Rotary drum composting of vegetable waste and tree leaves

High rate composting studies on institutional waste, i.e. vegetable wastes, tree leaves, etc., were conducted on a demonstration-scale (3.5 m³) rotary drum composter by evaluating changes in some physico-chemical and biological parameters. During composting, higher temperature (60–70 °C) at inlet zone and (50–60 °C) at middle zone were achieved which resulted in high degradation in the drum. As a result, all parameters including TOC, C/N ratio, CO₂ evolution and coliforms were decreased significantly within few days of composting. Within a week period, quality compost with total nitrogen (2.6%) and final total phosphorus (6 g/kg) was achieved; but relatively higher final values of fecal coliforms and CO₂ evolution, suggested further maturation. Thus, two conventional composting methods namely windrow (M1) and vermicomposting (M2) tried for maturation of primary stabilized compost. By examining these methods, it was suggested that M2 was found suitable in delivering fine grained, better quality matured compost within 20 days of maturation period.     

Changes in physical,chemical and microbial parameters during the composting of municipal sewage sludge

Changes in physical, chemical and microbial parameters were investigated during the composting of municipal sewage sludge. Raw sewage sludge (30% dry matter) was mixed with compost from sewage sludge (85% dry matter) in 3:1 ratio (v/v). The mixture was divided into 4 windrows which were composted under the same conditions except the turning factor. The turning was every 7, 10, 15 days and according to the temperature which must be (55–65°C) for windrow 1 (W1), windrow 2 (W2), windrow 3 (W3) and windrow 4 (W4), respectively. Water was added to adjust the moisture content (40–60%). The composting process consisted of 2 periods; fermentation (12 weeks) and maturation (4 weeks). The results showed that the temperature reached the maximum after 12 weeks for W1 and 11 weeks for W2, W3 and W4 and then decreased. The final compost was nearly odourless and black, especially in case of W4. The general trend indicates a decrease in organic matter, organic carbon and nitrogen (N), whereas ash, potassium (K) and phosphorus (P) increased and consequently C/K and C/P ratios decreased. There was a slight increase in C/N ratio. The pH increased and then decreased to near neutrality at the end. The mesophilic bacteria increased during the fermentation period and decreased after that, whereas the thermophilic ones increased with increasing of temperature, decreased after 2 weeks and increased again during the fermentation period and then decreased. The mesophilic and thermophilic fungi were present during the first week and disappeared after that. The final compost was pathogens-free as indicated by the counts of coliforms and Salmonella.     

Analysis of the bacterial community inhabiting an aerobic thermophilic sequencing batch reactor (AT-SBR) treating swine waste

The microflora of a self-heating aerobic thermophilic sequencing batch reactor (AT-SBR) treating swine waste was investigated by a combination of culture and culture-independent techniques. The temperature increased quickly in the first hours of the treatment cycles and values up to 72°C were reached. Denaturing gradient gel electrophoresis of the PCR-amplified V3 region of 16S rDNA (PCR-DGGE) revealed important changes in the bacterial community during 3-day cycles. A clone library was constructed with the near-full-length 16S rDNA amplified from a mixed-liquor sample taken at 60°C. Among the 78 non-chimeric clones analysed, 20 species (here defined as clones showing more than 97% sequence homology) were found. In contrast to other culture-independent bacterial analyses of aerobic thermophilic wastewater treatments, species belonging to the Bacilli class were dominant (64%) with Bacillus thermocloacae being the most abundant species (38%). The other Bacilli could not be assigned to a known species. Schineria larvae was the second most abundant species (14%) in the clone library. Four species were also found among the 19 strains isolated, cultivated and identified from samples taken at 40°C and 60°C. Ten isolates showed high 16S rDNA sequence homology with the dominant bacterium of a composting process that had not been previously isolated.An erratum to this article can be found at     

Bacterial diversity in surface sediments from the Pacific Arctic Ocean

In order to assess bacterial diversity within four surface sediment samples (0–5 cm) collected from the Pacific Arctic Ocean, 16S ribosomal DNA clone library analysis was performed. Near full length 16S rDNA sequences were obtained for 463 clones from four libraries and 13 distinct major lineages of Bacteria were identified (α, β, γ, δ and ε-Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, Firmicutes, Planctomycetes, Spirochetes, and Verrucomicrobia). α, γ, and δ-Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria were common phylogenetic groups from all the sediments. The γ-Proteobacteria were the dominant bacterial lineage, representing near or over 50% of the clones. Over 35% of γ-Proteobacteria clones of four clone library were closely related to cultured bacterial isolates with similarity values ranging from 94 to 100%. The community composition was different among sampling sites, which potentially was related to geochemical differences.     

Bacterial community and decomposition rate in long term fed-batch composting using woodchip and Polyethylene terephthalate (PET) as bulking agents

Long term fed-batch composting experiments were conducted for 200 days using two types of bulking agents; woodchip and PET flake, with periodic compost withdrawal through a washing process. The bacterial communities of composting materials in the two different bulking agents were also investigated by 16S rRNA gene clone analysis. The decomposition rate in both composting reactors was 86.1% and 88.2% of the total organic load, respectively. The control experiment of dead-end operation without compost withdrawal by washing process could not be maintained for more than 102 days because of its low performance. The reactor with compost withdrawal, however, improved the decomposition rate in the composting process, and could be applied in the long run. There was a significant difference in the bacterial community between the FBC reactor with woodchip and another with PET flake as the bulking agent though the decomposition rates were similar. The reactor with woodchip as the bulking agent consisted of 95% Bacillales while the PET flake reactor contained 54% of total bacteria count. In addition, Lactobacillales was dominant at 38% in the PET flake reactor and the bacterial community in general significantly differed from the woodchip reactor. Furthermore, there was a difference in the species composition in the Bacillales and the bacterial community showed a significant difference at the species level between the two reactors. Although bacterial community differed, the decomposition rates between the two reactors were similar and PET flake showed greater viability than woodchip as a bulking agent due to its high abrasion resistance and non-biodegradability.     

Physical Covering for Control of Escherichia coli O157:H7 and Salmonella spp. in Static and Windrow Composting Processes

This study investigated the effect of a 30-cm covering of finished compost (FC) on survival of Escherichia coli O157:H7 and Salmonella spp. in active static and windrow composting systems. Feedstocks inoculated with E. coli O157:H7 (7.41 log CFU/g) and Salmonella (6.46 log CFU/g) were placed in biosentry tubes (7.5-cm diameter, 30-cm height) at three locations: (i and ii) two opposing sides at the interface between the FC cover layer (where present) and the feedstock material (each positioned approximately 10 cm below the pile''s surface) and (iii) an internal location (top) (approximately 30 cm below the surface). On specific sampling days, surviving populations of inoculated E. coli O157:H7 and Salmonella, generic E. coli, and coliforms in compost samples were determined. Salmonella spp. were reduced significantly within 24 h in windrow piles and were below the detection limit after 3 and 7 days at internal locations of windrow and static piles containing FC covering, respectively. Likewise, E. coli O157:H7 was undetectable after 1 day in windrow piles covered with finished compost. Use of FC as a covering layer significantly increased the number of days that temperatures in the windrows remained ≥55°C at all locations and in static piles at internal locations. These time-temperature exposures resulted in rapid reduction of inoculated pathogens, and the rate of bacterial reduction was rapid in windrow piles. The sample location significantly influenced the survival of these pathogens at internal locations compared to that at interface locations of piles. Finished compost covering of compost piles aids in the reduction of pathogens during the composting process.     

Resistance of Faecal Coliforms and Enterococci Populations in Sludge and Biosolids to Different Hygienisation Treatments

The composition of the most abundant facultative anaerobic bacteria populations [faecal coliforms (FC) and enterococci (ENT)] in sludge can be modified after different treatments. These involve the disposal or reuse of sludge and include: anaerobic digesters, incineration, composting, pasteurization and lime treatments. In this study, three treatment types (mesophilic anaerobic digestion, composting and pasteurization) were compared in terms of their ability to reduce both bacterial populations. The diversity and any changes in composition of main phenotypic groups for both populations were also analyzed. Mesophilic anaerobic digestion (MAD) was carried out at 35°C for 20 days. Digested sludge was then dehydrated by centrifugation at 2,500 rpm. Composting (COM) was performed at 55°C with windrow phases. Pasteurization was assayed at 60°C for 90 min (P60), at 80°C for 60 min (P80). A 1–1.5 log unit reduction was observed for FC, and 1 log unit reduction was noted for ENT by MAD treatment. In composting, this reduction proved higher for FC than for ENT (6 log and 3–4 log units, respectively). Optimal pasteurization was obtained at 80°C for 60 min, resulting in a 5 log unit reduction for FC and a 2 log unit reduction for ENT. High diversity indices (Di) for both bacterial populations were detected both before and after implementation of the different treatments. Analyses of the population’s similarity provided that FC were diverse both before and after COM, P60 and P80 treatments. However, no differences were observed on the composition of ENT populations after the different treatments assayed.     

Bacterial diversity of the digestive gland of Sydney rock oysters,Saccostrea glomerata infected with the paramyxean parasite,Marteilia sydneyi

Aims: To determine whether the infestation by the protozoan paramyxean parasite, Marteilia sydneyi, changes the bacterial community of the digestive gland of Sydney rock oysters, Saccostrea glomerata. Methods and Results: Six 16S rDNA clone libraries were established from three M. sydneyi‐infected and three un‐infected oysters. Restriction enzyme analysis followed by sequencing representative clones revealed a total of 23 different operational taxonomic units (OTUs) in un‐infected oysters, comprising the major phyla: Firmicutes, Proteobacteria, Cyanobacteria and Spirocheates, where the clone distribution was 44, 36, 7 and 5%, respectively. Close to half of the OTUs are not closely related to any other hitherto determined sequence. In contrast, S. glomerata infected by M. sydneyi had only one OTU present in the digestive gland. Phylogenetic analysis of the 16S rDNA sequence reveals that this dominant OTU, belonging to the α‐Proteobacteria, is closely related to a Rickettsiales‐like prokaryote (RLP). Conclusions: The microbiota of the digestive gland of Sydney rock oysters is changed by infection by M. sydneyi, becoming dominated by a RLP, and generally less diverse. The bacterial community of un‐infected S. glomerata differs from previous studies in that we identified the dominant taxa as Firmicutes and α‐Proteobacteria, rather than heterotrophic γ‐Proteobacteria. Significance and Impact of the Study: This is the first culture‐independent study of the microbiota of the digestive glands of edible oysters to the species level. The commercial viability of the Sydney rock oyster industry in Australia is currently threatened by Queensland Unknown disease and the changes in the bacterial community of S. glomerata corresponding with infection by M. sydneyi sheds further light on the link between parasite infection and mortality in this economically damaging disease.     

Entamoeba Clone‐Recognition Experiments: Morphometrics,Aggregative Behavior,and Cell‐Signaling Characterization

Studies on clone‐ and kin‐discrimination in protists have proliferated during the past decade. We report clone‐recognition experiments in seven Entamoeba lineages (E. invadens IP‐1, E. invadens VK‐1:NS, E. terrapinae, E. moshkovskii Laredo, E. moshkovskii Snake, E. histolytica HM‐1:IMSS and E. dispar). First, we characterized morphometrically each clone (length, width, and cell‐surface area) and documented how they differed statistically from one another (as per single‐variable or canonical‐discriminant analyses). Second, we demonstrated that amebas themselves could discriminate self (clone) from different (themselves vs. other clones). In mix‐cell‐line cultures between closely‐related (E. invadens IP‐1 vs. E. invadens VK‐1:NS) or distant‐phylogenetic clones (E. terrapinae vs. E. moshkovskii Laredo), amebas consistently aggregated with same‐clone members. Third, we identified six putative cell‐signals secreted by the amebas (RasGap/Ankyrin, coronin‐WD40, actin, protein kinases, heat shock 70, and ubiquitin) and which known functions in Entamoeba spp. included: cell proliferation, cell adhesion, cell movement, and stress‐induced encystation. To our knowledge, this is the first multi‐clone characterization of Entamoeba spp. morphometrics, aggregative behavior, and cell‐signaling secretion in the context of clone‐recognition. Protists allow us to study cell–cell recognition from ecological and evolutionary perspectives. Modern protistan lineages can be central to studies about the origins and evolution of multicellularity.     

Archaeal community compositions at different depths (up to 30 m) of a municipal solid waste landfill in Taiwan as revealed by 16S rDNA cloning analyses

Archaeal 16S rDNA clone libraries were constructed for samples taken at 10, 20 and 30 m depth in a landfill, which corresponded approximately 3, 6 and 9 years operation, respectively. Sequencing and phylogenetic analyses of representative clones showed that all of the rDNAs were closely related to typical methanogens. The distributions of phylotypes in clone libraries were similar to each other. Dominant clones in all the clone libraries were closely related to thermophilic species, such as Methanothermobacter thermautotrophicus, suggesting that the temperatures at these sites were high. This was supported by the results of H₂-dependent methanogenic activity tests, showing that the activities of all samples at 55 °C were much higher than those at 25 °C.