Upflow Anaerobic Sludge Blanket Reactor Research Articles

Impact of chemical oxygen demand to nitrogen ratio on ANAMMOX bacterial growth in an up-flow anaerobic sludge blanket reactor

Impact of chemical oxygen demand to nitrogen ratio on ANAMMOX bacterial growth in an up-flow anaerobic sludge blanket reactor

Using amino acid waste liquid as functional supplement to change microbial community in up-flow anaerobic sludge blanket treatment of methanolic wastewater.

In this study, amino acid waste liquid was employed as a functional supplement (designated as amino acid-rich FS) in the up-flow anaerobic sludge blanket (UASB) treatment of methanolic wastewater. The effect of amino acid-rich FS was evaluated through repeated batch tests, showing that a 0.5% and 1% dosage increased the maximum methane production rate by 93.60% and 123.04%, respectively, by promoting faster methanol degradation. Additionally, long-term operation of the UASB reactor was conducted with increased dosages of amino acid-rich FS, resulting in improved performance. Microbial community analysis demonstrated that the addition of amino acid-rich FS enhanced microbial diversity, with the abundance of Sporomusa increasing by 47.5 times. Beyond the original cooperative relationships, an additional synergy between Sporomusa and Methanosarcina was observed. These findings could address the key challenge of limited microbial diversity in the anaerobic treatment of methanolic wastewater.

Treatment of sugarcane vinasse in AnMBR and UASB: process performance and microbial community comparison

Vinasse is a by-product of sugarcane processing which is often used in fertigation; however, the direct use of vinasse harms the environment and reduces soil productivity due to its physicochemical properties. Anaerobic digestion (AD) offers an alternative to mitigate part of the negative effects. Anaerobic high-rate reactors, which mainly rely on sludge granulation, are mostly used in AD of vinasse wastewater. However, the composition of vinasse such as high concentration of solids and organic matter, high salinity, low pH, and high concentrations of sulfate, affect granule formation, leading to sludge washout. Anaerobic membrane bioreactors (AnMBR) present an alternative for vinasse treatment, eliminating the need for sludge granulation and producing a nutrient-rich effluent with minimal residual organics and no suspended solids. Research on sugarcane vinasse treatment using AnMBRs is limited. Most studies have employed submerged internal membrane modules, highlighting the need for further research with different reactor configurations to enhance process performance. In this study, an AnMBR equipped with an external inside-out crossflow ultrafiltration membrane was compared to an upflow anaerobic sludge blanket (UASB) reactor for the treatment of sugarcane vinasse. At a volumetric organic loading rate of up to 6 g COD. L-1.d-1, the UASB reactor reached 75% ± 7% of COD removal efficiency whereas the AnMBR generated a solids-free effluent and reached 88% ± 2% of COD removal efficiency. Microorganisms such as Clostridia, Bacteroidia, Mesotaga, Syner-01, Dehalococcoidia, Bacteroidia-DMER64, and Methanolinea were found as the most abundant. The results highlight the AnMBR potential as an effective alternative for treating sugarcane vinasse while overcoming the challenges posed by unsatisfactory sludge granulation.

Sustainable biogas production via anaerobic co-digestion of cheese whey and cattle manure

In Mexico, specifically in Chiapas, the dairy cattle industry plays a significant role in cheese and milk production. However, the large quantities of cattle manure (CM) and cheese whey (CW) generated as byproducts pose environmental challenges if not managed properly. To address this issue, anaerobic digestion (AD) technology offers a sustainable solution by treating organic waste and producing biogas. This research study focuses on assessing the potential of CW and CM, both individually and in co-digestion, in an anaerobic environment. The study also evaluates biogas yield and composition using an up-flow anaerobic sludge blanket (UASB) reactor with different CW and CM mixtures. The findings indicate that the 30CM:70CW ratio exhibited the highest methane yield, surpassing other assays in co-digestion and mono-digestion. Furthermore, the UASB reactor showed that a mixture of 90CW:10CM produced 25.73 L of biogas per gram of volatile solids daily, comprising 60 % methane and 40 % carbon dioxide. This research demonstrates the potential for efficient and environmentally friendly treatment of CM and CW through optimized co-digestion and UASB technology, highlighting the opportunity to generate biogas while reducing waste.

The effect of Fenton sludge on anaerobic digestion of papermaking wastewater in an upflow anaerobic sludge blanket reactor

An upflow anaerobic sludge blanket (UASB) reactor was used to investigate the effect of adding Fenton sludge (FS) on the anaerobic digestion of actual papermaking wastewater. The results showed that a one-time addition of 10 g/L FS could sustainably promote the performance of UASB for more than 40 days. The organic matter removal efficiency increased by 15.56%, and the biogas production increased by 24.52%. The proportion of methane in biogas increased by 12.87%. Adding FS increased the capacitance values of sludge extracellular polymeric substances and the electron transfer system activity in reactor increased by 1.76 times. The dehydrogenase activity and coenzyme F420 of the sludge increased by 1.54 and 2.11 times, respectively. Adding FS enriched the iron-reducing bacteria (Thermodesulfobacteriota) and hydrolytic acid-producing bacteria (Chloroflexota and Synergistota), thereby promoting the hydrolysis and acidification process. Adding FS was beneficial to the enrichment of methanogen, especially Methanosaeta, significantly increasing the methane production.

Full-scale performance and microbial community evolution using dopamine modified ceramic membrane submerged membrane biological reactor in treating young landfill leachate

In this project, ceramic membrane submerged membrane biological reactor (SMBR) was integrated to dissolved air flotation (DAF)-up-flow anaerobic sludge blanket (UASB)-anoxic and aerobic (A/O) system in treating young landfill leachate with a capacity of 300 m3 /day over 185 days’ operation. High removal efficiencies of chemical oxygen demand (COD) (96.8 %), ammonia nitrogen (83.4 %) and total nitrogen (79.6 %) were achieved via DAF-UASB -A/O system. The membrane permeate COD was below 356 mg/L. The permeate turbidity was stable below 11 NTU, met the condition for further ultrafiltration treatment. The SMBR system was operated stability at the flux of 26 LMH because of excellent surface hydrophilicity of the dopamine modified ceramic membrane. Remarkably, immersed chemical cleaning can recover the filterability entirely, indicating the dopamine modified ceramic membrane SMBR can be recognized as fouling–free MBRs. The foulants removal after chemical cleaning on the ceramic membrane was detailly analyzed by scanning electron microscopy coupled with energy dispersive X-ray. The comparative microbial analysis between sludge Day-1 and Day-185 revealed that significant changes of microbial community occurred. Regarding the nitrifying and denitrifying bacteria, Thauera was identified as potential functional specie in simultaneous methanogensis and denitrification process in the UASB reactor. High populations of Proteobacteria, Planctomycetes, Bacteroidetes and Chloroflexi contributed the nitrification and denitrification in the A/O system. The anaerobic ammonia oxidation process might happen due to the identified Planctomycetes. At the genus level, genera, such as Thauera, Phycisphaerae and Betaproteobacteria, with high abundances were functional species ensuring the nitrogen removal in the A/O environment.

Innovative system to maximize methane production from fruit and vegetable waste.

Anaerobic digestion of fruit and vegetable waste (FVW) offers an environmentally friendly alternative for waste disposal, converting it into methane for energy recovery. Typically, FVW digestion is conducted in a continuously stirred tank reactor (CSTR) due to its ease of use and stability with solid concentrations between 5 and 10%. However, CSTRs are limited to organic loading rates (OLRs) of about 3kg COD/m3.day, resulting in large reactor volumes, low methane productivity, and costly wet digestate handling. This work introduces a novel method for methane production from FVW using a high-rate reactor system. The proposed approach involves grinding, centrifuging, and/or pressing the FVW to separate it into liquid and solid phases. The liquid phase is then digested in an up-flow anaerobic sludge blanket (UASB) reactor, while the solid phase undergoes digestion in a dry methanization reactor. A model incorporating all biological reactors was implemented in the Anaerobic Digestion Model 1 (ADM1) to provide a theoretical basis for the experimental development of this system. The current simulation scenarios offer initial references for operating the experimental system, which will, in turn, generate data for further model refinement. For instance, constrained liquid-gas mass transfer was considered for dry fermentation, with additional potential biochemical kinetic limitations to be incorporated following on experimental evidence. The success of this system could enable energy recovery in 72 Central Wholesale Markets across Brazil, offering a critical tool for planning, operating, and optimizing such systems.

Longitudinal wastewater-based surveillance of SARS-CoV-2 during 2023 in Ethiopia.

Although wastewater-based epidemiology (WBE) successfully functioned as a tool for monitoring the coronavirus disease 2019 (COVID-19) pandemic globally, relatively little is known about its utility in low-income countries. This study aimed to quantify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in wastewater, estimate the number of infected individuals in the catchment areas, and correlate the results with the clinically reported COVID-19 cases in Addis Ababa, Ethiopia. A total of 323 influent and 33 effluent wastewater samples were collected from three Wastewater Treatment Plants (WWTPs) using a 24-h composite Moore swab sampling method from February to November 2023. The virus was captured using Ceres Nanotrap® Enhancement Reagent 2 and Nanotrap® Microbiome A Particles, and then nucleic acids were extracted using the Qiagen QIAamp Viral RNA Mini Kit. The ThermoFisher TaqPath™ COVID-19 kit was applied to perform real-time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify the SARS-CoV-2 RNA. Wastewater viral concentrations were normalized using flow rate and number of people served. In the sampling period, spearman correlation was used to compare the SARS-CoV-2 target gene concentration to the reported COVID-19 cases. The numbers of infected individuals under each treatment plant were calculated considering the target genes' concentration, the flow rate of treatment plants, a gram of feces per person-day, and RNA copies per gram of feces. SARS-CoV-2 was detected in 94% of untreated wastewater samples. All effluent wastewater samples (n = 22) from the upflow anaerobic sludge blanket (UASB) reactor and membrane bioreactor (MBR) technology were SARS-COV-2 RNA negative. In contrast, two out of 11 effluents from Waste Stabilization Pond were found positive. Positive correlations were observed between the weekly average SARS-CoV-2 concentration and the cumulative weekly reported COVID-19 cases in Addis Ababa. The estimated number of infected people in the Kality Treatment catchment area was 330 times the number of COVID-19 cases reported during the study period in Addis Ababa. This study revealed that SARS-CoV-2 was circulating in the community and confirmed previous reports of more asymptomatic COVID-19 cases in Ethiopia. Additionally, this study provides further evidence of the importance of wastewater-based surveillance in general to monitor infectious diseases in low-income settings. Wastewater-based surveillance of SARS-CoV-2 can be a useful method for tracking the increment of COVID-19 cases before it spreads widely throughout the community.

Potential for nutrients reuse, carbon sequestration, and CO2 emissions reduction in the practice of domestic and industrial wastewater recycling into agricultural soils: A review

This review assesses the feasibility of reusing treated wastewater for irrigation in agricultural soils as a strategy for nutrients recycling and mitigation of CO2 emissions. Through a literature review, it was examined wastewater sources enriched with carbon and nutrients, including municipal wastewater and associated sludge, vinasse, swine wastewater, as well as wastewater from the food industry and paper and pulp production. The review also explores the dynamics of organic matter within the soil, discussing the aspects related to its potential conversion to CO2 or long-term storage. It was found that industrial wastewaters, owing to their higher organic matter and recalcitrance, exhibit greater potential for carbon storage. However, the presence of pollutants in wastewater necessitates careful consideration, particularly concerning their impact on soil quality. Toxic metals, microplastics, and organic compounds emerged as significant contaminants that could accumulate in the soil, posing risks to ecosystem health. To mitigate the environmental impacts, it was evaluated various wastewater treatment technologies and their associated carbon emissions. While advanced treatments may effectively reduce the contaminant load and mitigate soil impacts, their adoption is often associated with an increase in CO2 emissions. Membrane bioreactors, microfiltration, ultrafiltration, and up-flow anaerobic sludge blanket reactors were identified as promising technologies with lower carbon footprints. Looking ahead, future research should aim to enhance the understanding of carbon dynamics in soil and validate the environmental impacts of treated wastewater disposal. Despite remaining uncertainties, the literature indicates a positive outlook for wastewater recycling in soil, offering a viable strategy for carbon storage and mitigation of greenhouse gas emissions.

Performance evaluation of integrated Upflow Anaerobic Sludge Blanket reactor with trickling filter used for municipal wastewater treatment and effluent reuse potential for agriculture

Effluent reuse is a rapidly growing field of research where assessing the quality of effluent is one of the focus areas. This research examines the viability of using wastewater in agriculture by testing an integrated Upflow Anaerobic Sludge Blanket (UASB) reactor with a trickling filter (TF) system during the dry season. Compliance monitoring was conducted for 30 days from May 11 to June 9 of 2021. Samples were collected, handled, and analyzed following standard wastewater analysis procedures for biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), volatile suspended solids (VSS), cations, anions, heavy metals, E. coli, and helminth egg. The UASB-TF system in Kality wastewater treatment performed well in removing COD, BOD5, and TSS with average removal rates of 80.5%, 82.9%, and 80.9%, respectively, compared well with similar treatment configurations. The effluent quality satisfied the national inland discharge limit with a residual concentration of 125.1 mg/L for COD, 61.7 mg/L for BOD5 and 85.8 mg/L for TSS. On the other hand, high concentrations of chromium, nitrate-nitrogen, and helminth egg count restricted effluent reuse for agricultural purposes due to high health risks and environmental contamination. We found out that discharging industrial sewage into the domestic sewer network could inhibit microbial growth and affect the biological treatment processes. Furthermore, adopting integrated treatment systems in developing countries might face operational challenges and monitoring nitrate, helminth egg, and heavy metals would help provide timely operational feedback. An appropriate tertiary treatment unit—constructed wetlands or polishing ponds—is therefore needed to be introduced to ensure effluent reuse for agricultural purposes.

Investigating upflow anaerobic sludge blanket process to treat forward osmosis effluents of concentrated municipal wastewater under psychrophilic temperature

This work investigated the stability of the Upflow Anaerobic Sludge Blanket (UASB) reactor under psychrophilic temperatures with varying feed streams, simulating typical and concentrated sewage. In Phase I, treating municipal wastewater, chemical oxygen demand (COD) removal dropped from 77 ± 6 % to 41 ± 2 % as hydraulic retention time decreased from 24 to 12 h and organic loading rate (OLR) increased from 0.6 to 1.3 gCOD/(L∙d). In Phase II, at a similar OLR (≈1.2 gCOD/(L∙d)), the UASB treated organic-rich effluents (from 1.0 to 2.1 ± 0.1 gCOD/L) resulting from the pre-treatment of the forward osmosis (FO) process. The UASB performance improved significantly, achieving 87 ± 3 % COD removal and 63 ± 4 % methane recovery, with microbial analysis confirming methanogen growth. The COD mass balance showed up to 30 % more electrical energy recovery from sewage compared to conventional wastewater treatment plants (WWTPs), indicating that the FO-UASB combination is a promising approach to achieve energy-neutral operation in WWTPs.

Exposure pattern of triclosan and tetracycline change their impacts on methanogenic digestion microbiomes

Triclosan (TCS) and tetracycline (TC) as common antibacterial agents are frequently detected in the influent of wastewater treatment plants. The TCS and TC exposure patterns may determine their impacts on wastewater treatment microbiomes, on which information remains unknown. In this study, the impacts of sequential exposure of TCS and TC on methanogenic digestion microbiomes in upflow anaerobic sludge blanket (UASB) reactors were analyzed and compared with that of the same microbiomes being simultaneously exposed to TCS and TC. Results indicated that the UASB reactor 2 (MD2) with sequential TCS-TC exposure consistently demonstrated higher chemical oxygen demand (COD) removal efficiency (94.7 %). In contrast, in the MD1 reactor, COD removal efficiency decreased from 94.4 % to 82.7 % upon simultaneous exposure to TCS and TC. Accordingly, a 1.8 times higher enrichment of total antibiotic resistance genes (ARGs) was observed in MD1 relative to MD2. Using a dissimilarity-overlap approach, the MD2 microbiome with sequential exposure was predominantly mediated by deterministic factors in their community assembly (largely contributed by abundant and intermediate biospheres), resulting in microbial interaction networks with higher average clustering coefficients and shorter average path lengths, compared to the MD1 microbiomes. Our results could support sustainable management of TCS and TC contamination in wastewater treatment plants.

Synergistic enhancement of UASB reactor for leachate treatment using Fe2O3 nanomodified pumice and ozone oxidation

Pumice, a material with good application prospects in adsorption and water treatment, has less research on its improvement. In this study, the positive benefits of anaerobic reaction were explored by loading iron oxide on pumice and combined with ozone advanced oxidation. In the experiment, the Upflow Anaerobic Sludge Blanket (UASB) reactor was enhanced with pretreatment from an ozone generator (6 L/min flow rate, delivering 500 ± 5 % mg/L of ozone) and the addition of 250 ml of Fe2O3 Nanomodified Pumice (FP). The results showed that FP could play an active role in the formation of sludge particles. The addition of FP increased the level of interspecies electron transfer (DIET), improved the reaction of hydrolysis and acid production, methane production and the activity of dominant species. At the same time, the advanced oxidation of ozone and the improvement of FP on the decomposition ability avoid the accumulation of macromolecular volatile fatty acids and reduce the risk of reactor acidification. At the microbial level, the addition of FP better promoted the correlation between the three dominant strains of Firmicutes, Synergistota, and Desulfobacteriota, and promoted the connection between the reactions. Under these promoting effects, not only the start-up time of the reactor was accelerated, but also the anti-load capacity was improved, and the reactor could maintain a removal rate of more than 90 % at an organic load of 53.89 kgCOD / (m3 · d).

De novo anaerobic granulation with varying organic substrates: granule growth and microbial community responses

Anaerobic granulation from dispersed inoculum is recognized as a slow process. However, studies under saline conditions have shown that adding complex proteinaceous substrates can accelerate this process. To explore whether this holds true also under non-saline conditions, we conducted a 262-days experiment with four lab-scale upflow anaerobic sludge blanket reactors inoculated with digested sewage sludge. Each reactor received a synthetic feed containing varying amount of carbohydrate/protein substrate: glucose (RGlu), acetate/tryptone (RAc+Try), glucose/tryptone (RGlu+Try), and glucose/starch (RGlu+Sta). Development of granules with different influent composition was monitored with macroscopy, analysis of the extracellular polymeric substances, and microbial diversity. Granulation was faster in reactors RGlu+Try and RGlu+Sta. Increasing granule diameters positively correlated with the occurrence of bacteria from Muribaculaceae and Lachnospiraceae families, suggesting their involvement in de novo granulation. Granules of RGlu+Try also had high relative abundances of both fermenting bacteria (e.g. Lactococcus, Streptococcus, Trichococcus) and bacteria involved in the oxidation of volatile fatty acids (Smithella, Acetobacteroides). The results of this study provide a basis for strategies to enhance the sludge granulation rate in practice when granular inoculum is not available. Specifically, supplementing small amounts of waste protein during reactor start-up can be effective.

Methanogenesis kinetics of organic matter of the leachate in an up-flow anaerobic sludge blanket reactor

Understanding the treatment of leachate mediated by the development of anaerobic sludge makes it possible to create an effective design process of biodegradation technology. This study used an up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas–liquid-solid separator to capture CH4 for treating landfill leachate to improve understanding of methanogenesis kinetics of organic matter. The performance of UASB was able to remove 154.75 g/L of chemical oxygen demand (COD) content of the leachate originally anticipated to emit 2.99 L of CH4 production into the atmosphere. The trend in the variation of internal mass transfer (IMT) factor was close to the global mass transfer factor; however, it was far higher than that of external mass transfer (EMT) factor. After 30 days of the experiment, methanogenesis kinetics of organic matter of the leachate were supported mainly by the breakdown of complex molecules. The rate-limiting step of CH4 desorption was controlled by IMT at the beginning and then by EMT after 30 days of the experiment. The strongly decreased EMT factor was counterbalanced by an increased value of the IMT factor at before 5 days of the experiment. It would be of interest to predict the methanogenesis kinetics of CH4 desorption using the Generalized Fulazzaky equations, which cannot be evaluated using other models. Analysis of the methanogenesis kinetics of organic matter of the leachate provides a new insight into the performance of UASB reactor, which may contribute to advanced treatment of landfill leachate in the future.

Treatment of azo dye-containing wastewater in a combined UASB-EMBR system: Performance evaluation and membrane fouling study

This work investigated the treatment of azo dye-containing wastewater in an upflow anaerobic sludge blanket (UASB) reactor combined with an electro-membrane bioreactor (EMBR). Current densities of 20 A m−2 and electric current exposure mode of 6′ON/30′OFF were applied to compare the performance of the EMBR to a conventional membrane bioreactor (MBR). The results showed that dye (Drimaren Red CL-7B) removal occurred predominantly in the UASB reactor, which accounted for 57% of the total dye removal achieved by the combined system. When the MBR was assisted by electrocoagulation, the overall azo dye removal efficiency increased from 60.5 to 67.1%. Electrocoagulation batch tests revealed that higher decolorization rates could be obtained with a current density of 50 A m−2. Over the entire experimental period, the combined UASB-EMBR system exhibited excellent performance in terms of chemical oxygen demand (COD) and NH4+-N removal, with average efficiencies above 97%, while PO43--P was only consistently removed when the electrocoagulation was used. Likewise, a consistent reduction in the absorption spectrum of aromatic amines was observed when the MBR was electrochemically assisted. In addition to improving the pollutants removal, the use of electrocoagulation reduced the membrane fouling rate by 68% (0.25–0.08 kPa d−1), while requiring additional energy consumption and operational costs of 1.12 kWh m−3 and 0.32 USD m−3, respectively. Based on the results, it can be concluded that the combined UASB-EMBR system emerges as a promising technological approach for textile wastewater treatment.

Treatment appraisal and fate of HMs in up-flow anaerobic sludge blanket and trickling filter-based sewage treatment process: The case of a kaliti Centralized Wastewater Treatment Plant, Addis Ababa, Ethiopia

Heavy metals (HMs) in wastewater could pose a significant challenge to biological treatment systems such as in an Up-flow Anaerobic Sludge Blanket Reactor (UASBr) as well as Trickling Filter (TF) performances. These HMs are associated with retention and accumulation of solid precipitates, limitting solid-liquid separation, disrupting biochemical processes, which ultimately brings environmental risks, such as soil contamination and public health issues, dominantly due to the inhibited activities of degrading microorganisms. A cross-sectional study was applied to investigate the levels of HMs in sewage using composite and grab sampling taken from Kaliti Wastewater Treatment Plant and the samples were analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The HMs concentrations in mean±(SD) were, Ag ranges from below detection level (BDL) to 63.5 (13.5) mg/kg; Ba 60 (4.47) μg/l to 1291(58.5) mg/kg; Al, BDL to 2358.5(662.5) mg/kg; Cd 0 μg/l to 0.35(0.15) mg/kg; Cr 0 μg/l to 10.5(0.7) mg/kg; Cu 0 μg/l to 23.9(1.2) mg/kg; Zn 5.45 (12.3) to 165(5.4) mg/kg, and Mn 165 (49.5) μg/l to 92.5(3.8) mg/kg. Results indicated that Kaliti Wastewater Treatment Plant was effective in removing pollutants and thereby meeting local and international discharge limits. The plant was also found to be effective in removing Al, Cd, Cu, and Cr, but not in removing Ba and Zn. However, a real time data collection and monitoring of seasonal physicochemical parameters and HM levels in the wastewater treatment plant is suggested useful.

Ozonation process at neutral pH integrated with anaerobic treatment system to methylparaben removal

The incomplete removal of emerging pollutants, such as parabens, from wastewater effluents represents a major pathway for their release into the environment. The development of advanced technologies integrated into well-known conventional systems is a solution. Advanced oxidative processes (AOP), such as ozonation and its combinations, are technologies based on the generation of hydroxyl radicals (HO•) capable of removing these pollutants, representing an alternative solution to this problem. Therefore, the present study aimed to investigate the ozonation process combined with hydrogen peroxide (O3/H2O2) in the treatment of anaerobic effluent post-treated by a real-scale upflow anaerobic sludge blanket (UASB) reactor, enriched with methylparaben (MeP). The study was conducted under optimized conditions and at neutral pH of the effluent. To investigate the influence of variables, as ozone concentration, hydrogen peroxide concentration, pH and time, a 24 Factorial experimental design followed by a 22 Doehlert optimization design was implemented. The optimal degradation occurred with 25.0 mg L−1 of O3 and 30.0 mg L−1 of H2O2 at neutral effluent pH, achieving a removal efficiency of 71.6 % after 60 min and 85.5 % after 120 min. The optimized O3/H2O2 process after 60 min achieved a 95.0 % removal of organic matter by biochemical oxygen demand (BOD), reducing the initial concentration from 138 mg L−1 to 7 mg L−1. Acute toxicity test with Artemia salina and Lactuca sativa, indicated an absence of toxicity (TU < 0.4). The findings of this study indicate the positive efficiency of combining post-UASB effluent treatment with O3/H2O2 processes for the removal of methylparaben.

Boron induced multiple quorum-sensing circuits in parallel to assist in anaerobic digestion recovery from volatile fatty acids accumulation

Exogenous quorum sensing (QS) molecular can regulate the activity and granulation process of anaerobic sludge in anaerobic digestion process, but would be impractical as a standalone operation. Here we demonstrated that application of 1 mg L−1 boric acid assisted in an upflow anaerobic sludge blanket (UASB) reactor recovery from volatile fatty acids (VFAs) accumulation. After VFAs accumulation, the chemical oxygen demand (COD) removal suddenly reduced from 78.98% to 55.86%. The relative abundance of acetoclastic methanogens decreased from 55.79% to 68.28%–23.14%∼25.41%, and lead to the acetate accumulate as high as 1317.03 mg L−1. Granular sludge disintegrated and the average size of sludge decreased to 586.38 ± 42.45 μm. Application of 1 mg L−1 boric acid activated the interspecies QS signal (AI-2) and then induced the secretion of intraspecies QS signal (N-acyl-homoserine lactones, AHLs). AHLs were then stimulated the growth of syntrophic acetate oxidizing bacteria and hydrogenotrophic methanogen. Moreover, the concentration of acetate decreased to 224.50 mg‧L−1, and the COD removal increased to 75.10% after application of 1 mg L−1 boric acid. The activated AI-2 may induce multiple quorum-sensing circuits enhance the level of AI-2 and AHLs in parallel, and in turn assisted in anaerobic digestion recovery from VFAs accumulation.

Hydrolytic enzyme activity in high-rate anaerobic reactors treating municipal wastewater in temperate climates

Particulate matter hydrolysis is the bottleneck in anaerobic treatment of municipal wastewater in temperate climates. Low temperatures theoretically slow enzyme-substrate interactions, hindering utilization kinetics, but this remains poorly understood. β-glucosidase, protease, and lipase activities were evaluated in two pilot-scale upflow anaerobic sludge blanket (UASB) reactors, inoculated with different sludges and later converted to anaerobic membrane bioreactors (AnMBRs). Despite similar methane production and solids hydrolysis rates, significant differences emerged. Specific activity peaked at 37 °C, excluding the predominance of psychrophilic enzymes. Nevertheless, the Michaelis-Menten constant (Km) indicated high enzyme-substrate affinity at the operational temperature of 15–20 °C, notably greater in AnMBRs. It is shown, for the first time, that different seed sludges can equally adapt, as hydrolytic enzymatic affinity to the substrate reached similar values in the two reactors at the operational temperature and identified that membrane ultrafiltration impacted hydrolysis by a favourable enzyme Michaelis-Menten constant.