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This study investigated the integrated valorization of defatted rice bran (DRB) by converting it into lactic acid (LA) and subsequently utilizing the residues from LA production for biomethane generation through anaerobic digestion (AD). Processing 480 kg of DRB resulted in the production of 70 L of pure LA and generated significant waste streams, primarily consisting of 572 kg of decanted hydrolysate pellet (Pellet DEC) and 220 kg of microfiltration retentate (Retentate MF). Exceptionally high methane yields of 374‒434 LN kgVS-1 were observed for residues from LA fermentation in biochemical methane potential tests, indicating their high potential for biogas production. During long-term semi-continuous AD, varying organic loading rates (OLRs) from 0.5‒2.5 kgVS m-3 d⁻¹ demonstrated feedstock- and OLR-dependent methane production. Reactor failure at higher OLRs was attributed to the accumulation of total ammoniacal nitrogen (TAN). The co-digestion of Pellet DEC and Retentate MF proved to be more resilient, with OLRs up to 2 kgVS m-3 d-1, mitigating TAN inhibition. Methane yields, ranging from 265‒334 LN kgVS-1 before reaching inhibitory OLR levels, were higher than those found in the literature. Process integration has emerged as a promising approach because the biogas generated from residues could effectively offset the energy demands of LA production. Supported by life cycle assessment, the integrated processes showed a 67% lower environmental impact at the midpoint and a 71% lower environmental impact at the endpoint, along with an 80% reduction in energy costs compared to the standalone LA production. Results proved a significant enhancement of the sustainability and economic viability of this integrated biorefinery approach.

This study investigated the integrated valorization of defatted rice bran (DRB) by converting it into lactic acid (LA) and subsequently utilizing the residues from LA production for biomethane generation through anaerobic digestion (AD). Processing 480 kg of DRB resulted in the production of 70 L of pure LA and generated significant waste streams, primarily consisting of 572 kg of decanted hydrolysate pellet (Pellet DEC) and 220 kg of microfiltration retentate (Retentate MF). Exceptionally high methane yields of 374-434 LN kgVS -1 were observed for residues from LA fermentation in biochemical methane potential tests, indicating their high potential for biogas production. During long-term semi-continuous AD, varying organic loading rates (OLRs) from 0.5-2.5 kgVS m-3 d-1 demonstrated feedstock- and OLR-dependent methane production. Reactor failure at higher OLRs was attributed to the accumulation of total ammoniacal nitrogen (TAN). The co-digestion of Pellet DEC and Retentate MF proved to be more resilient, with OLRs up to 2 kgVS m-3 d-1, mitigating TAN inhibition. Methane yields, ranging from 265-334 LN kgVS-1 before reaching inhibitory OLR levels, were higher than those found in the literature. Process integration has emerged as a promising approach because the biogas generated from residues could effectively offset the energy demands of LA production. Supported by life cycle assessment, the integrated processes showed a 67% lower environmental impact at the midpoint and a 71% lower environmental impact at the endpoint, along with an 80% reduction in energy costs compared to the standalone LA production. Results proved a significant enhancement of the sustainability and economic viability of this integrated biorefinery approach. [ABSTRACT FROM AUTHOR]

Ammonium inhibition is a key limiting factor for anaerobic digestion when using chicken manure as the main substrate, especially in a digestion system with biogas slurry reflux. Air stripping is usually used as a recycled biogas slurry treatment. In this study, we carried out the anaerobic co-digestion of chicken manure and corn straw. The fermentation performance was investigated with and without air stripping at different biogas slurry reflux ratios and with an increasing organic loading rate. The results show that air stripping enhanced biogas production, system stability, and volatile solid removal efficiency via the mitigation control of ammonium inhibition. The total ammonium nitrogen in the digesters with air stripping was 20.24–46.40% lower than in those without air stripping. The highest specific biogas production and volatile solid removal efficiency values were obtained in the digesters at an organic loading rate of 3.3 g volatile solid (VS)/(L·d) and a reflux ratio of 75% with air stripping, reaching 480.43 mL/gVSadd and 63.36%, respectively. Moreover, air stripping also improved the organic loading rate and reflux ratio. Stable operation was achieved at an organic loading rate of 5.3 gVS/(L·d) and a reflux ratio of 75%, with specific biogas production of 392.35 mL/gVSadd and a volatile solid removal efficiency of 50.33%. The fermentation performance deteriorated when the organic loading rate was increased to 8.0 gVS/(L·d) at a reflux ratio of 75%, even when air stripping was conducted, indicating that a slighter lower reflux ratio (50%) could be more feasible at a higher organic loading rate (8.0 gVS/(L·d). Additionally, the methanogen community structure varied according to the use of air stripping, with a shift in the methanogenic pathway from hydrogenotrophic to acetoclastic methanogens. Overall, our findings support the adoption of air stripping for ammonium mitigation in anaerobic digestion with biogas slurry reflux. [ABSTRACT FROM AUTHOR]

Biogas upgrading via biomethanation has been extensively studied recently, but the influence of organic loading rate on process performance remains to be fully understood. This is particularly significant because both organic loading rate and hydrogen injection can lead to volatile fatty acid accumulation during anaerobic digestion. This study investigated the impact of a wide range of organic loading rates (from 1.25 to 3.25 g VS/L/d) on hydrogen consumption rates, organic acid accumulation, and microbial communities during in situ biomethanation. It also provided kinetics data and metabolite production data for different control reactors, including anaerobic digestion, ex situ biomethanation, and endogenous control reactors. Hydrogen was injected into parallel batch reactors using digestate from a semi-continuous lab-scale reactor subjected to increasing organic loading rates (1.25–3.25 g VS/L/d) as an inoculum. The inoculum was well adapted to each tested organic loading rate. The batch experiments were replicated following a 12 h hydrogen starvation period to assess the stability of hydrogen consumption rates. High organic loading rate values resulted in increased hydrogen consumption rates, peaking at 68 mg COD/L/h at an organic loading rate of 3.25 g VS/L/d (maximum value tested), with no significant organic acid accumulation despite the high hydrogen partial pressures. The hydrogen consumption rates were maintained after the starvation period. Furthermore, the addition of an organic substrate did not impact the hydrogen consumption rate (i.e., the in situ and ex situ rates were similar). A higher organic loading rate resulted in higher relative abundances of hydrogenotrophic methanogens (i.e., Methanospirillum sp.). This study highlights that increasing the organic loading rate can accelerate the rate of hydrogen consumption during in situ biomethanation, consequently reducing both capital and operational costs. [ABSTRACT FROM AUTHOR]

[Display omitted] • OLR of 2.5 g COD/L⋅d optimizes the methane yield of FW mono and co-digestion. • Accumulation of low biodegradable GPW reduces the methane yield in ACoD with FW. • ACoD of FW and PW enhances bacteria diversity, hydrolysis, and methane yield. • ACoD of FW and PW (2.5 g COD/L⋅d) shows synergistic effects (10 %) over FW digestion. • GPW hydrochar fulfills the ISO 17225-8 standard for industrial use as a solid fuel. The feasibility of anaerobic co-digestion in semicontinuous mode of two major urban biowaste, food waste (FW) and garden and park waste (GPW) (75 % FW and 25 % GPW) as well as the co-digestion of FW with the process water originated from the hydrothermal carbonization of GPW (95 % FW and 5 % process water), both on a COD basis, has been assessed. The effect of varying organic loading rate (OLR) from 1.5 to 3.5 g COD/L·d on methane yield, gross energy recovery, and microbiome population was evaluated. For comparison, anaerobic digestion of FW was also conducted to determine the best strategy for sustainable biowaste management. This study showed an optimal OLR of 2.5 g COD/L·d. Acetic and propionic acid content increased as OLR raised for each condition studied, while methane yield decreased at the highest OLR tested indicating overloading of the system. The anaerobic co-digestion of FW and process water showed a 10 % increase on methane production compared to anaerobic digestion of FW (324 vs. 294 mL CH 4 STP/L·d). Moreover, it enhances the process due to a greater abundance and diversity of hydrolytic and acidogenic bacteria belonging to Bacterioidota, Firmicutes, and Chloroflexi phyla, as well as promotes the hydrogenotrophic pathway under higher propionic concentrations which is not usually favoured for methane production. The integration of hydrothermal carbonization of GPW with the anaerobic co-digestion of 95 % FW and 5 % of process water results in the highest potential energy recovery and could be a good strategy for sustainable management of urban biowaste. [ABSTRACT FROM AUTHOR]

The use of aerobic granular sludge (AGS) for wastewater treatment has emerged as a promising biotechnology. A sodium alginate nucleus (SAN) incorporated into the AGS system can enhance aerobic granulation. Two important parameters influencing AGS formation and stability are the organic loading rate (OLR) and C/N ratio. In this study, AGS containing the SAN was cultivated under different OLR and C/N ratios. Through morphological analysis, physicochemical properties, and water quality analysis, the effects of the OLR and C/N ratio on the rapid formation and performance of AGS containing the SAN were investigated. The results showed that the most suitable OLR and C/N ratio in the SAN system were 1.4–2.4 kg/(m3∙d) and 10–15, respectively. A recovery experiment of sodium alginate (SA) showed that the group that formed AGS generally had a higher recovery efficiency compared with the group that did not form granular sludge. This work explored the suitable granulation conditions of AGS containing the SAN, and the results provide a theoretical basis for future practical applications. The recycling of SA as presented in this study may broaden the application prospects of SA. [ABSTRACT FROM AUTHOR]

The Anaerobic Baffled Reactor (ABR) is an effective solution for landfill leachate treatment using an anaerobic fermentation process, which helps to reduce operating costs and sludge volume. To better understand the biological, chemical, and physical processes involved, especially when combining the ABR with an aerobic component, the study aimed to investigate the performance of an Anaerobic–Aerobic Hybrid Baffled Reactor (AABR) that includes an Anaerobic Filter (AF) for treating landfill leachate. This research utilized two glass reactors. The first reactor, designated as AABR-AF, consisted of six independent rectangular glass chambers arranged side by side. The third and sixth chamber designed for aerobic treatment and AF, respectively. The second reactor was used as a control reactor and did not include any aerobic chamber. The highest Removal Efficiencies (REs) for turbidity, COD, BOD, TP, TKN, nitrate, TOC, and TSS in the AABR-AF and ABR-AF were found to be (65.4% and 56.3%), (98.3% and 94.1%), (98.1% and 93.2%), (86.4% and 65%), (89.2% and 76.7%), (81.2% and 64.4%), (88.2% and 79.4%), and (72.4% and 68.5%), respectively. These optimal REs were achieved at an HRT of 48 h and an OLR of 10 kg/m3.d. Also, the highest and the lowest REs in Heavy Metals (HMs) were 89.57% for manganese in AABR-AF and 6.59% for nickel in ABR-AF, in an OLR of 10 kg/m3.d, respectively. The effective removal of Organic Matters (OMs) from landfill leachate using the AABR-AF and ABR-AF was found to be strongly influenced by HRT and OLR. The AABR-AF configuration, featuring a single aerobic chamber in the reactor, exhibited a higher efficiency in removing OMs compared to the ABR-AF configuration. [ABSTRACT FROM AUTHOR]

Despite its numerous advantages, the aerobic granular sludge (AGS) process faces several challenges that hinder its widespread implementation. One such challenge is the requirement for high organic load ratios (OLR), which significantly impacts AGS formation and stability, posing a barrier to commercialization. In response to these challenges, this study investigates the granulation and treatment efficacy of the AGS process for treating high-concentration wastewater under various OLR and settling time. Three sequential batch reactors (R1, R2, R3) were operated at OLRs of 0.167, 0.33, and 1 kg COD/m3·day. The study focuses on analyzing key parameters including sludge characteristics, extracellular polymeric substances (EPS) content, PN/PS ratio, and microbial clusters. Results demonstrate that reducing settling time from 90 to 30 min enhances sludge settleability, resulting in a maximum 50.8 % decrease in SVI30 (from 98.1 to 122.8 mL/g to 51.9–81.3 mL/g), thereby facilitating the selection of beneficial microorganisms during granulation. Particularly, at R2, the PN/PS ratio was 4.3, and EPS content increased by 1.52-fold, leading to a 1.41-fold increase in sludge attachment. This observation suggests a progressive maturation of AGS. Additionally, analysis of microbial diversity and cluster composition highlights the influence of OLR variations on the ratios of Proteobacteria and Bacteroidetes. These findings emphasize the significant impact of SBR operational strategies on AGS process performance and biological stability, offering valuable insights for the efficient operation of future high-concentration wastewater treatment processes.

Biorefining biological waste to produce eco-friendly fuels and by-products is essential in transitioning from non-renewable energies. However, the analysis of the processes in the laboratory necessitates a substantial investment of both time and money. The present study has developed machine learning (ML) models for evaluating biofuel products through glycerol biorefining for the first time. This study evaluates the performance of different ML algorithms, including recurrent neural network (RNN), random forest (RF), adaptive boosting (AdaBoost), Bayesian ridge (BR), and elastic net linear regression (ENLR). This research by machine learning algorithms can be created the formulas and the models for the hydrogen content (H 2) by the hydrogen production and time, the hydrogen production by the H 2 and time, OLR by PH and time, OLR by the hydrogen production and time, and the hydrogen production by OLR and time. Using the RNN for predicting the future of H 2 , hydrogen production, and OLR with the least error. The best R-Squared for the formulas is between 0.951 and 0.994 with the linear and the polynomial forms (by degrees 2, 3, 4). The best R-Squared for the models is between 0.998 and 0.999 with the linear form. MAEs for the formula and the model of H 2, respectively, are 2.475347126 and 0.46588143, and MAEs for the formula and the model of the hydrogen production, respectively, are 23.44120285 and 7.03283978. MAEs of OLR by PH and OLR by the hydrogen production for formulas and models are 2.095157 and 000001 by PH and 3.148667 and 0.000001 by the hydrogen production. MAEs for the formula and the model of the hydrogen production by OLR, respectively, are 19.025255 and 2.718604. • Development of machine learning models for evaluating biofuel products through glycerol biorefining. • Evaluation of different ML algorithms in predicting hydrogen production, H 2 content, and organic loading rate in the biorefining process. • Creation of formulas and models for H 2 content, hydrogen production, and OLR by various factors. • Use of RNN for predicting the future of H 2 content, hydrogen production, and OLR with the least error. • Best R-Squared for the models is between 0.998 and 0.999 with the linear form. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is a polymer with a vast industrial application range and can be co-produced as a minor by-product during the biological production of polyhydroxyalkanoates (PHA). However, the influence of key parameters as tools for favouring the production of LA over PHA is still unclear. In this study, we investigated how several critical operational conditions, i.e., carbon-nitrogen ratio (C/N), organic loading rate (OLR) and airflow, can be optimised to favour LA accumulation over PHA production by a mixed microbial culture (MMC), using synthetic grape pomace (GP) hydrolysate as the substrate. The results showed that it was possible to direct the MMC towards LA accumulation instead of PHA. The maximum LA yield was 2.7 ± 0.2 g LA/(L·d) using a C/N of 35, an airflow of 5 L/min and an OLR of 4 g sCOD/(L·d). The OLR and, to a lesser extent, the C/N ratio were the main factors significantly and positively correlated with the biological synthesis of LA.

Wine production generates a high volume of wastewater with a significant fraction of biodegradable organic matter that must be removed before safe release into surface waters. Aerobic sequencing batch reactors (SBRs) have been successfully applied in the treatment of a wide range of wastewaters. However, only a few studies have described the use of the SBR process for the treatment of winery wastewater (WW). The effectiveness of using an aerobic SBR process was investigated for the treatment of WW using two activated sludge concentrations (i.e., 2 and 4 gVSS L−1) and nutrient-supplemented conditions. In nutrient-deficient conditions, COD removal efficiencies varied between 70% and 97% depending on the organic loading rate (OLR). In nutrient-supplemented assays, COD removal efficiencies remained above 91% in all conditions tested. However, the effluent quality decreased due to the increase in the total suspended solids concentration. Furthermore, the COD concentration of the treated effluent was unable to meet legal requirements (<0.150 g L−1) for safe wastewater discharge. Therefore, longer aeration periods and settling phases may be required in order to improve effluent quality under high organic loadings. Overall, these findings demonstrate the potential of SBR as a biological WW treatment process. [ABSTRACT FROM AUTHOR]

This study deals with the computational analysis of the kinetic processes of microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) for treating raw-waste-activated sludge (WAS), compared to conventional AD, as well as investigating the effect of the organic loading rate (OLR) on the system's performance. The aim was to derive a mathematical model for the study of MEC-AD using the ADM1 framework, which can be utilized to extract the effect of an applied potential on the kinetics of AD. The experimental data were obtained from the operation of two identical reactors (an AD reactor and an MEC-AD reactor), which were operated at different OLRs. The kinetic parameters extracted from the ADM1 showed that the MEC-AD reactor yielded improved biomass yields, substrate consumption, and first-order disintegration rates, with a predominant contribution to the disintegration of complex particulates, which increased fourfold compared to the AD reactor. Moreover, it enabled operation at higher OLRs (achieving the highest divergence from the AD reactor at the OLR of 4.14 gCOD/(L × d)), therefore accelerating WAS treatment, as well as showing an improved performance at increased solids retention time (SRT). The ADM1 exhibited efficient adaptability and predictability of the kinetic processes and can be effectively used for the optimization of the MEC-AD operation. [ABSTRACT FROM AUTHOR]

Sub-moderate temperature (ranging from low to moderate temperature) anaerobic digestion (AD) could balance fermentation efficiency and energy input. We investigated biogas production and the microbial community in wastewater AD at sub-moderate (15 °C, 20 °C, and 25 °C) and moderate (35 °C; control group) temperatures with the organic loading rate (OLR) incrementally increased over 200 days. The impact of temperature on biogas production was found to be minimal at a low OLR but became more significant at a high OLR. Notably, a temperature threshold ranging from 15 °C to 20 °C exerted a strong inhibitory effect on biogas production and disrupted the microbial community. And, SMT-AD is deemed by this study to be the optimal application strategy of wastewater with low temperature and low OLR. Bacterial richness was positively and linearly related to temperature. There is a relevance between methane production and archaeal diversity under the influence of temperature and OLR. Temperature and OLR shaped the ecological function of predominant bacteria. Anaerolineales, Thermotogales, and Lactobacillales were strongly influenced by temperature. Synergistales had a synergistic relationship with Desulfovibrionales. Clostridiales was responsible for acetate and butyrate production and closely related to Lactobacillales. Acetoclastic Methanosaetaceae was the predominant methanogen. Methanogens could survive and maintain their population even though methanogenesis was limited under high OLRs and low temperatures. [ABSTRACT FROM AUTHOR]

Introduction and purpose: One of the water resource management strategies is to accurately determine the per capita water consumption in various sectors, especially the drinking and sanitary sector. Therefore, the present study aimed to determine the per capita water consumption by field calculation and data collection from District 4 of Tehran subscribers who supply their water from the distribution network covered by the water and sewage company. In addition, the per capita wastewater production and the amount of biodegradable organic matter were estimated. Methods: In this study, the statistical population was the subscribers of Water and Wastewater Company, District 4 of Tehran, with 108603 subscribers from 2018-2020. Residential per capita water use is calculated by dividing the total volume of water sold to residential accounts by the number of people being served. The cost per water was calculated using the water tariff and the price per cubic meter of water. Results: Per capita water consumption for 2018, 2019, and 2020 were 172.33, 131, and 117.33 L/pd, respectively. The maximum and minimum per capita water consumption were obtained in May and April 2019, respectively (2576218 m3/month.S VS 677246 m3/month.S). In addition, the cost per water (in Rial/m3.month) for 2018, 2019, and 2020 were calculated as 145675, 164520 and 223944 respectively. Conclusion: The results demonstrated that the highest rate of water consumption and wastewater production pertained to April and May. As the cost of water consumption showed, it can be concluded that water prices are not an effective tool to reduce water consumption.

Biogas upgrading via biomethanation has been extensively studied recently, but the influence of organic loading rate on process performance remains to be fully understood. This is particularly significant because both organic loading rate and hydrogen injection can lead to volatile fatty acid accumulation during anaerobic digestion. This study investigated the impact of a wide range of organic loading rates (from 1.25 to 3.25 g VS/L/d) on hydrogen consumption rates, organic acid accumulation, and microbial communities during in situ biomethanation. It also provided kinetics data and metabolite production data for different control reactors, including anaerobic digestion, ex situ biomethanation, and endogenous control reactors. Hydrogen was injected into parallel batch reactors using digestate from a semi-continuous lab-scale reactor subjected to increasing organic loading rates (1.25–3.25 g VS/L/d) as an inoculum. The inoculum was well adapted to each tested organic loading rate. The batch experiments were replicated following a 12 h hydrogen starvation period to assess the stability of hydrogen consumption rates. High organic loading rate values resulted in increased hydrogen consumption rates, peaking at 68 mg COD/L/h at an organic loading rate of 3.25 g VS/L/d (maximum value tested), with no significant organic acid accumulation despite the high hydrogen partial pressures. The hydrogen consumption rates were maintained after the starvation period. Furthermore, the addition of an organic substrate did not impact the hydrogen consumption rate (i.e., the in situ and ex situ rates were similar). A higher organic loading rate resulted in higher relative abundances of hydrogenotrophic methanogens (i.e., Methanospirillum sp.). This study highlights that increasing the organic loading rate can accelerate the rate of hydrogen consumption during in situ biomethanation, consequently reducing both capital and operational costs.

Biological conversion of date wastes under continuous conditions is a challenge due to their high content of biodegradable organic matter. In this study, hydrogen (H 2) and methane (CH 4) production in a two-stage process to increase the energy recovery from date pulp wastes (DPW) was investigated. In the first stage, the effect of increasing organic leading rate (OLR) on dark fermentation (DF) performances was evaluated in a semi continuously stirred tank reactors (SCSTR) without nutrients addition. The highest volumetric H 2 production rate (VHPR) and specific H 2 yield (SHY) of 0.76 L/L.d and 81 LH 2 /kg volatile solid (VS), respectively were achieved at high OLR of 11.74 gVS/L.d. In the second stage, the DF effluent was used as substrate to feed the SCSTR of anaerobic digestion (AD). The highest volumetric methane production rate (VMPR) of 2.92 L/L.d was achieved with a high OLR (4.25 gVS/L.d) and short hydraulic retention time (HRT, 8 days), producing specific methane yield (SMY) of 530 LCH 4 /kgVS. Thus, the two-stage process can be an effective strategy for high rate renewable energy recovery (13 kJ/gVS inlet) and organic waste processing. [Display omitted] • Two-stage hydrogen and methane production from date pulp wastes (DPW). • Increasing organic loading rate improved biogas production. • Optimum DPW loading rate was 11.74 gVS/L.d for H 2 production. • High CH 4 yield of 530 LCH 4 /kgVS was achieved at OLR of 4.25 gVS/L.d. • High rate bioenergy recovery (13 kJ/g VS inlet) from two stage process. [ABSTRACT FROM AUTHOR]

Tunisia is one of the developing countries which faces crucial challenges, the most prominent of which are the production of organic waste, the need for an appropriate waste treatment, and the demand for water and energy conservation. To this end, the present research was designed to develop a technical concept on closed cycle "biowaste to bioenergy" treating food waste (FW) through combined biological processes. In this approach, semi-continuous anaerobic co-digestion (ACoD) of FW, wheat straw (WS), and cattle manure (CM) was tested to investigate the relationship between the effect of the feedstock mixtures and C:N ratio on biogas and digestate generation at different organic loading rates (OLRs) ranging from 2 to 3.6 kg VS/m3.d. Results showed that the mono-digested FW was optimal and reached 565.5 LN/kg VSin at an OLR of 2.4 kg VS/m3.d, and then a drop of biogas production was recorded. However, for co-digested substrates, the optimum mixture ratio was FW:CM 75:25, where 62%, 39.89%, 91.26%, 130.9%, and 119.97% of the biogas yield improved for OLRs ranging from 2 to 3.6 kg VS/m3.d, respectively. Admittedly, the target of this work was to enhance the ACoD process, but it also examined the exploitation of different AD effluents. Therefore, special attention was paid to the generated digestates to decide how it can be efficiently upcycled later. Thus, the closed cycle "biowaste to bioenergy" treatment met two of the major Tunisian concerns: efficient organic waste management and sustainable bioenergy production. [ABSTRACT FROM AUTHOR]

Performance of an anaerobic moving bed biofilm reactor (AnMBBR) was evaluated for pretreatment of real textile desizing wastewater at organic loading rate (OLR) of 1±0.05 to 6.3±0.37 kgCOD/m3/d. After OLR optimization, the performance of AnMBBR was evaluated for biodegradation of reactive dyes. AnMBBR was operated under a mesophilic temperature range of 30 to 36 °C, while the oxidation-reduction potential (ORP) and pH were in the range of 504 to 594 (-mV) and 6.98 to 7.28, respectively. By increasing the OLR from 1±0.05 to 6.3±0.37 kgCOD/m3/d, COD and BOD5 removal was decreased from 84 to 39% and 89 to 49%, respectively. While the production of biogas was increased from 0.12 to 0.83 L/L·d up to an optimum OLR of 4.9±0.43 kgCOD/m3/d. With increase in the dye concentration in the feed, COD, BOD5, color removal and biogas production reduced from 56, 63, 70% and 0.65 L/L·d to 34, 43, 41% and 0.08 L/L·d, respectively. Based on the data obtained, a cost-benefit analysis of AnMBBR was also investigated for the pretreatment of real textile desizing wastewater. Cost estimation of anaerobic pretreatment of textile desizing wastewater indicated a net profit of 21.09 million PKR/yr (114,000 €/yr) and a potential payback period of 2.54 years. [ABSTRACT FROM AUTHOR]

In a two-phase anaerobic digestion process, enhanced biogas production and organic pollutant removal depend on the stability and performance of the hydrolytic–acidogenic and methanogenic phases. Additionally, the hydrolytic–acidogenic phase is a rate-limiting step, which calls for the further optimization of operating parameters. The objective of this study was to optimize the operating parameters of the hydrolytic–acidogenic reactor (HR) in the two-phase anaerobic digestion treating slaughterhouse wastewater. The experiment was carried using bench-scale sequential bioreactors. The hydrolytic–acidogenic reactor operating parameters were optimized for six different hydraulic retention times (HRTs) (6–1 day) and organic loading rates (OLRs) (894.41 ± 32.56–5366.43 ± 83.80 mg COD/L*day). The degree of hydrolysis and acidification were mainly influenced by lower HRT (higher OLR), and the highest values of hydrolysis and acidification were 63.92% and 53.26% at an HRT of 3 days, respectively. The findings indicated that, at steady state, the concentrations of soluble chemical oxygen demand (SCOD) and total volatile fatty acids (TVFAs) decrease as HRT decreases and OLR increases from HRTs of 3 to 1 day and 894.41–1788.81 mg COD/L*day, respectively, and increase as the HRT decreases from 6 to 4 days. The concentration of NH4+-N ranges from 278.67 to 369.46 mg/L, which is not in the range that disturbs the performance and stability of the hydrolytic acidogenic reactor. It was concluded that an HRT of 3 days and an ORL of 1788.81 mg COD/L*day were selected as optimal operating conditions for the high performance and stability of the two-phase anaerobic digestion of slaughterhouse wastewater in the hydrolytic–acidogenic reactor at a mesophilic temperature. The findings of this study can be applicable for other agro-process industry wastewater types with similar characteristics and biowaste for value addition and sustainable biowaste management and safe discharge. [ABSTRACT FROM AUTHOR]

Mustard tuber wastewater (MTW) is an ultra-hypersaline high-strength acid organic wastewater. Aerobic granular sludge (AGS) has been demonstrated to have high tolerance to high organic loading rate (OLR), high salinity, and broad pH ranges. However, most studies were conducted under single stress, and the performance of AGS under multiple stresses (high salinity, high OLR, and low pH) was still unclear. Herein, mature AGS was used to try to treat the real MTW at 9% salinity, pH of 4.1–6.7, and OLR of 1.8–7.2 kg COD/m3·d. The OLR was increased, and the results showed that the upper OLR boundary of AGS was 5.4 kg COD/m3·d (pH of 4.2) with relatively compact structure and high removal of TOC (~93.1%), NH4+-N (~88.2%), and TP (~50.6%). Under 7.2 kg COD/m3·d (pH of 4.1), most of the AGS was fragmented, primarily due to the multiple stresses. 16S rRNA sequencing indicated that Halomonas dominated the reactor during the whole process with the presence of unclassified-f-Flavobacteriaceae, Aequorivita, Paracoccus, Bradymonas, and Cryomorpha, which played key roles in the removal of TOC, nitrogen, and phosphorus. This study investigated the performance of AGS under multiple stresses, and also brought a new route for highly-efficient simultaneous nitrification–denitrifying phosphorus removal of real MTW. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuels coupled with stringent environmental laws has encouraged us to develop sustainable renewable energy. Due to its numerous benefits, anaerobic digestion (AD) has emerged as an environment-friendly technology. Biogas generated during AD is primarily a mixture of CH4 (65–70%) and CO2 (20–25%) and a potent energy source that can combat the energy crisis in today's world. Here, an attempt has been made to provide a broad understanding of AD and delineate the effect of various operational parameters influencing AD. The characteristics of fruit and vegetable waste (FVW) and its feasibility as a potent substrate for AD have been studied. This review also covers traditional challenges in managing FVW via AD, the implementation of various bioreactor systems to manage large amounts of organic waste and their operational boundaries, microbial consortia involved in each phase of digestion, and various strategies to increase biogas production. [ABSTRACT FROM AUTHOR]

Highly nutrient content dead fish (DF) waste can be considered a potentially valuable substrate for the anaerobic digestion (AD) to produce biogas. The effects of stepwise increased organic loading rate (OLR) on the process performance were investigated during mono-digestion of DF waste in anaerobic sequencing batch reactor mode. Two different sets of experiments have been conducted using whole dead fish (RDF) and boneless dead fish (RBDF) and OLR increased in five steps (1.95, 2.39, 2.73, 3.19, and 3.64 g VS/L/days) during the operational period. With the increasing of OLR, the biogas production rate increased by 79.07% and 58.20% at the end of the operation of RDF and RBDF, respectively. Higher alkalinity values throughout the experiment maintained stable pH values in between 7.87 to 8.01 for both RDF and RBDF. Total volatile fatty acids kept accumulating with the increasing OLR and the final concentrations were 7.69 ± 0.16 and 8.33 ± 0.19 g/L in RDF and RBDF, respectively. Overall, decreasing COD and VS removal efficiencies resulted in decreasing methane yields. The energy recovery rate was maintained at > 60% with the maximum OLR of 3.64 g VS/L/d of DF waste demonstrating its feasibility in the AD process as the only carbon source. [ABSTRACT FROM AUTHOR]

A lab-scale up-flow anaerobic sludge blanket (UASB) reactor was used for biogas production from the citrus juice process wastewater (CPWW). The volume of the reactor was 11.5 L. During 200 days of the reactor, the organic loading rate (OLR) value changed from 1.8-21.9 kgCOD./m3.d, upflow velocities (Vup) 0.1-5.2 m/h and hydraulic retention time (HRT) changed from 0.042 to 4.16 days. The reactor showed a stable performance at all organic loadings. Experimental chemical oxygen demand (COD) removal efficiencies were 71.5±21% and 83.3±16.3% for total COD (TCOD) and soluble COD (SCOD), respectively. The acetic acid concentration changed from 135 to 650 mg/L. The temperature was kept in the range of 35.1±1.4 oC, the pH in the range of 6.6±0.2, and the alkalinity was controlled daily and kept in the range of 411±273 CaCO3 mg/L. After anaerobic reactions, 6283±3476 m3/d biogas was produced and the methane concentration in the biogas was 65.5±11.5%. Depending on the methane production, the annual energy value potential that can be obtained from the existing UASB reactor is estimated as 48,768 kWh. [ABSTRACT FROM AUTHOR]

BACKGROUND: Food waste (FW) and waste activated sludge (WAS) are complementary substrates that improve H2 production by dark fermentation. However, there is little experience in the process performance in the long‐term operation of reactors co‐processing FW–WAS. This study aims to determine the optimal FW–WAS ratio in batch H2 production and then feed this FW–WAS ratio to an anaerobic sequencing batch reactor (SBR) to evaluate the influence of three organic loading rates (OLR) – 15, 22 and 45 g volatile solids (VS) L−1 d−1 – on H2 performance and microbial composition. RESULTS: Batch tests showed that the FW–WAS ratio of 90–10 increased 22% of the H2 production compared to the individual FW. In the SBR operation, the OLR significantly influenced H2 performance, reaching the highest productivity of 733 ± 282 mL H2 L−1 d−1 at an OLR of 22 g VS L−1 d−1. The cooperative lactic acid cross‐feeding between Olsenella and Megasphaera resulted in the highest H2 productivity at an OLR of 22 g VS L−1 d−1. OLR promoted the prevalence of different taxa of hydrolytic bacteria, where Enterococcus and Veillonella were positively correlated, with the highest substrate hydrolysis of 50% at an OLR of 15 g VS L−1 d−1. Prevotella, a genus with a wide spectrum of hydrolytic enzymes, was predominant in the SBR operation regardless of the OLR. CONCLUSION: The SBR operation at OLR of 22 g VS L−1 d−1 improved H2 production by applying a 90–10 FW–WAS ratio. The change in OLR promoted different taxa of hydrolytic species in the SBR; however, Prevotella spp. prevailed at the three OLRs. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

This article aims to examine the performance of an aerobic sequential batch reactor in treating real textile wastewater under various hydraulic retention times. The proposed system was operated under various hydraulic retention times, and their effects on the removal efficiency of chemical oxygen demand, color, aromatic amines, and organic compounds from the woolen textile wastewater industry were investigated. The initial concentration of chemical oxygen demand and color was 1000 mg/L and 1000 American Dye Manufacturer's Institute, respectively. Aerobic sequential batch reactor application showed that chemical oxygen demand removal was almost between 86.6 and 90.1% with a slight increase of 4% when the hydraulic retention times were increased from 12 to 48 h, while the color removal was ranged from 62.44 to 77.78% when the hydraulic retention time varied between 12 and 48 h. Chromatographic analysis indicated that aromatic amines are biodegradable under aerobic conditions; simultaneously, the accumulation of aromatic amines on sludge increased by decreasing hydraulic retention times. Moreover, the GC–MS/MS analyses indicated that most of the organic compounds were removed after treating the textile wastewater with the aerobic sequential batch reactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-developed reactor improves the mass and heat transfer in AD process. • System operates stably at organic loading rate of 20 g VS/(L·d) with 1.55 L/(L·d). • Methane yield is best when the optimal spray time (9 times/d) is used in batch AD. • The processes of hydrolysis and acidification were enhanced. In this study, a new vertical plug-flow continuous dry anaerobic digestion reactor equipped with a spray percolation system was designed for rice straw and cow manure in dry AD. The findings indicated that the methane yield was 290.63 ± 19.16 mL/g VS when the optimal spray time (9 times/d) was used in batch AD. In addition, the results of continuous experiments under optimal spray time conditions showed that the volumetric methane production rate of the system was 1.55 L/(L·d) when the organic loading rate was 20 g VS/(L·d). In addition, hydrolysis and acidification steps were enhanced. This study demonstrated the potential of the new reactor for stable operation of high OLR dry AD. Digestate is already used as a substitute for synthetic fertilizers precisely because of the environmental benefits associated with its agronomic use. [ABSTRACT FROM AUTHOR]

Wine production generates a high volume of wastewater with a significant fraction of biodegradable organic matter that must be removed before safe release into surface waters. Aerobic sequencing batch reactors (SBRs) have been successfully applied in the treatment of a wide range of wastewaters. However, only a few studies have described the use of the SBR process for the treatment of winery wastewater (WW). The effectiveness of using an aerobic SBR process was investigated for the treatment of WW using two activated sludge concentrations (i.e., 2 and 4 gVSS L−1) and nutrient-supplemented conditions. In nutrient-deficient conditions, COD removal efficiencies varied between 70% and 97% depending on the organic loading rate (OLR). In nutrient-supplemented assays, COD removal efficiencies remained above 91% in all conditions tested. However, the effluent quality decreased due to the increase in the total suspended solids concentration. Furthermore, the COD concentration of the treated effluent was unable to meet legal requirements (−1) for safe wastewater discharge. Therefore, longer aeration periods and settling phases may be required in order to improve effluent quality under high organic loadings. Overall, these findings demonstrate the potential of SBR as a biological WW treatment process.

Sub-moderate temperature (ranging from low to moderate temperature) anaerobic digestion (AD) could balance fermentation efficiency and energy input. We investigated biogas production and the microbial community in wastewater AD at sub-moderate (15 °C, 20 °C, and 25 °C) and moderate (35 °C; control group) temperatures with the organic loading rate (OLR) incrementally increased over 200 days. The impact of temperature on biogas production was found to be minimal at a low OLR but became more significant at a high OLR. Notably, a temperature threshold ranging from 15 °C to 20 °C exerted a strong inhibitory effect on biogas production and disrupted the microbial community. And, SMT-AD is deemed by this study to be the optimal application strategy of wastewater with low temperature and low OLR. Bacterial richness was positively and linearly related to temperature. There is a relevance between methane production and archaeal diversity under the influence of temperature and OLR. Temperature and OLR shaped the ecological function of predominant bacteria. Anaerolineales, Thermotogales, and Lactobacillales were strongly influenced by temperature. Synergistales had a synergistic relationship with Desulfovibrionales. Clostridiales was responsible for acetate and butyrate production and closely related to Lactobacillales. Acetoclastic Methanosaetaceae was the predominant methanogen. Methanogens could survive and maintain their population even though methanogenesis was limited under high OLRs and low temperatures.

Fish canning wastewater is characterized by high salinity and organic matter, which makes its treatment particularly difficult. To this purpose, the use of an aerobic membrane bioreactor (AeMBR) process could be a perfect option for the treatment of this wastewater. The aim of this study was to evaluate the effect of different operational conditions on the performance of the biological process and ceramic ultrafiltration (UF) membrane in AeMBR pilot plant for fish canning wastewater treatment. The AeMBR pilot was operated under ambient conditions (21.5 °C), 12 days of sludge retention time (SRT) and for a hydraulic retention time (HRT) of 24 h. The effect of operational parameters including organic loading rate (OLR) (3–5 kg COD/m3.day); total dissolved solids (TDS) (2.5–5 g/L), oxygenation rate (700 and 1300 NL/h) and transmembrane pressure (TMP) (0.05–1.5 bar) affected the quality of the effluent. The main performance results were the removal of approximately 97% of COD, 98% of BOD, 90% of nitrate and over 97% of total Kjeldahl nitrogen (TKN) and total phosphorus (TP). The treated effluent at the output of the AeMBR meets the quality standards according to the Food and Agriculture Organization (FAO) directive and the Moroccan standards for the discharge and reuse of water for irrigation and watering.

• Co-digesting swine manure and waste kitchen oil allowed OLR up to 6 g VS/L/d. • A reasonable amount of oil increased biogas yield and bacterial alpha-diversity. • System imbalance occurred when oil was added beyond certain threshold. • "Inhibited steady state" phenomenon was observed at high OLRs. • Up to three months were needed to confirm system failure for middle to high OLRs. Anaerobic co-digestion of swine manure (SM) and waste kitchen oil (WKO) was conducted to evaluate the effect of high organic loading rates (OLRs) on biogas production efficiency and microbial changes. Combinations of different loading rates of SM and WKO, with total OLRs from 2 to 8 g VS (volatile solid)/L/d, were evaluated in a laboratory-scale study. While feeding more than 4 g VS SM /L/d did not result in higher biogas production in both mono- and co-digestion scenarios, the addition of WKO increased the total OLR up to 6 g VS/L/d without significant reduction of system productivity. Biogas yields of M2O1 (2 g VS SM /L/d + 1 g VS WKO /L/d) and M4O2 were 910 ± 35 and 849 ± 85 mL/g VS fed which were 25.2 % and 16.9 % higher than the mono-digestion of M2, respectively. A significant increase of bacterial alpha-diversity (Shannon index) was observed in M2O1, at 233.0 ± 3.6 compared with 218.7 ± 5.1 of M2 (p < 0.05). Less bacterial alpha-diversity and accumulation of volatile fatty acids were observed in M4O1 and M4O2, suggesting their potential instability. When digesters were fed with M2, the introduction of 1.4 g VS WKO /L/d or more did not increase biogas yield and could cause system imbalance. The study suggests the limit of WKO could be increased when higher OLRs of SM were applied but should not be more than 4 g VS SM /L/d, and ratio between SM and WKO should be considered to avoid failure. Some of the system disturbances took up to three months to show. [ABSTRACT FROM AUTHOR]

The large capacity production and low utilization rate increase the difficulty of fruit and vegetable wastes (FVW) treatment. Efficient and targeted recovery strategies can solve these problems. This study investigated and proposed combined strategies via pH and organic loading rate (OLR) to target and enhance ethanol- and butyrate-dominant acidogenic production in the FVW mixed culture fermentation. Under pH 4.0, OLR 18 gCOD/(L∙d), and mesophilic (35 °C), ethanol-dominant fermentation was formed. The long-term operation (168 days) showed that the highest ethanol yield was 0.33 g/gCOD which was greater than that in other studies. Also, the hydrolysis rate of ethanol-type fermentation reached 74.5%. Besides, butyrate-type fermentation was stable at yield 0.39 g/gCOD following conditions: pH 6.0, OLR 28 gCOD/(L∙d), and 35 °C, of which hydrolysis and acidogenic rate were 78.0% and 62.0%, respectively. The high relative abundance of Lactobacillus, Olsenella, and Bifidobacterium played positive role in achieving ethanol, butyrate, and lactate production among various metabolic pathways. The results revealed the pH value together with OLR was the valid parameter to affect product formation and composition during FVW fermentation. [ABSTRACT FROM AUTHOR]

The effects of the temporary increase of organic loading rate (OLR) combined with the simultaneous decrease of hydraulic retention time (HRT) on the stability of a pilot scale dry anaerobic digester were investigated. The separately collected organic fraction of municipal solid waste in mesophilic conditions (T = 40°C) was treated. The objective of this study was to verify whether it is possible to feed the digester for short periods, about three consecutive weeks, with higher OLRs and lower HRTs than those considered optimal without generating process failure or long-term instability. Starting from stable operation at a daily OLR of 10.0 kg of total volatile solids (TVS) for digester volume and an HRT of 23 d, the reactor was fed with an OLR of 10.8, 11.7 and 12.5 kg TVS m−3 d−1 corresponding to an HRT of 21, 19 and 18 d, respectively. It was observed that after using an OLR of 10.8 and 11.7 kg TVS m−3 d−1 for 3 weeks with satisfying results, it was possible to restore stable operating conditions at an OLR of 10.0 kg TVS m−3 d−1 in a short time. Otherwise, after using an OLR of 12.5 kg TVS m−3 d−1 the anaerobic digestion was deeply unbalanced and quickly failed. In this latter case, however, it was possible to fully recover and restore the stable conditions of the process within two months. [ABSTRACT FROM AUTHOR]

A hybrid anaerobic–aerobic treatability of real textile wastewater was investigated by using a lab-scale upflow anaerobic sludge blanket (UASB) coupled with a sequencing batch reactor (SBR). The performance of the integrated system was determined under various operational conditions. In phase I of the study, the UASB reactor was operated and optimized on real textile wastewater. The UASB was operated at a hydraulic retention time of 48 h in a semi-continuous mode with 12-h feeding and 12-h non-feeding cycle. Volatile fatty acid to alkalinity ratio was kept in the range of 0.42–0.72, while pH was strictly maintained between 6.8 and 7.2 under mesophilic conditions (35 ∘ C). In phase II of the study, SBR was coupled with a UASB reactor and operated on real textile wastewater. The SBR was operated at an HRT of 6 h and solids retention time of 20 days. The integrated system was optimized with maximum removal efficiencies of 98% for chemical oxygen demand, 94% for color, 93% for total Kjeldahl nitrogen, and 89% for orthophosphate phosphorus. The results indicated that the integrated system is robust and flexible for the treatment of textile wastewater. [ABSTRACT FROM AUTHOR]

This study aims at addressing inconsistencies in literature regarding the organic loading rate (OLR) and hydraulic retention time (HRT) effect on caproic acid production, using biomass activity as an indicator. Xylose was fully consumed in the reference CSTR and SBR (HRT = 1-day; OLR = 12 gCOD/(L·d)), but different caproic acid yields (0.02 vs 0.11 Cmol/Cmol-s) were observed, which was linked to differences in biomass activity (12 vs 3.5 g/(g VSS·d)). At HRT 0.5 days, xylose conversion was incomplete and lactic acid and ethanol appeared, reducing caproic acid production. However, increasing xylose concentration in the feeding to 24 g COD/L did not change the caproic acid yield (0.12 Cmol/Cmol-s), which was explained by similar biomass activity as in the reference SBR (4.8 g/(g VSS·d)). These findings indicate that the SBR is the optimal configuration, since it allows maintaining a low biomass activity and therefore a high caproic acid yield., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Marta Carballa reports financial support was provided by European Regional Development Fund. Juan Iglesias-Riobó, Miguel Mauricio Iglesias and Marta Carballa report financial support was provided by Xunta de Galicia. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper]., (Copyright © 2024. Published by Elsevier Ltd.)

Anaerobic digestion, one of the most currently remarkable techniques for biogas production, has provided a method of high organic solid waste disposal. Operating temperature, especially in the winter of northern city, makes biomass degradation less efficient. The microorganisms that take on the role of gas production are greatly affected by temperature. In our study, solar energy was selected for anaerobic digestion and winter was selected as the experimental environment. Anaerobic digestion was performed with solar heating and electric heating separately. Parameters were tested (pH, soluble chemical oxygen demand, total ammonia nitrogen, total volatile fatty acids), and microbial structure was monitored. The volume of methane produced was measured over 60 days. The methane yield differed by 15.92% under different conditions. It is clearly shown that methane yield can be improved by a steady temperature environment. Nevertheless, dominant bacteria and microbial structure did not seem to be much different. This study may provide more energy-saving ideas for winter anaerobic digestion projects in northern regions. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) have gained a lot of attention for wastewater treatment due to robustness and natural pollutant mitigation characteristics. This widely acknowledged technology possesses enough merits to derive direct electricity in collaboration with microbial fuel cell (MFC), thus taking advantage of microbial metabolic activities in the anoxic zone of CWs. In the present study, two identical lab-scale CWs were selected, each having 56 L capacity. One of the CW integrated with MFC (CW-MFC) contains two pairs of electrodes, i.e., carbon felt and graphite plate. The first pair of CW-MFC consists of a carbon felt cathode with a graphite plate anode, and the second pair contains a graphite plate cathode with a carbon felt anode. The other CW was not integrated with MFC and operated as a traditional CW for evaluating the performance. CW-MFC and CW were operated in continuous up-flow mode with a hydraulic retention time of 3 days and at different organic loading rates (OLRs) per unit surface area, such as 1.45 g m−2 day−1 (OLR-1), 2.43 g m−2 day−1 (OLR-2), and 7.25 g m−2 day−1 (OLR-3). The CW-MFC was able to reduce the organic matter, phosphate, and total nitrogen by 92%, 93%, and 70%, respectively, at OLR of 1.45 g m−2 day−1, which was found to be higher than that obtained in conventional CW. With increase in electrochemical redox activities, the second pair of electrodes made way for 3 times higher power density of 16.33 mW m−2 as compared to the first pair of electrodes in CW-MFC (5.35 mW m−2), asserting carbon felt as a good anode material to be used in CW-MFC. The CW-MFC with carbon felt as an anode material is proposed to improve the electro-kinetic activities for scalable applications to achieve efficient domestic wastewater treatment and electricity production. [ABSTRACT FROM AUTHOR]

An Upflow Anaerobic Sludge Blanket reactor combined with a two-stage membrane bioreactor were operated for 193 days in order to evaluate the biological removal of carbamazepine (CBZ) from low-strength municipal wastewater. The system worked in three different organic load stages (0.7 ± 0.1 kg COD·m−3·d−1, 0.4 ± 0.1 kg COD·m−3·d−1 and 0.1 ± 0.0 kg COD·m−3·d−1) to assess the impact of the influent OLR on operational parameters such as anaerobic and aerobic sludge retention time (SRT), acidity, volatile fatty acids (VFAs), biomass activity or biogas production. The highest carbamazepine removals were achieved during the anaerobic stage (UASB reactor), reaching averages of 48.9%, 48.0% and 38.2% operating at high, medium and low OLR, respectively. The aerobic treatment (MBR) served as post-treatment, improving the removals, and the global UASB-MBR system reached averages of 70.0%, 59.6% and 49.8% when the influent was at medium and low OLR, respectively. The results demonstrate the potential of combined biological systems on the removal of recalcitrant pharmaceuticals. HIGHLIGHTS UASB-MBR was proposed for the removal of the anti-epileptic drug carbamazepine.; The CBZ removal rates of the UASB-MBR combined system were highly dependent on the organic loads of the influent.; UASB-MBR system proved to be particularly suitable for treating municipal wastewater containing CBZ at OLR above 0.7 kg COD·m−3·d−1.; UASB reactor was the main contributor to degradation of the pharmaceutical CBZ.;

• Low OLR promoted ARGs spread by boosting ARB proliferation and functional profiles. • System instability can induce the accumulation of antibiotics, ARGs, and HPB. • A high OLR operation without digestate recirculation enriched HPB and MGEs. • Digestate recirculation reduced antibiotics abundance by 19.66–31.69 % at high OLR. • Digestate recirculation reduced effects of functional profiles and ARBs on ARGs HGT. Organic loading rate (OLR) is crucial for determining the stability of dry anaerobic digestion (AD). Digestate recirculation contributes to reactor stability and enhances methane production. Nevertheless, the understanding of how OLR and digestate recirculation affect the abundance and diversity of antibiotics and antibiotic resistance genes (ARGs), as well as the mechanisms involved in the dissemination of ARGs, remains limited. This study thoroughly investigated this critical issue through a long-term pilot-scale experiment. The metabolome analyses revealed the enrichment of various antibiotics, such as aminoglycoside, tetracycline, and macrolide, under low OLR conditions (OLR ≤ 4.0 g·VS/L·d) and the reactor instability. Antibiotics abundance decreased by approximately 19.66–31.69 % during high OLR operation (OLR ≥ 6.0 g·VS/L·d) with digestate recirculation. The metagenome analyses demonstrated that although low OLR promoted reactor stability, it facilitated the proliferation of antibiotic-resistant bacteria, such as Pseudomonas, and triggered functional profiles related to ATP generation, oxidative stress response, EPS secretion, and cell membrane permeability, thereby facilitating horizontal gene transfer (HGT) of ARGs. However, under stable operation at an OLR of 6.0 g·VS/L·d, there was a decrease in ARGs abundance but a notable increase in human pathogenic bacteria (HPB) and mobile genetic elements (MGEs). Subsequently, during reactor instability, the abundance of ARGs and HPB increased. Notably, during digestate recirculation at OLR levels of 6.0 and 7.0 g·VS/L·d, the process attenuated the risk of ARGs spread by reducing the diversity of ARGs hosts, minimizing interactions among ARGs hosts, ARGs, and MGEs, and weakening functional profiles associated with HGT of ARGs. Overall, digestate recirculation aids in reducing the abundance of antibiotics and ARGs under high OLR conditions. These findings provide advanced insights into how OLR and digestate recirculation affect the occurrence patterns of antibiotics and ARGs in dry AD. [Display omitted] [ABSTRACT FROM AUTHOR]

The organic loading rate (OLR) is a critical parameter affecting the stability of dry anaerobic digestion (AD) of kitchen waste (KW), and significantly impacting the variations in physicochemical parameters and microbial communities. However, the evolution of quorum sensing (QS) and their role on anaerobic biochemical metabolism during the increase in OLR in dry AD remain unknown. Therefore, this study systematically elucidated the matter through multi-omics analysis based on a pilot-scale dry AD of KW. The results demonstrated that fluctuations in the OLR significantly influenced the microbial QS in dry AD. When the OLR ≤4.0 g·VS/L·d, the system operated stably, and methane production increased. The enrichment of Proteobacteria was crucial for sustaining high levels of functional genes associated with various types of QS, including acyl-homoserine lactones (AI-1), autoinducer-2 (AI-2), autoinducer-3 (AI-3), and gamma-aminobutyric acid (GABA). This enabled cooperative communication among microbes under low OLR. Furthermore, most genes associated with these QS processes positively affected hydrolysis, acidogenesis, and methanogenesis. When the OLR increased to 6.0 g·VS/L·d, the fatty acids and hydrogen partial pressure increased significantly. The autoinducing peptides (AIP)-type became the predominant QS and was positively correlated with fatty acids abundance. Syntrophaceticus and Syntrophomonas may promote syntrophic oxidation of acetate at high OLR through AIP-type QS. These findings provided new insights into the QS processes of microbes during dry AD of KW and a theoretical foundation for optimizing biochemical metabolic processes in dry AD through QS. [Display omitted] • The changes in OLR obviously affected the QS process of microbes in dry AD. • QS processes were dominated by AI-1, AI-2, AI-3, GABA, PQS, and others, at low OLR. • The AIP-type was the predominant QS system at high OLR. • Syntrophaceticus and Syntrophomonas may promote the SAO via AIP-type QS. • QS led by AI-1, AI-2, GABA, and other peptides enhanced AD biochemical metabolism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dynamic interspecies electron transfer in a stage-separated MAHR was investigated. • DIET can be stimulated by activated carbon (AC) in the methanogenic zone (Mm). • Duale drive of MIET and DIET can be achieved in Mm with AC addition. • The electron fluxes of MIET and DIET in Mm were dynamic with OLR variation. • DIET was effectively at OLR ≤ 40 g COD/L/d and MIET was competitive at 80 g COD/L/d. Understanding and regulation of interspecies electron transfer, including hydrogen-mediated interspecies electron transfer (MIET) and direct interspecies electron transfer (DIET), is crucial for enhancing anaerobic digestion (AD). In this study, MIET and DIET were regulated in a multistage anaerobic hythane reactor (MAHR) via inoculum management, activated carbon (AC) addition, and organic loading rate (OLR) adjustment. The operational stability, organic removal, and methane production can be enhanced, with AC addition in the methane production zone (Mm) (R p C Mm and R np C Mm). The reactors of R p C Mm and R np C Mm achieved start-up within 20 days and showed a 20 % and 104 % increase in maximum methane production rates, respectively. Microbial community characteristics confirmed that AC in Mm could facilitate DIET establishment, but its addition in Mh could not. This assertion was supported by the observed tighter and more positive correlation between biofilm conductivity and DIET-related microbes in R p C Mm and R np C Mm , as opposed to R p C Mh and R np C Mh. Further, the dual drive of DIET and MIET was revealed through the comprehensive analysis of operational performances and microbial community with the structure equation model. The electron fluxes analysis highlighted a dynamic shift of DIET and MIET in the methanogenic stage with AC addition and OLR variation. The DIET was proved more efficient than MIET in Mm with AC addition and OLR below 40 g COD/L/d, while high OLR (80 g COD/L/d) favored MIET with lower methane production efficiency. The results of this study shed light on the nuanced characteristics of interspecies electron transfer, providing valuable insights for the further design and operation of stage-separated AD. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) for biogas production is affected by many factors that includes organic loading rate (OLR). This OLR appears to be closely linked to various other factors and understanding these linkages would therefore allow the sole use of OLR for process performance monitoring, control, as well as reactor design. This review's objective is to collate the various AD factor specific studies, then relate these factors' role in OLR fluctuations. By further analyzing the influence of OLR on the AD performance, it would then be possible, once all the other factors have been determined and fixed, to manage an AD plant by monitoring and controlling OLR only. Decisions on reactor design, process kinetics, biogas yield and process stability can then be made much more quickly and with minimal troubleshooting steps. [ABSTRACT FROM AUTHOR]

Featured Application: This work provides important insights into the effect of the hydraulic retention time (HRT) and organic loading rate (OLR) in the production of bioH2 by the dark fermentation (DF) of the organic fraction of municipal solid wastes (OFMSW). The experimental data reported in this work are useful in the design and optimization of full-scale DF bioreactors used in the dark fermentation of OFMSW for bioH2 production. Food wastes represent one third of all food produced worldwide. It is crucial to both prevent the production of food waste and recover the wasted fraction with the aim to valorizing it. In this context, the conversion of the organic fraction of municipal solid wastes (OFMSW) into bioH2 by dark fermentation (DF) is an important technology to valorize these wastes into renewable fuel. Nevertheless, the DF of OFMSW needs to be optimized for critical operational parameters. The main purposes of this study were to investigate (i) the effect of HRT during continuous bioH2 production through DF and (ii) the effect of organic loading rate (OLR) ruled by HRT. In this work, three HRTs (4, 5, and 6 d) were tested in a mesophilic continuous stirred-tank reactor (CSTR). The HRTs of 4, 5, and 6 days, corresponding to OLRs of 23.6, 18.0, and 10.6 g volatile solids (VS)·L−1·d−1, respectively, showed bioH2 yields of 8.48, 18.2, and 1.64 L·kg−1 VSinfluent with an H2 content of approximately 25, 32, and 5% v/v, respectively. An accumulation of volatile fatty acids (VFAs) was registered with the decrease in HRT, causing a decrease in bioH2 production. The 5 d HRT was the most favorable condition. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of the organic loading rate (OLR) (60, 90, and 120 g Chemical Oxygen Demand (COD). L−1. d−1) on hydrogen production from cheese whey and glycerol fermentation as cosubstrates (50% cheese whey and 50% glycerol on a COD basis) in a thermophilic fluidized bed reactor (55 °C). The increase in the OLR to 90 gCOD.L−1. d−1 favored the hydrogen production rate (HPR) (3.9 L H 2. L−1. d−1) and hydrogen yield (HY) (1.7 mmol H 2. gCOD−1 app) concomitant with the production of butyric and acetic acids. Employing 16S rRNA gene sequencing, the highest hydrogen production was related to the detection of Thermoanaerobacterium (34.9%), Pseudomonas (14.5%), and Clostridium (4.7%). Conversely, at 120 gCOD.L−1. d−1, HPR and HY decreased to 2.5 L H 2. L−1. d−1 and 0.8 mmol H 2. gCOD−1 app , respectively, due to lactic acid production that was related to the genera Thermoanaerobacterium (50.91%) and Tumebacillus (23.56%). Cofermentation favored hydrogen production at higher OLRs than cheese whey single fermentation. [Display omitted] • The organic loading rate was evaluated in a thermophilic fluidized bed reactor. • Cofermentation of cheese whey and glycerol was suitable for bio-H 2 production. • A higher H 2 yield of 1.7 mmol. gCOD−1 app was observed at 90 gCOD.L−1. d−1. • The highest H2 yield was concomitant with butyric acid (41.1% molar) production. • Thermoanaerobacterium was the main genus involved in H 2 production. [ABSTRACT FROM AUTHOR]

The discharge of wastewater containing both high salinity and high organic content without prior treatment is detrimental to aquatic life and water hygiene. In order to integrate the advantages of membrane treatment and biological treatment, and exert the phosphorus removal efficiency of dewatered alum sludge, in this study, an aerobic membrane reactor based on dehydrated alum sludge was used to treat mustard tuber wastewater with salinity of 6.8-7.3 % under the conditions of 30 °C, 20 kPa trans-membrane pressure (TMP) and chemical oxygen demand (COD) of 3300-3900 mg/L. Three replicate reactors were applied to assess the operational performance under different organic loading rate (OLR). The results showed that all reactors were effective in removing COD, ammonia nitrogen (NH4+-N) and soluble phosphate (SP) under the conditions of 30 °C and 20 kPa of TMP. Meanwhile, the effluent concentration of COD, NH4+-N and SP all increased while OLR was changed from 1.0 to 3.0 kg COD/m3/day, and the effluent COD and NH4+-N concentration except for SP could reach the B-level of Chinese "Wastewater quality standards for discharge to municipal sewers" when OLR was less than 3.0 kg COD/m3/day. This indicates that dewatered alum sludge-based aerobic membrane reactor is a promising bio-measure for treating high salinity wastewater. [ABSTRACT FROM AUTHOR]