Anaerobic Fermentation System Research Articles

Operating tests analysis of liquid biologically degradable waste processing by anaerobic fermentation

This study concerns the analysis of operating anaerobic fermentation systems of agricultural biogas station and implementing a suitable system enabling the use of liquid biowaste. Based on the comparison of the technological solutions and operating parameters of specific equipment a system enabling the utilisation of biowaste has been designed. The tests made use of liquid substrates commercially offered to biogas station operators. The study evaluates practical measurements at an agricultural biogas station in order to evaluate the biogas production from these substrates and the efficiency of transforming input material to usable energy. The use of such treated substrates for the anaerobic fermentation technology may have a substantial influence on the volume of dosed energy crops. The mixture of input substrates consisting of liquid cattle excrements, silage corn, liquid food-processing waste, animal waste and glycerine water was experimentally validated. This mixture was compared with the operation using liquid cattle excrements and silage corn. It was concluded that the proposed composition of input raw materials makes it possible to increase the production of biogas and el. power. On the other hand, it was identified that the energy content of the input raw materials is not optimally transformed into usable energy. Therefore, the proposed mixture of input materials with biowaste is not recommended for use.

Measuring Biomass Energy Flows of a Rural Energy Engineering

Energy consumption in the Chinese rural areas features massive use of low-grade energy commodities and the distempered structure of exorbitant leaning on biomass energy. This has provoked an increasingly exacerbating environment and exerted a depressing effect on agriculturally sustainable development. Pilot energy engineering practices of efficient utilization environment improvement have seen a surge on a vast extent of rural lands. As a typical engineering of energy resources for methane production, the four-dimension-inone-geometry model concerning ecological agriculture has triggered scholarly attention. The aim of this study is to deal with energy flows in this system whereby to put forward measures for its upgrading and ultimately offer policies for rural energy development and use. First, the study depicts the models structure and working process, and the methodology of estimating its energy flows. Next, taking a three member household as an example, the study estimates the quantity in its energy flows, finding that the whole system imports 1,195,102 MJ of energy and generates 35,728MJ, with 47.3% yielded by the breeding system, 32.1% by the anaerobic fermentation system, and 20.6% by the planting system. Comparatively, this model has neither achieved the artificially auxiliary energy-output ratio of 2.4:1, a criterion for high yield, nor reached the national high output standard of 38.1GJ/hm2 in inorganic energy investment and the height of 124.3 GJ/hm2 of farmland energy input in the bio-energy zones of good harvest. On this ground, this study presents countermeasures to further improve the models energy efficiency and strategies related to rural energy development. Those suggestions might apply to other rural areas.

Research on the Efficiency of Acid-Producing and Gas-Producing Based on the Enhancement of High-Performance Composite Strains

A batch test was carried out to investigate the effect of acid-producing fermentative characteristic of a new complex strains LZF-12 with high lignocellulose-degradation ability, which straw was the only carbon source in acidogenic phase. Simultaneity, the biogas-producing performance was also researched by shifting the liquid end products from acidongenic phase to methane phase, which fermentative substrate was the mixture of cow dung and kitchen waste. The results indicated that major fermentation products of acidogenic phase was acetic acid accounted for 70% of total volatile acid, which would be in favor of microorganisms growth of methanogenic phase. In two-phase anaerobic fermentation system, the straw degradation rate of composite strains LZF-12 reached the maximum at 72 hour, among which the degradation rate of cellulose, hemicellulose and lignin reached 55%, 67% and 13% respectively. The methane percentage of biogas-producing phase was more than 50% and 134.7mL/g VS of methane production rate was obtained.

Analysis of production tests in processing the mixture of solid and liquid biologically degradable wastes by anaerobic fermentation

This study concerns the analysis of operating anaerobic fermentation systems of agricultural biogas station and implementing a suitable system enabling the use of a mixture of solid and liquid biowaste. The tests made use of liquid substrates commercially offered to biogas station operators. The study evaluates practical measurements at an agricultural biogas station in order to evaluate the biogas production from these substrates and the efficiency of transforming input material to usable energy. The use of such treated substrates for the anaerobic fermentation technology may have a substantial influence on the volume of dosed energy crops. The mixture of input substrates consisting of liquid cattle excrements, silage corn, solid and liquid waste from food processing, animal waste and glycerine water was experimentally validated. This mixture was compared with the operation using liquid cattle excrements and silage corn. It was concluded that the proposed composition of input raw materials makes it possible to increase the production of biogas and el. power. On the other hand, it was identified that the energy content of the input raw materials is not optimally transformed into usable energy. This is why the proposed mixture of input materials with biowaste is not recommended for use at the used proportion.

Feasibility and Characteristics of Denitrification Using Excess Sludge as the Sole Carbon Source

Adequate carbon source is critical for biological nutrients removal from wastewater, and waste activated sludge (WAS) treatment or disposal is costly and difficult in wastewater treatment plants. In this study, a novel sludge fermentation process was launched to develop the internal carbon source of WAS to enhance biological nitrogen removal, nitrite and nitrate was directly added into anaerobic fermentation system and then formed WAS anoxic fermentation denitrification system (AFD), in which, the sludge fermentation and denitrification were expected to proceed simultaneously. Experimental results of 40 days’ fermentation showed that 0.12 gNO2--N/gVSS and 0.11 gNO3--N/gVSS, or 0.26 gNO2--N/gVSS-reduction and 0.24 gNO3--N/gVSS-reduction, could be simultaneously obtained in AFD, and it could be calculated that 37.9% of total VSS and 80.7% of VSS reduction was utilized for nitrite or nitrate removal, which suggested a good performance of denitrification driven by WAS in AFD. The highest accumulation amount, 204 mg/L, of volatile fatty acids was occurred in the 11th day, which proved a rapid fermentation was present in AFD. Furthermore, the variations of pH or ORP in AFD could well indicate the progress of fermentation and denitrification.

Efficacy of natamycin to control fungal growth in natural black olive fermentation

The effect of natamycin as a fungal control agent in natural black olive fermentation according to the traditional anaerobic system was studied. Black Conservolea olives were subjected to spontaneous fermentation in 8% (w/v) NaCl brine solution (control treatment) or brine supplemented with 0.01% (w/v) natamycin (active compound) for an overall period of 60 days. The changes in the microbial association (lactic acid bacteria, yeasts, Enterobacteriaceae), pH, titratable acidity, organic acids, and volatile compounds were monitored throughout fermentation. The initial microbiota consisted of lactic acid bacteria, yeasts, and Enterobacteriaceae. The addition of natamycin in the brine inhibited the growth of yeasts, without affecting the population dynamics of bacteria, resulting in a more vigorous fermentation with higher titratable acidity compared to spontaneous control process. Moreover, the presence of natamycin inhibited mould spoilage caused by the development of fungal mycelium on the surface of the brine during the traditional anaerobic fermentation system employed widely in Greece in natural black olive processing. Natamycin could be an important component of a processing system to control fungal growth in natural black olive fermentation and at the same time it has the potential to enhance the process by favouring the growth of the indigenous population of lactic acid bacteria against other competing microorganisms.

Comparative Assessment of Olive Oil Mill Effluents from Three-phase and Two-phase Systems, Treated for Hydrogen Production

By-products of a two-phase and a three-phase olive oil mill process treated in an anaerobic fermentation system for hydrogen production, were evaluated by three bioassays: the zebrafish Danio rerio embryo test and two microbiotests, Thamnotoxkit F and Daphtoxkit F™ pulex. Samples from both processes were classified as "very toxic" with LC(50) values ranging from 1.52% (T. platyurus 24 h test) to 4.48% (D. pulex 48 h-LC₅₀). Toxicity values were differently correlated to physicochemical parameters showing different degree of influence. The treated effluents of both process systems remained very toxic showing the necessity for further treatment, aiming to environmentally safe discharges.

Biohydrogen production from sewage sludge using a continuous hydrogen fermentation system with a heat treatment vessel

An anaerobic hydrogen fermentation system with a thermophilic flow-through reactor (55°C) for hydrogen production and a boiling retention vessel (100°C) for continuous heat treatment, was studied for enhanced continuous hydrogen fermentation using sewage sludge. The performance of the hydrogen fermentation system was tested at various Hydraulic Retention Times (HRTs) ranged from 1 to 5 days. The heat treatment of the fermenting sludge using the boiling retention vessel was an effective to select hydrogen producing bacteria, and to increase the hydrolysis of particulate organics in sewage sludge. The VS reduction from the hydrogen fermentation system with the boiling retention vessel was increased from 22.2% to 37.9% according to the HRT ranged from 1 to 5days, caused by the heat treatment of the fermenting sludge. However, higher maximum yield of hydrogen compared to previous studies was 3.07 mmol H2/g TS, which was obtained at 3 days HRT. The hydrogen yield and hydrolysis rate were significantly affected by pH condition, and proper pH for the hydrogen fermentation was from 5.5 to 6.5. The hydrogen production was limited by the hydrolysis for 1day HRT and by the hydrogen consumption activity for 5days HRT.

Enhancement of Waste Activated Sludge Protein Conversion and Volatile Fatty Acids Accumulation during Waste Activated Sludge Anaerobic Fermentation by Carbohydrate Substrate Addition: The Effect of pH

Volatile fatty acids (VFAs), the carbon source of biological nutrients removal, can be produced by waste activated sludge (WAS) anaerobic fermentation. However, because of high protein content and low carbon to nitrogen mass ratio (C/N) of WAS, the production of VFAs, especially propionic acid, a more preferred VFA than acetic acid for enhanced biological phosphorus removal (EBPR), is limited. After the addition of carbohydrate (rice was used as the model matter) to the WAS anaerobic fermentation system to balance the C/N ratio, the effect of pH on WAS protein conversion and VFAs production was investigated in this paper. Experimental results showed that the addition of carbohydrate matter caused a remarkable enhancement of WAS protein conversion and protease activity, and an apparent synergistic effect between WAS and carbohydrate matter was observed. The study of pH effect revealed that pH influenced not only the total VFAs production but the percentage of individual VFA. The maximal VFAs production (520.1 mg COD per gram of volatile suspended solids (VSS)) occurred at pH 8.0 and a fermentation time of 8 d, which was more than three times that at uncontrolled pH (150.2 mg COD/g VSS). The analysis of the composition of VFAs showed that propionic acid ranked first at pH 6.0-9.0 (around 50%) whereas acetic acid was the dominant product at other pHs investigated. Thus, the suitable conditions for propionic acid-enriched VFAs production were pH 8.0 and a time of 8 d. Further investigation showed that as there was more fermentation substrate consumption with lower biogas generation at pH 8.0, improved VFAs production was observed. Also, the key enzymes relevant to propionic acid formation exhibited the highest activities at pH 8.0, which resulted in the greatest propionic acid content in the fermentative VFAs. The 16S rRNA gene clone library demonstrated that Clostridia, beta-Proteobacteria, and Bacteroidetes were the dominant microbial community when the current anaerobic fermentation system was operated at pH 8.0. With the fermentative VFAs as the additional carbon source of municipal wastewater, the EBPR performance was significantly increased.

Environmental Hazard Assessment of Cheese Manufacturing Effluent Treated for Hydrogen Production

Toxicity of effluents after treatment in an anaerobic fermentation system for hydrogen production is evaluated with three biotests: The zebrafish Danio rerio embryo test, the Thamnotoxkit F and the Daphtoxkit F(TM) magna. Samples were classified from "very" to "extremely toxic". Average toxicity values for zebrafish were 1.55% (24 h) and 0.75% (48 h), for Thamnocephalus 0.69% (24 h) and for Daphnia 2.51% (24 h) and 1.82% (48 h). Statistical analysis between physicochemical parameters and LC(50) values revealed that PO(4)(-3), SO(4)(-2), NH(3)N and NO(3)(-) have the major contribution to toxicity. Based on results, this treatment is considered an environmentally ineffective way of managing the specific wastes.

Changes in microbial community composition following treatment of methanogenic granules with chloroform

AbstractEliminating hydrogen consuming bacteria is a critical step in anaerobic fermentation for biohydrogen production. Treatment of anaerobic granular sludge with chloroform was reported as effective in transforming a methane‐producing system into a hydrogen‐producing system by eliminating methane production. This study, using 16S rRNA gene sequences, further assessed changes in microbial community composition as a result of chloroform treatment and during continuous cultivation of chloroform‐treated granules in a continuous upflow reactor employing immobilized cells. Profiles of terminal restriction fragment length polymorphisms (T‐RFLP) of 16S rRNA genes sequences cloned from samples before and after chloroform treatment showed that methanogenic hydrogen consumers and Methanosaeta harundinacea sp. were eliminated. Methanosaeta concilii, however, was not eliminated from the hydrogen‐producing system, which might explain, in part, the granulation phenomena in the anaerobic hydrogen fermentation system. The results also showed that Clostridium butyricum dominated the hydrogen‐production system. © 2009 American Institute of Chemical Engineers Environ Prog, 2009

Molecular monitoring of microbes in a continuous hydrogen-producing system with different hydraulic retention time

An anaerobic continuous-flow fermentation system with condensed molasses fermentation soluble (CMS) from monosodium glutamate production as substrate was developed for the biohydrogen production. The production rate of the system was increased, while hydraulic retention time (HRT) was varied from 12 to 3 h and the optimal hydrogen production rate was obtained at HRT 3 h. The major bacterial composition of each HRT was analyzed by 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE). Acidaminococcus sp. that could evolve hydrogen from glutamate was the only hydrogen producer and could be also detected from substrate. Hydrogenase mRNA-targeted reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed that except HRT 3 h, two clusters of clostridial hydrogenase gene sequences were obtained. RT-PCR-DGGE analysis was employed to illustrate the active clostridial strains confirming that clostridial strains were not present at HRT 3 h. Acidaminococcus sp. existing in substrate might be the major strain that contributes to hydrogen production at HRT 3 h.

Flow-FISH analysis and isolation of clostridial strains in an anaerobic semi-solid bio-hydrogen producing system by hydrogenase gene target

By using hydrogenase gene-targeted polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR), the predominant clostridial hydrogenase that may have contributed to biohydrogen production in an anaerobic semi-solid fermentation system has been monitored. The results revealed that a Clostridium pasteurianum-like hydrogenase gene sequence can be detected by both PCR and RT-PCR and suggested that the bacterial strain possessing this specific hydrogenase gene was dominant in hydrogenase activity and population. Whereas another Clostridium saccharobutylicum-like hydrogenase gene can be detected only by RT-PCR and suggest that the bacterial strain possessing this specific hydrogenase gene may be less dominant in population. In this study, hydrogenase gene-targeted fluorescence in situ hybridization (FISH) and flow cytometry analysis confirmed that only 6.6% of the total eubacterial cells in a hydrogen-producing culture were detected to express the C. saccharobutylicum-like hydrogenase, whereas the eubacteria that expressed the C. pasteurianum-like hydrogenase was 25.6%. A clostridial strain M1 possessing the identical nucleotide sequences of the C. saccharobutylicum-like hydrogenase gene was then isolated and identified as Clostridium butyricum based on 16S rRNA sequence. Comparing to the original inoculum with mixed microflora, either using C. butyricum M1 as the only inoculum or co-culturing with a Bacillus thermoamylovorans isolate will guarantee an effective and even better production of hydrogen from brewery yeast waste.

Molecular detection of the clostridia in an anaerobic biohydrogen fermentation system by hydrogenase mRNA-targeted reverse transcription-PCR

Molecular biological approaches were developed to monitor the potential biohydrogen-producing clostridia in an anaerobic semisolid fermentation system that used brewery yeast waste as the fermentation substrate. The denaturing gradient gel electrophoresis with 16S rDNA gene-targeted polymerase chain reaction (PCR) analysis was employed to confirm the existence of clostridia in the system. Remarkably, reproducible nucleotide sequences of clostridia were obtained from different hydrogen production stages by using hydrogenase gene-targeted reverse transcription (RT)-PCR. These RNA-based information suggested that the predominant hydrogen-producing strains possess either a specific Clostridium pasteurianum-like or a specific Clostridium saccharobutylicum-like hydrogenase sequence. Comparison of the hydrogenase gene-targeted sequence profiles between PCR and RT-PCR revealed that the specific C. pasteurianum-like hydrogenase harboring bacterial strains were dominant in both mRNA and bacterial population level. On the other hand, the specific C. saccharobutylicum-like hydrogenase harboring strains expressed high level of hydrogenase mRNA but may not be dominant in population. Furthermore, quantitative real-time RT-PCR analysis showed the expression pattern of the clostridial hydrogenase mRNA and may serve as an activity index for the system.

食品製造廃棄物の水素・メタン二段発酵システムによる電気・熱エネルギー変換に関する実鉦研究(バイオマス利用への機械工学的アプローチ-前処理技術から(バイオマス利用への機械工学的アプローチ-前処理技術から廃棄物発電まで-(1),バイオマス利用への着小合工学的アプローチ-前処理技術から廃棄物発電まで-)

Methane fermentation by the Upflow Anaerobic Sludge Blanket (UASB) system is extensively applied to treatment of brewery effluents. However, the UASB system is not suited to process solid sludge. Therefore, the feed solution requires a pretreatment to remove any suspended solid matter. This report introduces the hydrogen and methane two-stage anaerobic fermentation system, which produces hydrogen in the former stage and methane in the latter stage, for the purpose of effective treatment by energy conversion from food processing-wastes including solid waste. The hydrogen gas produced from this process will be able to use for a fuel cell, without any chemical converting. By the usual manner, the produced methane can be used as a boiler combustion gas. Therefore, this process will enable the simultaneous supply of electricity and heat. We conducted fermentation and power generation experiments using a bench pilot fermentor and a small-scale fuel cell, respectively. A comparison was made between the two-stage fermentation and the conventional methane single fermentation. The two-stage hydrogen and methane fermentation excelled the methane single fermentation in terms of energy balance.

Mixed culture fermentation studies on the effects of synbiotics on the human intestinal pathogens Campylobacter jejuni and Escherichia coli

Batch and continuous culture anaerobic fermentation systems, inoculated with human faeces, were utilised to investigate the antimicrobial actions of two probiotics, Lactobacillus plantarum 0407, combined with oligofructose and Bifidobacterium bifidum Bb12, combined with a mixture of oligofructose and xylo-oligosaccharides (50:50 w/w) against E. coli and Campylobacter jejuni. In batch fermenters, both E. coli and C. jejuni were inhibited by the synbiotics, even when the culture pH was maintained at around neutral. In continuous culture C. jejuni was inhibited but the synbiotic failed to inhibit E. coli. Although no definitive answer in addressing the mechanisms underlying antimicrobial activity was derived, results suggested that acetate and lactate directly were conferring antagonistic action, rather than as a result of lowering culture pH. In the course of the study culturing and fluorescent in situ hybridisation (FISH) methodologies for the enumeration of bacterial populations were compared. Bifidobacterial populations were underestimated using plating techniques, suggesting the non-culturability of certain bifidobacterial species.

Direct fermentation of gelatinized sago starch to acetone-butanol-ethanol by Clostridium acetobutylicum

Direct fermentation of gelatinized sago starch into solvent (acetone–butanol–ethanol) by Clostridium acetobutylicum P262 was studied using a 250 ml Schott bottle anaerobic fermentation system. Total solvent production from fermentation using 30 g sago starch/l (11.03g/l) was comparable to fermentation using corn starch and about 2-fold higher than fermentation using potato or tapioca starch. At the range of sago starch concentration investigated (10–80 g/l), the highest total solvent production (18.82 g/l) was obtained at 50 g/l. The use of a mixture of organic and inorganic nitrogen source (yeast extract + NH4NO3) enhanced growth of C. acetobutylicum, starch hydrolysis and solvent production (24.47 g/l) compared to the use of yeast extract alone. This gave the yield based on sugar consumed of 0.45 g/g. Result from this study also showed that the individual concentrations of nitrogen and carbon influenced solvent production to a greater extent than did carbon to nitrogen (C/N) ratio.

Anaerobic Gasification of Liquefied Okara

It is necessary to utilize Okara which is a byproduct of soybean processing. For this purpose, an anaerobic methane fermentation system is proposed to transform Okara to biogas which is used as recycling energy. In thisexperiment, a bench scale anaerobic contact process which is composed of CSTR's was experimentally used to treat the supernatant of liquefied Okara from the liquefaction reactors in the steady state. Four experimental runs with COD loading rates from 1980 to 3440 mg/L/d were conducted at 30 days of HRT. It was found that the gasification process worked and showed the VS removal ratio from 72 to 80 % as long as its pH was controlled within the range of neutrality. Obtained Vmax and Ks as apparent kinetic parameters based on the material balance and the growth model for the process were 0.55 mg-COD/mg-VSS/d and 5400 mg-COD/L respectively. They indicated that the phase separation of methane fermentation activated the microbial growth and the reactors required the improvement in the mixing method. The simulation based on the energy yields in this experiment revealed that the feasibility of the anaerobic methane fermentation system to produce the recycling energy from Okara would be best improved by increasing the VA yield for the liquefaction rather than trying to improve the methane yield for the gasification

Fecal short-chain fatty acids in patients with diarrhea-predominant irritable bowel syndrome: in vitro studies of carbohydrate fermentation.

Colonic bacterial production of short-chain fatty acids (SCFA) plays an important role in the salvage of unabsorbed carbohydrate and in colonic absorption of electrolytes and water. The objective of this study was to determine whether patients with diarrhea-predominant irritable bowel syndrome (DP-IBS) have a different pattern and rate of fermentation of carbohydrate and fiber to SCFA compared with controls. Fecal homogenates from 10 patients with DP-IBS and 10 age-matched controls were studied. SCFA were measured by gas chromatography in baseline fecal samples and in fecal homogenates in an in vitro anaerobic fermentation system after incubation with no additional substrate, lactulose, potato starch, citrus pectin, and hemicellulose over a 24-hour period. Net SCFA production rates were calculated for the first 6 h of the incubation period. Patients with DP-IBS had a consistently different pattern of less total SCFA, a lower percentage of acetate (p < 0.05), and a higher proportion of n-butyrate (p < 0.05) than controls. In stool homogenates from both controls and DP-IBS patients, lactulose fermentation resulted in the highest rate of SCFA production followed by pectin, starch, and hemicellulose. However, at all time points, the fecal homogenates from controls generated a higher concentration of total SCFA, acetate, and propionate with all substrates tested. SCFA production rates were higher in controls incubated with lactulose, starch, and hemicellulose. The fecal SCFA profile of patients with DP-IBS is characterized by lower concentrations of total SCFA, acetate, and propionate and a higher concentration and percentage of n-butyrate. Fecal flora from these patients produced less SCFA in an in vitro fermentation system in response to incubations with various carbohydrates and fibers. Differences in SCFA production by colonic bacterial flora in patients with DP-IBS may be related to the development of gastrointestinal symptoms.

Modelling struvite precipitation in anaerobic treatment systems

Struvite precipitation is common in waste water systems containing high concentrations of dissolved orthophosphates, free and saline ammonia and magnesium ions, such as in anaerobic fermentation systems, often leading to severe fouling. It appears that a reduction of the partial pressure of CO2, ie. pCO2 is a trigger mechanism for struvite precipitation. An algorithm was developed, based on equilibrium chemistry, to quantitatively predict the struvite precipitation potential of the water in such a process. This was then extended, to predict the change in state together with precipitation potential due to chemical perturbations, particularly variations of pCO2. Experimental verification of the algorithms is presented.