Search Results (60)

This study addresses the microbial corrosion of cement-based materials in coastal urban sewer networks, systematically investigating the kinetic mechanisms of sulfur biogeochemical cycling under seawater infiltration conditions. Through dynamic monitoring of sulfide concentrations and environmental parameter variations in anaerobic pipelines, a multiphase coupled kinetic model integrating liquid-phase, gas-phase, and biofilm metabolic processes was developed. The results demonstrate that moderate salinity enhances the activity of sulfate-reducing bacteria (SRB) and accelerates sulfate reduction rates, whereas excessive sulfide accumulation inhibits SRB activity. At 35 °C, the mathematical model coefficient “a” for sulfate reduction in the reactor with 3 g/L salinity was significantly higher than those in reactors with 19 g/L and 35 g/L salinities, with no significant difference observed between the latter two. Overall, high sulfate concentrations do not act as limiting factors for sulfide oxidation under anaerobic conditions; instead, they enhance the reaction within specific concentration ranges. The refined kinetic model enables prediction of sulfur speciation in tropical coastal urban sewer pipelines, providing a scientific basis for corrosion risk assessment. Full article

The majority of extant studies concentrate on the reactivation of dormant Anammox biomass or the recovery of activity under specific storage conditions. Research on rehabilitation strategies for anaerobic ammonium oxidation (Anammox) systems is limited, with the exception of research on inhibitory factors. The recovery characteristics of biofilm systems after collapse induced by varying degrees of ammonia-nitrogen and small-molecular organic compound composite shocks have not been thoroughly elucidated. This study addresses the collapse of Anammox biofilm systems caused by sodium acetate inhibition through multi-phase rehabilitation strategies, stoichiometric analysis, and microbial community succession dynamics. Two regression algorithms—Support Vector Regression (SVR) and eXtreme Gradient Boosting (XGBoost)—were employed to construct predictive models for Total Nitrogen Removal Efficiency (TNRE) and Total Nitrogen Removal Rate (TNRR) in the CANON system, with model performance evaluated via coefficient of determination (R²) and root mean square error (RMSE). Results demonstrated that after terminating moderate-to-high sodium acetate dosing (300 mg/L and 500 mg/L), reactors R300 and R500 achieved TNRE recovery to 57.98% and 58.86%, respectively, and TNRR of 0.281 and 0.275 kgN/m³·d within 60–100 days, indicating the reversibility of high-concentration sodium acetate inhibition but a positive correlation between recovery duration and inhibition intensity. Microbial community analysis revealed that Planctomycetota (including Candidatus_Kuenenia) rebounded to 46–49% relative abundance in R100, synchronized with TNRE improvement. In contrast, R300 and R500 exhibited ecological niche replacement of denitrifiers (Denitratisoma) and partial TNRE restoration despite enhanced performance. Model comparisons showed SVR outperformed XGBoost in TNRE prediction, whereas XGBoost demonstrated superior TNRR prediction accuracy with R² approaching 1 and RMSE nearing 0, significantly surpassing SVR. This work provides critical insights into recovery mechanisms under organic inhibition stress and establishes a robust predictive framework for optimizing nitrogen removal performance in CANON systems. Full article

The partial nitrification–anammox process offers a cost-effective, energy-efficient, and environmentally sustainable approach for nitrogen removal in wastewater treatment. However, its application under low ammonia nitrogen conditions faces operational challenges including prolonged start-up periods and excessive nitrite oxidation. This study employed a strategy combining polyurethane surface positive charge enhancement and zeolite loading to develop a carrier capable of microbial enrichment and inhibition of nitrate generation, aiming to initiate the partial nitrification-anammox process in a sequencing batch reactor. Operational results demonstrate that the modified carrier enabled the reactor to achieve a total nitrogen removal efficiency of 78%, with the effluent nitrate nitrogen reduced to 6.03 mg-N/L, successfully initiating the partial nitrification-anammox process. The modified carrier also exhibited accelerated biofilm proliferation (both suspended and attached biomass increased). Additionally, 16S rRNA revealed a higher relative abundance of typical anammox bacteria Candidatus Brocadia in the biofilm of the modified carrier compared to the original carrier, alongside a decline in nitrifying genera, such as Nitrolancea. These microbial shifts effectively suppressed excessive nitrite oxidation, limited nitrate accumulation, and sustained efficient nitrogen removal throughout the reactor’s operation. Full article

In this study, we explore the use of C. kluyveri in synthetic biofilms for the production of 1-butyrate and 1-hexanoate, investigating the impact of inoculation temperature during biofilm formation and the presence of yeast extract. Therefore, a novel synthetic biofilm reactor has been designed and constructed. Prior to investigating synthetic biofilms in this reactor, we carried out preliminary batch experiments in anaerobic flasks containing an inoculated agar hydrogel fixed at the bottom and overlaid medium. For the operation of the novel synthetic biofilm reactor, specific volumes of inoculated agar hydrogel were dispensed into a cylindrical mold with a diameter of 102 mm, forming the synthetic biofilm with a height of 4 mm, which was then transferred into the biofilm reaction chamber onto the support grid. The biofilm support grid separates the gas phase (CO₂, N₂) above the synthetic biofilm from the aqueous phase (medium) below. Our results show that C. kluyveri remains metabolically active at biofilm preparation temperatures of up to 45 °C, with extended lag phases observed at 70 °C. The synthetic biofilm demonstrated efficient chain elongation in batch processes, converting ethanol and acetate into 1-butyrate and 1-hexanoate, with final concentrations of 2.7 g L⁻¹ and 10.1 g L⁻¹, respectively, with yeast extract in the circulating liquid medium of the synthetic biofilm reactor setup. The maximum estimated space-time yields for 1-butyrate and 1-hexanoate, referenced to the biofilm volume, were 1.331 g L⁻¹ h⁻¹ and 4.947 g L⁻¹ h⁻¹, respectively. Experiments without yeast extract lead to final concentrations of 2.0 g L⁻¹ 1-butyrate, and 7.3 g L⁻¹ 1-hexanoate and maximum estimated space-time yields, referenced to the biofilm volume, were 0.332 g L⁻¹ h⁻¹ and 1.123 g L⁻¹ h⁻¹, respectively. The use of synthetic biofilms, even without yeast extract, eliminates the need for significant cell growth during chain elongation. However, product concentrations were lower without yeast extract. Full article

Many small communities rely on on-site wastewater treatment systems such as septic tanks; however, there are concerns regarding the level of wastewater treatment being achieved. Appropriate solutions for these communities are needed to upgrade existing septic tanks. Anaerobic filters are a potential solution, which can be added downstream of the septic tank and operate by containing media which allow a biofilm to form. Ideally, this media would be easily accessible and affordable. In this work, the use of brown coconut husks is investigated, and it is found that 68% of the chemical oxygen demand (COD) can be removed by these systems. Nutrient levels were also monitored in the effluent to determine whether the leaching of nutrients from the coconut husks is a concern. It was found that initially some nitrogen and phosphorus had leached but these were washed out of the reactor very quickly and had a minimal impact on the effluent concentrations. Examination of the coconut husks after 10 months of operation showed no signs of the coconut husks beginning to break down, suggesting that the use of coconut husks as media in anaerobic filters should be investigated further. Full article

Precise control of operational parameters in anaerobic digestion reactors is crucial to avoid imbalances that could affect biomethane production and alterations in the microbiota. Restoring the methanogenic microbiota after a failure is essential for recovering methane production, yet no published strategies exist for this recovery. In this study, we restored the methanogenic microbiota in an anaerobic SBR reactor that operates with both biofilm and suspended biomass simultaneously, aiming to treat tequila vinasses. Four strategies were evaluated for restoring the methanogenic microbiota: reducing the initial vinasse concentration, increasing the reaction time (RT), adjusting the carbon/nitrogen (C/N) ratio, and progressively increasing the initial vinasse concentration. Among these, adjusting the C/N ratio emerged as a critical parameter for restoring organic matter removal efficiency and reestablishing methanogenic microbiota. The operational conditions under which the methanogenic activity and microbiota were restored were as follows: Operating the A-SBR with an initial vinasse concentration of 60%, an RT of 168 h, a pH of 6.9 ± 0.2, a temperature of 35 ± 2 °C, and a C/N ratio adjusted to 100/1.9 resulted in stable COD removal efficiency of 93 ± 3% over a year and a high percentage of methanogenic microorganisms in both the suspended microbiota (69%) and biofilm (52%). The normalized methane production (0.332 NL CH₄/g CODr) approached the theoretical maximum value (0.35 L CH₄/g CODr) after restoring the population and methanogenic activity within the reactor. Full article

Tomato waste, characterized by high organic matter and moisture content, offers a promising substrate for anaerobic digestion, though rapid acidification can inhibit methanogenic activity. This study investigated the performance of a 10.25 L anaerobic fixed biofilm reactor for biogas production using liquid tomato waste, processed through grinding and filtration, at high organic loading rates, without external pH control or co-digestion. Four scouring pads were vertically installed as a fixed bed within a fiberglass structure. Reactor performance and buffering capacity were assessed over three stages with progressively increasing organic loading rates (3.2, 4.35, and 6.26 gCOD/L·d). Methane yields of 0.419 LCH4/gCOD and 0.563 LCH4/g VS were achieved during the kinetic study following stabilization. Biogas production rates reached 1586 mL/h, 1804 mL/h, and 4117 mL/h across the three stages, with methane contents of 69%, 65%, and 72.3%, respectively. Partial alkalinity fluctuated, starting above 1500 mg CaCO₃/L in Stage 1, dropping below 500 mg CaCO₃/L in Stage 2, and surpassing 3000 mg CaCO₃/L in Stage 3. Despite periods of forced acidification, the system demonstrated significant resilience and high buffering capacity, maintaining stability through hydraulic retention time adjustments without the need for external pH regulation. The key stability indicators identified include partial alkalinity, effluent chemical oxygen demand, pH, and one-day cumulative biogas. This study highlights the effectiveness of anaerobic fixed biofilm reactors in treating tomato waste and similar fruit and vegetable residues for sustainable biogas production. Full article

Anaerobic digestion (AD) produces useful biogas and waste streams with high levels of dissolved methane (CH₄) and ammonium (NH₄⁺), among other nutrients. Membrane biofilm reactors (MBfRs), which support dissolved methane oxidation in the same reactor as simultaneous nitrification and denitrification (ME-SND), are a potential bubble-less treatment method. Here, we demonstrate ME-SND taking place in single-stage, AD digestate liquid-fed MBfRs, where oxygen (O₂) and supplemental CH₄ were delivered via pressurized membranes. The effects of two O₂ pressures, leading to different O₂ fluxes, on CH₄ and N removal were examined. MBfRs achieved up to 98% and 67% CH₄ and N removal efficiencies, respectively. The maximum N removal rates ranged from 57 to 94 mg N L⁻¹ d⁻¹, with higher overall rates observed in reactors with lower O₂ pressures. The higher-O₂-flux condition showed NO₂⁻ as a partial nitrification endpoint, with a lower total N removal rate due to low N₂ gas production compared to lower-O₂-pressure reactors, which favored complete nitrification and denitrification. Membrane biofilm 16S rRNA amplicon sequencing showed an abundance of aerobic methanotrophs (especially Methylobacter, Methylomonas, and Methylotenera) and enrichment of nitrifiers (especially Nitrosomonas and Nitrospira) and anammox bacteria (especially Ca. Annamoxoglobus and Ca. Brocadia) in high-O₂ and low-O₂ reactors, respectively. Supplementation of the influent with nitrite supported evidence that anammox bacteria in the low-O₂ condition were nitrite-limited. This work highlights coupling of aerobic methanotrophy and nitrogen removal in AD digestate-fed reactors, demonstrating the potential application of ME-SND in MBfRs for the treatment of AD’s residual liquids and wastewater. Sensor-based tuning of membrane O₂ pressure holds promise for the optimization of bubble-less treatment of excess CH₄ and NH₄⁺ in wastewater. Full article

To expedite enrichment of anaerobic ammonia-oxidizing bacteria (AnAOB) as a way to reduce the start-up time, leading to a quicker transition into stable operation, the anaerobic ammonia oxidation (anammox) process was initiated by a biofilm reactor with polyurethane porous material. The enrichment of anammox bacteria was studied by progressively increasing the influent substrate concentration while simultaneously decreasing hydraulic retention time. Following a 73 d start-up and subsequent 103 d enrichment phase, the removal rates of ammonia and nitrite reached 97.87% and 99.96%, respectively, and the community was characterized by the development of brick-red anammox biofilms and granules. The predominant bacterial phyla within the reactor were Planctomycetota, Chloroflexi, and Proteobacteria, with relative abundances of 25.25%, 29.41%, and 14.3%, respectively, and the dominant genus was Candidatus brocadia, comprising 20.44% of the microbial community. These findings indicate that the polyurethane porous material biofilm reactor is conducive to the enrichment of AnAOB. After enrichment, the anaerobic microbial community exhibited significant richness and diversity, with anammox bacteria as the primary group. Full article

Nutrient removal in conventional wastewater treatment systems is expensive due to the high aeration costs. An alternative method for effective and sustainable nitrogen removal in wastewater treatment is anaerobic ammonium oxidation (Anammox) implemented with other innovative technologies, such as membrane-aerated biofilm reactors (MABRs). A major challenge associated with the Anammox process is effective control of nitrite-oxidizing bacteria (NOB). High temperature operation in wastewater treatment systems can promote Anammox bacterial growth and inhibit NOB activity. This research aims to investigate the feasibility of integrating Anammox processes with a lab-scale MABR and to examine the effects of high temperature aeration supplied to MABR systems on Anammox bacterial growth and NOB suppression. Experimental results indicate that the membrane’s air permeability was a critical parameter for the successful operation of Anammox-integrated MABR systems due to its influence on the system’s dissolved oxygen concentration (0.41 ± 0.39 mg O₂/L). The ammonia removal by AOB and Anammox bacteria was determined to be 7.53 mg N/L·d (76.5%) and 2.12 mg N/L·d (23.5%), respectively. High temperature aeration in MABRs with the Anammox process shows a promising potential for improving energy consumption and sustainable nitrogen removal in wastewater treatment systems. Full article

Anaerobic ammonium oxidation (ANAMMOX) has emerged as a promising sustainable nitrogen removal technology that offers significant advantages over conventional nitrification–denitrification processes, such as reduced energy consumption, a 60% reduction in oxygen demand, and a 90% reduction in sludge production. However, the practical application of ANAMMOX is hindered by several challenges, including the slow growth of ANAMMOX bacteria, long start-up periods, and high sensitivity to environmental disturbances. Recent studies have highlighted the crucial role of extracellular polymeric substances (EPSs) in the formation, activity, and stability of ANAMMOX biofilms and granules. An EPS is a complex mixture of high-molecular-weight polymers secreted by microorganisms, mainly composed of polysaccharides, proteins, nucleic acids, and lipids. The diverse physicochemical properties and functional groups of EPSs enable them to serve as a structural scaffold, protective barrier, sorption site, electron shuttle, and nutrient source for ANAMMOX bacteria. This review aims to provide an overview of the latest research progress on harnessing the potential of EPSs to enhance the ANAMMOX process. The characteristics, compositions, and extraction methods of ANAMMOX-derived EPSs are summarized. The mechanisms of how EPSs facilitate the enrichment, immobilization, aggregation, and adaptation of ANAMMOX bacteria are elucidated. The strategies and effects of EPS supplementation on improving the performance and robustness of ANAMMOX reactors under various stresses are critically reviewed. The challenges and future perspectives of the EPS-mediated optimization of the ANAMMOX process are also discussed. This review sheds new light on exploiting EPSs as a renewable bioresource to develop more efficient and stable ANAMMOX applications for sustainable wastewater treatment. Full article

The integration of a microbial electrolysis cell (MEC) is an effective strategy for enhancing the efficiency and stability of an anaerobic digestion (AD) system for energy recovery from waste-activated sludge (WAS). Typically, electrodes are arranged as separate components, potentially disrupting mixing and complicating the reactor configuration, posing challenges for the scaling up of AD-MEC coupling systems. In this study, electrodes were introduced into a continuous stirring tank reactor (CSTR) in a “stealth” manner by integrating them with the inner wall and stirring paddle. This electrode arrangement approach was validated through a sequential batch digestion experiment, resulting in a remarkable 1.5-fold increase in cumulative methane production and a shortened lag period compared to the traditional CSTR with a nonconductive inner wall and stirring paddle. Both the conductive materials (CMs) employed in the electrodes and the electrochemical processes equally contributed to the observed enhancement effect of the electrodes by regulating the evolution of the microbial community within the electrode biofilms, with a specific emphasis on the enrichment of methanogens (primarily Methanobacterium). This research offers a potential avenue to solve the contradiction between the electrode introduction and the mixing operation in AD-MEC coupling systems and to contribute to its future commercial application. Full article

Much emphasis has been given to algal biomass growth in dairy farm wastewater. Most of the systems examined require productive land to be converted and/or freshwater use to dilute high concentrations of nutrients found in dairy effluent. A rotating algal biofilm (RABR) provides the capacity to grow algae without sacrificing productive land or freshwater. In theory, this system would overcome some of the economic and environmental challenges that other systems have. A combination of theoretical information, nutrient uptake formulas, and economic formulas were used to calculate the potential of biogas production from algae grown in an RABR with dairy effluents. The average nutrient uptake was 0.8 mgN/m² per day and 0.1 mgP/m² per day. The maximum methane production from the anaerobic digestion of algae was 112 m³/RABR·year. The minimum and maximum economic scenarios resulted in gross profits of NZD −2101 and −1922. After evaluating this system for the first time in the New Zealand dairy farming context, it was found that biogas production from an RABR is not a feasible option for New Zealand dairy farmers. Full article

The current investigation delved into the utilization of cattle and municipal sanitary inocula for anaerobic digestion of poultry wastes, addressing a crucial and pragmatic challenge in waste management. The emphasis on poultry waste is pertinent due to its well-documented impediments in anaerobic digestion, attributed to heightened levels of ammonia and volatile fatty acids (VFAs). The strategic selection of cattle and municipal sanitary inocula suggests an approach aimed at bolstering the anaerobic digestion process. In this study, we evaluated the use of cattle and municipal sanitary inocula for the anaerobic digestion of various poultry wastes, which is often challenged by high levels of ammonia and volatile fatty acids (VFAs). The substrates tested included belt waste (Poultry A), poultry litter plus feed residues (Poultry B), tray hatchery ©, and stillage. These substrates were processed in two continuous stirred tank reactors (CSTRs), R-1 (with antibiotic monensin) and R-2 (without monensin). Initially, both reactors operated with the same hydraulic retention time (HRT), using a substrate ratio of stillage: belt: tray hatchery (S:B:T) of 70:15:15. On the 41st day, the HRT was adjusted to 20 days, and the substrate ratio was changed to S:A:T 70:40:40. The specific methane yield for R-1 started at 10.768 L g⁻¹ COD, but decreased to 2.65 L g⁻¹ COD by the end of the experiment. For R-2, the specific methane yield varied between 0.45 L g⁻¹ COD and 0.243 L g⁻¹ COD. Microbial composition in the reactors changed over time. In R-1, bacteroides were consistently dominant, while firmicutes were less abundant compared to R-2. Proteobacteria were initially low in abundance, but spirochetes were found in both reactors throughout the experiment. The study concluded that Poultry B substrates, due to their rich nutrient and trace element composition, are suitable for biogas plants. Municipal sanitary inocula also showed promise due to their resilience in high ammonia concentrations. Further research into biofilm interactions is recommended to better understand microbial responses to high ammonia concentrations, which can lead to propionate production in anaerobic digestion (AD). Full article

A combined anaerobic–anoxic–oxic moving bed biofilm reactor (A²O-MBBR) constructed wetlands process was used to treat low carbon-to-nitrogen (C/N) simulated sewage. The results showed that the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) by this process were 94.06%, 94.40%, 67.11%, and 84.57%, respectively, and the concentrations of COD, NH₄⁺-N, TN, and TP in the effluent were lower than the Class I-A standard of GB18918-2002. In the anoxic zone, NH₄⁺-N had an inhibitory effect on phosphorus uptake via phosphorus-accumulating organisms (PAOs). The highest community diversity was observed in the anoxic zone sludge at 24 d. During the water-quality-shock loads stage, microbial community diversity decreased in a combined A²O-MBBR constructed wetlands reactor. At the phylum level, bacteria within the mature activated sludge were dominated by Proteobacteria, while Planctomycetes bacteria were the dominant species in the constructed wetlands. At the genus level, Tolumonas spp. were the dominant species in the 12 d and 24 d constructed wetlands and the anaerobic zone, with relative abundance percentages ranging from 20.24 to 33.91%. In the water-quality-shock loads stage, they were replaced by denitrifying bacteria such as Herbaspirillum spp. Unclassified_Burkholderiales was the dominant species in the constructed wetlands, with a relative abundance of 33.09%. Full article