Effects of heat treatment on microbial communities of granular sludge for biological hydrogen production

2012 ◽  
Vol 66 (7) ◽  
pp. 1483-1490 ◽  
Author(s):  
Luca Alibardi ◽  
Lorenzo Favaro ◽  
Maria Cristina Lavagnolo ◽  
Marina Basaglia ◽  
Sergio Casella
Keyword(s):  
Heat Treatment ◽  
Hydrogen Production ◽  
Microbial Communities ◽  
Granular Sludge ◽  
Dark Fermentation ◽  
Anaerobic Granular Sludge ◽  
Batch Test ◽  
Ph Values ◽  
Pre Treatment ◽  
Selection Of

Dark fermentation shares many features with anaerobic digestion with the exception that to maximize hydrogen production, methanogens and hydrogen-consuming bacteria should be inhibited. Heat treatment is widely applied as an inoculum pre-treatment due to its effectiveness in inhibiting methanogenic microflora but it may not exclusively select for hydrogen-producing bacteria. This work evaluated the effects of heat treatment on microbial viability and structure of anaerobic granular sludge. Heat treatment was carried out on granular sludge at 100 °C with four residence times (0.5, 1, 2 and 4 h). Hydrogen production of treated sludges was studied from glucose by means of batch test at different pH values. Results indicated that each heat treatment strongly influenced the granular sludge resulting in microbial communities having different hydrogen productions. The highest hydrogen yields (2.14 moles of hydrogen per mole of glucose) were obtained at pH 5.5 using the sludge treated for 4 h characterized by the lowest CFU concentration (2.3 × 103CFU/g sludge). This study demonstrated that heat treatment should be carefully defined according to the structure of the sludge microbial community, allowing the selection of highly efficient hydrogen-producing microbes.

Emerging investigator series: inhibition and recovery of anaerobic granular sludge performance in response to short-term polystyrene nanoparticle exposure

2018 ◽  
Vol 4 (12) ◽  
pp. 1902-1911 ◽  
Author(s):  
Yue Feng ◽  
Li-Juan Feng ◽  
Shu-Chang Liu ◽  
Jian-Lu Duan ◽  
Yi-Bing Zhang ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Granular Sludge ◽  
Anaerobic Granular Sludge ◽  
Short Term ◽  
Nanoparticle Exposure ◽  
Performance Recovery

Microbial communities and methanogenic genes are main reasons for AGS performance recovery from PS-NPs exposure.

scholarly journals Tribomechanical Behaviour of TiAlN and CrAlN Coatings Deposited onto AISI H11 with Different Pre-Treatments

Coatings ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 519 ◽  
Author(s):  
Wolfgang Tillmann ◽  
Diego Grisales ◽  
Dominic Stangier ◽  
Timo Butzke
Keyword(s):  
Heat Treatment ◽  
Steel Substrate ◽  
Life Time ◽  
Substrate Material ◽  
Substrate Preparation ◽  
Metalworking Industry ◽  
Steel Aisi ◽  
Pre Treatment ◽  
Forming Tools ◽  
Selection Of

In the metalworking industry, different processes and applications require the utilisation of custom designed tools. The selection of the appropriated substrate material and its pre-treatment as well as the protective coating are of great importance in the performance and life time of forming tools, dies, punches and coated parts in general. TiAlN and CrAlN coatings have been deposited onto the hot work tool steel AISI H11 by means of Direct Current Magnetron Sputtering. Prior to the deposition, the steel substrate was modified by the implementation of three different pre-treatments: nitriding of the annealed substrate [Nitr.], heat treatment of the steel (quenching and double tempering) [HT] and nitridation subsequent to a heat treatment of the substrate [HT + Nitr.]. The purpose of this research is to obtain valuable information on the microstructural properties and tribomechanical behaviour of two of the most promising ternary transition metal nitride coatings, TiAlN and CrAlN, when deposited on the AISI H11 steel with different initial properties. The different pre-treatments performed to the steel prior to the deposition favour the tailoring during the design and construction of tools for specific applications. The microstructure, the adhesion and the wear resistance of TiAlN coatings were highly influenced by the substrate preparation. Contrarily, CrAlN results were more independent of the substrate preparation and no high influences were found. For instance, the adhesion of the TiAlN coating varied from 17 to 43 N for the coating deposited onto the HT + Nitr. substrate and the HT substrate respectively, while the lowest and highest adhesion of the CrAlN coating varied between 42 and 53 N for the HT and the HT + Nitr. respectively. Likewise, the wear coefficient of the CrAlN were ten times smaller than those found for the TiAlN coatings, presumably due to the presence of hex-AlN phases and the small differences on the Young´s Modulus of the substrate and the CrAlN coatings.

scholarly journals Dynamics and Complexity of Dark Fermentation Microbial Communities Producing Hydrogen From Sugar Beet Molasses in Continuously Operating Packed Bed Reactors

2021 ◽  
Vol 11 ◽  
Author(s):  
Anna Detman ◽  
Daniel Laubitz ◽  
Aleksandra Chojnacka ◽  
Ewa Wiktorowska-Sowa ◽  
Jan Piotrowski ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Hydrogen Production ◽  
Sugar Beet ◽  
Microbial Communities ◽  
Packed Bed ◽  
Dark Fermentation ◽  
Shotgun Metagenomics ◽  
Packed Bed Reactors ◽  
Beet Molasses

This study describes the dynamics and complexity of microbial communities producing hydrogen-rich fermentation gas from sugar-beet molasses in five packed-bed reactors (PBRs). The bioreactors constitute a part of a system producing hydrogen from the by-products of the sugar-beet industry that has been operating continuously in one of the Polish sugar factories. PBRs with different working volumes, packing materials, construction and inocula were tested. This study focused on analysis (based on 16S rRNA profiling and shotgun metagenomics sequencing) of the microbial communities selected in the PBRs under the conditions of high (>100 cm3/g COD of molasses) and low (<50 cm3/g COD of molasses) efficiencies of hydrogen production. The stability and efficiency of the hydrogen production are determined by the composition of dark fermentation microbial communities. The most striking difference between the tested samples is the ratio of hydrogen producers to lactic acid bacteria. The highest efficiency of hydrogen production (130–160 cm3/g COD of molasses) was achieved at the ratios of HPB to LAB ≈ 4:2.5 or 2.5:1 as determined by 16S rRNA sequencing or shotgun metagenomics sequencing, respectively. The most abundant Clostridium species were C. pasteurianum and C. tyrobutyricum. A multiple predominance of LAB over HPB (3:1–4:1) or clostridia over LAB (5:1–60:1) results in decreased hydrogen production. Inhibition of hydrogen production was illustrated by overproduction of short chain fatty acids and ethanol. Furthermore, concentration of ethanol might be a relevant marker or factor promoting a metabolic shift in the DF bioreactors processing carbohydrates from hydrogen-yielding toward lactic acid fermentation or solventogenic pathways. The novelty of this study is identifying a community balance between hydrogen producers and lactic acid bacteria for stable hydrogen producing systems. The balance stems from long-term selection of hydrogen-producing microbial community, operating conditions such as bioreactor construction, packing material, hydraulic retention time and substrate concentration. This finding is confirmed by additional analysis of the proportions between HPB and LAB in dark fermentation bioreactors from other studies. The results contribute to the advance of knowledge in the area of relationships and nutritional interactions especially the cross-feeding of lactate between bacteria in dark fermentation microbial communities.

Bio-hydrogen production from wastewater

2004 ◽  
Vol 4 (1) ◽  
pp. 77-85 ◽  
Author(s):  
H.H.P. Fang ◽  
H. Liu ◽  
T. Zhang
Keyword(s):  
Hydrogen Production ◽  
Microbial Communities ◽  
Organic Pollutants ◽  
Production Efficiency ◽  
Dark Fermentation ◽  
Controlling Factors ◽  
Biomass Density ◽  
Fermentation Conditions ◽  
Step Process ◽  
Sludge Granulation

The technically feasibility of converting organic pollutants in wastewater into hydrogen by a continuous two-step process was demonstrated. Two carbohydrates, i.e. glucose and sucrose, in wastewater were respectively acidified by dark fermentation at pH 5.5 with 6–6.6 hours of hydraulic retention in a 3-l fermentor, producing an effluent containing mostly acetate and butyrate, and a methane-free biogas comprising mostly hydrogen. The acidified effluent was then further treated by photo fermentation for hydrogen production. The overall yield based on the substrate consumed was 31–32%, i.e. 17–18% for dark fermentation and 14% for photo fermentation. It was found that under certain dark fermentation conditions, hydrogen-producing sludge was agglutinated into granules, resulting in a higher biomass density and increased volumetric hydrogen production efficiency. DNA-based analysis of microbial communities revealed that the respective predominant bacteria were Clostridium in dark fermentation and Rhodobacter in photo fermentation. Further investigations are warranted, particularly, in areas such as improving reactor design, treating protein and lipid rich wastewaters, and studying sludge granulation mechanisms and controlling factors.

scholarly journals Effect of pH on the Economic Potential of Dark Fermentation Products from Used Disposable Nappies and Expired Food Products

2021 ◽  
Vol 11 (9) ◽  
pp. 4099
Author(s):  
Dimitris Zagklis ◽  
Marina Papadionysiou ◽  
Konstantina Tsigkou ◽  
Panagiota Tsafrakidou ◽  
Constantina Zafiri ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Hydrogen Production ◽  
Volatile Fatty Acids ◽  
Food Products ◽  
Treatment Method ◽  
Dark Fermentation ◽  
Biodiesel Production ◽  
Economic Potential ◽  
Fermentation Products ◽  
Ph Values

Used disposable nappies constitute a waste stream that has no established treatment method. The purpose of this study was the assessment of the dark fermentation of used disposable nappies and expired food products under different pH values. The biodegradable part of the used disposable nappies was recovered and co-fermented with expired food products originating from supermarkets. The recoverable economic potential of the process was examined for different volatile fatty acids exploitation schemes and process pH values. The process pH strongly affected the products, with optimum hydrogen production at pH 6 (4.05 NLH2/Lreactor), while the amount of produced volatile fatty acids was maximized at pH 7 (13.44 g/L). Hydrogen production was observed at pH as low as pH 4.5 (2.66 NLH2/Lreactor). The recoverable economic potential was maximized at two different pH values, with the first being pH 4.5 with minimum NaOH addition requirements (181, 138, and 296 EUR/ton VS of substrate for valorization of volatile fatty acids through microbial fuel cell, biodiesel production, and anaerobic digestion, respectively) and the second being pH 6, where the hydrogen production was maximized with the simultaneous production of high amounts of volatile fatty acids (191, 142, and 339 EUR/ton VS of substrate respectively).

scholarly journals Fermentative Conversion of Two-Step Pre-Treated Lignocellulosic Biomass to Hydrogen

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 858 ◽  
Author(s):  
Karolina Kucharska ◽  
Hubert Cieśliński ◽  
Piotr Rybarczyk ◽  
Edyta Słupek ◽  
Rafał Łukajtis ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Lignocellulosic Biomass ◽  
Lignin Content ◽  
Dark Fermentation ◽  
Biomass Composition ◽  
Total Phenolic ◽  
High Hydrogen ◽  
Fermentative Hydrogen Production ◽  
Pre Treatment ◽  
Fermentative Hydrogen

Fermentative hydrogen production via dark fermentation with the application of lignocellulosic biomass requires a multistep pre-treatment procedure, due to the complexed structure of the raw material. Hence, the comparison of the hydrogen productivity potential of different lignocellulosic materials (LCMs) in relation to the lignocellulosic biomass composition is often considered as an interesting field of research. In this study, several types of biomass, representing woods, cereals and grass were processed by means of mechanical pre-treatment and alkaline and enzymatic hydrolysis. Hydrolysates were used in fermentative hydrogen production via dark fermentation process with Enterobacter aerogenes (model organism). The differences in the hydrogen productivity regarding different materials hydrolysates were analyzed using chemometric methods with respect to a wide dataset collected throughout this study. Hydrogen formation, as expected, was positively correlated with glucose concentration and total reducing sugars amount (YTRS) in enzymatic hydrolysates of LCMs, and negatively correlated with concentrations of enzymatic inhibitors i.e., HMF, furfural and total phenolic compounds in alkaline-hydrolysates LCMs, respectively. Interestingly, high hydrogen productivity was positively correlated with lignin content in raw LCMs and smaller mass loss of LCM after pre-treatment step. Besides results of chemometric analysis, the presented data analysis seems to confirm that the structure and chemical composition of lignin and hemicellulose present in the lignocellulosic material is more important to design the process of its bioconversion than the proportion between the cellulose, hemicellulose and lignin content in this material. For analyzed LCMs we found remarkable higher potential of hydrogen production via bioconversion process of woods i.e., beech (24.01 mL H2/g biomass), energetic poplar (23.41 mL H2/g biomass) or energetic willow (25.44 mL H2/g biomass) than for cereals i.e., triticale (17.82 mL H2/g biomass) and corn (14.37 mL H2/g biomass) or for meadow grass (7.22 mL H2/g biomass).

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