Anaerobic Stirred Tank Reactor Research Articles

Pengaruh Biomassa dan Waktu Fermentasi Mikroalga Alami dengan Penambahan Kotoran Sapi untuk Produksi Biogas

Biogas is one of the alternative energy sources that has become increasingly popular. Several studies have found that microalgae are effective in producing biogas. This research aims to explore the potential of natural microalgae as an alternative energy source for biogas production. The study was conducted by utilizing microalgae naturally present in bozzem water and drainage. The reactor used in this study is an Anaerobic stirred-tank reactor. The addition of cow manure is used as a supplementary substrate to enhance nutrient levels during the fermentation process. Various fermentation times and biomass concentrations were applied to determine the optimal reactor conditions for biogas production. Natural microalgae from the drainage and bozzem water have an impact on biogas production. The produced biogas was analyzed to determine CH4 (methane) and CO2 (carbon dioxide) concentrations. The best results in this study were obtained from drainage microalgae, which produced biogas with CH4 concentration of 50.17% and CO2 concentration of 40.14% at a biomass concentration of 40%. Meanwhile, bozzem microalgae produced biogas with CH4 concentration of 32.28% and CO2 concentration of 25.02% at a biomass concentration of 30%.

Microbial transformation of solid phase impacts quality of recovered water during consolidation of bioreactor-treated oil sands tailings

Tailings produced from surface-mined oil sands ores are retained in ponds on-site, pending water recovery for re-use and reclamation of solids. To enhance dewatering of tailings, we previously demonstrated that incubation of mature fine tailings (MFT) amended with an agricultural byproduct as a substrate in an anaerobic stirred tank reactor (STR) stimulated microbial activity and accelerated porewater expression (water recovery) and MFT consolidation by >50 %. Here, we report how microbial activity stimulated by STR treatment transformed MFT minerals and affected the quality of recovered porewater during subsequent MFT consolidation. STR treatment (methanogenesis) created strong reducing conditions with slight decrease in pH that induced transformation of the tailings solid phase. The concentrations of major ions (Ca2+, Mg2+, and HCO3−) increased in the recovered porewater presumably due to dissolution/precipitation of carbonate minerals. Iron (Fe) fractionation of solids revealed that FeIII-bearing minerals in STR-treated MFT were transformed into FeII minerals, predominantly amorphous in nature, such as iron sulfides (FeS). The concentrations of trace elements (V, As, Co, Ni, and Sr) also increased in the recovered porewater, potentially released from ionically-bound and strongly adsorbed fractions of metal(oid)s determined through sequential extraction. Zn, Cu and Cd were not detected in porewater after STR treatment; these metals might have precipitated as sulfide minerals. MFT biodensification is a promising approach for tailings management, however, the quality of recovered porewater warrants optimization of substrate and STR retention time. These results also inform environmental monitoring of submerged tailings reclamation sites, particularly end-pit lakes.

Accelerated consolidation of oil sands tailings using an anaerobic bioreactor

Bitumen extraction from oil sands ores generates enormous volumes of fluid tailings in on-site repositories where slow consolidation of suspended solids and porewater recovery hamper tailings reclamation. Here, we demonstrate proof-of-concept where mature fine tailings (MFT) amended with hydrolyzed canola meal incubated in an anaerobic stirred tank reactor (STR) for 8 weeks stimulated indigenous microbes and subsequently accelerated consolidation and porewater recovery in columns and methane (CH4) production in sealed microcosms. Compared to untreated MFT, 5 weeks of STR treatment enhanced consolidation (solids increased from 23.2 to 39.4 wt%) and expression of porewater (four-fold more porewater in one-third the time), and up to 30-fold more CH4. The microbial community shifted towards diverse fermentative taxa and different methanogens. This approach suggests a potential technology to reduce tailings pond volumes and increase water use efficiency, decreasing freshwater demand in the bitumen extraction process while converting low-value substrate to CH4 for on-site utilization.

Techno-economic assessment of anaerobic digestion in a typical Kraft pulp mill to produce biomethane for the road transport sector

Renewable waste-based fuels may decrease the resource use and environmental impact of the road transport sector; one of the options is biogas produced via anaerobic digestion of waste streams from pulp and paper mills. This paper describes process simulation and economic assessments for two options for integrating anaerobic digestion and production of liquid biogas in a typical Nordic Kraft pulp mill: (1) a high-rate anaerobic reactor in the wastewater treatment, and (2) an external anaerobic stirred tank reactor for the treatment of primary and secondary sludge as well as Kraft evaporator methanol condensate. The results revealed an annual production potential of 26–27 GWh biogas in an average Nordic Kraft pulp mill, which is equivalent to a daily production of 7600 L of diesel in terms of energy, and the production cost was estimated to €0.47–0.82 per litre diesel equivalent, comparable with the Swedish price of €0.68 per litre diesel.However, for the cases with liquid biogas (LBG), a discounted payback period of about 8 years may not be considered profitable by the industry. Other pre-requisites may, however, improve the profitability: a larger mill; production of compressed biogas instead of liquid biogas; or, for case 1, a comparison with the alternative cost for expanding the wastewater treatment capacity with more process equipment for activated sludge treatment. The results reveal that anaerobic digestion at pulp mills may both expand the production of renewable vehicle fuel but also enable increased efficiency and revenue at Kraft pulp mills.

Sulfate-reducing bacteria as new microorganisms for biological hydrogen production

Sulfate-reducing bacteria (SRB) have an extremely high hydrogenase activity and in natural habitats where sulfate is limited, produce hydrogen fermentatively. However, the production of hydrogen by these microorganisms has been poorly explored. In this study we investigated the potential of SRB for H2 production using the model organism Desulfovibrio vulgaris Hildenborough. Among the three substrates tested (lactate, formate and ethanol), the highest H2 production was observed from formate, with 320 mL L−1medium of H2 being produced, while 21 and 5 mL L−1medium were produced from lactate and ethanol, respectively. By optimizing reaction conditions such as initial pH, metal cofactors, substrate concentration and cell load, a production of 560 mL L−1medium of H2 was obtained in an anaerobic stirred tank reactor (ASTR). In addition, a high specific hydrogen production rate (4.2 L g−1dcw d−1; 7 mmol g−1dcw h−1) and 100% efficiency of substrate conversion were achieved. These results demonstrate for the first time the potential of sulfate reducing bacteria for H2 production from formate.

Evaluation of Kinetic Parameters for Bio Hydrogen Production by Anaerobic Suspended Growth Reactor Using Synthetic Feed and Up Scaling Anaerobic Suspended Growth Reactor Using Complex Feed

The objective of the present study is the Evaluation of Kinetic Parameters for hydrogen production by anaerobic suspended growth reactor using synthetic feed and Up scaling Anaerobic suspended growth reactor using complex feed. Hydrogen production through anaerobic fermentation of synthetic feed was then studied in an up flow suspended film batch reactor. Synthetic feed consists of specific concentrations of several nutrients required for anaerobic fermentation. The process parameters were set depending on the optimization studies. This process aimed at establishing hydrogen production in a 1 liter suspended reactor. Similar studies were performed in a suspended growth anaerobic system (stirred tank reactor) having an in-built turbine and operated by a magnetic stirrer. The hydrogen production was monitored and sequencing results were used to estimate the kinetic parameters of the reaction. The suspended growth anaerobic system was fed with optimized substrate. The reactor operation was monitored by monitoring the process parameters such as pH, ORP, VFA, etc. The anaerobic stirred tank reactor showed consistency in its results on feeding with the synthetic feed. This set of experiments aims at studying the variation of process parameters on using the optimized co-substrate and nitrogen source as the feed for the reactor. The complex feed containing sucrose and DAP for Up scaling Anaerobic suspended growth reactor.

Combined strategy for the precipitation of heavy metals and biodegradation of petroleum in industrial wastewaters

The precipitation of chromium(III), copper(II), manganese(II) and zinc(II) by biogenic hydrogen sulfide generated by sulfate-reducing bacteria, Desulfovibrio sp., and the degradation of total petroleum hydrocarbons (TPH) in the presence of heavy metal by Pseudomonas aeruginosa AT18 have been carried out. An anaerobic stirred tank reactor was used to generate hydrogen sulfide with Desulfovibrio sp. culture and the precipitation of more than 95% of each metal was achieved in 24 h (metal solutions contained: 60, 49, 50 and 80 mg L −1 of chromium, copper, manganese and zinc sulfates). A stirred tank reactor with P. aeruginosa AT18, in the presence of the heavy metal solution and 2% (v/v) of petroleum, led to the degradation of 60% of the total petroleum hydrocarbons and the removal of Cr(III) 99%, Cu(II) 93%, Zn(II) 46% and Mn(II) 88% in the medium through biosorption phenomena. These results enabled the development of an integrated system in which the two processes were combined. The overall aim of the study was achieved, with 84% of TPH degraded and all of the metals completely removed. Work is currently underway aimed at improving this system (decrease in operation time, culture of P. aeruginosa in anaerobic conditions) in an effort to apply this process in the bioremediation of natural media contaminated with heavy metals and petroleum.

Evaluation of the methanogenic step of a two-stage anaerobic digestion process of acidified olive mill solid residue from a previous hydrolytic–acidogenic step

A study of the second step or methanogenic stage of a two-stage anaerobic digestion process treating two-phase olive oil mill solid residue (OMSR) was conducted at mesophilic temperature (35 degrees C). The substrate fed to the methanogenic step was the effluent from a hydrolytic-acidogenic reactor operating at an organic loading rate (OLR) of 12.9 g chemical oxygen demand (COD) L(-1) d(-1) and at a hydraulic retention time (HRT) of 12.4 days; these OLR and HRT were found to be the best values to achieve the maximum total volatile fatty acid concentration (14.5 g L(-1) expressed as acetic acid) with a high concentration in acetic acid (57.5% of the total concentration) as the principal precursor of methane. The methanogenic stage was carried out in an anaerobic stirred tank reactor containing saponite as support media for the immobilization of microorganisms. OLRs of between 0.8 and 22.0 g COD L(-1) d(-1) were studied. These OLRs corresponded to HRTs of between 142.9 and 4.6 days. The methanogenic reactor operated with high stability for OLRs lower than 20.0 g COD L(-1) d(-1). This behaviour was shown by the total volatile fatty acids/total alkalinity ratio, whose values were always kept 0.12 for HRTs>4.6 days. The total COD (T-COD) removed was in the range of 94.3-61.3% and the volatile solids (VS) removed between 92.8% and 56.1% for OLRs between 0.8 and 20.0 g COD L(-1) d(-1). In the same way, a reduction of 43.8% was achieved for phenolic content. The low concentration of total volatile fatty acids (TVFA) observed (below 1 g L(-1) expressed as CH(3)COOH) in the methanogenic reactor effluents showed the high percentage of consumption and conversion of these acids to methane. A methane yield of 0.268+/-0.003 L CH(4) at standard temperature and pressure conditions (STP) g(-1) COD eliminated was achieved.