In the present note we provide combinatorial constraints on certain conic arrangements in the plane admitting
A
5
and
A
7
singularities. As a corollary, we provide upper bounds on the number of
A
5
...and
A
7
singularities for such arrangements.
The use of algae as a potential substrate in biogas production processes has been discussed sporadically, therefore this manuscript provides an overview of reference data published so far on that ...matter. The goal of this review is to present possibilities of applying algae biomass for biogas production purposes and to determine the effectiveness of the fermentation process of algae belonging to various taxonomic groups, originating from various biocenoses and characterized by different morphology and properties. Finally, this work reports on methods and technological solutions for algae biomass production as well as impediments and opportunities stemming from algae biomass use in biogas production technologies.
The extraction of lipids from microalgae cells of
Botryococcus braunii
and
Chlorella vulgaris
after ultrasonic and microwave pretreatment was evaluated. Cell disruption increased the lipid extraction ...efficiency, and microwave pretreatment was more effective compared with ultrasonic pretreatment. The maximum lipid yield from
B. braunii
was 56.42% using microwave radiation and 39.61% for ultrasonication, while from
C. vulgaris
, it was respectively 41.31% and 35.28%. The fatty acid composition in the lipid extracts was also analyzed. The methane yield from the residual extracted biomass pretreated by microwaves ranged from 148 to 185 NmL CH
4
/g VS for
C. vulgaris
and from 128 to 142 NmL CH
4
/g VS for
B. braunii
. In the case of ultrasonic pretreatment, the methane production was between 168 and 208 NmL CH
4
/g VS for
C. vulgaris
, while for
B. braunii
ranging from 150 to 174 NmL CH
4
/g VS. Anaerobic digestion showed that lipid-extracted biomass presented lower methane yield than non-lipid-extracted feedstock, and higher amount of lipid obtained in the extraction contributed less methane production. Anyway, anaerobic digestion of the residual extracted biomass can be a suitable method to increase economic viability of energy recovery from microalgae.
Though deemed a prospective method, the bioconversion of organic waste to biohydrogen via dark fermentation (DF) has multiple drawbacks and limitations. Technological difficulties of hydrogen ...fermentation may, in part, be eliminated by making DF a viable method for biohythane production. Aerobic granular sludge (AGS) is a little-known organic waste spurring a growing interest in the municipal sector; its characteristics indicate the feasibility of its use as a substrate for biohydrogen production. The major goal of the present study was to determine the effect of AGS pretreatment with solidified carbon dioxide (SCO
) on the yield of H
(biohythane) production during anaerobic digestion (AD). It was found that an increasing dose of SCO
caused an increase in concentrations of COD, N-NH
, and P-PO
in the supernatant at the SCO
/AGS volume ratios from 0 to 0.3. The AGS pretreatment at SCO
/AGS ratios within the range of 0.1-0.3 was shown to enable the production of biogas with over 8% H
(biohythane) content. The highest yield of biohythane production, reaching 481 ± 23 cm
/gVS, was obtained at the SCO
/AGS ratio of 0.3. This variant produced 79.0 ± 6% CH
and 8.9 ± 2% H
. The higher SCO
doses applied caused a significant decrease in the pH value of AGS, modifying the anaerobic bacterial community to the extent that diminished anaerobic digestion performance.
The present study aimed to determine the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). The SMF had a significant ...impact on methane (CH4) production efficiency, the levels of fermentation rate (ηFMSS) vs. removal rate (ηVS), and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production. The highest CH4 yield (431 ± 22 dm3CH4/kgVS) and the highest methane content in the biogas (66.1% ± 1.9%) were found in the variant in which the SMF exposure time was 144 min/day. This variant also produced the highest ηFMSS and ηVS values, reaching 73.8% ± 2.3% and ηVS 36.9% ± 1.6%, respectively. Longer anaerobic sludge retention time in the SMF area significantly decreased AD efficiency and caused a significant reduction in the number of methanogens in the anaerobic bacteria community. The lowest values were observed for SMF exposure time of 432 min/day, which produced only 54.8 ± 1.9% CH4 in the biogas. A pronounced reduction was recorded in the Archaea (ARC915) and Methanosaeta (MX825) populations in the anaerobic sludge, i.e., to 20% ± 11% and 6% ± 2%, respectively.
Anaerobic wastewater treatment is still a dynamically developing technology ensuring the effective degradation of organic compounds and biogas production. As evidenced in the large scale-up, this ...technological solution surpasses aerobic methods in many aspects. Its advantages stem from the feasibility of operation at a high organic load rate, the smaller production of difficult-to-manage sewage sludge, the smaller space and cubature required, and the high-methane biogas ultimately produced. The exploitation of anaerobic reactors is in line with the assumption of a circular economy, material recycling by reduced CO2 emissions and energy consumption, and the production of renewable energy. Despite their unquestionable advantages, there is still a need to seek novel approaches and improve the currently exploited installations. The key avenues of research entail improvements in the stability of bioreactor operations and the enhancement of bioreactor adaptability to changing and unfavorable process parameters. The versatility of such systems would also be greatly improved by increasing nitrogen and phosphorus removal rates. Attempts have been made to achieve these goals by setting up separate zones within bioreactors for the individual steps of methane fermentation, incorporating active fillings to promote nutrient removal, and introducing chemical and physical treatments. An interesting solution is also the use of microwave radiation to stimulate temperature conditions and induce non-thermal phenomena, such as enhancing the enzymatic activity of methanogenic microflora. Another prospective approach is to integrate digesters into microalgal biomass production systems. The aim of this review paper is to present the thus-far technological knowledge about anaerobic wastewater treatment, including standard solutions and innovative ones, the effectiveness of which has been corroborated in pilot-scale installations.
The aim of the study was to investigate the potential of microalgal cultivation on anaerobic liquid digestate as a growth medium. The two methods of liquid digestate treatment including ...centrifugation and distillation and the two algal strains (
Chlorella vulgaris
and
Arthrospira platensis
) were compared. Additionally, the volume of the liquid digestate used to prepare the culture medium constituted from 10 to 50% of the medium volume. The study demonstrated that the highest
C. vulgaris
and
A. platensis
biomass productions of 2490 mg TS/L and 2990 mg/L, respectively, were obtained by adding 50% of distilled digestate to a growth medium. Regarding centrifuged liquid digestate, only 10% dilution was required to obtain the maximum final biomass concentration.
A. platensis
removed 81.1% and 66.4% of the total nitrogen from medium prepared on distilled and centrifuged digestate, respectively, while
C. vulgaris
ensured 64.1% and 47.1% of removal, respectively. The phosphorus removal from both culture media was higher than 94.2% with
A. platensis
, while it was 70.4% from distilled and 87.4% from centrifuged media with
C. vulgaris
. The study confirmed a great potential of microalgal biomass production on anaerobic liquid digestate with a high treatment efficiency of digestate.
The aim of the study was to optimize methane fermentation of food waste products based on the composition of substrates mixture and technical parameters of anaerobic digestion to obtain the highest ...biogas and methane production. The study was conducted in the laboratory scale in the mesophilic (37°C) and thermophilic (55°C) conditions. Also the effects of the organic loading rates (OLRs) on the biogas productivity and composition were analysed. The highest biogas yield was obtained in mesophilic digestion of the substrates mixture containing 50% of meat, 40% dairy products, 10% fruit and vegetables. It amounted to 740.4 ± 19.9 cm3·g ODM−1 of biogas with 68.6 ± 1.8% of methane. Biogas potential in thermophilic digestion was from 2.1 to 2.8 times lower for analogical feedstock. It was caused by high concentration of volatile fatty acids (VFAs) in the reactor chamber. The ratio of VFAs to alkalinity was on the level from 0.5 ± 0.1 to 0.8 ± 0.1. In continuous experiments, the average biogas production rate was from 2646.9 ± 117.3 cm3·d−1 for OLR of 2 g ODM·dm−3·d−1 to 9893.4 ± 362.0 cm3·d−1 for OLR amounting to 8 g ODM·dm−3·d−1. Methane content in biogas was between 65.6 ± 2.5 and 65.5 ± 1.9%, respectively. It was confirmed that applying OLR above 6 g ODM·dm−3·d−1 causes inhibition of methane fermentation.
•740.36 ± 19.85 cm3·g ODM−1 was generated during mesophilic fermentation.•Biogas productivity in thermophilic process was from 2.1 to 2.8 times lower.•OLR above 6 gODM·dm−3·d−1 completely inhibited the process.
The rapid growth in dairy production leads to increasing outputs of high-load effluent, necessitating new methods of treating such waste. Anaerobic processes have been increasingly popular but are ...hamstrung by limited nutrient removal efficiency. The aim of the present study was to investigate whether low-cost recycled filling (LCRF) improves the anaerobic treatment of dairy effluent. The addition of LCRF was found to increase both COD removal (86.1 ± 2.6%–92.8 ± 1.6%) and Ptot. removal (22.1 ± 3.5% to 36.9 ± 4.6%) from the wastewater. The LCRF ensured near-neutral pH and stabilized the structure of the anaerobic microbe community (including Archaea) across all pollutant loads tested. This translated to efficient biogas production and high methane content in the LCRF reactors, peaking at 0.35 ± 0.01 m3/kg CODremoved and 68.2 ± 0.6% (respectively) in the best-performing variant.
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