Search Results (72)

The anaerobic ammonium oxidation (anammox) process offers potential for saline wastewater treatment but is hindered by salt inhibition. This study investigates the salt tolerance mechanisms of granular (R1), biofilm-carrier (R2), and floccular (R3) sludge in up-flow anaerobic sludge blanket (UASB) reactors under 0–20 g/L NaCl. Granular sludge outperformed other biomass types, maintaining >90% ammonia nitrogen (${\mathrm{NH}}_4^{+}$-N) removal at 20 g/L NaCl due to structural stability and extracellular polymeric substances (EPS) adaptation (shift from hydrophobic proteins to polysaccharides). Microbial analysis revealed a transition from Planctomycetes/Proteobacteria to salt-tolerant Pseudomonadota, with Candidatus_Kuenenia replacing Candidatus_Brocadia as the dominant anaerobic ammonium oxidation bacteria (AnAOB) (reaching 14.5% abundance in R1). Genetic profiling demonstrated coordinated nitrogen metabolism: Hzs/Hdh inhibition (>85%) and NirBD/NrfAH activation (0.23%) elevated ${\mathrm{NH}}_4^{+}$-N, while NarGIV/NapA decline (1.10%→0.58%) increased nitrate nitrogen (${\mathrm{NO}}_3^{-}$-N). NxrB/NirSK maintained low nitrite nitrogen (${\mathrm{NO}}_2^{-}$-N), and GltBD upregulation (0.43%) enhanced osmoregulation. These findings underscore the superior resilience of granular sludge under high salinity, linked to microbial community shifts and metabolic adaptations. This study provides critical insights for optimizing anammox processes in saline environments, emphasizing the importance of biomass morphology and microbial ecology in mitigating salt inhibition. Full article

Sugarcane vinasse, a byproduct of ethanol production, presents environmental challenges due to its high organic content and occasional contamination with antibiotics, such as monensin. This study successfully evaluated thermophilic two-phase anaerobic digestion for simultaneous monensin degradation and biogas production. The system, consisting of an acidogenic anaerobic structured-bed bioreactor (ASTBR) operating at with a hydraulic retention time (HRT) of 7.5 h followed by a methanogenic reactor at HRT = 24 h, with two options of the methanogenic phase, an upflow anaerobic sludge blanket (UASB), and an ASTBR, operated continuously for 254 days with incremental monensin concentrations (0–2000 ng·mL⁻¹). The acidogenic reactor consistently removed over 70% of monensin across all phases, demonstrating its effectiveness as a pretreatment step. At realistic residual concentrations (20–100 ng·mL⁻¹), monensin not only failed to inhibit biogas production but enhanced methane yield by up to 100% through selective pressure on the microbial community. This study demonstrated that anaerobic digestion can effectively degrade monensin while increasing the value of vinasse, providing a scalable solution for mitigating antibiotic contamination and enhancing bioenergy recovery in the sugarcane–ethanol industry. Full article

The biotechnological conversion of CO₂ to biomethane represents an energy-efficient, environmentally friendly, and sustainable approach within the waste-to-energy cycle. This process, in which CO₂ and H₂ are converted to biomethane in anaerobic bioreactors, is referred to as hydrogenotrophic biomethane production. While several studies have investigated hydrogenotrophic biomethane production, there is a lack of research comparing flocculent and granular sludge inoculum in continuously operated systems fed with a gas substrate. Both granular and flocculent sludge possess distinct advantages: granular sludge offers higher density, stronger microbial cohesion, and superior settling performance, whereas flocculent sludge provides faster substrate accessibility and more rapid initial microbial activity. In this study, two UASB (Upflow Anaerobic Sludge Blanket) reactors operated under mesophilic conditions were continuously fed with synthetic off-gas composed of pure H₂ and CO₂ in a 4:1 ratio and were compared in terms of microbial community shifts and their effects on hydrogenotrophic biomethane production. Biomethane production reached 75 ± 2% in the granular sludge reactor, significantly higher than the 64 ± 1.3% obtained with flocculent sludge. Although hydrogen consumption did not differ significantly, the granular sludge reactor exhibited higher CO₂ removal efficiency. Microbial analyses further revealed that granular sludge was more effective in supporting methanogenic archaea under conditions of gas substrate feeding. These findings offer advantageous suggestions for improving biogas production, enhancing waste gas management, and advancing sustainable energy generation. Full article

Sanitary landfill leachate treatment was evaluated using magnetite-catalyzed ozone, an upflow anaerobic sludge blanket (UASB) reactor, and microalgae, both individually and in combination, to improve biodegradability and remove organic matter, solids, metals, and nutrients. Leachates were characterized before and after each treatment, and their impacts on methanogenic activity, aerobic toxicity, and the BOD₅/COD ratio were assessed. Magnetite-catalyzed ozone pretreatment enhanced biodegradability, enabling an optimal coupling point with the UASB at 40 min when the specific methanogenic activity reached 0.22 g CH₄-COD/(gVSS·d). The UASB achieved COD removal rates of up to 75%, but high concentrations were maintained in the effluent with low ammoniacal nitrogen and phosphorus removal rates. Microalgae promoted nutrient removal, reducing total nitrogen and phosphorus by up to 65% and 70%, respectively, although with lower efficiency in terms of organic matter removal. Process coupling demonstrated that ozonation followed by UASB application improved anaerobic degradation, whereas the use of microalgae after biological treatment optimized the final effluent quality. Despite the improvements achieved, the final values for some parameters still exceeded the discharge limits, indicating the need for operational adjustments or additional treatments to ensure effective purification. Full article

Removal of micropollutants using biological treatment systems remains a challenge, since conventional bioprocess systems require adaptations to provide more advanced treatment. An ambient temperature upflow anaerobic sludge blanket (UASB) reactor was employed, followed by a two-stage (saturated and unsaturated) vertical subsurface flow (VSSF) constructed wetland (CW) system, to treat domestic wastewater from a nearby settlement and investigate the occurrence and fate of 10 contaminants of emerging concern (CECs) in decentralized, non-conventional treatment systems. The integrated UASB—two-stage CW system achieved high performance regarding abatement of target CECs across all periods. Removal efficiencies ranged from 78% ± 21% (ketoprofen) to practically 100% (2-hydroxybenzothiazole). The pilot system was found to be robust performance-wise and provided enhanced treatment in comparison to a conventional wastewater treatment plant operating in parallel. Most of the target CECs were successfully treated by UASB, saturated and unsaturated CWs, while ibuprofen, bisphenol A and diclofenac were mostly removed in the unsaturated CW. Environmental risk assessment revealed that triclosan poses a significant ecological risk to algae during treated wastewater disposal into the aquatic environment. Additionally, cumulative risk quotient indicated that the potential for mixture toxicity should be carefully considered across all trophic levels. Full article

Sewage treatment is essential to prevent disease transmission and adverse environmental impacts. This study evaluated the performance of four Sewage Treatment Plants (STPs) in two cities in the state of Minas Gerais, Brazil. Two STPs (Santana and São José) that have Up-Flow Anaerobic Sludge Blanket (UASB) reactors as the sole biological treatment stage did not comply with the discharge standards in receiving water bodies, particularly for SetS, TSS and O&G parameters. This shows the need for improvements, such as the implementation of post-treatment. For the other plants that have UASB reactors followed by an activated sludge system (Industrial Complex STP) or an up-flow anaerobic filter (Carbonita STP) as post-treatment, only the O&G parameter was not met. With the exception of one of the STPs that lackes post-treatment (São José STP), the other three met the required minimum removals of 60% for BOD₅ and 55% for COD. The Carbonita STP promoted the highest average removals of BOD₅ and COD, at 90% and 86%, respectively. Despite the discharge of industrial wastewater into the sewage collection network of one of the cities in this study, the biodegradability of the raw sewage remained high (BOD₅/COD ratio > 0.4). The wastewater treated by the STPs that have post-treatment showed greater potential for reuse in agricultural practices. Full article

This study investigated nutrient removal in tubular photobioreactors (PBR) illuminated by Light-Emitting Diodes (LEDs), treating the effluent from an Up-Flow Anaerobic Sludge Blanket (UASB) system followed by a Biological Percolator Filter (BPF). Designed as a tertiary treatment step, the PBRs aimed to minimize eutrophication while promoting microalgal growth through CO₂ assimilation released by bacterial activity—resulting in biomass with potential for value-added applications. The objective of this study was to elucidate the mechanisms responsible for nitrogen and phosphorus removal under a controlled environment. A key novelty of this work lies in the comparative evaluation of red and blue LED illumination in the pilot-scale PBRs used for wastewater treatment. All systems achieved >99% ammoniacal nitrogen removal, while soluble phosphorus removal achieved up to 95%. The highest nitrogen removal rate was observed under red light (10.60 mg L⁻¹ d⁻¹), although there was no difference for blue light, while blue light was more effective for phosphorus removal (3.28 mg L⁻¹ d⁻¹). Assimilation was the primary removal mechanism, supported by microalgae–bacteria interactions and artificial CO₂ injection. The research highlights distinct advantages of each light illumination: the blue-light photobioreactor was more suitable for tertiary treatment, whereas the red-light system showed potential for microalgal biomass-based co-product generation. Full article

Propionate, a critical intermediate in anaerobic digestion, and its syntrophic removal, is sensitive to stress. To our knowledge, this study investigates for the first time the response of a metabolic gene panel to organic loading rate (OLR) stress in propionate-degrading methanogenic consortia in lab-scale upflow anaerobic sludge blanket (UASB) reactors. The experimental phases included stabilisation (1.4–2.8 g COD/L/day), electroactive enrichment, OLR shock (6 g COD/L/day), and early recovery. Quantitative PCR was used to assess the abundance of key functional genes (16SrRNA, mcrA, pilA, and hgtR). During stabilisation, ~200 mLCH₄/h was produced, the mcrA/16SrRNA ratio was 0.78–2.64, and pilA and hgtR abundances were 1.29–2.27 × 10⁵ and 2.12–4.37 × 10⁴ copies/gVS. Following the OLR shock, methane production ceased entirely, accompanied by a sharp decline in the mcrA/16S ratio (0.08–0.24) and significant reductions in pilA (1.43-log) and hgtR (1.34-log) abundance. Partial recovery of pilA and hgtR abundance (1.19 × 10⁵ and 8.57 × 10⁴) was observed in the control reactor after the early recovery phase. The results highlight the utility of mcrA, 16SrRNA, pilA, and associated ratios, as reliable indicators of OLR stress in lab-scale UASB reactors. This study advances the understanding of molecular stress responses in propionate-degrading methanogenic consortia, focusing on direct interspecies electron transfer in process stability and recovery. Full article

This study investigates the use of a UASB (Upflow Anaerobic Sludge Blanket) reactor operating under continuous anoxic conditions to remediate Pb(II) contamination in aqueous environments. Two experimental runs were conducted to evaluate the microbiome’s performance in removing Pb(II) at varying concentrations, ranging from 80 to 2000 ppm, while monitoring nitrate and Pb(II) levels. Metabarcoding of the 16S rRNA gene was done to understand the detoxification mechanisms utilised by the microbial community in Pb(II) removal. The system demonstrated high robustness, achieving up to 99% Pb(II) removal efficiency with sufficient nutrient availability, particularly at 15 g/L yeast extract (YE), compared to lower nutrient levels of 5 g/L YE. Denitrification was identified as the dominant mechanism of detoxification, supported by additional processes such as biosorption, sulfur-reducing bacterial activity, bioprecipitation, and bioremoval. Analysis of the precipitate recovered from the reactor indicated the presence of elemental lead, PbS, and PbO, highlighting the potential for lead recovery. These findings suggest that the system not only effectively removes Pb(II) from contaminated environments but also offers a sustainable pathway for lead recovery through smelting, making it a promising circular bioremediation strategy. The results indicate that this biological approach is a viable solution for lead pollution and recovery in industrial applications. Full article

Anaerobic wastewater treatment technology has been intensively and extensively investigated in the industry and scientific research. Inspired by the advantages of multi-stage and multi-phase anaerobic reactor technology (SMPA) in recent years, a three-stage anaerobic reactor (3S-AR) was designed and applied to treat poplar chemical–mechanical pulp wastewater, and various operation parameters, including the volume loading rate (VLR), hydraulic retention time (HRT), ascending velocity, reflux ratio, pH and temperature of the 3S-AR, were optimized to evaluate the reactor’s removal efficiency for poplar wastewater. The properties of anaerobic granular sludge and the composition of wastewater were also characterized to assess microorganism growth and pollutant migration. Results show that the COD removal rate was over 75% with a volume loading rate range of 15–25 gCOD/(L·d) in the 3S-AR; the hydraulic retention time was also found to be an important factor affecting the performance of the 3S-AR reactor. The volume loading rate and degradation efficiency of the 3S-AR reactor are higher than those of the up-flow anaerobic sludge blanket (UASB) reactor. Microorganism separation can be achieved in the 3S-AR, which is conducive to the growth and methanogenesis activity of bacteria, thereby leading to enhanced removal and buffering efficiency. After treatment in the 3S-AR, the main pollutants of poplar wastewater were benzene aromatic acids and long-chain esters, which do no biodegrade easily; in contrast, most of the fatty acid substances with small molecules were completely degraded. Full article

To meet Colombia’s energy needs by 2050, a total installed capacity of 42 MW across its power generation infrastructure is required. To achieve this, transitioning to cleaner energy sources, such as biomass—a non-conventional renewable energy—is necessary. Biomass is a promising renewable source for thermal and electrical energy production. This study researched the production of biogas from swine manure using a UASB reactor to valorize this waste. Swine manure was collected every 20 days from a pig farm with a capacity of 200 sows, located in Santa Rosa de Osos, Antioquia. The flow rate was increased three times (1.30 L d⁻¹, 1.62 L d⁻¹, and 2.08 L d⁻¹) to reduce the hydraulic retention time (HRT) and enhance biogas production. The volatile and total solids, chemical oxygen demand (COD), alkalinity, and biogas composition were measured over one year. The proposed system achieved 87.40% COD remotion from the feed stream and generated a yield of 507 mLCH₄ g_VS⁻¹, with an HRT of 19 days and an OLR of 4.27 gCOD L⁻¹ d⁻¹. The reactor produced biogas with a CH₄ content of 67.7%, CO₂ content of 18.1%, and H₂S content of 1413 ppm. This study highlights the effectiveness of the UASB reactor for biogas production using swine manure as a substrate. Full article

Wastewater treatment is now required because of the problems caused by water constraints. Wastewater is anaerobically digested to produce biogas, which can be used as a source of energy for things like lighting and heating. The upflow anaerobic sludge blanket (UASB) reactor has been recognized as an important wastewater treatment technology among anaerobic treatment methods. Although their treated effluent typically does not meet most discharge criteria, UASB reactors are generally stated to have a chemical oxygen demand (COD) reduction ranging from 60 to 90% for most types of wastewater. In comparison to traditional anaerobic procedures, anaerobic municipal wastewater treatment using membranes can produce higher effluent quality in terms of COD, suspended solids (SSs) and pathogen counts, as well as a steady treatment performance to fulfill strict discharge regulations. The objective of this review was to perform a literature review on parameters to consider when selecting a membrane to include in a UASB reactor. Membranes that are available in the market were compared in terms of both physical and chemical properties. Polyvinylidene fluoride (PVDF) membranes were found be superior to the others, and their modification also reduced the fouling propensity. When comparing modified PVDF (PVDF/PVDF-g-PEGMA) to pristine PVDF (116 L·m⁻² h⁻¹), a higher pure water flux (5170 L·m⁻² h⁻¹) was noted. The main drawback of such modifications could significantly increase the final membrane production costs. Research is still lacking when it comes to research on comparing the membranes and PVDF and UASB reactor technology interaction, including effects of its modification as discussed (stability, longevity of improved flux, etc. Full article

Brewery (BW) and dairy (DW) wastewater are two types of agro-industrial wastewater that are generated in large amounts and, therefore, should be treated effectively and in an environmentally beneficial manner. Both these wastewater types are characterized by a high COD, BOD₅, and nutrient content, and conventional wastewater treatment methods such as an activated sludge process may prove to be inefficient due to the possibility of foaming, large biomass production, low activity at low temperatures, and risk of overloading the reactor with a load of organic pollutants. In the context of the described difficulties, anaerobic processes seem to be the best alternative. An interesting research area is the co-digestion of these wastewaters. However, this research direction, so far, has not been frequently reported. Given the gap in the current knowledge, this literature review aims to assess the possibility of BW and DW digestion in anaerobic reactors and provide up-to-date data on the post-treatment methods of effluent generated after the anaerobic digestion process. Despite numerous advantages, anaerobic treatment often requires post-effluent treatment to complete the treatment cycle. Full article

Slaughterhouse wastewater is characterized by high concentrations of organic matter. This creates a need to explore methods for its treatment before discharge. This study evaluated the efficiency of an integrated treatment process consisting of a laboratory-scale upflow anaerobic sludge blanket reactor and a pilot-scale horizontal subsurface flow wetland. This treatment was used for (i) the removal of organic matter through anaerobic–aerobic microbiological processes, (ii) the conversion of organic matter from hydraulic processes, and (iii) for bioremediation and phytoremediation. The treatment system was evaluated at hydraulic retention times (HRTs) of 7.5, 5.0, and 2.5 d; during the investigation, the influence of the HRTs on the removal efficiency of the system was evaluated. High efficiencies of 85% and 75% were obtained for COD_T and BOD, respectively, at an HRT of 7.5 d. The highest overall efficiency for the removal of total solids was observed at an HRT of 2.5 d. The results obtained confirm the feasibility of implementing the suggested system as an alternative for the adequate and sustainable treatment of slaughterhouse wastewater, and the system can be applied to slaughterhouses with similar conditions to those in this study. Full article

Anaerobic digestion of food waste still faces important challenges despite its world-wide application. An important fraction of food waste is composed of organic material having a low hydrolysis rate and which is often not degraded in digesters. The addition of this less hydrolysable fraction into anaerobic digesters requires a longer hydraulic residence time, and therefore leads to oversizing of the digesters. To overcome this problem, the conversion of the highly biodegradable liquid fraction from fruit and vegetable waste in a up-flow anaerobic sludge blanket (UASB) digester is proposed and demonstrated. The more easily biodegradable fraction of the waste is concentrated in the liquid phase using a 2-stage screw press separation. Then, this liquid fraction is digested in a 3.5 L UASB digester at a high organic loading rate. A good and stable performance was observed up to an organic loading rate (OLR) of 12 g COD/(Lrx.d), with a specific methane production of 2.6 L CH₄/(Lrx.d) and a degradation of 85% of the initial total COD. Compared to the conversion of the same initial waste with a continuously stirred tank reactor (CSTR), this new treatment strategy leads to 10% lower COD degradation, but can produce the same amount of methane with a digester that is twice as small. The scale-up of this process could contribute to reduced costs related to the anaerobic digestion of food waste, while reducing management efforts associated with digestate handling and increasing process stability at high organic loading rates. Full article