Pilot-scale System Research Articles

Compact pilot-scale aerobic granular sludge system treating real wastewater continuously for over 500 days

This long-term investigation provides a step-wise optimization of a pilot-scale continuous flow reactor (CFR, total volume ∼ 200 L) using aerobic granular sludge (AGS) to treat municipal wastewater (MW) at temperatures of 18.2 ± 1.8 °C and with organic loading rates of 1.39 ± 0.89 kg COD·m−3·d−1. Short settling times of about 10 min which led to a high selection pressure allowed for a complete granulation after day 47 — i.e., >80 % of the mixed liquor suspended solids (MLSS) larger than 200 μm in diameter and sludge volume indexes of ∼40 mL·g−1. Following a start-up and optimization period of 187 days, the system was stably operated with ∼6.1 g MLSS·L−1 over one year. The best-performance was achieved with an aerobic/anaerobic volume ratio of 2/1 and intermittent aeration. Furthermore, for most of the time a NH4+-N removal of 99 % was possible with low oxygen concentrations (2.0 to 2.5 mg·L−1), and despite the high‑nitrogen ratios of CODt:TN:TP (100:15:1.7).

X-ray Absorption Spectroscopy Reveals Mechanisms of Calcium and Silicon Fouling on Reverse Osmosis Membranes Used in Wastewater Reclamation

Reverse osmosis (RO) is widely employed to provide clean water from nontraditional sources (e.g., seawater or municipal wastewater). One of its key challenges is membrane fouling, which leads to reduced flux and increased operational costs. Despite its practical relevance, fundamental understanding of membrane fouling is limited. Toward this end, we investigated calcium (Ca) and silicon (Si) fouling under real RO feed conditions using μ-X-ray fluorescence (μ-XRF) mapping and μ-X-ray absorption near-edge fine structure (μ-XANES) spectroscopy. These techniques are distinctly suited to identify the spatial distribution and (local) chemical speciation of foulants, thereby providing unique insight into the mechanisms of fouling under realistic conditions. Specifically, we investigated RO membranes harvested from a pilot-scale RO system operated at the Orange County Water District (OCWD) Groundwater Replenishment System (GWRS) Advanced Water Purification (AWP) Facility, which received the same feed water as the full-scale plant. Both Ca and Si were found to be abundant in the fouling layer. Despite the use of a commercial antiscalant to inhibit mineral formation, several Ca minerals were present in the fouling layer as minority species, including sulfates, phosphates, and carbonates; most of these minerals were found in particles that were aligned with the feed spacer used to separate the membranes. In contrast, organic-bound Ca and silica occurred across the entire membrane. Our work provides novel insight into the synergistic mechanism of RO fouling by Ca, Si, and organics on RO membranes.

Technical and economic analysis of a pilot-scale hydrogen system: From production to application

The uneven distribution of renewable energy resources and different levels of development have produced a large amount of abandoned electricity. Hydrogen production from the electrolysis of water can effectively consume abandoned electricity. And hydrogen energy has been hailed as the ultimate energy source in the 21st century. However, the many branches of the industry have made the overall layout of local hydrogen energy a tricky issue. Therefore, combining the characteristics and development status, and pilot project data, this article selects three typical hydrogen energy industry routes with high development potential for focused study. These three routes cover the main hydrogen production, storage and transportation technologies, and hydrogen energy application scenarios. A modeling-based approach is applied to calculate the energy utilization and economics of each route. The analysis is then combined with the current development status to obtain the advantages and disadvantages, suitable conditions, and development potential of each route. Among the three routes, the PEMFC route has the highest energy efficiency of 46.6% but is less economical. Suitable for construction in and around power plants to improve energy utilization. The hydrogen transportation route has a lower energy utilization rate of 34.9%. However, this route is more economical, with a conservative estimate of hydrogen refueling cost of about 60 RMB/kg at the current demonstration level. Suitable for medium and large cities with mature hydrogen energy development. The transportation cost of pipeline hydrogen transportation is low, but the preliminary pipeline construction and modification are more complicated. Based on the research results and local conditions, the government or enterprises can personalize the design of the hydrogen energy industry chain faster and more effectively.

Performance of an aerobic granular sludge membrane filtration in a full-scale industrial plant.

This study quantifies the hydraulic performance of a pilot-scale ultrafiltration system integrated into a full-scale industrial aerobic granular sludge (AGS) plant. The treatment plant consisted of parallel AGS reactors, Bio1 and Bio2, with similar initial granular sludge properties. During the 3-month filtration test, a chemical oxygen demand (COD) overloading episode took place, affecting the settling properties, morphology, and microbial community composition in both reactors. The impact on Bio2 was more severe than on Bio1, with higher maximal sludge volume index values, a complete loss of granulation, and the excessive appearance of filamentous bacteria extending from the flocs. The membrane filtration properties of both sludges, with these different sludge qualities, were compared. The permeability in Bio1 varied between 190.8 ± 23.3 and 158.9 ± 19.2 L·m-2·h-1·bar-1, which was 50% higher than in Bio2 (89.9 ± 5.8 L·m-2·h-1·bar-1). A lab-scale filtration experiment using a flux-step protocol showed a lower fouling rate for Bio1 in comparison with Bio2. The membrane resistance due to pore blocking was three times higher in Bio2 than in Bio1. This study shows the positive impact of granular biomass on the long-term membrane filtration properties and stresses the importance of granular sludge stability during reactor operation.

Pilot-scale assessment reveals effects of anode type and orthophosphate in governing antimicrobial capacity of copper for Legionella pneumophila control

Copper (Cu) is sometimes applied as an antimicrobial for controlling Legionella in hot water plumbing systems, but its efficacy is inconsistent. Here we examined the effects of Cu (0 - 2 mg/L), orthophosphate corrosion inhibitor (0 or 3 mg/L as phosphate), and water heater anodes (aluminum, magnesium, and powered anodes) on both bulk water and biofilm-associated L. pneumophila in pilot-scale water heater systems. Soluble, but not total, Cu was a good predictor of antimicrobial capacity of Cu. Even after months of exposure to very high Cu levels (>1.2 mg/L) and low pH (<7), which increases solubility and enhances bioavailability of Cu, culturable L. pneumophila was only reduced by ∼1-log. Cu antimicrobial capacity was shown to be limited by various factors, including binding of Cu ions by aluminum hydroxide precipitates released from corrosion of aluminum anodes, higher pH due to magnesium anode corrosion, and high Cu tolerance of the outbreak-associated L. pneumophila strain that was inoculated into the systems. L. pneumophila numbers were also higher in several instances when Cu was dosed together with orthophosphate (e.g., with an Al anode), revealing at least one scenario where high levels of total Cu appeared to stimulate Legionella. The controlled, pilot-scale nature of this study provides new understanding of the limitations of Cu as an antimicrobial in real-world plumbing systems.

Fabric dyeing wastewater treatment and salt recovery using a pilot scale system consisted of graphite electrodes based on electrooxidation and nanofiltration

In this study, color removal, suspended solids removal, and salt recovery were investigated from different fabric dyeing wastewaters using a pilot scale treatment system. A pilot scale system was installed in the wastewater outlet area of five different textile companies. Experiments were planned for pollutant removal and salt recovery from wastewater. First, the wastewater was treated by electrooxidation (EO) using graphite electrodes. After a reaction time of 1 h, the wastewater was passed throughout the granular activated carbon (AC) coloumn. The pre-treated wastewater was passed through the membrane (NF) system to recover the salt in the wastewater. Finally, the recovered salt water was used for fabric dyeing. In the pilot scale treatment system (EO + AC + NF), 100% of suspended solids (SS) and an average of 99.37% of color were removed from fabric dyeing wastewaters. At the same time, a high amount of salt water was recovered and reused. Optimum conditions were determined as 4 V current, 1000 A power, wastewater's own pH values and 60 min of reaction time. The energy and operating cost for treatment of 1 m3 of wastewater were determined as 40.0 kWh/m3 and 2.2 US$/m3, respectively. In addition to the prevention of environmental pollution by the treatment of wastewater using the pilot-scale treatment system, the reuse of the recovered water will contribute to the protection of our valuable water resources. In addition, using the NF membrane process after the EO system, it will be possible to recover salt from wastewater with high salt content such as textile wastewater.

Sorbent-coated carbon fibers for direct air capture using electrically driven temperature swing adsorption

•Sorbent-coated carbon fibers exhibit rapid temperature swing by Joule heating •The DAC system can fully regenerate in under 10 min •Wind-driven DAC modules recover CO2 product from the air at ∼82% purity •The cost of CO2 from this wind-driven DAC system is projected to be ∼$160/tonne Direct air capture (DAC) by electrically driven temperature swing adsorption (ETSA) is an emerging technology due to its simplicity and ease of pairing with renewable electricity energy sources. Herein, we describe the preparation of sorbent-coated carbon fibers via roll-to-roll process that exhibit 400 ppm CO2 adsorption of ∼1.2 mmol gfiber−1. The fibers exhibit Joule heating upon application of a potential, reaching CO2 regeneration temperatures within 1 min. DAC modules show fast electrothermal CO2 desorption with directly applied electric potential, releasing the adsorbed CO2 six times faster than externally driven thermal desorption. The simplicity and modularity of the sorbent-coated carbon fibers and their rapid adsorption/desorption cycling by ETSA have the potential to improve the productivity of DAC systems. A techno-economic analysis of a pilot-scale ETSA-DAC system projects an overall cost of about 160 $ tCO2−1, with convective energy losses to the ambient accounting for only 7% of the Joule heating input during desorption. Direct air capture (DAC) by electrically driven temperature swing adsorption (ETSA) is an emerging technology due to its simplicity and ease of pairing with renewable electricity energy sources. Herein, we describe the preparation of sorbent-coated carbon fibers via roll-to-roll process that exhibit 400 ppm CO2 adsorption of ∼1.2 mmol gfiber−1. The fibers exhibit Joule heating upon application of a potential, reaching CO2 regeneration temperatures within 1 min. DAC modules show fast electrothermal CO2 desorption with directly applied electric potential, releasing the adsorbed CO2 six times faster than externally driven thermal desorption. The simplicity and modularity of the sorbent-coated carbon fibers and their rapid adsorption/desorption cycling by ETSA have the potential to improve the productivity of DAC systems. A techno-economic analysis of a pilot-scale ETSA-DAC system projects an overall cost of about 160 $ tCO2−1, with convective energy losses to the ambient accounting for only 7% of the Joule heating input during desorption.

Essential oil extraction for all: A flexible and modular system for citrus biomass waste

The essential oil industry is a growing sector that generates 5.41 billion USD annually worldwide. Essential oils are widely used in medicine, agriculture, and perfumery. Although there are available systems in the market for domestic essential oil extraction, replacing the entire equipment in case of repair or malfunction can be costly. To address this problem, a pilot-scale essential oil extractor system was developed that operates through hydrodistillation. This system was used to process various citrus wastes such as green and yellow lemons, oranges, grapefruits, and Eucalyptus globulus. A factorial design was performed, and the best conditions were used to extract other biomass residues. GC-MS analysis revealed that the primary compound for orange, grapefruit, and green lemon essential oils is D-imonene, with 95.4%, 95.5%, and 49.2%, respectively. For yellow lemon the primary compound appeared to be D-limonene with 73.0% content, though the GC/MS data were less clear, and for eucalyptus, it is eucalyptol with 71.0%. The estimated production costs were 0.01 USD/mL, 0.04 USD/mL, 0.06 USD/mL, 0.07 USD/mL, and 0.15 USD/mL for orange, grapefruit, green lemon, yellow lemon, and eucalyptus essential oils, respectively. Therefore, the developed system is a competitive option for pilot-scale essential oil extraction.

Performance of a Pilot-Scale Continuous Flow Ozone-Based Hospital Wastewater Treatment System.

Antimicrobial resistance (AMR) is becoming a global concern. Recently, research has emerged to evaluate the human and environmental health implications of wastewater from medical facilities and to identify acceptable wastewater treatment methods. In this study, a disinfection wastewater treatment system using an ozone-based continuous flow system was installed in a general hospital located in Japan. The effectiveness of antimicrobial-resistant bacteria (ARB) and antimicrobials in mitigating the environmental impact of hospital wastewater was evaluated. Metagenomic analysis was conducted to characterize the microorganisms in the wastewater before and after treatment. The results demonstrated that ozone treatment enables effective inactivation of general gut bacteria, including Bacteroides, Prevotella, Escherichia coli, Klebsiella, DNA molecules, and ARGs, as well as antimicrobials. Azithromycin and doxycycline removal rates were >99% immediately after treatment, and levofloxacin and vancomycin removal rates remained between 90% and 97% for approximately one month. Clarithromycin was more readily removed than the other antimicrobials (81-91%), and no clear removal trend was observed for ampicillin. Our findings provide a better understanding of the environmental management of hospital wastewater and enhance the effectiveness of disinfection wastewater treatment systems at medical facilities for mitigating the discharge of pollutants into aquatic environments.

Evaluation of Heterogeneous Catalytic Ozonation Process for the Removal of Micropollutants from Water/Wastewater: Application of a Novel Pilot-Scale Continuous Flow System

The present study evaluates the removal of micropollutants from water/wastewater contaminated sources through the application of a heterogeneous catalytic ozonation process, using a pilot-scale continuous operation unit, composed of a membrane module for the diffusion and effective dilution of ozone into the liquid phase to be treated and a plug flow reactor/continuous stirred tank reactor (PFR/CSTR) contact reactor system in series, where the catalyst is recirculated in dispersion mode. The solid materials tested as catalysts are natural and calcined zeolite, Bayoxide and alumina, whereas the examined micropollutants, used in this case as probe compounds, are p-chlorobenzoic acid (p-CBA), atrazine, benzotriazole and carbamazepine. A high-performance liquid chromatography system was used to determine the removal of micropollutants. In the case of p-CBA, an ozone-resistant compound, the addition of catalyst was found to significantly enhance its degradation rate, leading to &gt;99% removal under the optimum defined conditions, i.e., in terms of catalyst concentration, pH, temperature, and process time. On the other hand, in the case of atrazine, a different ozone-resistant compound, the introduction of examined catalysts in the ozonation process was found to reduce the degradation of micropollutant, when compared with the application of single ozonation, indicating the importance of specific affinity between the pollutant and the solid material used as catalyst. Benzotriazole, a moderately ozone-reactive compound was degraded by more than 95% under all experimental conditions and catalysts tested in the pilot unit, while carbamazepine, a highly ozone-reactive compound, was completely removed even during the first stage of treatment process (i.e., at the membrane contactor). When increasing the pH value (in the range 6–8) and the contact time, the performance of catalytic ozonation process also improved.

Gas segregation in a pilot-scale ebullated bed system: Experimental investigation and model validation

Gas hold-up reduction inside hydroprocessors is critical to improving the efficiency of bitumen conversion. The use of internal gas/liquid segregation devices, such as recycle cups, has been the focus of much past research and development over the previous five decades. In this study, the effects of different recycle cup designs and working fluids were evaluated using a pilot-scale cold-flow ebullated bed reactor and compared to multiphase flow simulation predictions. Two recycle cup designs from the literature were fabricated using 3D printing technology and two working fluids were used: air-water and air-5 wt% ethanol aqueous solutions. The addition of ethanol helped create high gas hold-up and foaming conditions frequently observed in commercial hydroprocessors. It was observed that in foaming systems, the performance of the recycle cups deteriorated. Additionally, increasing the liquid flow rate, either through the inlet or increased recycle, resulted in diminished gas/liquid segregation efficiency. The accuracy of simulations using the two-fluid model was evaluated to predict gas hold-up in the pilot scale system as well as inside the recycle line. In the homogeneous flow regime, given the proper bubble size, the simulations predicted the gas hold-up in the column with less than 5% error. However, unlike the experimental observations, simulations did not predict any gas entrained in the recycle line, which is attributed to variation in the average bubble size and limitations of the existing momentum exchange closures.

A preliminary techno-economic analysis of photofermentative hydrogen production

Photofermentative hydrogen production promises sustainable energy using cheap feedstock and sunlight. While successful laboratory and pilot-scale photofermentative production studies are widespread, overall economic feasibility remains to be demonstrated. In this study, a preliminary techno-economic analysis of photofermentative production based on current technology was carried out, and the results were compared to alternatives such as photovoltaic electrolysis.Specific photofermentative hydrogen cost was estimated based on an existing outdoor, pilot-scale (20 L) photobioreactor system. The annual capital cost was calculated as 124 USD/year including equipment and land. Operating cost was calculated as 42 USD/year including maintenance, energy consumption and feedstock. The specific hydrogen production cost was found as 2.7 USD/mol (1362 USD/kg H2), and 395 USD/kg H2 when equipment cost is subsidized. Further analysis shows that utilization of wastewater as feedstock and a boost in hydrogen productivity could reduce specific cost of hydrogen to levels competitive with alternative technologies.

Application of hybrid vertical flow constructed wetland systems to treatment of greywater for their use to irrigation in rural areas

Access to water supply is currently one of the biggest social and economic challenges in many parts of the world. Iran is currently experiencing serious water problems. One of the appropriate solutions to overcome the existing challenge is to pay attention to alternative water sources such as treated greywater. In the present study the performance of greywater treatment system consists of a vertical flow constructed wetland followed by column filled with combined inexpensive adsorbents in a series was investigated. The absorption capacity of incinerator bottom ash (IBA), rice husk, pumice, dried stems of Phragmites Australis (PA) and activated carbon (as control) absorbents were assessed by analyzing the quality of the influent and effluent streams through testing COD, PO4−3, NO3−, EC and TSS in greywater. After evaluating the treatment capacity of the above absorbents, it was concluded that IBA and dried stems of PA are the most effective material to reach the irrigation water quality. Then, using them, a hybrid pilot-scale experimental system was designed to study the treatment of greywater. This hybrid system efficiently removes COD, NO3− –N and PO4−3 by up to 90.35%, 100% and90.2%, respectively.

Virus rejection and removal in pilot-scale air-gap membrane distillation

Membrane distillation (MD) is a thermally-driven process that can treat high concentration streams and provide a dual barrier for rejection and reduction of pathogens. Thus, MD has potential applications in treating concentrated wastewater brines for enhancing water recovery and potable water reuse. In bench-scale studies, it was demonstrated that MD can provide high rejection of MS2 and PhiX174 bacteriophage viruses, and when operating at temperatures greater than 55 °C, can reduce virus levels in the concentrate. However, bench-scale MD results cannot directly be used to predict pilot-scale contaminant rejection and removal of viruses because of the lower water flux and higher transmembrane hydraulic pressure difference in pilot-scale systems. Thus far, virus rejection and removal have not been quantified in pilot-scale MD systems. In this work, the rejection of MS2 and PhiX174 at low (40 °C) and high (70 °C) inlet temperatures is quantified in a pilot-scale air-gap MD system using tertiary treated wastewater. Both viruses were detected in the distillate which suggests the presence of pore flow; the virus rejection at a hot inlet temperature of 40 °C for MS2 and PhiX174 were 1.6-log10 and 3.1-log10, respectively. At 70 °C, virus concentrations in the brine decreased and were below the detection limit (1 PFU per 100 mL) after 4.5 h, however, viruses were also detected in the distillate in that duration. Results demonstrate that virus rejection is lower in pilot-scale experiments because of increased pore flow that is not captured in bench-scale experiments.

Investigation of control performance on an absorption/stripping system to remove CO2 achieving clean energy systems

Control study is crucial to ensure smooth operation of any unit operation for clean energy system. There has been growing attention on the utilization of advanced model-based controllers in control studies for CO2 capture. However, such advanced controllers are expensive hence proper performance justifications are needed prior to investment. In the current study, both Proportional-Integral (PI) and Model Predictive Control (MPC) control strategies are investigated and implemented on a pilot scale natural gas CO2 absorption/ stripping system running at higher pressure as well as higher CO2 content, utilizing MATLAB/SIMULINK-Aspen Plus Dynamics interface. The novelty of the work is mainly on the investigation study between the efficiency of the standard PI and MPC controllers for a high pressure and high CO2 content pilot-scale CO2 absorption system. For such high pressure and high CO2 content system, it is imperative to evaluate whether special focus on the control strategy is needed or not. This work simulates and investigates the dynamic behavior and performances of PI and MPC controllers of a high-pressure absorption/stripping system. In addition, a second order model of the system has been developed, which is useful for future studies. Controller performance of the Proportional-Integral (PI) and Model Predictive Controller (MPC) are compared using the features of the responses as well as the residual error index i.e., Integral Absolute Error (IAE). The performance of the PID and MPC controllers based on set point tracking of both the controlled variables for 5% and 15% step changes have been evaluated. Compared to the PI controller, the MPC controller has no peak overshoots, i.e., it shows 10% and 2.86% lower error in the IAE index, and it is capable of handling interactions between the variables of the absorption/stripping system.

Exploring resistomes and microbiomes in pilot-scale microalgae-bacteria wastewater treatment systems for use in low-resource settings

Antibiotic resistance genes (ARGs) released into the environment are an emerging human and environmental health concern, including ARGs spread in wastewater treatment effluents. In low-to-middle income countries (LMICs), an alternate wastewater treatment option instead of conventional systems are low-energy, high-rate algal ponds (HRAP) that use microalgae-bacteria aggregates (MABA) for waste degradation. Here we studied the robustness of ARG removal in MABA-based pilot-scale outdoor systems for 140 days of continuous operation. The HRAP system successfully removed 73 to 88 % chemical oxygen demand and up to 97.4 % ammonia, with aggregate size increasing over operating time. Fourteen ARG classes were identified in the HRAP influent, MABA, and effluent using metagenomics, with the HRAP process reducing total ARG abundances by up to 5-fold from influent to effluent. Parallel qPCR analyses showed the HRAP system significantly reduced exemplar ARGs (p < 0.05), with 1.2 to 4.9, 2.7 to 6.3, 0 to 1.5, and 1.2 to 4.8 log-removals for sul1, tetQ, blaKPC, and intl1 genes, respectively. Sequencing of influent, effluent and MABAs samples showed associated microbial communities differed significantly, with influent communities by Enterobacteriales (clinically relevant ARGs carrying bacteria), which were less evident in MABA and effluent. In this sense, such bacteria might be excluded from MABA due to their good settling properties and the presence of antimicrobial peptides. Microalgae-bacteria treatment systems steadily reduced ARGs from wastewater during operation time, using sunlight as the energetic driver, making them ideal for use in LMIC wastewater treatment applications.

Rapid start-up and stable maintenance of the mainstream nitritation process based on the accumulation of free nitrous acid in a pilot-scale two-stage nitritation-anammox system

Two-stage partial nitritation (PN) and anammox (AMX) systems showed promising results for applying autotrophic nitrogen removal under mainstream conditions. In this study, a pilot-scale (600 L per reactor) two-stage PN/AMX system was installed in a municipal wastewater treatment plant (WWTP) provided with a high-rate activated sludge (HRAS) system for organic carbon removal. The PN/AMX system was operated without temperature control (ranging from 11 to 28 °C) and was subjected to the same variations in wastewater characteristics as the WWTP (22 to 63 mg NH4+- N/L). The developed strategy is simple, does not require the addition of chemicals and is characterised by short start-up periods. The PN process was established by applying a high hydraulic load and maintained by in situ accumulated free nitrous acid (FNA) of 0.015–0.2 mg HNO2-N/L. Based on pH value, a controlled aeration strategy was applied to achieve the target nitrite to ammonium ratio in the effluent (1.1 g NO2–-N/g NH4+-N) to feed the AMX reactor. Although NOB were not fully washed out from the system, nitrite accumulation remained (>99 %) stable with no evidence of NOB activity. In the AMX reactor, an overall nitrogen removal efficiency of 80 % was achieved. Regarding effluent quality, 12 ± 3 mg TN/L was obtained, but 5 mg NO3–-N/L was already in the HRAS effluent. The relative abundance of NOB showed a strong negative correlation with the FNA concentration, providing a good strategy for establishing PN under mainstream conditions.

Microbubble-Assisted Cleaning-in-Place Process for Ultrafiltration System and Its Environmental Performance

Membrane filtration is a key technology in dairy processing for the separation of dairy liquids to clarify, concentrate, and fractionate a variety of dairy products. Ultrafiltration (UF) is widely applied for whey separation, protein concentration and standardization, and lactose-free milk production, though its performance can be hindered by membrane fouling. As an automated cleaning process commonly used in the food and beverage industries, cleaning in place (CIP) uses large amounts of water, chemicals, and energy, resulting in significant environmental impacts. This study introduced micron-scale air-filled bubbles (microbubbles; MBs) with mean diameters smaller than 5 μm into cleaning liquids to clean a pilot-scale UF system. During the UF of model milk for concentration, cake formation was identified as the dominant membrane fouling mechanism. The MB-assisted CIP process was conducted at two bubble number densities (2021 and 10,569 bubbles per mL of cleaning liquid) and two flow rates (130 and 190 L/min). For all the cleaning conditions tested, MB addition largely increased the membrane flux recovery by 31-72%; however, the effects of bubble density and flow rate were insignificant. Alkaline wash was found to be the main step in removing proteinaceous foulant from the UF membrane, though MBs did not show a significant effect on the removal due to the operational uncertainty of the pilot-scale system. The environmental benefits of MB incorporation were quantified by a comparative life cycle assessment and the results indicated that MB-assisted CIP had up to 37% lower environmental impact than control CIP. This is the first study incorporating MBs into a full CIP cycle at the pilot scale and proving their effectiveness in enhancing membrane cleaning. This novel CIP process can help reduce water and energy use in dairy processing and improve the environmental sustainability of the dairy industry.

Insight into suppression of dibutyl phthalate on DOM removal during municipal sewage treatment using fluorescence spectroscopy with PARAFAC and moving-window 2D-COS

Dibutyl phthalate (DBP) has been widely detected in municipal and industrial wastewater, which could indirectly inhibit pollutant removals, especially degradation of dissolved organic matter (DOM). Here, the inhibition of DBP on DOM removal from wastewater in pilot-scale A2O-MBR system was investigated by fluorescence spectroscopy with two-dimensional correlation (2D-COS) and structural equation modeling (SEM). Seven components were extracted from DOM using parallel factor analysis, i.e., tryptophan-like (C1 and C2), fulvic-like (C4), tyrosine-like (C5), microbial humic-like (C6) and heme-like (C7). The tryptophan-like had a blue-shift at DBP occurrence, defined as blue-shift tryptophan-like (C3). DBP with 8 mg L−1 exhibited a stronger inhibition on removals of DOM fractions, extraordinarily tyrosine-like and tryptophan-like in anoxic unit than DBP of 6 mg L−1 by moving-window 2D-COS. The indirect removals of C1 and C2 through the C3 removal were more strongly inhibited by 8 mg L−1 DBP than those by 6 mg L−1 DBP, while the former exhibited a weaker inhibition on the direct degradation of C1 and C2 than the latter via SEM. Based on metabolic pathways, abundances of key enzymes secreted by microorganism in anoxic unit, degrading tyrosine-like and tryptophan-like, were higher in wastewater with 6 mg L−1 DBP than those with 8 mg L−1 DBP. These could provide a potential approach for online monitoring of DBP concentrations in wastewater treatment plants, which could rectify operating parameters, and then enhance the treatment efficiencies.

Bed inventory balance and stability of dual circulating fluidized bed systems

Experiments and modelling are conducted for general understanding on the imbalance phenomenon and for discussion on the strategies to improve the bed inventory balance and stability of a dual circulating fluidized bed (DCFB) system. The experiments are carried out in a 15.5 m high pilot-scale DCFB cold test system. A fluid-dynamic DCFB model is developed based on a 1.5-dimensional semi-empirical model of an industrial CFB boiler, validated by experimental data. The effects of control methods and operation conditions on the bed inventory balance and on the stability of the pilot- and large-scale DCFB systems are discussed. A “stable-unbalanced” state, where the system reaches a steady state, consisting of unbalanced bed inventories, is observed in both experiments and model simulation. To maintain a balanced state and similar bed inventory in the DCFB systems with similar cross-sectional areas, it is recommended to keep similar total pressure drops or gas velocities in both reactors.