Unraveling the active microbial populations involved in nitrogen utilization in a vertical subsurface flow constructed wetland treating urban wastewater

The dynamics of the active microbial populations involved in nitrogen transformation in a vertical subsurface flow constructed wetland (VF) treating urban wastewater was assessed. The wetland (1.5 m2) operated under average loads of 130 g COD m- 2 d- 1 and 17 g TN m- 2 d- 1 in Period I, and 80 g COD m- 2 d- 1 and 19 g TN m- 2 d- 1 in Period II. The hydraulic loading rate (HLR) was 375 mm d- 1 and C/N ratio was 2 in both periods. Samples for microbial characterization were collected from the filter medium (top and bottom layers) of the wetland, water influent and effluent at the end of Periods I (Jun–Oct) and II (Nov–Jan). The combination of qPCR and high-throughput sequencing (NGS, MiSeq) assessment at DNA and RNA level of 16S rRNA genes and nitrogen-based functional genes (amoA and nosZ-clade I) revealed that nitrification was associated both with ammonia-oxidizing bacteria (AOB) (Nitrosospira) and ammonia-oxidizing archaea (AOA) (Nitrososphaeraceae), and nitrite-oxidizing bacteria (NOB) such as Nitrobacter. Considering the active abundance (based in amoA transcripts), the AOA population revealed to be more stable than AOB in both periods and depths of the wetland, being less affected by the organic loading rate (OLR). Although denitrifying bacteria (nosZ copies and transcripts) were actively detected in all depths, the denitrification process was low (removal of 2 g TN m- 2 d- 1 for both periods) concomitant with NOx-N accumulation in the effluent. Overall, AOA, AOB and denitrifying bacteria (nosZ) were observed to be more active in bottom than in top layer at lower OLR (Period II). A proper design of OLR and HLR seems to be crucial to control the activity of microbial biofilms in VF wetlands on the basis of oxygen, organic-carbon and NOx-N forms, to improve their capacity for total nitrogen removal.Peer ReviewedPostprint (author's final draft

Characterization of microbial community dynamics during the anaerobic co-digestion of thermally pre-treated slaughterhouse wastes with glycerin addition

Microbial community dynamics during the anaerobic co-digestion of pig manure, pasteurized slaughterhouse waste and glycerin were studied in a lab-scale CSTR. The feed composition was optimized through progressive co-substrate additions for enhanced methane production and organic matter removal without accumulation of intermediate compoundsPostprint (author's final draft

Microbial community dynamics in two-chambered microbial fuel cells : effect of different ion exchange membranes

BACKGROUND: The utilization of different kinds of ion exchange membrane is a common practice in bioelectrochemical systems such as two-chambered microbial fuel cells (MFCs). However, little is known about the effect of membrane materials on the anodic microbial community diversity.; RESULTS: The effect of two cationic and one anionic exchange membranes (Nafion N-117, Ultrex CMI-7000, and Ultrex AMI-7000) on the microbial community dynamics of Eubacteria and Archaea has been assessed in two-chambered MFCs. The experimental results indicated that the eubacterial community in the anodic chamber was not affected by the membrane materials, being predominantly populations of Bacteroidetes (Porphyromonadaceae) and -proteobacteria (Alcaligenaceae and Comamonadaceae). On the other hand, the archaeal counterpart appears to be highly dependent on the type of membrane used, as was evidenced by the selective enrichment of Methanosarcina sp. in the MFC equipped with the membrane Nafion N-117 which was the MFC that showed the highest current production.; CONCLUSIONS: The results obtained in the present study suggest that membrane materials affect archaeal diversity whereas both anodofilic eubacteria and methanogenic archaea populations could play an important role in the overall MFC process performance.Peer ReviewedPostprint (author’s final draft

Effects of partially saturated conditions on the metabolically active microbiome and on nitrogen removal in vertical subsurface flow constructed wetlands

Nitrogen dynamics and its association to metabolically active microbial populations were assessed in two vertical subsurface vertical flow (VF) wetlands treating urban wastewater. These VF wetlands were operated in parallel with unsaturated (UVF) and partially saturated (SVF) configurations. The SVF wetland exhibited almost 2-fold higher total nitrogen removal rate (5 g TN m−2 d−1) in relation to the UVF wetland (3 g TN m−2 d−1), as well as a low NOx-N accumulation (1 mg L−1 vs. 26 mg L−1 in SVF and UVF wetland effluents, respectively). After 6 months of operation, ammonia oxidizing prokaryotes (AOP) and nitrite oxidizing bacteria (NOB) displayed an important role in both wetlands. Oxygen availability and ammonia limiting conditions promoted shifts on the metabolically active nitrifying community within ‘nitrification aggregates’ of wetland biofilms. Ammonia oxidizing archaea (AOA) and Nitrospira spp. overcame ammonia oxidizing bacteria (AOB) in the oxic layers of both wetlands. Microbial quantitative and diversity assessments revealed a positive correlation between Nitrobacter and AOA, whereas Nitrospira resulted negatively correlated with Nitrobacter and AOB populations. The denitrifying gene expression was enhanced mainly in the bottom layer of the SVF wetland, in concomitance with the depletion of NOx-N from wastewater. Functional gene expression of nitrifying and denitrifying populations combined with the active microbiome diversity brought new insights on the microbial nitrogen-cycling occurring within VF wetland biofilms under different operational conditions.Postprint (published version

Effects of partially saturated conditions on the metabolically active microbiome and on nitrogen removal in vertical subsurface flow constructed wetlands

Nitrogen dynamics and its association to metabolically active microbial populations were assessed in two vertical subsurface vertical flow (VF) wetlands treating urban wastewater. These VF wetlands were operated in parallel with unsaturated (UVF) and partially saturated (SVF) configurations. The SVF wetland exhibited almost 2-fold higher total nitrogen removal rate (5 g TN m−2 d−1) in relation to the UVF wetland (3 g TN m−2 d−1), as well as a low NOx-N accumulation (1 mg L−1 vs. 26 mg L−1 in SVF and UVF wetland effluents, respectively). After 6 months of operation, ammonia oxidizing prokaryotes (AOP) and nitrite oxidizing bacteria (NOB) displayed an important role in both wetlands. Oxygen availability and ammonia limiting conditions promoted shifts on the metabolically active nitrifying community within ‘nitrification aggregates’ of wetland biofilms. Ammonia oxidizing archaea (AOA) and Nitrospira spp. overcame ammonia oxidizing bacteria (AOB) in the oxic layers of both wetlands. Microbial quantitative and diversity assessments revealed a positive correlation between Nitrobacter and AOA, whereas Nitrospira resulted negatively correlated with Nitrobacter and AOB populations. The denitrifying gene expression was enhanced mainly in the bottom layer of the SVF wetland, in concomitance with the depletion of NOx-N from wastewater. Functional gene expression of nitrifying and denitrifying populations combined with the active microbiome diversity brought new insights on the microbial nitrogen-cycling occurring within VF wetland biofilms under different operational conditions

Mental health grant 2001/2002

Review date: 31 March 2002, also known as Health Service Circular HSC 2001/004Available from British Library Document Supply Centre-DSC:5290.0065(2001/5) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Characterization of microbial community dynamics during the anaerobic co-digestion of thermally pre-treated slaughterhouse wastes with glycerin addition

Microbial community dynamics during the anaerobic co-digestion of pig manure, pasteurized slaughterhouse waste and glycerin were studied in a lab-scale CSTR. The feed composition was optimized through progressive co-substrate additions for enhanced methane production and organic matter removal without accumulation of intermediate compound

The influence of non-linear material behaviour on strong vibration effects due to explosion loading

Includes bibliographical referencesAvailable from British Library Document Supply Centre- DSC:7761. 864(118) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Occurrence of perchlorate in groundwater samples from Catalonia

The perchlorate ion competitively blocks iodine from entering the thyroid gland, which may lead to a decrease in production of thyroid hormones (T3 and T4) that are essential for neurodevelopment (Wolff, J., 1998). The United States Environmental Protection Agency (EPA) established in 2005 a reference dose for perchlorate of 0.7 µ g (kg body weight) -1 dayPostprint (published version

Effects of enhanced denitrification on hydrodynamics and microbial community structure in a soil column system

Enhanced heterotrophic denitrification by adding glucose was investigated by means of a soil column experiment which simulated the groundwater flow. The carbon-to-nitrogen ratio was the main factor determining denitrification potential under experimental conditions. The influence of stimulated denitrification on the autochthonous microbial community was investigated by quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). The qPCR detection of the nosZ genes encoding nitrous oxide reductase, and the comparison of the abundances of 16S rRNA genes revealed that the addition of glucose enhanced denitrification leading to an increase in both the total eubacteria and, in particular, in the ratio of denitrifying bacteria, which represented the 21% of the total native eubacteria on the basis of nosZ/16S rRNA gene ratio. Microbial community profiling by DGGE indicated that ribotypes closely related to the genera Acidovorax and Hydrogenophaga (Comamonadaceae family) became enriched in the soil column. The effects of biomass occurrence in the column system on soil hydrodynamics, assessed by tracer studies, revealed a reduction of porosity and a significant increase of dispersivity that could be caused by the appearance of new functional microbial biomass in the aquifer material under enhanced denitrifying conditions. The importance of investigating the microbial growth in relation to the hydrodynamic effects, during enhanced denitrification, has been revealed in the column system experiments associated with the bioremediation. Combining microbial characterisation and hydrodynamic data in a soil column system permits us to gain an insight to the limiting factors of different stimulation strategies that can be applied in the field.Peer Reviewe