A review of biological sulfate conversions in wastewater treatment.

High frequency ultrasound pretreatment for sludge anaerobic digestion: effect on floc structure and microbial population.

Transmissible spongiform encephalopathies (TSEs) are fatal, infectious neurodegenerative diseases that affect humans and other mammals. The etiological agent in TSEs is the prion and is thought to be composed of aggregated, β-sheet-rich conformers of the prion protein (PrPTSE) derived from misfolding of a benign cellular form of the same protein. Prions are remarkably resistant to inactivation and can persist and remain infectious in the environment for years. Environmental routes of TSE transmission are implicated in chronic wasting disease (CWD) of deer, elk and moose and in scrapie of sheep and goats. Soil is thought to be an important reservoir of CWD and scrapie infectivity. The extent to which prions are inactivated by natural processes in soils is unclear, and methods for inactivating TSE agents in soil are currently lacking. This critical review discusses current knowledge on the degradation of PrPTSE and inactivation of prions by individual bacterial species, mixed microbial consortia, and isolated bacterial and archaeal enzymes, and highlights areas warranting further research. Research conducted to date indicates that few microorganisms are able to degrade PrPTSE. Fungi have not been evaluated for their ability to inactivate TSE agents. Of proteases reported to degrade PrPTSE, most are serine proteases and many require harsh conditions (e.g., elevated temperature, high pH, detergent) for optimal PrPTSE-degrading activity. Declines in the levels of PrPTSE are not always accompanied by equivalent decreases in TSE infectivity. Most biodegradation studies reported to date did not examine effects on TSE infectivity and must therefore be considered inconclusive with respect to the likely impact on prion disease transmission. Improved understanding of the factors affecting prion inactivation is required to discern natural routes of prion inactivation or implement effective practices outside of the laboratory.

Microbial and enzymatic inactivation of prions in soil environments

En esta investigacion se compararon las abundancias microbianas presentes en el lodo granular de dos reactores anaerobios de manto de lodo con flujo ascendente (UASB): el primero alimentado con aguas de produccion de petroleo liviano (31.1-39.0°API), provenientes de la region zuliana (Venezuela) (APP) y el segundo con glucosa. En tal sentido, se monitorearon las poblaciones de bacterias fermentadoras de glucosa (BFG), bacterias acetogenicas (BAC), metanogenos (MET), bacterias sulfato-reductoras (BSR), bacterias nitrato-reductoras (BNR) y heterotrofos, usando medios de cultivo selectivos. La densidad de los grupos microbianos estuvo correlacionada con los parametros fisicoquimicos: pH, alcalinidad total, DQO, SO4=, NO3-, asi como con los porcentajes de CH4, CO2 y de N2 en el biogas. Los resultados exhiben diferencias significativas entre la diversidad microbiana de ambos reactores, con una proporcion de BFG > BSR > MET > BAC > BNR para el reactor con glucosa y de MET > BNR > BAC > BSR > BFG para las APP. La abundancia de bacterias en el reactor con glucosa estuvo en el orden de 108, mientras que en el reactor con APP fue de 105, lo cual resulta de la composicion organica y mineral de los afluentes. Los resultados presentados en este estudio aportan evidencias sobre la dinamica poblacional en lodos de reactores anaerobios UASB, durante el tratamiento de aguas de produccion petrolera.

/pdf/diversidad-microbiologica-del-lodo-anaerobio-durante-el-ppv61158f5.pdf

Diversidad microbiológica del lodo anaerobio durante el tratamiento de aguas de producción petroleras venezolanas

A soil column filled with sandy soil was constructed to investigate changes of terminal electron acceptors (TEA) and TOC in redox zones of landfill leachate pollution plume, and their models were established, respectively. Results indicated that the time of peak-concentration appearance of different reducing products was related to the ability of terminal electron acceptors to compete for terminal electrons. The most competitive ones showed sharp concentration increased earlier. For example, the peak concentration of NO2(-) appeared earlier than that of Fe2+. The concentration of TOC increased in methanogenic zone, iron reduction zone, nitrate reduction zone and oxygen reduction zone, and its rate was 8.27, 8.56, 8.85, 9.06 and 9.11 mg/(L h), respectively. Degradation rate of contaminants by different microbes mainly depended on the amount and availability of terminal electron acceptors. The reaction rate was related to ability of terminal electron acceptors to compete for terminal electron, that is the stronger the ability of terminal electron acceptors to compete for terminal electrons, the easier could be used and consumed by microorganisms and the more sensitive to reflect on environmental pollution.

Terminal electron acceptor process in landfill leachate pollution plume

The need for clean water is increasing and anaerobic wastewater treatment can be used as a cost-effective solution for purification of organically polluted industrial waste streams. This thesis presents results from microbiological investigations of several full-scale and lab-scale anaerobic wastewater treatments systems. Anaerobic wastewater treatment has gained popularity and is now one of the key technologies in environmental biotechnology. However, knowledge of the microbial community structure – function relationships is limited. A combination of cultivation-dependent and cultivation-independent techniques can be used to improve this knowledge. In this thesis, batch serial dilution incubations from a methanol-fed lab-scale thermophilic (55°C) methanogenic bioreactor indicated that syntrophic interspecies hydrogen transfer-dependent methanol conversion is at least equally important as direct methanogenesis in this lab-scale reactor. A direct methanol-utilizing Methanomethylovorans hollandica-related strain was detected up to a 10 8 -fold dilution, while Thermodesulfovibrio relatives and Methanothermobacter thermoautotrophicus strains were found till 10 9 –fold dilutions in the presence of H 2 /CO 2 . Microbial diversity was further evaluated in two expanded granular sludge bed reactors fed with increasing oleic acid loading rates. The archaeal community in the reactor inoculated with granular sludge stayed quite stable and active, whereas the relative abundance of Methanosaeta-like organisms gradually decreased in the reactor inoculated with suspended sludge when oleate loads were increased to 8 kg of chemical oxygen demand m -3 day -1 . Desulfomicrobium and Methanobacterium were found to dominate the start-up of a full-scale synthesis gas fed gas-lift reactor treating metal and sulphate rich wastewater. Most Probable Number (MPN) counts confirmed that heterotrophic sulphate reducing bacteria (SRB) were dominant (10 11 -10 12 cells/g VSS) compared to homoacetogens (10 5 -10 6 cells/g VSS) and methanogens (10 8 -10 9 cells/g VSS). Methanogens can still persist in sulphate-reducing bioreactors with short sludge retention time, since competition for hydrogen is determined by Monod kinetics and not by hydrogen threshold values. The microbial community in a full-scale upflow anaerobic sludge blanket reactor treating paper mill wastewater operated at 37°C was relatively stable over a period of 3 years as indicated by a high similarity (>75%) of denaturing gradient gel electrophoresis profiles of 16S ribosomal RNA gene fragments. Batch incubations at different temperatures resulted in microbial community changes. While the archaeal community composition differed significantly between incubations at 45 and 55°C, the bacterial composition changed between 37 and 45°C. Overall the bacterial community was dominated by Firmicutes (68% of the clones) and Delta-Proteobacteria (17% of the clones). A sequential degradation of first butyrate and then propionate at 37°C was linked to strong presence of Syntrophomonas sp. and Desulfobulbus propionicus, respectively. MPN series allowed estimating the number of micro-organisms per ml sludge that could use propionate without sulphate (10 9 ), propionate and sulphate (10 5 ), butyrate without sulphate (10 8 ), butyrate with sulphate (10 5 ), glucose (10 9 ) and H 2 /CO 2 (10 10 ). Archaea were mainly dominated by Methanosaeta, but also Crenarchaeota-relatives were identified. Bacterial clone sequences were related to a variety of different known species, with expected functions in anaerobic digestion like fermentative bacteria, syntrophic short chain fatty acids oxidisers and SRB. However, about 80% of the clones was similar to sequences in the database without close cultured relatives, but many of these appeared to be present in anaerobic environments. It is important to improve knowledge of these unknown micro-organisms and fast accurate monitoring and identification could be instrumental in realising this. Therefore, a pilot macro-array was developed and tested. It appeared that combining probes generated by PCR amplification of the V1 and V6 variable regions of the 16S rRNA gene provided accurate differentiation of closely related organisms. The integrated application of molecular and cultivation dependent analyses of microbiota structure and function of a broad variety of anaerobic wastewater treatment systems described in this thesis has been used to improve insight of the ecophysiology in such reactors. Some general commonalities of anaerobic systems have been found, but also system-specific characteristics. This provides potential identification of general and system-specific indicator populations, allowing improved diagnostics and reactor predictability.

/pdf/microbial-community-analysis-in-sludge-of-anaerobic-4d1ym4zwxv.pdf

Microbial community analysis in sludge of anaerobic wastewater treatment systems : integrated culture-dependent and culture-independent approaches

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Microbial community analysis in sludge of anaerobic wastewater treatment systems : integrated culture-dependent and culture-independent approaches