Upflow Anaerobic Sludge Blanket Reactor Research Articles

Process performance and microbial community structures in three ANAMMOX-mediated systems with different mixing conditions

Anaerobic ammonium oxidation (ANAMMOX) represents an efficient, cost-effective, but sensitive nitrogen removal process for wastewater treatment. Different reactor configurations have been used in full-scale applications but each configuration has unique characteristics, which could influence process performance and community dynamics. The objective of this study is thus to analyze the impact of mixing conditions on nitrogen removal and community structures in a hybrid up-flow anaerobic sludge blanket reactor (H-UASB), moving bed biofilm reactor (MBBR) and gas-lift reactor (GLR). Community dynamics were studied through shotgun sequencing, while concentrations of NH4+, NO3- and NO2- were determined colorimetrically. During the study, MBBR displayed the highest average nitrogen removal efficiency (NRE) (67%) followed by H-UASB (63%), and then GLR (54%). The relative abundance of AMX in the suspended biomass was consistently higher in H-UASB than in MBBR and GLR, while that of nitrite-oxidizing bacteria (NOB) and complete ammonia-oxidizing bacteria (CMX) was higher in MBBR than in GLR and H-UASB. It was observed that the relative abundance of ammonia-oxidizing bacteria (AOB) in the suspended biomass fluctuated across the reactors. The relative abundance of CMX and Nitrospira in the biofilms in H-UASB and GLR was higher than in the suspended biomass, while comparable abundance was observed in MBBR. On the contrary, the relative abundance of AMX in the suspended biomass in H-UASB and MBBR was higher than in the biofilms, whereas it was comparable in the GLR. It was thus concluded that the mixing conditions in the three reactors influenced process performance and community dynamics.

Impact of feedwater protein contents on calcium phosphate mineralization in anaerobic digesters

Calcium phosphate (CaP) mineralization and accumulation in anaerobic digesters represent an attractive approach to recovery phosphorus (P) from wastewater. Previous studies demonstrated that under certain anaerobic digestion conditions, favorable localized environment can be developed to facilitate CaP granule growth. However, factors that trigger the CaP nucleation in anaerobic reactors have not been elucidated. In this study, to examine the driving forces in the microenvironment for the CaP nucleation, two laboratory upflow anaerobic sludge blanket (UASB) reactors fed with two types of synthetic wastewater were operated under mesophilic conditions. The feed of one reactor (G reactor) had glucose as the sole carbon source, and the feed of the other reactor (G+B reactor) had glucose (60% chemical oxygen demand (COD)) and bovine serum albumin (BSA, 40% COD) as the combined carbon sources. The results showed that P and Ca removals were only observed in the G+B reactor. The main difference between the two reactors was the elevated pH in the G+B reactor, which may be attributed to the degradation of amino acids. The elevated pH caused the deprotonation of the negatively charged functional groups in the sludge, creating available active surfaces for Ca2+ complexation. The high availability of OH- and the enriched Ca in the G+B reactor built a favorable microenvironment to overcome the activation energy barriers hindering the CaP nucleation. The stabilized CaP mineralization largely depended on the well-established microbial community, where the efficient hydrogenotrophic methanogens and syntrophic acetogens may maintain a stabilized pH environment to prevent the dissociation of CaP minerals.

A comprehensive review on application of bioreactor for industrial wastewater treatment.

In the recent past, wastewater treatment processes performed a pivotal role in accordance with maintaining the sustainable environment and health of mankind at a proper hygiene level. It has been proved indispensable by government regulations throughout the world on account of the importance of preserving freshwater bodies. Human activities, predominantly from industrial sectors, generate an immeasurable amount of industrial wastewater loaded with toxic chemicals, which not only cause dreadful environmental problems, but also leave harmful impacts on public health. Hence, industrial wastewater effluent must be treated before being released into the environment to restrain the problems related to industrial wastewater discharged to the environment. Nowadays, biological wastewater treatment methods have been considered an excellent approach for industrial wastewater treatment process because of their cost-effectiveness in the treatment, high efficiency and their potential to counteract the drawbacks of conventional wastewater treatment methods. Recently, the treatment of industrial effluent through bioreactor has been proved as one of the best methods from the presently available methods. Reactors are the principal part of any biotechnology-based method for microbial or enzymatic biodegradation, biotransformation and bioremediation. This review aims to explore and compile the assessment of the most appropriate reactors such as packed bed reactor, membrane bioreactor, rotating biological contactor, up-flow anaerobic sludge blanket reactor, photobioreactor, biological fluidized bed reactor and continuous stirred tank bioreactor that are extensively used for distinct industrial wastewater treatment.

Efficiencies of anaerobic hybrid and UASB reactors to alleviate the adverse effect of elevated salinity in wastewater

AbstractBACKGROUNDUntreated high‐strength salinity wastewaters pose a serious threat to the environment. Anaerobic treatment is an effective process with double advantages of waste stabilization and energy production. However, high organic compound and sodium toxicity in high‐salinity wastewaters adversely affect the performance of anaerobic treatment. In this study, anaerobic hybrid (AH) and upflow anaerobic sludge blanket (UASB) reactors were investigated for their efficiencies to alleviate the negative effects of high‐salinity wastewater.RESULTSDouble increases in the NaCl concentration drastically deteriorated the performances of both reactors. The activities of acetoclastic methanogens (ACM) and hydrogenotrophic methanogens (HTM) in both reactors decreased to 22–28% and 36–40% compared to the previous period, respectively. However, the methanogen population (Methanosarcinales and Methanobacteriales) was not affected negatively. The AH reactor exhibited excellent performance during the recovery and restart periods, which only required 7 days to complete the recovery period. Furthermore, during the restart period, the AH reactor showed high chemical oxygen demand (COD) removal efficiency, methane (CH4) production and yield as ≈90%, 2600 mL day−1 and 0.30 m3 CH4 kg−1 CODremoved, respectively. The rate of biomass washout from the AH reactor also was lower compared to the UASB reactor. The concentration of attached biomass in the packed zone of the AH reactor gradually increased indicating the growth of an active microbial biofilm.CONCLUSIONThe excellent performance of the AH reactor was presumably a result of its packed zone configuration which provided the supporting media to entrap smaller microbial aggregates, reduce biomass washout and support the growth of active biofilm. © 2021 Society of Chemical Industry (SCI).

Management and kinetics of methane production from anaerobic batch reactors treating PET bottle washing wastewater

The study evaluated the methanogenic potential of anaerobic sludge in Wastewater from the Washing of PET (Polyethylene terephthalate) bottles sent for Recycling (WWPR). The bioreactors were inoculated with sludge from an upflow anaerobic sludge blanket reactor treating poultry waste. The operation occurred under anaerobic conditions at 35 °C and 150 rpm for three bioreactors in triplicate with the initial COD concentration of 2000 mg L−1 (C1), 5000 mg L−1 (C2), and 10,000 mg L−1 (C3). The inhibition in the anaerobic biological treatment caused by high surfactant concentration impaired the wastewater biodegradation. COD removals were 67.8 ± 0.4% (C1), 67.6 ± 2.7% (C2), and 59.1 ± 2.9% (C3), indicating a process inhibition in the latter condition. The modified Gompertz model indicated a cumulative methane production of 290 mL for condition C1 with an adjustment coefficient of 99.11%. The methane potential for the production of electricity revealed a maximum annual production of 188,292 MWh. Annual thermal energy from condition C1 could produce 1.01 × 108 PET bottles. Therefore, the anaerobic treatment of WWPR is an alternative to wastewater management, avoiding greenhouse gases emission and potentiating the generation of electrical and thermal energy.

Microaerophilic treatment enhanced organic matter removal and methane production rates during swine wastewater treatment: A long-term engineering evaluation

Anaerobic biotechnology has been widely used for swine wastewater (SWW) treatment. However, its organic loading rate (OLR) is far lower than expected, mainly because of the low rate of hydrolysis. In this study, the comparative process performance and efficiency of an up-flow anaerobic sludge blanket (UASB) reactor (R1) and an up-flow microaerobic sludge blanket (UMSB) reactor (R2) were evaluated for SWW treatment, operating for 264 days under higher OLRs and lower hydraulic retention times than those found in the literature. The R2 was subjected to the three different air doses: 0.09 (stage I), 0.17 (stage II), and 0.25 (stage III) LO2 Lfeed−1 d−1 aiming at enhancing the hydrolysis step of the anaerobic digestion (AD). The overall results showed that 0.17 LO2 Lfeed−1 d−1 was the best experimental condition evaluated, which provided volatile suspended solids, total chemical oxygen demand, and particulate chemical oxygen demand removal efficiencies of 85.0 ± 1.9%, 83.8 ± 2.5%, and 82.1 ± 4.8%, respectively. This performance was due to the higher organic matter hydrolysis, resulting in higher methane production. Therefore, the UMSB reactor treatment was demonstrated to be a feasible alternative for SWW, although some strategies to control biomass washout must be investigated.

Feammox process driven anaerobic ammonium removal of wastewater treatment under supplementing Fe(III) compounds

Ammonium removal in wastewater treatment plants demands large quantities energy input, such as aeration for wastewater and the addition of organics for nitrate reduction. Anaerobic ammonium oxidation coupled to Fe(III) reduction, called Feammox process play a crucial role in natural nitrogen cycle, which has been rarely investigated in the field of wastewater treatment. Besides, Iron-reducing bacteria (FeRB) as function bacteria of Feammox could transfer electrons to iron oxide by oxidizing organics. The possibility of anaerobic ammonium removal coupled with organics should be investigated to assess the potential of Feammox process for conventional wastewater treatment. In this study, five Fe(III) compounds, Fe2O3, Fe3O4, Fe(OH)3, Citrate-Fe and pyrite were supplemented to investigate the effect of iron oxides on ammonium removal in serum bottles with working volume of 100 mL. It was found that ammonium removal efficiency of the Fe2O3 group was the highest. To simulate wastewater treatment process in sewage treatment plant, three Up-flow anaerobic sludge blanket reactors with volume of 250 mL adding Fe2O3 were applied with influent of ammonium and carbon sources. It was found that the organics significantly inhibited the ammonium removal by Feammox process. This was attributed to that carbon sources and ammonium could be used as electron donors for Fe(III) reduction. In addition, this nitrogen removal was also likely related with the iron cycle, i.e., Fe(III) reduction with ammonium oxidation and Fe(II) oxidation with nitrate/nitrite reduction. This study provides a promising alternative technology for anaerobic ammonium removal in wastewater treatment. Optimizing nitrogen removal and carbon sources applied in conventional wastewater plants are required in future.

Response of anaerobic granular sludge to long-term loading of roxarsone: From macro- to micro-scale perspective

Extensive use of organoarsenic feed additives such as roxarsone has caused organoarsenicals to occur in livestock wastewater and further within anaerobic wastewater treatment systems. Currently, information on the long-term impacts of roxarsone on anaerobic granular sludge (AGS) activity and the underlying mechanisms is very limited. In this study, the response of AGS to long-term loading of roxarsone was investigated using a laboratory up-flow anaerobic sludge blanket reactor spiked with 5.0 mg L−1 of roxarsone. Under the effect of roxarsone, methane production decreased by ∼40% due to the complete inhibition on acetoclastic methanogenic activity on day 260, before being restored eventually. Over 30% of the influent arsenic was accumulated in the AGS and the capability of AGS to prevent intracellular As(III) accumulation increased with time. The AGS size was reduced by ∼30% to 1.20‒1.26 mm. Based on morphology and confocal laser scanning microscopy analysis, roxarsone exposure stimulated the excretion of extracellular polymeric substances and the surface spalling of AGS. High-throughput sequencing analysis further indicated roxarsone initially altered the acidogenic pathway and severely inhibited the acetoclastic methanogen Methanothrix. Acetogenic bacteria and Methanothrix were finally enriched and became the main contributor for a full restoration of the initial methane production. These findings provide a deeper understanding on the effect of organoarsenicals on AGS, which is highly beneficial for the effective anaerobic treatment of organoarsenic-bearing wastewater.

Influences of humic-rich natural materials on efficiencies of UASB reactor: A comparative study

Two humic-rich natural materials namely peat soil and lignite were supplemented in up-flow anaerobic sludge blanket (UASB) bioreactors for the treatment of phenolic wastewater. Peat soil improved phenol degradation and resistance to shock load; ultimately, contributing to higher COD removal efficiency (83.3%), methane production (4532 mL d-1), and better reactor’s stability. Accordingly, the amount of extracellular polymeric substances (EPS) and coenzyme F420 in sludge were increased to 1.3-fold and 2.5-fold, respectively, as compared to the control treatment. The addition of lignite however displayed poor phenol degradation and no effects on the secretion of EPS and F420. The peat soil significantly influenced the microbial community structures, whereas the effect of lignite was inconspicuous. In the presence of peat soil, the abundance of syntrophic fermentation bacteria and methanogens was significantly increased. This study illustrates the potential use of peat soil in UASB for the treatment of phenolic wastewaters.

Use of artificial neural network and adaptive neuro-fuzzy inference system for prediction of biogas production from spearmint essential oil wastewater treatment in up-flow anaerobic sludge blanket reactor

Two artificial intelligence (AI)-based models, namely feed-forward backpropagation artificial neural network (ANN) and multi-layer adaptive neuro-fuzzy inference system (ANFIS), were developed to estimate the biogas production in an up-flow anaerobic sludge blanket (UASB) reactor. The models' input variables including influent chemical oxygen demand (COD), pH, effluent mixed liquor suspended solids, effluent mixed liquor volatile suspended solids, turbidity removal, oil and grease removal, COD removal, phenol removal, and effluent volatile fatty acids and alkalinity were collected from an UASB reactor fed with spearmint essential oil wastewater (SEOW) during 141 consecutive operating days. The determination coefficient, root mean square error, and relative root mean the ANN model's square error reached 0.975, 2650 mL/d, and 0.234%, respectively, while those of ANFIS model reached 0.956, 3517 mL/d, and 0.315%, respectively. The results achieved herein demonstrated that two AI-based models were successful to estimate the biogas production in a lab-scale UASB reactor treating SEOW with high accuracy and low error.

Removal and Survival of Fecal Indicators in a Constructed Wetland after UASB Pre-Treatment

The experimentation plant, based on a sub-surface horizontal flow phytodepuration (SSHFP) unit with a pre-treatment by an upflow anaerobic sludge blanket (UASB) reactor, proved valuable in treating the sewage of a small rural community located in north Brazil. During a six-month trial, the plant achieved an average removal efficiency of 98.2% (1.74 log removal) for fecal coliforms (FC) and 96.0% (1.40 log removal) for Enterococci (EN), as well as 95.6% for BOD5, 91.0% for COD,00 and 95.4% for suspended solids (SS). The contribution of the UASB reactor to this overall performance was very significant as, alone, it achieved a yield of 62.7% for FC and 60% for EN, in addition to 65.2% for BOD5 and 65.0% for SS. EN was chosen, in addition to FC, because of its higher specificity and strong environmental persistence, leading to an increased risk to human health. In fact, the experimental results confirmed its lower removal efficiency compared to FC. The mechanical and biological mechanisms that led to such a removal efficiency of the two fecal indicators (FIs) are outlined in the article. The same mechanisms led to a good level of equivalence between the removal efficiency of the two FIs with the removal efficiency of SS and BOD5, for both the whole plant and the UASB reactor alone. The research demonstrated the close correlation between the concentrations of EN and FC for the plant effluent. This correlation can be explained by the following mathematical expression of the regression line Log EN = 0.2571 Log FC + 3.5301, with a coefficient of determination R2 = 0.912. This implies that the concentration of the more specific indicator EN could be calculated, with acceptable approximation, from the simple analysis of FC and vice versa. The experimental plant brought important health benefits to the local population. In particular, there were no significant odor emissions; moreover, the risk of fecal pathogenic diseases was drastically reduced; finally, there was no proliferation of insects and other disease vectors, due to the absence of stagnant or semi-stagnant water exposed to the atmosphere.

The use of solar pre-treatment as a strategy to improve the anaerobic biodegradability of microalgal biomass in co-digestion with sewage

Sustainable sewage treatment plants (STPs) have been intensively investigated in search for low-cost, environmental-friendly options. Anaerobic-aerobic treatment solutions, as upflow anaerobic sludge blanket (UASB) reactors followed by high rate algal ponds (HRAP) have already proved to be efficient for pollutants and micropollutants removal, as well as for energy recovery from the co-digestion of raw sewage and microalgal biomass. Since microalgae cells have complex structures that make them resistant to anaerobic digestion, pre-treatment techniques may be applied to improve microalgal biomass solubilisation and methane yield. Among the thermal pre-treatments, the use of solar energy for biomass solubilisation has yet to be investigated. Therefore, this study aimed at evaluating the performance of a solar thermal microalgal biomass pre-treatment prior to the anaerobic co-digestion with raw sewage, comparing a UASB reactor feed only raw sewage and other UASB reactor feed with raw sewage and pre-treated microalgal biomass. The results showed that, the solar pre-treatment step reached an organic matter solubilisation of 32% (COD). Furthermore, the methane yield was increased by 45% (from 81 to 117 NL CH4 kg−1 COD), after the anaerobic co-digestion with pre-treated microalgae as compared to the mono-digestion of raw sewage, indicating significant difference between the evaluated UASB reactors. The energy assessment showed a positive energy balance, as the total energy produced was twice the energy consumed in the system.

Development of long-term dynamic BioWin® model simulation for ANAMMOX UASB micro-granular process

Three different innovative mathematical models were established to assess the volumetric nitrogen conversion rates of a lab-scale ANAMMOX upflow anaerobic sludge blanket reactor. Despite the vast technological and economical advantages of ANAMMOX, major challenges in process implementation call for mathematic simulations of the process, optimization of operating conditions, and kinetic/statistical analysis of the entire process. In this study, all developed mathematical models implemented via BioWin®, were calibrated and validated, with adequate representations of a bench-scale micro-granular ANAMMOX process, to understand the potential setbacks of ANAMMOX process start-up and stabilization. Fundamental calculations of the kinetic and stoichiometric constants were integrated in the BioWin® software, and the adjusted parameters based on experimental analysis were applied for the assessments. Based on the results from the statistical approach, one of the models (Model III) exhibited a precise prognosis of the effluent data for the entire operational phases with a mean relative error (MRE) of approximately 1.96, 4.36 and 2.54% for nitrogen removal efficiency, removal rate and loading rate, respectively. Evaluating alkalinity and pH during the operation, led to identifying an acceptable fit between the experiment and Model III results, with a MRE of −7.19 and −0.35%, correspondingly. This study confirms the reliability of ANAMMOX-based process modeling and high predictive ability with BioWin®. The presented simulation constants and modeling outline, can be further employed in full-scale applications design and development.

Modelling and Life Cycle Assessment of Sewage Treatment Plant (STP) in Lucknow City

The implementation of wastewater treatment plants has been a challenge for most countries. Economic resources, political will, institutional strength, and cultural background are important factors that define the trajectory of pollution control in many countries. Technology is sometimes mentioned as one of the reasons hindering further development. Therefore, a key objective of this research is to evaluate the performance of a plant based on the 345 MLD Upflow Anaerobic Sludge Blanket (UASB) technology by analyzing the physical and chemical parameters of the water treated by UASB to evaluate the performance of the plant located. at Bharwara Tech from Gomti Nagar Lucknow. In this study, the performance of the wastewater treatment plant and the UASB reactor was calculated. Wastewater is mixed with domestic wastewater, so the concentration of BOD and COD is relatively low. The amount of biogas produced by the UASB reactor is also less than its design value. All STP inlet and outlet water concentration results are displayed graphically.

A new non-steady-state mass balance model for quantifying microbiome responses to disturbances in wastewater bioreactors

Herein we proposed an ecology model, based on a non-steady-state mass balance (16S rRNA MiSeq reads normalized by volatile suspended solids), to quantify microbiome responses to disturbances in wastewater bioreactors. Rather than focusing on the most abundant microbial groups commonly used in the literature, the goal of the model was to identify active species within the community. The model incorporated the temporal changes of operational taxonomic units following a disturbance, through considering the density and type of genotypes in the influent entering the bioreactor, in the effluent leaving the bioreactor, growing in the bioreactor, and in the waste sludge discharged from the bioreactor continuously or instantaneously, as well as the prior microbial community and the sludge characteristics. One application of this model demonstrated that significant differences existed between the key populations responding to an increasing organic loading rate and the dominant species in a high-rate thermophilic upflow anaerobic sludge blanket reactor.

Assessing main process mechanism and rates of sulfate reduction by granular biomass fed with glycerol under sulfidogenic conditions

Sulfate-reducing bioreactors for sulfide production are the initial stage of processes targeting elemental sulfur recovery from sulfate-rich effluents. In this work, the principal reactions involved in glycerol fermentation and sulfate reduction using glycerol and its fermentation products as electron donors were assessed together with their specific consumption/production rates. A battery of batch activity tests with and without sulfate were performed with glycerol and with each fermentation product using a non-methanogenic but sulfidogenic granular sludge from an up-flow anaerobic sludge blanket (UASB) reactor operated under long-term while fed with crude glycerol. As a result, a mechanistic approach based on the experimental observations is proposed in this work. Glycerol was mainly fermented to 1,3-propanediol, ethanol, formate, propionate and acetate by fermentative bacteria. All organic intermediates were found to be further used by sulfate reducing bacteria (SRB) for sulfate reduction except for acetate. The most abundant genus detected under sulfidogenic conditions were Propionispora (15.2%), Dysgonomonas (13.2%), Desulfobulbus (11.6%) and Desulfovibrio (10.8%). The last two SRB genera accounted for 22.4% of the total amount of retrieved sequences, which were probably performing an incomplete oxidation of the carbon source in the sulfidogenic UASB reactor. As single substrates, specific sulfate reduction rates (SRRs) using low molecular weight (MW) carbon sources (formate and ethanol) were 39% higher than those using high-MW ones (propionate, 1,3-propanediol and butanol). However, SRRs in glycerol-fed tests showed that 1,3-propanediol played a major role in sulfate reduction in addition to formate and ethanol.

Evaluation of the continuous methane production from an enzymatic agave bagasse hydrolysate in suspended (CSTR) and granular biomass systems (UASB)

Methane production from an enzymatic agave bagasse hydrolysate was evaluated in a continuous stirred tank reactor (CSTR) and in an upflow anaerobic sludge blanket reactor (UASB). The effect of different organic loading rates (OLRs) and hydraulic retention times (HRTs) on volumetric methane production rate (VMPR) was tested. To hydrolyze the bagasse, Cellulase 50XL, a food-grade enzyme, allowed a saccharification yield of lignocellulosic biomass similar to Celluclast 1.5L, which is used to treat lignocellulosic substrates. The UASB reactor operated at larger OLR (e.g., 20 g CODs/L-d) and shorter HRT (e.g., 30 h) than the CSTR (e.g., OLR of 7.3 g CODs/L-d and HRT of 66 h). The UASB achieved a VMPR of 4.5 ± 0.1 L CH4/L-d and COD removal of 94% while the CSTR had a VMPR of 1.92 ± 0.03 L CH4/L-d and COD removal of 88%. The better performance of the UASB than the CSTR can be explained by the high solid retention time (SRT) and the microbial community composition, which was less diverse than the CSTR’s community. Hydrogenotrophic methanogens were abundant in the UASB while acetoclastic methanogens dominated in the CSTR. The high VMPR obtained by the UASB reactor and the use of Cellulase 50XL can be advantageous features for future industrial application.

Nitrogen removal performance using anaerobic ammonium oxidation considering variable conditions.

The anaerobic nitrogen removal performance of anammox at 30°C, 25°C, and 16°C were studied by using the UASB (Up flow Anaerobic Sludge Blanket) reactor and the influent concentration of NH4+-N and NO2--N were 16.9 and 20.6 mg L-1 respectively. Experimental results showed that high-efficiency anammox nitrogen removal could be achieved at 30°C, when hydraulic retention time (HRT) was 0.14 h, the nitrogen removal rate (NRR) was 5.73 kg N m-3 d-1. The anammox reactor operated stably for more than 80 days under the condition of 16°C-20°C, and the high NRR of 2.78 kg N m-3 d-1 was obtained. In this experiment, DO had little effect on the activity of anammox granular sludge, and the nitrogen removal performance could be quickly recovered in a short period of time after being affected by DO. Moreover, the stoichiometric ratio of NO2--N and NH4+-N consumption (ΔNO2--N/ΔNH4+-N) and the stoichiometric ratio of NO3--N production and NH4+-N conversion (ΔNO3--N/ΔNH4+-N) were 1.21 ± 0.11and 0.25 ± 0.06 respectively at 30°C, which were very close to the theoretical value, it indicated that anammox bacteria were the dominant bacteria at 30°C.

Development of an Automated Tracer Testing System for UASB Laboratory-Scale Reactors

Residence time distribution (RTD) curves play an essential role in the hydraulic characterization of reactors. Current approaches for obtaining RTD curves in laboratory-scale reactors are time-consuming and subject to large errors. Thus, automated systems to obtain RTD curves in laboratory-scale reactors are of great interest for reducing experimental errors due to human interaction, minimizing experimentation costs, and continuously obtaining experimental data. An automated system for obtaining RTD curves in laboratory-scale reactors was designed, built, and tested in this work. During the tests conducted in a cylindrical upflow anaerobic sludge blanket (UASB) reactor, the system worked properly using the stimulus–response pulse technique with sodium chloride as a tracer. Four main factors were found to affect the representativeness of the RTD curves: flow stabilization time, test water conductivity, temperature, and surface tension. A discussion on these factors and the corresponding solutions is presented. The RTD curves of the UASB reactor are left-skewed with a typical tank reactor’s flow shape with channeling and dead zones. A transitory flow behavior was evidenced in the reactor, which indicates the influence of internal turbulent flow structures. The system proposed herein is expected to help study the hydraulics of reactors using laboratory-scale models more efficiently.

Perchlorate bioreduction in UASB reactor: S2--autotrophic granular sludge formation and sulphate generation control

ABSTRACT Perchlorate () industrial wastewater requires efficient removal to prevent adverse environmental impacts, however, high concentration and low biodegradability give rise to poor bioreduction performance. -autotrophic granular sludge (-AuGS) was firstly cultivated for high concentration perchlorate () removal in the upflow anaerobic sludge blanket (UASB) reactor (: 150 mg L−1). Simultaneously, the was utilized to control the generation as electron donor, the effluent concentration (190 mg L−1) was satisfied with drinking water standard (250 mg L−1). Under the optimized condition of hydraulic retention time (HRT) (6 h) and / molar ratio (2.2), more EPS was secreted, which promoted the -AuGS formation and stability. Though acclimation of 146 d, the -AuGS was formed with a large average granular sludge size (612 μm) and an excellent settleability (sludge volume index: SVI5/SVI30 = 1). With the mature -AuGS formation, the highest and loading was increased to 1.06 and 0.75 kg m−3 d−1. Interestingly, Georgfuchsia, Methyloversatilis, Sulfurisoma, and Exiguobacterium were the main microbial community in the -AuGS. This study proposed to form a novel -AuGS for developing the high concentration removal performance and to utilize the as an electron donor for controlling the excessive generation.