•BMP assays were performed to assess the effect of US application on the TPAD of WAS.•Sonication at the beginning and the end of the thermophilic stage was tested.•Different behaviours were observed ...between the thermophilic and mesophilic stages.•Similar CH4 yields were achieved by the TPAD systems in which US was applied.•This new treatment, combining TPAD and US, improves the anaerobic digestion of WAS.
Biochemical methane potential assays were performed to assess the influence of ultrasonic pretreatment on the temperature-phased anaerobic digestion (TPAD) of waste-activated sludge (WAS). Ultrasound (specific energy=3380kJkg−1 TS) was applied to the WAS before the thermophilic stage or to the effluent after the thermophilic stage. In addition, a control system without pretreatment was also carried out. No significant differences were found in the overall performance of the TPAD process, but different behaviours were observed between the thermophilic and mesophilic stages. Total methane production was enhanced by more than 50% and the volatile solid removal increased by 13% in comparison to the TPAD control process. Finally, a previously defined kinetic model was applied successfully to the experimental data and showed an excellent fit.
The effect of ammonia on methanogenic biomass from a full-scale agricultural digester treating nitrogen-rich materials was characterized in batch activity assays subjected to increasing ...concentrations of total ammonia N. Acetotrophic and methanogenic profiles displayed prolonged lag phases and reduced specific activity rates at 6.0 gN-TAN L−1, though identical methane yields were ultimately reached. These results agreed with the expression levels of selected genes from bacteria and methanogenic archaea (qPCR of 16S rRNA and mrcA cDNA transcripts). Compound-specific isotope analysis of biogas indicated that ammonia exposure was associated to a transition in methanogenic activity from acetotrophy at 1.0 gN-TAN L−1 to intermediate and complete hydrogenotrophy at 3.5 and 6.0 gN-TAN L−1. Such pattern matched the results of 16S-Illumina sequencing of genes and transcripts in that predominant methanogens shifted, along with increasing ammonia, from the obligate acetotroph Methanosaeta to the hydrogenotrophic Methanoculleus and the poorly understood methylotrophic Methanomassiliicoccus. The underlying bacterial community structure remained rather stable but, at 6.0 gN-TAN L−1, the expression level increased considerably for a number of ribotypes that are related to potentially syntrophic genera (e.g. Clostridium, Bellilinea, Longilinea, and Bacteroides). The predominance of hydrogenotrophy at high ammonia levels clearly points to the occurrence of the syntrophic acetate oxidation (SAO), but known SAO bacteria were only found in very low numbers. The potential role of the identified bacterial and archaeal taxa with a view on SAO and on stability of the anaerobic digestion process under ammonia stress has been discussed.
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•N-adaptation of biomass in a full-scale digester ensued robust reactor performance.•NH3 quickly shifted metabolism from acetotrophic to hydrogenotrophic methanogenesis.•Gene expression in several syntrophic bacteria was stimulated under high NH3 exposure.•A novel archaeal Methanoculleus/Methanomassiliicoccus syntrophism is proposed.•The functional biodiversity of the SAO process still remains rather unexplored.
The increase in energy and fertilizer consumption makes it necessary to develop sustainable alternatives for agriculture. Anaerobic digestion and digestates appeared to be suitable options. However, ...untreated digestates still have high water content and can increase greenhouse gas emissions during storage and land application. In this study, manure-derived digestate and solid fraction of digestate after separation were treated with a novel solar drying technology to reduce their water content, combined with acidification to reduce the gaseous emissions. The acidified digestate and acidified solid fraction of digestate recovered more nitrogen and ammonia nitrogen than their respective non-acidified products (1.5–1.3 times for TN; 14 times for TAN). Ammonia and methane emissions were reduced up to 94% and 72% respectively, compared to the non-acidified ones, while N2O increased more than 3 times. Dried digestate and dried acidified digestate can be labeled as NPK organic fertilizer regarding the European regulation, and the dried solid fraction and the improved dried acidified solid fraction can be labeled as N or P organic fertilizer. Moreover, plant tests showed that N concentrations in fresh lettuce leaves were within the EU limit with all products in all the cases. However, zinc concentration appeared to be a limitation in some of the products as their concentration exceeded the European legal limits.
•A solar drying greenhouse was used to produce organic fertilizers from digestate.•Acidification reduced up to 94% and 72% emissions for NH3 and CH4 respectively.•The resulting products were compared with the current fertilizer EU legislation.•Phytotoxicity of the resulting organic fertilizers was tested with lettuce pot trials.
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•Including catch crops in maize rotation reduces nutrient leaching.•Catch crops showed a higher nutrient uptake (N and P) than spontaneous herbage.•Ensiling increases methane ...production potential for all catch crops assayed.•Catch crops as co-substrates improved the anaerobic digestion of manure.
Three catch crop species, ryegrass, forage rape and black oat, were grown between successive rotations of maize to reduce nitrogen leaching due to maize fertilization with digested dairy manure. Catch crops showed a high nutrient uptake, but with a wide range, depending on the year and the specie. Ensiling was shown to be a feasible storing method increasing catch crop methane production per hectare between 14–36% compared with fresh catch crop. In semi-continuous co-digestion experiments, methane production was increased between 35–48%, in comparison with anaerobic digestion of dairy manure alone. Catch crops were shown to be a good co-substrate, being a sustainable option to prevent leaching of nutrients to the environment, thus closing the loops from production to utilization by optimal recycling measures.
The thermophilic anaerobic digestion (TAD) of sewage sludge has often been found to be less stable than mesophilic treatment. In comparison to mesophilic digesters, thermophilic reactors treating ...sludge are generally characterized by relatively high concentrations of volatile fatty acids (VFA) in the effluent along with poor effluent quality, indicating a lower level of process stability. However, reviewing the literature related to the procedure for obtaining a thermophilic inoculum, it seems that most of the problems associated with the instability and the accumulation of organic intermediates are the result of the manner in which the thermophilic sludge has been obtained. In this paper, the different options available for obtaining an anaerobic digester operating at thermophilic temperature (55°C) have been reviewed. In this light, rapid heating to the target temperature followed by the development of thermophilic microorganisms, which can be determined by VFA dropping to ≤500 mg acetic acid L−1 before increasing the organic loading rate (OLR), has been determined the most suitable means of establishing TAD.
The main objective of this research was to propose two methods to quantify faecal coliforms and
Salmonella spp. in both raw sludge and mesophilic digested sludge. Besides, a performance of a ...mesophilic digester operating at 30 and 20 days of solid retention time (SRT) was studied. The microbiological methods were carried out according to the Standard Methods (APHA, 1998) and to the American Environmental Protection Agency (US EPA, 1992) and new stages were suggested to determine pathogen concentrations in raw sludge as well as digested biosolids. The results showed that the anaerobic mesophilic digestion is able to remove high percentages of faecal coliforms and
Salmonella spp. giving rise to digested sludge that can be classified as Class B biosolid, i.e. an effluent with faecal coliforms density less than 2 × 10
6 colonies g
−1 total solids. Viable helminth eggs are not necessarily reduced in Class B biosolids.
To investigate gene and protein expression profiles of neural receptors found in the mouse meibomian gland. RNA and protein levels were determined for neuropeptide Y (NPY) receptor, vasoactive ...intestinal peptide (VIP) receptor, substance P (SP) receptor, and muscarinic cholinergic receptor (mAChR) subtypes M1-M5 in the mouse meibomian gland.
Frozen sections of Balb/c mouse eyelids were subjected to laser capture microdissection to isolate pure samples of meibomian gland ductal and acinar cells. Real-time polymerase chain reaction, immunolabeling, and Western blot analysis for SP receptor, VIP receptor, NPY receptor, and mAChR subtypes M1-M5 were performed on meibomian gland ductal and acinar cells.
Expression of NPY1 receptor, VIP receptor 1, SP receptor, and all 5 mAChR subtypes was found in all meibomian gland ductal and acinar cells analyzed by real-time polymerase chain reaction. Immunolabeling and Western blot analysis confirmed the presence of NPY1 receptor, VIP receptor 1, SP receptor, and all 5 mAChR subtypes in the meibomian gland. The levels were variable with the duct showing greater levels of NPY1 receptor, SP receptor, and mAChRs 1, 2, 4, and 5 than with the gland.
VIP receptor 1, SP receptor, NPY1 receptor, and mAChR subtypes may be involved in the regulation of meibomian gland secretion. Laser capture microdissection in conjunction with gene expression analysis provides an excellent approach for studying meibomian gland cells about which relatively little is known at the molecular level.
An elegant technique of synthesizing semiconductor lead sulfide nanoparticles (PbS-NPS) embedded in Langmuir-Blodgett (LB) films is presented here. Stearic acids have been used as a matrix to form ...and grow the quantum-sized PbS. Pure Y-type Pb-salts of stearic acid (SA) LB films were prepared at a dipping speed of 15 mm/min and surface pressure of 28 mN/m. PbS-NPs were formed inside LB films of SA by exposure the LB films to hydrogen sulfide (H2S) gas. The preparation of PbS-NPs is discussed in terms of particle formation and growth. The presence of PbS-NPs was investigated by UV-visible absorption. It was found that the PbS-NPs within SA LB films indicated a large blue shift of the optical absorption edge. The estimation of the size distribution performed by optical measurements allows one to attribute the particle range a few nanometers. This figure seems to depend upon the reaction conditions as well as the quality of the initial LB films.
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