献
Multivariate analysis was used for interpreting data from a pot experiment using samples of three Spanish soils. Samples of soil fertilized with compost were compared with untreated control samples. We also compared the effect of adding the compost to soil with a controlled moisture content of 50% of its water holding capacity (WHC), and to a near-saturated soil (95% WHC). Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used; they perfectly differentiated sample groups both as a function of the treatment applied and by sampling date. The compost samples were characterized by higher pH, electrical conductivity (EC), organic matter (OM) content and cation exchange capacity (CEC), together with nutrient concentrations than the control pots. The pots with a soil–compost mixture at 95% WHC presented lower values of EC, CEC, inorganic N, K, Na and B than the mixtures at 50% WHC. Multivariate methods may therefore be useful for the analysis and interpretation of a large number of data in soil research. 相似文献
Since compost is widely used as soil amendment and the fact that during the processing of compost material high amounts of microorganisms are released into the air, we investigated whether compost may act as a carrier for thermophilic methanogens to temperate soils.
All eight investigated compost materials showed a clear methane production potential between 0.01 and 0.98 μmol CH4 g dw−1 h−1 at 50 °C. Single strand conformation polymorphism (SSCP) and cloning analysis indicated the presence of Methanosarcina thermophila, Methanoculleus thermophilus, and Methanobacterium formicicum.
Bioaerosols collected during the turning of a compost pile showed both a highly similar SSCP profile compared to the corresponding compost material and clear methane production during anoxic incubation in selective medium at 50 °C. Both observations indicated a considerable release of thermophilic methanogens into the air.
To analyse the persistence of compost-borne thermophilic methanogens in temperate oxic soils, we therefore studied their potential activity in compost and compost/soil mixtures, which was brought to a meadow soil, as well as in an agricultural soil fertilised with compost. After 24 h anoxic incubation at 50 °C, all samples containing compost showed a clear methanogenic activity, even 1 year after application.
In combination with the in vitro observed resilience of the compost-borne methanogens against desiccation and UV radiation we assume that compost material acts as an effective carrier for the distribution of thermophilic methanogens by fertilisation and wind. 相似文献
To date, composting has been regarded as an aerobic process but it has been shown that composting piles are often sources of atmospheric methane. In order to gain a more comprehensive view on the diversity of methanogenic Archaea in compost, gas chromatographical methods and molecular cloning were used to study relationships of thermophilic archaeal communities and changes in methane production potential during compost maturation. According to the thermophilic methane production potential, wide differences could be detected between differently aged compost materials. In material derived from 3- and 4-week-old piles, low and no thermophilic methane production potential, respectively, was observed at 50 degrees C. Material from a 6-week-old pile showed the maximum methane production. With compost maturation, the production slowly decreased again with 6 weeks, 8 weeks, and mature compost showing an optimum methane production potential at 60 degrees C. At 70 degrees C, only 6-week-old material showed a comparable high production of methane. The 16S rRNA-based phylogenetic surveys revealed an increase of archaeal diversity with compost maturation. In the 6-week-old material, 86% of the sequences in the archaeal 16S rRNA library had the highest sequence similarities to Methanothermobacter spp. and the remaining 14% of the clones were related to Methanosarcina thermophila. Quantification of methanogens in 6-week-old material, on the basis of the methane production rate, resulted in values of about 2x10(7) cells per gram fresh weight. In 8-week-old and mature compost material, the proportion of sequences similar to Methanothermobacter spp. decreased to 34% and 0%, respectively. The mature compost material showed the highest variation in identified sequences, although 33% could be assigned to as yet uncultured Archaea (e.g. Rice cluster I, III, and IV). Our results indicate that compost harbours a diverse community of thermophilic methanogens, with changing composition during the maturation process, presumably due to altered pile conditions. Likewise, compost may act as a potential carrier for thermophilic methanogens in temperate soils because it is widely used as a soil amendment. 相似文献
We isolated ammonia-assimilating microorganisms from the livestock manure treatment systems and evaluated their ammonia-assimilating
ability. Many isolates utilized ammonia at high rates when they were purely cultivated in a nitrogen-limited medium to which
sterilized lagoon extract had been added. Some isolates that were immobilized in polyvinyl alcohol (PVA) utilized ammonia
present in the media containing viable lagoon microorganisms. Staining with 4′,6′-diamidino-2-phenylindole (DAPI) indicated
that the immobilized high ammonia-assimilating isolates grew dominantly within the PVA beads. High ammonia-assimilating isolates
in the mixed culture containing viable lagoon microorganisms were identified as Pseudomonas spp. and member of Rhizobiaceae species by partial sequencing of the 16S ribosomal DNA. 相似文献