Organic Loading Rate Research Articles

Biological H2(g) Production and Modelling with Computational Fluid Dynamics (CFD)

In this study, bio-hydrogen gas [bio-H2(g)] production and modeling with a three-phase computational fluid dynamics (CFD) model, heat and mass transfer of bio-hydrogen production, reaction kinetics, and fluid dynamics; It was investigated by dark fermentation process in an anaerobic continuous plug flow reactor (ACPFR). The three-phase CFD model was used to determine the bio-H2(g) production in an ACPFR. The effect of different operating parameters, increasing hydrolic retention times (HRTs) (1, 2, 4, 8, and 12 days), different pH values (4.0, 5.0, 6.0, 7.0, and 8.0), and increasing feed rate as organic loading rates (OLRs) (0.5, 1.0, 2.0, 4.0, 8.0 and 10.0 g COD/l.d) on the bio-H2(g) production rates were operated in municipal sludge wastes (MSW) with Thermoanaerobacterium thermosaccharolyticum SP-H2 methane bacteria during dark fermentation for bio-H2(g) production. The effect of HRT, pH, and feed rate on the bioH2(g) efficiencies and H2(g) production rates were examined in the simulation stage. Production of volatile fatty acids (VFAs) namely, acetic acids, butyric acids, and propionic acids were important points influencing the bio-H2(g) production yields. The artificial neural network (ANN) model substrate inhibition on bio-H2(g) production to the methane (CH4) bacteria was also investigated. The reaction kinetics model used Thermotoga neapolitana microorganisms with the Andrews model of substrate inhibition. Furthermore, the ANN model was well-fitted to the experimental data to simulate the bio-H2(g) production from chemical oxygen demand (COD).

Predictive modeling based on artificial neural networks for membrane fouling in a large pilot-scale anaerobic membrane bioreactor for treating real municipal wastewater

Membrane fouling is the primary obstacle to applying anaerobic membrane bioreactors (AnMBRs) in municipal wastewater treatment. This issue holds critical significance as efficient wastewater treatment serves as a cornerstone for achieving environmental sustainability. This study uses machine learning to predict membrane fouling, taking advantage of rapid computational and algorithmic advances. Based on the 525-day operation data of a large pilot-scale AnMBR for treating real municipal wastewater, regression prediction was realized using multilayer perceptron (MLP) and long short-term memory (LSTM) artificial neural networks under substantial variations in operating conditions. The models involved employing the organic loading rate, suspended solids concentration, protein concentration in extracellular polymeric substance (EPSp), polysaccharide concentration in EPS (EPSc), reactor temperature, and flux as input features, and transmembrane pressure as the prediction target output. Hyperparameter optimization enhanced the regression prediction accuracies, and the rationality and utility of the MLP model for predicting large-scale AnMBR membrane fouling were confirmed at global and local levels of interpretability analysis. This work not only provides a methodological advance but also underscores the importance of merging environmental engineering with computational advancements to address pressing environmental challenges.

Study on the treatment of corn alcohol wastewater by the internal circulation anaerobic reactor.

To comprehensively assess the efficacy of employing the internal circulation (IC) anaerobic reactor for corn alcohol wastewater treatment and investigate its feasibility, this study focused on anaerobic digestion parameters, energy balance, and the composition of the prokaryotic microbial community. During the operation of the reactor, the hydraulic retention time was progressively reduced from 4.8 to 1.6 days while achieving an average organic loading rate of 12.46 kg chemical oxygen demand (COD)/(m3·d). Moreover, the removal rate of COD exceeded 98%, and the energy balance (ΔE) reached 10.29 kJ/g fed COD. The initial manifestation of organic acidosis in the reactor was a decline in gas production, which is primarily caused by propionic acid accumulation. The subsequent analysis revealed a high diversity of prokaryotes in granular sludge, with the predominant archaea primarily involved in methane production through the acetic acid pathway. The IC anaerobic reactor shows exceptional performance in treating corn alcohol wastewater by optimizing its operating conditions. Energy balance analysis confirmed the feasibility of the process. The findings of this study may offer valuable insights for optimizing control strategies and engineering applications.

Enhancing anaerobic digestion of dewatered sewage sludge through thermal hydrolysis pretreatment: Performance evaluation and microbial community analysis

This study explored the effectiveness of thermal hydrolysis (TH) in conditioning dewatered sewage sludge (DSS) for enhanced anaerobic digestion (AD). The TH pretreatment employed in this study (30 min at 170°C and 6 bar) significantly improved the bioavailability of DSS. The degree of solubilization varied with the physicochemical characteristics of DSS collected over three seasons: 16.8–24.8% on a volatile solids (VS) basis and 9.4–33.7% on a chemical oxygen demand (COD) basis. Correspondingly, the dissolved fraction of VS in DSS increased by 2.1–3.4-fold, and the soluble fraction of COD rose by 1.4–2.9-fold. The duplicate anaerobic reactors treating the TH-pretreated DSS did not achieve steady-state operation at the intended design organic loading rate (OLR) of 3.8 g VS/L·d, but showed stable performance at an OLR of 3.4 g VS/L·d with significantly higher methane yield (0.26–0.29 L/g VS fed) and VS removal (35–38%) than those reported for untreated DSS and comparable to TH-pretreated DSS. The reactors' microbial community structures changed dynamically as the OLR varied, with shifts in dominance between acetoclastic and hydrogenotrophic methanogens. The results highlight the promising potential of TH-AD process for efficiently treating DSS while emphasizing the importance of optimizing OLR for stable operation.

Response of antibiotic resistance genes expression and distribution on extracellular polymeric substances and microbial community in membrane biofilm during greywater treatment

This study evaluated how organic loading affects antibiotic resistance genes (ARGs) expression and distribution in the membrane biofilm. Organic surface loading rate of 4.65 g chemical oxygen demand (COD)/m2·d achieved the maximum biofilm thickness, concentration and linear alkylbenzene sulfonate (LAS) removal ratio of 136.9 ± 4.7 μm, 5.4 ± 0.1 g VSS/m2 and 99.4 %, respectively. Extracellular polymeric substances (EPS), EPS-attached LAS, and ARGs gradually increased in the membrane air inlet, middle and air outlet. AGRs and Intl1 were abundant in biofilm. LAS promoted EPS secretion, biofilm growth and ARGs proliferation. EPS, protein and carbohydrate were significantly correlated with most of biofilm ARGs, but not corrected with liquid-based ARGs. Microbial community structure impacted ARGs proliferation and transfer in the system. The findings indicated that EPS and microbial community play a crucial role in ARGs proliferation, spread and distribution, which lay the foundation for front-end control of ARGs during biofilm-based wastewater treatment.

Characteristics of the digestates from OFMSW methane production at psychrophilic, mesophilic, and thermophilic conditions under different organic loading rates

ABSTRACT The anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) has shown to be a viable alternative since it allows energy recovery in the form of methane and generates a residue (digestate) that can be applied effectively as a soil improver or fertiliser. The potential for methane production and the digestates’ characteristics depend on the substrate characteristics and the process variables such as temperature, solids retention time, and organic load. This study dealt with OFMSW anaerobic digestion under different organic loading rates and temperatures and the characteristics of the resulting digestates. Three semi-continuous reactors were operated at 20, 35, and 55°C and fed daily with ground, fresh OFMSW from Mexico City. The inoculum was temperature-adapted UASB granular sludge. The main results indicate that the anaerobic digestion was adequate, as the pH values were slightly alkaline, which is sufficient for methanization, and the alkalinity was not a limiting factor. Potassium and PO4-P increased with the organic load, and Kjeldahl nitrogen decreased. At 20°C, total organic carbon (TOC) increased substantially with the organic load; at 35°C, it remained without significant changes; and at 55°C, TOC slightly decreased with the organic load. The C/N ratio changed accordingly to TOC variations. At 20°C, the residual biogas potential increased with the organic load; at 35 and 55°C, it decreased with increasing organic load; the residual biogas potential increased with residual fatty acids concentrations. To comply with international standards for agricultural use, the digestates need only dewatering and supplementing with PO4-P.

Relationship between organic removal and power production in a dual-chamber microbial fuel cell with intermittent mode

Unoptimised simultaneous performance in microbial fuel cell (MFC) is still a big concern due to a lack of information on the correlation between organic removal and power production. Its correlation becomes more substantial owing to the main factors which affect a concurrent condition. To contribute new insight, this study aimed to analyze the relationship between the main factors for determining the optimal condition of MFC performance. Dual-chamber MFC (DCMFC) was designed by modifying the anode chamber into two compartments, namely double anode chamber DCMFC (DAC-DCMFC), operated within 8 days running with intermittent mode. The differences of organic loading rate (OLR), 0.4; 1.0; 2.5 kg.m−3.d−1 represented low to high organic loadings and electrode material-based reactor types, were used to assign the optimal concomitant performance in DCMFC. A closed circuit voltage (CCV) wiring system plugged onto the data logger within running time was employed to evaluate the synchronous achievement. This study result was medium OLR 1.0 kg.m−3.d−1, and GNPs anode-PTFE cathode attained optimally in the performance. In addition, higher OLR does not indicate higher organic removal correlating linearly with power production. This finding contributes to the limitation of organic loading that biological role capabilities can use.

Optimization of alkalinity supplementation in the AnSBBR using acidified cassava starch wastewater

In aiming to enhance performance and minimize costs, it is important to conduct research centered on the significance of alkalinity supplementation in anaerobic reactors. This study evaluated the impacts of alkalinity supplementation in the methane production, in a second-stage anaerobic sequencing batch biofilm reactor (AnSBBR) fed by acidified cassava wastewater. The AnSBBR was operated at 30 °C, cycle time (CT) of 8 and 6 h and sodium bicarbonate (gNaHCO3.gCOD[chemical oxygen demand]−1. L−1) of 1, 0.66, 0.33 and 0. The organic loading rate (OLR) were 17.1 and 22.8 gCOD.L−1d−1 for the CT of 8 and 6 h, in that order. The results showed that the reactor has been able to supply the alkalinity demand in the system, presenting removal of COD higher than 70%, even without alkalinity supplementation in the influent. The methane production rates (MPR) reached 3.42 ± 0.21 LCH4 L−1d−1 in the condition with 1 gNaHCO3.gCOD−1. L−1, with CT of 6 h. The main soluble metabolite was acetic acid and butyric acid. There was a decrease in methane production and greater instability in the reactor monitoring parameters without NaHCO3 supply. However, the degree of acidification was low, compared to the conversion of organic matter in all conditions. Thus, the AnSBBR maintained stable up to the ratio of 0.66 gNaHCO3.gCOD−1. L−1. Conditions with 1 gNaHCO3.gCOD−1. L−1. (CT 8 and 6 h) exhibited notable energy potential (≥90.2 KJ.d−1), underscoring their capacity for energy generation, even within shorter CT (6 h), thus rendering them suitable for application in industrial facilities.

Biohydrogen production from lactic acid: Use of food waste as substrate and evaluation of pretreated sludge and native microbial community as inoculum

Nowadays, lactic acid (HLa) has caught the eye as a precursor of H2 production from substrates that harbor a significant amount of lactic acid bacteria (LAB), such as Lactobacillus and Lactococcus. Since the native microbial community of food waste (FW) is dominated by LAB, the production of H2 during dark fermentation might be inhibited by the displacement of H2-producing bacteria by LAB. Therefore, lactate-driven dark fermentation in two steps is an alternative to overcome the overproliferation of LAB. In this process, FW is converted into HLa, which can subsequently be transformed into H2 by HLa-consuming bacteria during a cross-feeding mechanism with H2-producing bacteria. In the present study, FW was evaluated for HLa production at different organic loading rates (OLR) (12.5, 25.0, 37.5, and 50.0 gVS/L/d) in a semi-continuous reactor, and the HLa obtained was used for the H2 production. Results showed that OLR significantly influences HLa production during the self-fermentation of FW (p < 0.05). The highest ORL of 50.0 gVS/L/d and an HRT of 1.25 days generated the net maximum HLa production of 10.8 g/L. The HLa production was companied by the presence of acetate, propionate, and succinate, which accounted for only 20 % of the total organic acids produced. Then, effluent with HLa concentrations of 5.0, 10.0, 15.0, 20.0, and 25.0 g/L was evaluated for H2 production in batch tests using thermally pretreated sludge and the native microbial community of the effluent as inoculum. Even though different metabolic pathways for H2 production can be noted during the fermentation, which differs from one inoculum to another, the highest value of H2 production of 596.3 mL/Lreactor was obtained with the native microbial community at the highest concentration of HLa (25.0 g/L). During the fermentation process for H2 production, HLa and propionate were mainly transformed into butyrate and acetate. The present study demonstrated the feasibility of obtaining H2 from a complex substrate, such as effluent from a previous fermentation, using different inocula.

Application of full-scale aerobic granular sludge technology for removing nitrate from groundwater intended for human consumption

The dependence on groundwater for human consumption has increased worldwide in the last decades. Nitrate (NO3−) often reaches groundwater and causes significant degradation in groundwater quality. In an effort to address this issue, a full-scale water treatment plant using aerobic granular sludge (AGS) technology was built to remove NO3− from nitrate-polluted groundwater intended for human consumption in a rural village. The impact of changes in the operational conditions of hydraulic retention time (HRT) and organic matter loading (OML) rate on NO3− removal, overall system performance, and the granule microbiome were studied. Regardless of the HRT, the AGS technology was successful in removing NO3− with removal rates >50 % with an optimal OML rate of 75 mg L−1. No significant variations in the total abundance of any of the denitrification genes were observed. The composition of prokaryotic and eukaryotic communities was affected by changes in the HRT and OML rate. Specific prokaryotic taxa were identified as responsive to changes in operational parameters and their abundances were linked to the removal of NO3−, confirming that the microbes are critical to the NO3− removal process. This study demonstrates that the AGS technology can be successfully implemented to treat nitrate-polluted groundwater in rural villages to produce water of drinking quality. In addition, the reported hydraulic retention times and organic matter loading rate can be used to further improve the system performance to remove nitrate from groundwater.

Development of indigenous household kitchen waste biogas digester

ABSTRACT Large quantities of nutrition-rich food wastes reach dumpsites due to improper management. Anaerobic digestion (AD) has the potential to produce biogas from such wastes and reduce carbon footprint. The present study was aimed at developing an indigenous, user-friendly, compact digester to produce biogas from household kitchen waste (KW) in decentralized manner. A survey (1041 households) showed 0.5 kg/d KW generation per family. The mixed KW has average 0.08 g total solids (TS) and 0.048 g total volatile solids (VS). The study involved for the first time, a comparison of the efficacy of cow dung inoculum from rural/urban areas with different feeding bases. Ten each (30 L) rural (RCD)/urban (UCD) digesters (average 24kgVS/m3 feedstock concentration, FC; 0.8 kgVS/m3 organic loading rate, OLR) were run in AD cycle for 90d. RCD digesters produced 173–462 mL/gVS, while only four UCD digesters produced biogas (115–273 mL/gVS). Amongst various substrate-to-water ratios, 1:3 ratio gave the best biogas yield (352–384 mL/gVS). Scale-up parameters were calculated for designing 0.5/0.25 kg/d KW fed digester. The study is novel in reporting for the first time significant effect of inoculum source and developing compact indigenous biogas reactor for in situ management/utilization of KW to produce clean cooking fuel with scope for add-on controls.

Ultra-stable mixotrophic denitrification coupled with anammox under organic stress for mainstream municipal wastewater treatment

Sulfur-based autotrophic denitrification (SAD) coupled with anammox is a promising process for autotrophic nitrogen removal in view of the stable nitrite accumulation during SAD. In this study, a mixotrophic nitrogen removal system integrating SAD, anammox and heterotrophic denitrification was established in a single-stage reactor. The long-term nitrogen removal performance was investigated under the intervention of organic carbon sources in real municipal wastewater. With the shortening of hydraulic retention time, the nitrogen removal rate of the mixotrophic system dominated by the autotrophic subsystem reached 0.46 Kg N/m³/d at an organic loading rate of 0.57 Kg COD/m³/d, with COD and total nitrogen removal efficiencies of 82.5 % and 94 %, respectively, realizing an ideal combination of autotrophic and heterotrophic systems. The 15NO3−-N isotope labeling experiments indicated that thiosulfate-driven autotrophic denitrification was the main pathway for nitrite supply accounting for 80.6 %, while anammox exhibited strong competitiveness for nitrite under the dual electron supply of sulfur and organic carbon sources and contributed to 65.1 % of nitrogen removal. Sludge granulation created differential functional distributions in different forms of sludge, with SAD showing faster reaction rate as well as higher nitrite accumulation rate in floc sludge, while anammox was more active in granular sludge. Real-time quantitative PCR, RT-PCR and high-throughput sequencing results revealed a dynamically changing community composition at the gene and transcription levels. The decrease in heterotrophic denitrification bacteria abundance indicated the effectiveness of the operational strategy for introduction of thiosulfate and maintaining the dominance of SAD in denitrification process in suppressing the excessive growth of heterotrophic bacteria in the mixotrophic system. The high transcriptional expression of sulfur-oxidizing bacteria (SOB) (Thiobacillus and Sulfurimonas) and anammox bacteria (Candaditus_Brocadia and Candidatus_Kuenenia) played a crucial role in the stable nitrogen removal.

A Short Review on Dye-Wastewater Valorization Using Up-Flow Anaerobic Sludge Blanket Reactors

Dye-containing effluent generated in textile industries is polluting and complex wastewater. It should be managed adequately before its final destination. The up-flow anaerobic blanket (UASB) reactor application is an ecofriendly and cost-competitive treatment. The present study briefly reviews the UASB application for dye-containing wastewater valorization. Bioenergy and clean-water production potential during dye-containing wastewater treatment are emphasized to promote resource recovery in textile industries. Hydraulic retention time (HRT), organic loading rate (OLR), pH, temperature, and hydraulic mixing influence sludge granulation, microbial activity, and dye removal. HRT and OLR ranges of 6–24 h and 1–12 kg m−3 d−1 of chemical oxygen demand (COD) at a mesophilic temperature (30–40 °C) are recommended for efficient treatment. In these conditions, efficiencies of color and COD of 50–97% and 60–90% are reported in bench-scale UASB studies. Complex dye structures can hinder biomineralization. Pretreatment may be necessary to reduce dye concentration. Carbon-source and redox mediators are added to the UASB reactor to expedite kinetic reactions. A biogas yield of 1.48–2.70 L d−1 in UASB, which treats dye-containing effluents, is documented. Cotreatment of dye wastewater and locally available substrate could increase biogas productivity in UASB reactors. Organic waste generated in the textile industry, such as dye sludge, cotton, and starch, is recommended to make cotreatment cost competitive. Bioenergy production and water reuse allow environmental and economic benefits. Studies on combined systems integrating UASB and membrane processes, such as ultrafiltration and nanofiltration, for the production of reusable water and pretreatment of wastewater and sludge for improvements in biogas production might realize the complete potential for resource recovery of UASB technology. UASB bioenergy usage for integrated treatment trains can reduce operating costs and assist process sustainability in the textile industry.

A new efficient paradigm of energy and resource recovery from sewage: AnMBR treating chemically pre-precipitated concentrate in sidestream

Urged by the requirement for sustainable development, the recovery of energy and resources from sewage is imperative. In this study, a lab-scale anaerobic membrane bioreactor (AnMBR) treating chemically pre-concentrated real sewage with a high content of carbon, phosphorus, and iron in sidestream was established, and its performance at organic loading rate (OLR) varied from 0.67 to 2 g-COD/(L⋅d) was assessed comprehensively. When OLR ≤ 1.33 g-COD/(L⋅d), it achieved high COD removal (∼99 %), and around 60 % of the total influent COD was converted to methane (0.21 L-CH4/g-CODinf). Gaseous methane accounted for up to 95 % of the biogas. Only 1.5 % of yield methane was lost in permeate, far less than the dissolved methane in AnMBR treating sewage in mainstream. Considerable phosphorus (85 %-98 %) was retained in AnMBR. When OLR reached 2 g-COD/(L⋅d), the treatment performance was exacerbated with volatile fatty acids accumulation. The sludge flocs disintegrated with smaller particle sizes. The microbial community of mixed liquor shifted towards that of the pre-concentrated sewage. A specific relative abundance of Epsilonbacteraeota (a biomarker in this research) can be set as a warning of overloading. Compared with AnMBRs treating sewage in the mainstream, this sidestream AnMBR provided a new perspective and paradigm for treating sewage in an energy-efficient, resource-recovered, and low-carbon way.

Significant enhancement of biomethane recovery in up-flow anaerobic sludge blanket reactor treating starch wastewater through oyster shells conditioning

The up-flow anaerobic sludge blanket (UASB) reactor for treating starch wastewater exhibits poor resistance to organic loading rate shocks and low efficiency in biomethane recovery. This study proposed a solution to address this issue by using oyster shells as an alternative conditioner. Results indicated that the UASB reactor with oyster shells conditioning exhibited a significant increase in methane production from 243 to 435 mL/g-chemical oxygen demand (COD)removed, as the organic loading rate increased from 2.5 to 7.1 kg-COD/(m3·d). This value surpassed that of the control reactor, which experienced a sharp decline in performance. Furthermore, it also exceeded the majority of reported methane yields ranging from 150 to 330 mL/g-CODremoved. The pH adjustment and additional supply of carbon dioxide from oyster shells was primarily responsible for the substantial increase in methane production. Moreover, oyster shell conditioning also resulted in improvements in specific methanogenic activity, extracellular polymeric substances protection, and settling capacity of anaerobic granular sludge, as well as the enrichment in Methanosaeta abundance, and strengthening of methanogenic functional activity. All these factors contributed to the successful methanogenesis of starch wastewater in UASB reactor through oyster shell conditioning. These findings highlighted the potential of using oyster shells as a favorable conditioner for optimizing UASB treatment of easily acidified wastewater (e.g., starch wastewater), which presented promising practical applications.

Co-enhancing effects of zero valent iron and magnetite on anaerobic methanogenesis of food waste at transition temperature (45 °C) and various organic loading rates

Deoiling of food waste (FW) after hydrothermal pretreatment occurs at high temperatures, and more energy is required for substrate cooling before the anaerobic digestion (AD) process. AD at the transition temperature (for example 45 °C) is good for energy saving and carbon emission reducing when treating deoiling FW. However, the metabolic activity of methanogens must increase at the transition temperatures. This study proposes the use of zero-valent iron (Fe0) and magnetite (Fe3O4) to boost CH4 yield from deoiling FW. The results showed a co-enhancing effect on CH4 yield upgradation when using Fe0 and Fe3O4 simultaneously, and the highest CH4 yield reached 536.23 mLCH4/gVS, which was 67.5 % higher than that of Fe0 alone (320.14 mLCH4/gVS). In addition, a high organic loading was favorable for increasing the CH4 yield from deoiling FW. Microbial diversity analysis suggested that the dominant methanogenic pathway at 45 °C was hydrogenotrophic methanogenesis. Herein, a potential metabolic pathway analysis revealed that the co-enhancing effects of Fe0 and Fe3O4 enhanced syntrophic methanogenesis and possibly boosted electron transfer efficiency.

Solving the seasonality issue in sugarcane biorefineries: High-rate year-round methane production from fermented sulfate-free vinasse and molasses

Anaerobic digestion (AD) has been recently highlighted as the most efficient approach to manage vinasse in sugarcane biorefineries, providing both a renewable energy source (biogas) and a mineralized and nutrient-rich effluent suitable for agricultural use. However, the high sulfate concentrations (ca. 2 g L−1) present in vinasse and its seasonal availability (7–8 months) hinder the maximization of methane production in AD plants. This study investigated the use of sulfate-free vinasse (season) and molasses (off season), both pre-fermented in fermentative-sulfidogenic systems, as substrates to obtain enhanced year-round methane production in sugarcane biorefineries. Two second stage methanogenic structured-bed reactors operated at different temperatures (30 °C and 55 °C) were subjected to increasing organic loading rate (OLR) levels (1.0–20.0 kg COD m−3 d−1) in an experimental simulation of sequential periods of season, off season and season. An efficient start-up strategy enabled achieving operating stability in the full load project (10.0 kg COD m−3 d−1) in 37 d, which means anticipating the maximization of bioenergy production. Pre-fermenting vinasse and molasses was imperative for maintaining efficient organic matter conversion (80–90 %) into methane, regardless of the significant differences in lactate and phenols availability. A methane content in biogas ≥ 80 % and methane yield ≥ 330 NmL CH4 g−1COD were observed in both reactors, with no apparent observation of organic overloads. The results point towards a highly efficient strategy to maintain year-round high-rate biogas production from sugarcane vinasse, although the relatively high molasses demands can trigger an internal competition (with ethanol production) for substrate.

Co-digestion of solid-liquid waste from citrus agroindustrial: Effect of hydraulic retention time and organic loading rate on H2 production in a long-term continuous operation leach bed reactor

The Leach Bed Reactor (LBR) application is a promising alternative for the anaerobic digestion of solid waste and wastewater. In this study, the LBR was continuously operated for 160 days in four different phases, for co-fermentation of solid and liquid waste from the citrus agroindustry, at 37 °C, evaluating the effect of hydraulic retention time (HRT) and organic loading rate (OLR). The maximum volumetric hydrogen production (VHPR) was observed at an HRT of 12h (958.3 mLH2.L-1.d-1); however, the highest hydrogen yield (HY) was identified at an HRT of 24h (104.9 mLH2.g-1CHO). Based on the metabolic characteristics of microorganisms identified in higher relative abundance, by 16S rRNA sequencing, such as Lactobacillus, Caproicoproducens, Bifidobacterium, Olsenella, and Solobacterium, an occurrence of chain elongation pathways in the production of butyric and caproic acids was inferred, with hydrogen production resulting from the lactic acid oxidation. The maximum electricity production potential of 16.3 kWh.m-3 liquor was estimated.

Energy balance survey for the design and auto-thermal thermophilic aerobic digestion of algal-based membrane bioreactor for Landfill Leachate Treatment(under organic loading rates): Experimental and simulation-based ANN and NSGA-II

Although algal-based membrane bioreactors (AMBRs) have been demonstrated to be effective in treating wastewater (landfill leachate), there needs to be more research into the effectiveness of these systems. This study aims to determine whether AMBR is effective in treating landfill leachate with hydraulic retention times (HRTs) of 8, 12, 14, 16, 21, and 24 h to maximize AMBR's energy efficiency, microalgal biomass production, and removal efficiency using artificial neural network (ANN) models. Experimental results and simulations indicate that biomass production in bioreactors depends heavily on HRT. A decrease in HRT increases algal (Chlorella vulgaris) biomass productivity. Results also showed that 80% of chemical oxygen demand (COD) was removed from algal biomass by bioreactors. To determine the most efficient way to process the features as mentioned above, nondominated sorting genetic algorithm II (NSGA-II) techniques were applied. A mesophilic, suspended-thermophilic, and attached-thermophilic organic loading rate (OLR) of 1.28, 1.06, and 2 kg/m3/day was obtained for each method. Compared to suspended-thermophilic growth (3.43 kg/m3.day) and mesophilic growth (1.28 kg/m3.day), attached-thermophilic growth has a critical loading rate of 10.5 kg/m3.day. An energy audit and an assessment of the system's auto-thermality were performed at the end of the calculation using the Monod equation for biomass production rate (Y) and bacteria death constant (Kd). According to the results, a high removal level of COD (at least 4000 mg COD/liter) leads to auto-thermality.

Organic stabilization and methane production under different organic loading rates in UASB treating swine wastewater.

This study proposes the was to evaluate the stability and methane production with organic load differents in an upflow anaerobic sludge blanket reactor (UASB) treating swine wastewater by methods of multivariate analysis. Four organic loads were used with average hydraulic holding times of one day. The methods of data analysis of linear regression, Pearson correlation, principal component analysis and hierarchical clustering analysis were used for understanding stability and methane production in the reactor. The highest concentrations of bicarbonate alkalinity of 683 mgL-1 CaCO3 and total volatile acids of 1418 mgL-1 HAc with maximum organic loading applied were obtained. The optimal stability conditions occurred at an intermediate and partial alkalinity ratio between 0.24 and 0.25 observed in initial phases with a chemical oxygen demand (COD) removal of 47-57%. Maximum methane production was 9.0 L CH4 d-1 observed with linear regression positive and occurred at the highest applied organic load, corresponding to the highest COD removal efficiency and increased microbial biomass. Positive and negative correlation between functional stability in anaerobic digestion showed regular activity between acids, alkalinity and organic matter removal. This fact was also proven by the analysis of principal components that showed three components responsible for explaining 83.2% of the data variability, and the alkalinity, organic matter influent and organic acids had the greatest effects on the stability of the UASB reactor. Hierarchical clusters detected the formation of five groupings with a similarity of 50.1%, indicating that temperature and pH were variables with unitary influences on data dimensionality.