Pilot-scale Experiments Research Articles

Study on the photocatalytic degradation of metronidazole antibiotic in aqueous media with TiO2 under lab and pilot scale

Nowadays, the increased consumption of antibiotics, such as metronidazole (MTZ), leads to their introduction in wastewater as well as in the receiving surface waters due to their incomplete removal by conventional wastewater treatment plants. Heterogeneous photocatalysis is a versatile technology that can efficiently degrade such organic contaminants. In the present research, the photocatalytic degradation of MTZ with TiO2 P25 was studied under lab and pilot (CPC reactor) conditions. The antibiotic was efficiently removed at high rates in both cases (100 % and 91 %) following pseudo-first order kinetics with rate constants equal to 0.0452 min−1 (±RSD% = 0.68 % - 2.57 %) and 0.0462 L KJ−1 (±RSD% = 8.94 % - 21.64 %) respectively. Also, by scavenging lab scale experiments, the contribution of the generated reactive species was investigated and hydroxy radicals (HO•) were proposed as the predominant species. By applying high resolution mass spectrometry techniques, the transformation products (TPs) were identified and possible transformation pathways were proposed. The ecotoxicity of the TPs was assessed in silico using the ECOSAR software with the results revealing that most of them were less toxic than the parent compound. Similarly, the mutagenicity, developmental toxicity and bioconcentration factors of the TPs were predicted by utilizing the T.E.S.T. software and in their majority, were found to be less mutagenic and developmentally toxic than MTZ. The ecotoxicity monitoring with the Vibrio fischeri bioassay in both laboratory and pilot scale experiments indicated that through heterogeneous photocatalysis it is possible to reduce the toxicity of wastewater containing MTZ. Finally, the stability and reusability of the photocatalyst was investigated through three consecutive catalytic cycles with the results showing that the performance of TiO2 decreased after each use. For the heterogeneous photocatalysis with TiO2 to be a “real life” applicable technique, further studies focusing on catalyst regeneration and optimization of the catalytic conditions must be conducted.

Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms

Filter-feeding mussels blend suspended particles into faeces and pseudo-faeces enhancing organic matter flows between the water column and the bottom, and strengthening benthic-pelagic coupling. Inside operating farms, high bivalve densities in relatively confined areas result in an elevated rate of organic sinking to the seabed, which may cause a localized impact in the immediate surrounding. Deposit-feeding sea cucumbers are potentially optimal candidates to bioremediate mussel organic waste, due to their ability to process organic-enriched sediments impacted by aquaculture waste. However, although the feasibility of this polyculture has been investigated for a few Indo-Pacific species, little is known about Atlanto-Mediterranean species. Hence, for the first time, in the present study, we conducted a comparative investigation on the suitability of different Mediterranean sea cucumber species, to be reared in Integrated Multitrophic Aquaculture (IMTA) with mussels. A pilot-scale experiment was accomplished operating within a mussel farm where two sea cucumbers species, Holothuria tubulosa and Holothuria polii, were caged beneath the long-line mussel farm of Mytilus galloprovincialis. After four months, H. tubulosa showed high survivorship (94%) and positive somatic growth (6.07%); conversely H. polii showed negative growth (− 25.37%), although 92% of specimens survived. Furthermore, sea cucumber growth was size-dependent. In fact, smaller individuals, independently from the species, grew significantly faster than larger ones. These results evidenced a clear difference in the suitability of the two sea cucumber species for IMTA with M. galloprovincialis, probably due to their different trophic ecology (feeding specialization on different microhabitats, i.e. different sediment layers). Specifically, H. tubulosa seems to be an optimal candidate as extractive species both for polycultures production and waste bioremediation in M. galloprovincialis operating farms.

G-C3N4 as Photocatalyst for the Removal of Metronidazole Antibiotic from Aqueous Matrices under Lab and Pilot Scale Conditions

The presence of pharmaceuticals in water is a problem of utmost importance due to the various adverse effects that these compounds may have on aquatic organisms and also humans. Since conventional wastewater treatment plants fail to efficiently remove many of these compounds, new techniques such as heterogeneous photocatalysis have been developed that are capable of degrading them. In this study, graphitic carbon nitride (g-C3N4) was used as photocatalyst to remove metronidazole (MTZ), which is a widely prescribed antibiotic that has been reported as a potential carcinogen. The experiments were performed under lab and pilot scale conditions. During the lab scale experiments, 90.6% of the initial pharmaceutical concentration was removed after 360 min of irradiation and its removal followed a pseudo first order kinetic model with a degradation rate constant of k = 0.00618 min−1. Moreover, scavenging studies indicated that the indirectly produced hydroxy radicals contribute very little to the degradation mechanism. Through high precision mass spectrometry techniques, eight transformation products (TPs) were identified, and possible transformation pathways were suggested. Similarly, in the case of pilot scale experiments, 100 and 200 mg L−1 of g-C3N4 were used and the antibiotic’s removal also followed pseudo first order kinetics with k = 0.00827 min−1 and k = 0.00942 min−1, respectively. However, starting from low level inherent concentrations, only two TPs were identified. By using in silico tools (ECOSAR and T.E.S.T.), various ecotoxicological values were predicted for the TPs, which were generally found to be less toxic than the parent compound and with lower mutagenic and bioaccumulative potential. Moreover, the monitoring of the ecotoxicity with the in vitro Microtox bioassay showed that at the end of all the photocatalytic processes, the toxicity was reduced. In conclusion, this technique could have the potential to remove MTZ and other similar pharmaceuticals in full-scale applications. However, for this to happen with the highest possible efficiency, further studies must be conducted, focusing on improving the catalyst’s performance and reusability, improving the separation of catalyst as well as finding the optimum conditions for this process.

(Micro)Biological Sediment Formation in a Non-Chlorinated Drinking Water Distribution System

Sediment formation in drinking water distribution systems can lead to brown water at customer taps. Previous studies have shown that sediment formation is closely linked with (micro)biological processes in the distribution system, however the mechanism is not fully understood. Most available studies on discoloration or sediment formation mechanism are based on modeling, pilot-scale experiments, or low frequency data collected during pipe flushing. In this study, long-term sediment development in a large-scale drinking water distribution system was studied at one location over 11 years and at several locations along a known water trajectory during one year. Particulate material was collected at several locations using built-in and mobile filters that were connected to transport and distribution pipes in a semi-continuous manner. The volume of the collected material varied seasonally and the highest volumes were collected in the summer season. The material followed similar variations as temperature, invertebrates biomass and concentration of Aeromonas. The results showed that particulate matter of the sediment at downstream distribution locations was not released by the treatment works but instead forms along the distribution network, with increasing particle/floc size, biomass and Fe and Mn content. The large crustacean, Asellus, contributed to material production through feces excretion and formation of detritus by degradation of exoskeletons of dead animals. Detailed chemical characterization of the collected material showed the presence of proteins, calcium carbonate and iron precipitates. A similar sediment composition in a reference distribution system where customer complaints about brown water are experienced less frequently suggests that the sediment formation mechanism is the same but that water quality of the treatment effluent impacts the extent of material formation and growth of invertebrates. Overall, the results indicate that sediment formation in the distribution system is the result of complex combinations of (micro)biological and bio-chemical processes, including aggregation of particles with organic and inorganic matter, microbial growth on particles and biofilm, biomineralization, and growth of invertebrates. The determining factors to limit sediment formation, however, could not be identified. Further research is required to focus on the impact of treatment on shaping the distribution system ecosystem.

Real-Time Identification and Positioning of Sewer Blockage Based on Liquid Level Analysis in Rural Area

Sewer blockages delay sewage discharge or cause it to overflow, which pollutes the environment and is a public health hazard. This necessitates the quick and accurate identification and positioning of sewer blockages. Following a sewer blockage, the sewage is intercepted and the liquid level at the upstream and downstream of the blocking point changes. This study established a method for identifying sewer blockages by analyzing the range and rate of the liquid level change at the upstream and downstream of the blocking point. Through pilot-scale and full-scale experiments, this study summarized the threshold values of the liquid level change rate and the liquid level fluctuation range of the drainage pipeline in normal operation, as well as the threshold values of the liquid level change rate and the liquid level fluctuation range of the upstream and downstream of the sewer blocking point. Moreover, the sewer blockage identification matrix was completed. Sewer blockage in rural areas can be identified and positioned using mathematical tools such as the data-driven model. This research method allows for real-time monitoring and timely warning of the sewer status, thereby reducing the labor and material consumption and unnecessary earthwork excavation to ensure the stable operation of the drainage pipeline.

Effect of bulk nanobubbles on ultrafiltration membrane performance: Physiochemical, rheological, and microstructural properties of the resulting skim milk concentrate dispersions

The objective of this study was to evaluate the influence of bulk nanobubble (BNB) incorporation during ultrafiltration (UF) process. Both lab and pilot-scale UF experiments were conducted to evaluate effect of BNB incorporation on UF process by evaluating permeate flux, membrane microstructure, fouling resistance, and energy consumption. Additionally, control and BNB incorporated skim milk concentrate (SMC) dispersions were characterized in terms of physicochemical properties, rheology, and microstructure. Operating UF with BNB incorporation gave better membrane performance, evidenced by better permeation flux. The permeation flux of control SMC was 9.27, and 6.89 kg/h∙m 2 and with BNB incorporation permeate flux significantly increased (P < 0.05) to 14.57 and 9.59 kg/h∙m 2 for lab and pilot-scale UF runs, respectively. BNB incorporation also resulted in a significant decrease (P < 0.05) in apparent viscosity and showed marked changes in microstructure of resultant skim milk concentrate dispersions. In conclusion, BNB incorporation helped to improve UF membrane performance, and therefore this study suggests the potential of using BNB incorporation for a more efficient UF processing. • Bulk nanobubbles (BNB) generated by acoustic and hydrodynamic cavitation improved ultrafiltration membrane performance. • Higher permeate flux can be achieved with BNB incorporation. • The apparent viscosity of resultant skim milk concentrate dispersions reduced with BNB incorporation. • Less membrane depositions with the BNB incorporation. • Permeate flux enhancement of ⁓50% can be achieved with the BNB incorporation. • BNB incorporation influenced the rheological and microstructural properties of skim milk concentrate dispersions.

Assessing the Effects of Material Properties on Load Behavior in Dry Ball Mills Using DEM

Understanding how the mill load behaves is crucial for enhancing ball mill effectiveness. This study aimed to create a discrete element method (DEM) model to simulate the motion charge in ball mills and to analyze how the simulation material properties affected the load behavior. The steel balls were modelled as a collection of distinct particles, each of which was subject to Newton’s laws of motion and tracked in a Lagrangian manner. Hertzian contact law was used to describe inter-particle collisions. Then, this numerical model was coded using the open-source C++ program LAMMPS Improved for General Granular and Granular Heat Transfer Simulation (LIGGGHTS) to mimic laboratory and pilot-scale ball mills. The load positions measured from the DEM simulations were compared to the published experimental data and empirical models of comparable laboratory and pilot-scale experiments to validate the findings. The angular shoulder position ranged between 137° to 154° for the range of Young’s modulus of 0.5 to 1000 MN/mm2. Angular shoulder and toe positions had a variation of less than 10% from the laboratory and pilot-scale experimental data. The outcomes demonstrated a significant relationship between load position and material characteristics such as Young's modulus in DEM simulation. This preliminary model can be used for choosing the appropriate material parameters for ball mills both with DEM and coupled CFD–DEM multiphase simulations. This assessment concluded that material properties affect the load behavior in computer simulations of ball mills.

Model‐based Scale Up of Solid Bowl Centrifuges Using Experimentally Determined Material Functions

AbstractThe scale up of solid bowl centrifuges is a major challenge as the process and material behavior are complex and difficult to describe. A common approach to forecast the process behavior is to use analytical models and transfer the experience gained from the lab to the industrial scale. In this context, time‐consuming and cost‐intensive pilot scale experiments are necessary. This paper presents a methodology to improve the scale up process and make it more sustainable by using a numerical model that allows the real‐time tracking of the process and a more reliable scale up process. For this approach, the material behavior is derived from laboratory experiments whereby the scalability is given. Here, the determination of material functions allows an accurate representation of the material behavior for solid bowl centrifuges of different scales. The focus of this paper is the detailed explanation of material related functions for the scale up of decanter centrifuges.

Removal of chlorine, microparticles and water from high-viscosity liquids by a sand filter coupling hydrocyclone

Separation energy consumption in industrial production accounts for 10–15 % of global energy consumption. Nonthermal separation represented by sand filtration can open a new door to separation energy savings. Traditional sand filters cannot be regenerated completely, which limits their efficiency. A sand filter coupling hydrocyclone (SFCH) was proposed to enhance regeneration. The performance of SFCHs with different separation particle sizes was systematically analyzed, as indicated by turbidity, water, and chlorine in a pilot-scale experiment. The larger the sand particle size of the SFCH was, the longer it took to reach saturation. The efficiency and cycle were balanced by combining SFCHs with particle sizes of 1–2 mm and 0.5–1 mm. The average turbidity, water and chlorine decreased from 793 NTU, 1439 mg/L, and 126 mg/L to 155 NTU, 389 mg/L, and 88 mg/L, respectively, with a cycle of 88 h. Under the same conditions, the effluent turbidity of the SFCH was half of that of the original disc centrifuge, which indicates that the life of the downstream alumina bed was doubled. Almost 260 t/year alumina consumption can be reduced in a 200,000 tons/year-capacity petroleum resin plant, saving 600,000 USD/year, mainly due to the extension of the service life of the alumina bed.

Chemically enhanced high-loaded membrane bioreactor (CE-HLMBR) for A-stage municipal wastewater treatment: Pilot-scale experiments and practical feasibility evaluation

A-stage technology is acknowledged as a promising process for organic recovery. Due to its superior separation performance, the high-loaded membrane bioreactor (HLMBR) is a competitive variant of the A-stage. In this study, a pilot-scale chemically enhanced HLMBR (CE-HLMBR) was established to enhance the practical feasibility of the process. Polyaluminium chloride (PAC) and activated carbon (AC) were added to address membrane fouling, dependence on intensive aeration, and inadequate concentration factors. Eight conditions were designed to investigate the role of chemicals and aeration in filtration, pollutant removal, and organic recovery. Stable filtration (8–10 LMH) was achieved at SS concentrations of 15–20 g/L, benefiting from the dynamic formation and shedding of the protective cake layer, as well as the reduction of extracellular polymer substances (EPS). Over 75 % soluble organics and 80 % soluble phosphorous were removed by CE-HLMBR, mainly subject to the chemicals. Simultaneous nitrification–denitrification occurred due to uneven oxygen distribution. The influent organics were concentrated by factors ranging from 27 to 80 and the loss rate was less than 15 %. Meanwhile, methane production may not be an efficient method of resource extraction. The practical feasibility of the proposed CE-HLMBR was confirmed based on an additional three-month stable operation. This study will open new possibilities for the application of HLMBR systems.

Homogeneous Photo-Fenton Degradation and Mineralization of Model and Simulated Pesticide Wastewaters in Lab- and Pilot-Scale Reactors

The homogeneous photocatalytic degradation of model pesticide clopyralid (CLPR) has been investigated under various experimental setups. Lab-scale experiments under UV-A radiation in an acidic environment showed that the degradation rate generally increased when increasing either Fe3+ or H2O2 concentration up to a point beyond which (i.e., 100 mg L−1 for peroxide or 7 mg L−1 for ferric ions) Fenton reagents had little or even detrimental effect on degradation. Thus, there is an optimum concentration of Fenton reagents for maximizing treatment performance, beyond which degradation rates are not enhanced. Excessive concentrations of peroxide and/or catalyst may (i) introduce unnecessary treatment costs, (ii) reduce performance due to scavenging effects, and (iii) raise environmental concerns associated with the disposal of, e.g., high concentrations of iron in the receiving water courses. Switching from UV-A to visible light led to similar rates of degradation, i.e., 86% and 82.2%, respectively, after 90 min of reaction, highlighting the potential of using renewable energy, i.e., natural sunlight, to drive the process. Treatment for 120 min also led to 90% mineralization and quantitative release of nitrogen originally present in the pesticide; this was also accompanied by complete elimination of eco-toxicity to Vibrio fischeri. Pilot-scale experiments were performed in a fountain-type reactor using a commercial pesticide formulation containing CLPR. Both the degradation and mineralization rates increased with increasing the intensity of the incident UV-A radiation from 1.88 to 4.03 mW cm−2. Experiments were also conducted with different liquid volumes, i.e., from 3 to 8 L. Illumination of 5 L wastewater resulted in 80% mineralization after 60 min and this only slightly decreased to 73% at 8 L. Overall, the findings underline the promising perspectives of the application of the treatment method in upgrading the quality of water and liquid waste containing pesticides.

Application of different packing media for the biofiltration of gaseous effluents from waste composting

ABSTRACT A pilot-scale experiment was implemented in a waste bioreactor with an inner capacity of 1 m3 in order to simulate a real-scale composting process. The waste underwent composting conditions that are typical of the initial bio-oxidation phase, characterised by a high production of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and odorants. The waste bioreactor was fed with an intermittent airflow rate of 6 Nm3/h. The target of this study was to investigate the air treatment performance of three biofilters with the same size, but filled with different filtering media: (1) wood chips, (2) a two-layer combination of lava rock (50%) and peat (50%), and (3) peat only. The analyses on air samples taken upstream and downstream of the biofilters showed that the combination of lava rock and peat presents the best performance in terms of mean removal efficiency of odour (96%), total VOCs (95%) and H2S (77%) concentrations. Wood chips showed the worst abatement performance, with respective mean removal efficiencies of 90%, 88% and 62%. From the results obtained, it is possible to conclude that the combination of lava rock and peat can be considered as a promising choice for air pollution control in waste composting facilities.

Fabrication of an inexpensive injection molding instrument for rapid prototyping of high precision parts

Polymeric drug delivery devices are among the most promising avenues to improve the equitable distribution of life-saving medications throughout the world. At present, most research into manufacturing these devices relies heavily on solvent-based methods, limiting scalability, reproducible manufacture, and potentially leading to cytotoxicity. Solvent-free polymeric biomedical implants manufactured through traditional thermal processing methods eliminate the bulk of these concerns. However, they are difficult to manufacture in a research laboratory setting. Investigation of manufacturing techniques such as injection molding has been limited in the past due to the high upfront cost of polymer equipment and the large scale necessary to conduct pilot experiments. This study describes a low-cost bench-top milliliter-volume vacuum injection-molding system capable of pilot-scale injection molding of small shapes of arbitrary geometry. The plans presented herein open this convenient and scalable manufacturing technique to academic research laboratories interested in pilot-scale experiments with polymeric devices. Polymers relevant for polymeric drug or vaccine delivery are investigated, and a demonstration of the fabrication of simple geometric parts and solvent-free polymeric microneedle patches is described. In particular, microneedle patches demonstrate the capabilities and limitations of producing fine feature sizes for biomedically relevant products.

Disinfestation of wheat seed from Sitophilus granarius (L.), S. oryzae (L.), and Rhyzopertha dominica (F.) by packing under vacuum in high-barrier multi-layered plastic bags

Conditioning under low-oxygen modified atmosphere in sealed enclosures, containers or bags is widely used for the disinfestation of grain from insect pest species. The effect of hermetic vacuum storage on the survival of primary insect pests of cereals still lacks relevant documentation. To enhance knowledge on this topic, a pilot scale experiment was undertaken. Prior to the study, batches of wheat seeds were infested by some of the most harmful insects of stored cereals, Sitophilus oryzae, S. granarius, and Rhyzopertha dominica, in order to obtain infested seed samples by all development stages. Then, 5-kg sound wheat seed lots were placed inside multilayer aluminium-plastic flexible bags and 200 g of previously infested seeds were included before vacuum packing the bags at depression levels: 30, 50 or 70 kPa. In addition to storage at an average temperature of 25.8 °C, survival rate and progeny production of insects were checked at regular time intervals after opening a series of bags. After adult recovery by sieving, the 200 g-samples were incubated for 42 d at 25.8 °C for hidden stages recovery. The exposure time for 99% reduction of survival rate and progeny production (LT99) by S. oryzae and S. granarius, at 70 kPa depression level, was observed after 37.5 and 31 d exposure, respectively. For R. dominica, LT99 was assessed at 63.5, 75.6 and 88.5 d at 70, 50 and 30 kPa depression level, respectively. Rhyzopertha dominica was observed much more tolerant than the two weevil species, especially when depression level was more than 50 kPa. This species was able to produce progeny under vacuum. The origin of the differences in susceptibility between the weevils and the lesser grain borer in relation to storage under vacuum inside flexible high-barrier multilayer aluminium-plastic bags are discussed.

Enhanced Photo-Fenton Activity Using Magnetic Cu0.5Mn0.5Fe2O4 Nanoparticles as a Recoverable Catalyst for Degrading Organic Contaminants

Interest in using various nanoparticle catalysts to activate H2O2 with light for organic contaminant and wastewater treatment is steadily increasing. We successfully synthesized magnetically recoverable Cu0.5Mn0.5Fe2O4 nanoparticles using a simple co-precipitation method followed by melamine-assisted calcination. Material characterization revealed that melamine acted as a coordinating agent during the calcination process that promoted a ferrite structure. Copper (Cu)-substitution effectively decreased material aggregation and promoted catalytic activities. Cu0.5Mn0.5Fe2O4 nanoparticles showed outstanding catalytic performance on several organic contaminants (87.6–100.0% removal within 2 h). Using oxytetracycline (OTC) as a surrogate wastewater constituent, we found that the hydroxyl radical (•OH) and superoxide anions (•O2−) were the active radical species involved in OTC degradation. Cu0.5Mn0.5Fe2O4 nanoparticles exhibited excellent photo-Fenton catalytic ability in real wastewater and demonstrated high material stability, even after four consecutive uses (i.e., fourth cycle). In a pilot-scale experiment (10 L), we provide proof that our rigorous treatment system was able to remove remnant OTC, TOC, and also any available colloidal particles to only 1 NTU. Ecotoxicity studies using an aquatic plant (Hydrilla verticillata) and zooplankton revealed that treated water could be reused in various ratios. Furthermore, at 5% of treated water, rapid leaf recovery and a significant increase in rotifer numbers were reported. These observations support the use of Cu0.5Mn0.5Fe2O4/H2O2/light as an efficient and environmentally friendly catalytic system for treatment of organic contaminants, and a radical generating mechanism is proposed.

Highly efficient removal of hexavalent chromium from electroplating wastewater by ferrous/ferric hydroxide complex: From lab-scale to pilot-scale study

Low electron-transfer efficiency and cumbersome processes are widely known to negatively affect the application of Fe-based materials for treating electroplating wastewater. In this study, ferrous/ferric hydroxide complex (FHC) was successfully synthesized to greatly improve the electron-transfer efficiency for Cr(VI) removal; meanwhile, the effect of the interlayer type on Cr(VI) removal and the possible removal mechanisms were well investigated. The sulfate interlayer of FHC was shown to strongly promote Cr(VI) removal, with 10.4 % and 29.0 % improvements over those achieved by chloride and carbonate interlayers, respectively, in close association with the amounts of surface structural Fe(II), surface –OH, and adsorbed water. The initial pH value was demonstrated to exert almost no effect on Cr(VI) removal by FHC(SO42−) owing to the buffering effect of the surface –OH. These results were different from some previously reported Cr(VI) removal of Fe-based materials. Moreover, the results of characterization and lab-scale experiments indicated that most of Cr(VI) binds rapidly with the surface –OH owing to electrostatic attraction. The peak at 618 cm−1 in the FT-IR spectra shifted to 549 cm−1 and new peaks at 576.79 and 586.39 eV in the XPS spectra were observed after the reaction, which was attributed to the formation of CrOOH and FeCr2O4 owing to reduction and coprecipitation. Pilot-scale experiments revealed that the chemical cost and sludge yield during the FHC process decreased by 71.3 % and 54.1 %, respectively, compared with those in the NaHSO3 process. These findings provide new insight for utilizing different interlayers to improve the reactivity of FHCs in remediating electroplating wastewater containing Cr(VI).

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics, efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al2O3 was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O2–, and 1O2), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al2O3 catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ∼ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ∼ 0.032$/m3, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al2O3 exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.

Characterisation and perspectives of energetic use of dissolved gas recovered from anaerobic effluent with membrane contactor

Biogas is a source of renewable energy, and its production and use has been validated in anaerobic-based sewage treatment plants (STPs). However, in these systems, a large amount of methane is lost as dissolved methane (D-CH4) in the liquid effluent. In this study, the characteristics and potential energetic uses of the gas recovered during the desorption of D-CH4 from anaerobic effluents with hollow fibre membrane contactors were investigated. A pilot-scale experiment was performed using sewage and two types of membrane contactors. The recovered gas contained considerable amounts of CH4, CO2, H2S, N2, and O2; therefore, a gas upgrade is required prior to its use as a biofuel. The recovery process should be energetically self-sustainable, and induce a considerable decrease in the STP carbon footprint. Recovering D-CH4 with membrane contactors could increase the energetic potential of anaerobic-based STPs up to 50 % and allow for more sustainable systems.

Elimination of pesticide from high salinity wastewater by electrochlorination process: Active chlorine species and scale-up performance

Active chlorine species-mediated electrochemical process is a promising strategy for refractory pollutants and ammonia removal in high salinity organic wastewater. Herein, we constructed an electrochlorination (E-Cl) process with the help of the high concentration of chloride ions (Cl−) in the wastewater to realize the efficient treatment of pesticide wastewater. The E-Cl process exhibited excellent chemical oxygen demand (COD, 86.43%) and atrazine (ATZ, 98.67%) removal efficiency for the actual pesticide wastewater since active chlorine species, including free chlorine and reactive chlorine species (RCS), and hydroxyl radical (•OH) were all in-situ produced during the electrolysis process. The quenching experiments indicated that the free chlorine was the primary oxidizing substance for the decomposition of ATZ, and the RCS and •OH mainly enhanced the mineralization of intermediate products. In addition, the inhibition mechanism of different background substances in the E-Cl process was different. The toxicity test and three-dimensional fluorescence spectrum all proved that the E-Cl process could effectively remove ATZ and other organic matter from the actual pesticide wastewater. Finally, an E-Cl pilot reactor was designed and the pilot-scale experiments showed that the COD and NH4+-N of the actual pesticide wastewater after the treatment of the E-Cl process were < 50 mg/L and < 1.5 mg/L, and the energy consumption (EC) was ∼4.98 kWh/m3. The successful treatment of actual pesticide wastewater by the E-Cl process suggests that this is a promising method for treating organic pollutants and ammonia under highly salinity conditions.

Analysis of Hydrothermal Solid Fuel Characteristics Using Waste Wood and Verification of Scalability through a Pilot Plant

Increases in energy demand and waste are a major cause of natural resource depletion and environmental pollution, and technology capable of processing waste to convert it into energy is required to mitigate this issue. Hydrothermal carbonization (HTC) is an example of this technology that can convert waste into energy, and various studies have been conducted using it for fuel conversion. This study focused on the production of a solid fuel equivalent to coal for power generation through HTC processes using waste wood. Unlike previous work, which consists only of laboratory-scale HTC experiments, we confirmed scalability through pilot-scale HTC experiments. Overall, it was possible to convert waste wood into HTC solid fuel with a calorific value of over 27,000 kJ/kg through the pilot plant HTC process. Additionally, heavy metal and hazardous substance analyses proved that it can be used as a biosolid fuel.