Engineering and Technology, Industrial Biotechnology, Teknik och teknologier, Industriell bioteknik, floating MBR, syngas-to-biomethane conversion, high gas hold-up, inoculum-to-syngas ratio, Resource Recovery, and Resursåtervinning

The low gas-to-liquid mass transfer rate is one of the main challenges in syngas biomethanation. In this work, a new concept of the floating membrane system with high gas hold-up was introduced in order to enhance the mass transfer rate of the process. In addition, the effect of the inoculum-to-syngas ratio was investigated. The experiments were conducted at 55 °C with an anaerobic mixed culture in both batch and continuous modes. According to the results from the continuous experiments, the H2 and CO conversion rates in the floating membrane bioreactor were approximately 38% and 28% higher in comparison to the free (suspended) cell bioreactors. The doubling of the thickness of the membrane bed resulted in an increase of the conversion rates of H2 and CO by approximately 6% and 12%, respectively. The highest H2 and CO consumption rates and CH4 production rate recorded were approximately 22 mmol/(L·d), 50 mmol/(L·d), and 34.41 mmol/(L·d), respectively, obtained at the highest inoculum-to-syngas ratio of 0.2 g/mL. To conclude, the use of the floating membrane system enhanced the syngas biomethanation rates, while a thicker membrane bed resulted in even higher syngas conversion rates. Moreover, the increase of the inoculum-to-syngas ratio of up to 0.2 g/mL favored the syngas conversion.

Biodegradation, Environmental, Kinetics, Membranes, Artificial, Sewage, Waste Water chemistry, Benzothiazoles analysis, Bioreactors, Triazoles analysis, Waste Disposal, Fluid methods, and Water Pollutants, Chemical analysis

Lab-scale membrane bioreactors (MBRs), with aerated activated sludge and internal microfiltration module, were used for the treatment of municipal wastewater containing high, yet environmentally relevant, concentrations of benzothiazole (BT) and benzotriazole (BTA). These high production volume compounds are commonly used in the industry and households, and therefore occur ubiquitously in municipal wastewater and the aquatic environment. The aim of this study was to assess the removal of BT and BTA from synthetic municipal wastewater in MBRs and to estimate the contribution of elimination processes and to identify potential biotransformation products. The overall removal of BT and BTA was high, and after the adaptation period, it reached 99.8% and 97.2%, respectively, but recurring periods of unstable BTA removal occurred. The removal due to biotransformation was 88% for BT and 84% for BTA and the disposal with waste sludge accounted for only <1% of the removed load. The remaining fraction of the removed load of BT and BTA was attributed to be retained by phenomena associated with membrane fouling. The adaptation process was reflected in multifold increase in biodegradation kinetic coefficient (kbiol) for BT (reported for the first time) and BTA. Biodegradation was attributed to catabolic mechanism rather than to cometabolism. Hydroxylation was observed to be the main transformation reaction for BT, whereas for BTA hydroxylation, methylation and cleavage of benzene ring were noted. This study has shown the feasibility of treating municipal wastewater with high concentrations of BT and BTA in MBRs and identified potential challenges for the removal of BTA.
(Copyright © 2019 Elsevier Ltd. All rights reserved.)

Feasibility Studies, Filtration, Nylons chemistry, Thermodynamics, Time Factors, Bioreactors microbiology, Membranes, Artificial, and Sewage microbiology

In dynamic membrane bioreactors (DMBRs), a dynamic membrane (DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh (25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process (within 240 min). Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process (including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time (permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge < sludge with poor flocculability. Moreover, normal sludge (regarding settleability, dewaterability, flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance (short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid-based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.
(Copyright © 2018. Published by Elsevier B.V.)

Acetic Acid administration dosage, Anaerobiosis, Bacteria classification, Biodegradation, Environmental, Flame Retardants metabolism, Halogenation, Microbiota, Oxidation-Reduction, Sewage chemistry, Waste Water chemistry, Acetic Acid metabolism, Bacteria metabolism, Bioreactors, Polybrominated Biphenyls metabolism, and Water Pollutants, Chemical metabolism

The detection of increasing concentrations of tetrabromobisphenol A (TBBPA) in wastewater treatment plants is raising concerns as TBBPA has been identified as a potentially toxic flame retardant. The objectives of this study were to evaluate the effect of acetate biostimulation on TBBPA microbial reductive debromination, and the response of anaerobic sludge associated microbial communities repeatedly exposed to TBBPA. Results indicate that the bulk of the microbial community did not experience significant shifts as a result of TBBPA exposure, and that only a small fraction of the community responded to the presence of TBBPA. Taxa most likely responsible for TBBPA transformation affiliated to Clostridiales and the wastewater sludge group Blvii28. The biostimulating effect of acetate was only observed during reactor startup, when acetogenesis was likely not yet occurring. However, when acetate likely started to be microbially generated in the reactor, acetate addition resulted in a slight but significant inhibiting effect on TBBPA transformation. A significant increase of hydrogenotrophic methanogens in the TBBPA-spiked reactor overtime implies that TBBPA degraders were not in direct competition with methanogens for H2. These results strongly suggest that TBBPA degrading taxa might have been primarily using acetate as an electron donor for the reductive debromination of TBBPA.
(Copyright © 2018. Published by Elsevier B.V.)

Industriell bioteknik, Industrial Biotechnology, Bioteknologi med applikationer på växter och djur, Agricultural Biotechnology, Inhibition, Patchouli oil, Patchouli biomass, Anaerobic digestion, and Methane

Patchouli oil is an essential oil extracted from aromatic crop Pogostemon cablin and is widely used in perfumery industry, food industry, or even as medicine. The leaves have 4.6% oil that is extracted by steam but leaves an enormous amount of wastes with ca 0.8% oil. The fresh patchouli plants and its waste were examined in this study for biogas production. The methane yield of these materials were 86 and 179 NmL CH4/gVS, respectively. The patchouli oil showed antibacterial effect, where with the addition of 0.05, 0.5 and 5 g/l patchouli oil reduced biogas production by 16.2 %. 27.2% and more than 100% after 50 days digestion.

Carbon, Nitrates, Bioreactors, Denitrification drug effects, Waste Disposal, Fluid methods, and Wood

Woodchip-based denitrification bioreactors are widely used for treatment of high loads of nitrate pollution in agricultural run-off water. A concern raised recently, as a consequence of various organic fillings being experimented with, is whether the positive effect given by nitrate reduction could override the negative effects of such bioreactors, mainly caused by degradation of wood and the production of potentially harmful conditions for aquatic ecosystems. This paper presents the results of the experimental testing of two different filling materials: birch (BWCH) and spruce (SWCH) woodchip, and their mixture with washed gravel (WG) in volumetric ratio 10:1. We have focused on the leaching of organic carbon and phenols, and its impact on selected aquatic organisms, as well as on their denitrification efficiency and NO3- load removal rate (LRT). The results show that TOC, DOC and FNI (phenolic index) leaching is higher for the pure woodchip materials and is closely correlated with the growth inhibition of tested organisms (Vibrio fischeri, Daphnia magna, Desmodesmus subspicatus, Lemna minor). The highest denitrification efficiency and the highest load removal rates were recorded in mixed filling material (96% and 1.4 mg NO3-·dm3·d-1 for WG:BWCH; 85% and 1.2 mg NO3-·dm3·d-1 for WG:SWCH). Denitrification bioreactors with mixed woodchip filling material present a promising, cheap, and extensive technology for the treatment of agricultural field run-offs.
(Copyright © 2018 Elsevier B.V. All rights reserved.)

Biotechnology, Carbon Dioxide chemistry, Bioreactors, Methane chemistry, and Oxygenases metabolism

The ability of methanotrophs to rapidly respond to intentional or accidental stress conditions caused by operational failures or process fluctuations is of utmost importance to guarantee the robustness of CH4 abatement biotechnologies. In this study, the performance of a continuous and two feast-famine (5:5 days feast-famine cycles) stirred tank reactors treating diluted CH4 emissions (4-5% v/v) was comparatively assessed for 149 days. The robustness of the three bioreactors towards a 5 days CH4 deprivation episode was thoroughly evaluated at a molecular level (pmoA gene expression level) and correlated to macroscopic process performance. The bioreactors recovered their steady-state abatement performance (in terms of CH4 elimination capacity and CO2 production rate) within 1.5-2 h following CH4 supply resumption concomitantly with a maximum in pmoA gene expression, regardless of the previous operational mode. However, while methanotrophs from the continuous unit maintained higher basal levels of pmoA expression as a strategy for a rapid CH4 metabolism initiation, the strategy of the feast-famine adapted-methanotrophs consisted on a more accurate regulation of their pmoA transcripts levels along with a higher and/or more rapid induction of the pmoA gene by CH4 availability.
(Copyright © 2018 Elsevier Ltd. All rights reserved.)

Mannitol -- Physiological aspects, Sugarcane -- Physiological aspects, Plant tissue culture -- Methods, Euclidean geometry -- Usage, Geometry, Plane -- Usage, Geometry, Solid -- Usage, and Bioreactors -- Physiological aspects

Plant scientists usually record several indicators in their abiotic factor experiments. The common statistical management involves univariate analyses. Such analyses generally create a split picture of the effects of experimental treatments since each indicator is addressed independently. The Euclidean distance combined with the information of the control treatment could have potential as an integrating indicator. The Euclidean distance has demonstrated its usefulness in many scientific fields but, as far as we know, it has not yet been employed for plant experimental analyses. To exemplify the use of the Euclidean distance in this field, we performed an experiment focused on the effects of mannitol on sugarcane micropropagation in temporary immersion bioreactors. Five mannitol concentrations were compared: 0, 50, 100, 150 and 200 mM. As dependent variables we recorded shoot multiplication rate, fresh weight, and levels of aldehydes, chlorophylls, carotenoids and phenolics. The statistical protocol which we then carried out integrated all dependent variables to easily identify the mannitol concentration that produced the most remarkable integral effect. Results provided by the Euclidean distance demonstrate a gradually increasing distance from the control in function of increasing mannitol concentrations. 200 mM mannitol caused the most significant alteration of sugarcane biochemistry and physiology under the experimental conditions described here. This treatment showed the longest statistically significant Euclidean distance to the control treatment (2.38). In contrast, 50 and 100 mM mannitol showed the lowest Euclidean distances (0.61 and 0.84, respectively) and thus poor integrated effects of mannitol. The analysis shown here indicates that the use of the Euclidean distance can contribute to establishing a more integrated evaluation of the contrasting mannitol treatments.

BIOLOGICAL nutrient removal, SEWAGE, BIOREACTORS, SEWAGE purification, HOUSEHOLDS, and WASTEWATER treatment

Our paper presents results of nutrient removal from household wastewater in the bioreactors with nonwoven filters. The experimental system was constructed from two groups of bioreactors in laboratory scale with gravity-fed wastewater supply. The variable differentiating the work of both tested systems was the method of sewage dosing. In both experimental groups, there was a statistically significant reduction ratio of nitrite nitrogen, ammonia nitrogen, phosphate, and sulfide ions. In spite of the marked difference between concentrations of investigated nutrients in treated wastewater between the experimental groups was not possible to demonstrate in most cases the statistically significant differences. The bioreactors fed once every 12 hours showed an additional effect of desiccation of part of a nonwoven filter and a significant deterioration in the quality of treated sewage. The tested systems of reactors provide the scientific promises for their use on an industrial scale as a system with partial treatment of household sewage. The contents of nutrients in treated wastewater, however, still exceeds the permissible level specified in the standard for treated sewage. [ABSTRACT FROM AUTHOR]

Air, Equipment Design, Escherichia coli, Gases, Hydrodynamics, Kinetics, Viscosity, Bioreactors, Fermentation, and Oxygen chemistry

Miniaturized bubble columns (MBCs) have different hydrodynamics in comparison with the larger ones, but there is a lack of scientific data on MBCs. Hence, in this study, the effect of gas hold-up, flow regimes, bubble size distribution on volumetric oxygen mass transfer coefficient at different pore size spargers and gas flow rates in MBCs in the presence and absence of microorganisms were investigated. It was found that flow regime transition occurred around low gas flow rates of 1.18 and 0.85 cm/s for small (16-40 µm) and large (40-100 µm) pore size spargers, respectively. Gas hold-up and KLa in MBC with small size sparger were higher than those with larger one, with an increasing effect in the presence of microorganisms. A comparison revealed that the wall effect on the flow regime and gas hold-up in MBCs was greater than bench-scale bubble columns. The KLa values significantly increased up to tenfold using small pore size sparger. In the MBC and stirred tank bioreactors, the maximum obtained cell concentrations were OD600 of 41.5 and 43.0, respectively. Furthermore, it was shown that in MBCs, higher KLa and lower turbulency could be achieved at the end of bubbly flow regime.