Full-scale Process Research Articles

A pilot-scale SNAD-MBBR process for treating anaerobic digester liquor of swine wastewater: performance and microbial community.

In this pilot-scale study, simultaneous partial nitrification, anammox, and denitrification (SNAD) process was achieved successfully in a moving bed biofilm reactor (MBBR) for treating anaerobic digester liquor of swine wastewater. After 95days of operation, when the total nitrogen loading rate of SNAD-MBBR process was 1.09kg TN/m3/day, the total nitrogen removal rate could reach 0.87kg TN/m3/day, and the removal efficiencies of ammonium and total nitrogen were 92.0% and 79.7%, respectively. The optimum pH and temperature for SNAD-MBBR process were 8.5 and 35°C, respectively, and the optimum dissolved oxygen for SNAD1 and SNAD2 were 0.30 and 0.07mg/L, respectively. The 16S rRNA sequencing suggested that Candidatus Kuenenia, Candidatus Brocadia, Nitrosomonas, and Denitratisoma were the dominant nitrogen removal bacteria. Some of the co-existing bacteria (Truepera, Limnobacter, and Anaerolineaceae uncultured) promoted ammonium oxidation and guaranteed the growth of the anammox bacteria under adverse environmental conditions. Overall, this study demonstrated that the SNAD-MBBR process would be an energy-saving and cost-effective method for the removal of nitrogen from swine wastewater and provided important process parameters for stable operation of the full-scale SNAD process.

Optimization of Fe(II)/SPC Sludge Conditioning and Dewatering Process Based on Response Surface Methodology: Full-Scale Application

Sludge conditioning is a crucial step in sludge dewatering aimed at minimizing excessive sludge production. The Fenton process, which harnesses oxidative radicals to dismantle extracellular polymeric substances (EPS) and microorganisms, has been unequivocally proven to enhance sludge dewaterability. However, the widespread adoption of the Fenton process is hampered by its high costs and logistical challenges in transportation. In contrast, the Fe(II)-activated sodium percarbonate (Fe(II)/SPC) process has emerged as a promising technology for sludge conditioning due to its remarkable performance and safe operation. However, limited information is available regarding the optimization of Fe(II)/SPC for sludge conditioning and dewatering at full scale. This study conducted the sludge conditioning and dewatering process within a full-scale wastewater treatment plant, utilizing the response surface methodology (RSM) to optimize the Fe(II)/SPC process. Furthermore, this study investigated its impact on sludge structure and compared the economic benefits of the Fe(II)/SPC process with other full-scale conditioning processes. The results of bound water and LDH analysis revealed that the Fe(II)/SPC process not only degraded EPS but also disrupted microbial cells, thereby releasing intracellular water. Based on the RSM results, we successfully established a polynomial prediction model to determine the optimal capillary suction time (CST) and moisture content. The optimal parameters determined through RSM were an initial pH of 3.02, Fe(II) dosage of 0.05 g/g TSS, and SPC dosage of 0.07 g/g TSS. The validation test confirmed the accuracy of the prediction results, with the conditioned sludge exhibiting a CST of 31.6 s and a moisture content of 51.47%. Furthermore, when compared to the PFS and Fenton processes, the Fe(II)/SPC process demonstrated higher economic efficiency and safety, while maintaining good dewatering performance. Overall, the Fe(II)/SPC treatment shows promise as a prospective sludge dewatering and conditioning process.

From concrete waste to walls: An investigation of reclamation and digital technologies for new load-bearing structures

The research presented in this paper highlights current practices for the end-of-life of concrete and explores opportunities in using unaltered concrete rubbles from demolition for the digital construction of structural walls. Through research by iterative making performed by the authors, relevant upcycling processes and design strategies are identified and explored to shape new tectonics specific to reclaimed concrete rubbles with non-standard variable geometries. This iterative research proposes accessible and scalable digital processes to overcome the challenges inherent to this untapped construction material. Results from small-scale prototypes provide valuable insights for full-scale processes to advance the digitization of construction and alleviate its environmental impact.

CFD-DEM models for matte droplet settling in a flash smelting settler

The flash smelting process is widely used in copper production. In the process, sulfidic feed and flux are oxidized. The heat released in the reactions melts the feed which forms a slag layer through which matte droplets must settle. Understanding the different phenomena affecting the settling is important to minimize losses. Due to the high temperature, simulation methods were employed to study settling. In this work, coupled CFD-DEM was used to study the effect of coalescence and reactions with in-house built submodels and scaled-down geometries. Colliding droplets often coalesce into larger droplets while reactions decrease their size and make them denser. These increase the settling velocity which is further enhanced by the formation of a channeling flow. Channels make the droplet cluster denser causing more collisions. This method enables the phenomena to be studied at the individual droplets' details, although simulating a full-scale process is beyond the available computational resources.

Combining large-scale investigation and quantum chemical calculation of pharmaceuticals: Spatiotemporal patterns of occurrence and structural insights into removal

This study investigated the spatiotemporal distribution of 17 pharmaceuticals in wastewater treatment plants (WWTPs) from 17 provinces across China, and explored structural insights into their removal in full-scale wastewater treatment processes by quantum chemistry. Briefly, 10 pharmaceuticals were detected in above 85 % of samples, of which ibuprofen and sulfamethoxazole dominated with concentrations up to the μg/L level. Seasonally, concentrations of psychoactive drugs (PDs) were 1.3–2.6 times higher in summer than in other seasons. Spatially, higher average concentrations were detected in northern WWTPs, and regions with similar economic levels exhibited similar contamination patterns. Pharmaceutical removal in WWTPs ranged from 41.4 % (carbamazepine) to 87.2 % (sulfamethizole), with the secondary treatment segment, especially aerobic treatment units, maintaining an important position. Molecular structural mechanisms behind these removal performances were further revealed. Firstly, we demonstrated a significant association of pharmaceutical overall removal with electrophilicity index (ωcubic) as well as the lowest unoccupied molecular orbital energy (ELUMO). Highly electrophilic pharmaceuticals may persist in WWTPs and their sensitivity to electron exchange reactions accounted for the discrepant removal. In terms of treatment segments, pharmaceuticals with reaction sites masked in molecular structure, such as ibuprofen and venlafaxine, showed a propensity for tertiary treatment suitability. Furthermore, enzymes of aerobic units exhibited excellent docking affinity to pharmaceutical molecules with an average affinity of −7.2 kcal/mol, and hydrogen-bond interactions played an important factor in promoting biodegradation. Our results emphasize the necessity of assessing pharmaceutical contamination on a larger spatiotemporal scale. Moreover, the structural insights into removal phenomena offer scientific molecular-level justification for the design and optimization of pharmaceutical treatment technologies in WWTPs.

Investigation on molecular characteristics of organic compounds during a full-scale landfill leachate treatment process based on non-targeted analysis

In this study, a new methodology for evaluating full-scale landfill leachate treatment processes by non-targeted analysis using comprehensive two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOF-MS) was proposed. The method revealed the chemical complexity of organic compounds in landfill leachate samples at the molecular level and evaluated the removal efficiency of the anaerobic-anoxic-oxic (A2O) - membrane bioreactor (MBR) - nanofiltration (NF) treatment process in conjunction with multi-level classification of organic compounds. Results showed that the results of non-targeted analysis combined with multi-level classification of organic compounds had a significant correlation with the conventional water quality parameters and can be used to evaluate the treatment process. A total of 2508 organic compounds were detected in 6 samples. 17 emerging contaminants (ECs) with known potentially hazards were detected, including Diisobutyl Phthalate (DIBP), which is toxic to male reproduction and development, and 4-Tert-Butylphenol, which causes endocrine disruption in animals. The removal rate of organic compounds by this full-scale landfill leachate treatment processes reached 79.14%. The anaerobic tank played a crucial role with 64.98% contribution. For compounds, the removal rate of heterocyclics was as high as 94.67%, and the removal rate of aliphatics was poor, only 63.49%. This treatment process had almost perfect removal effect on the steroids in alicyclics and phenols in aromatics, but poor treatment effect on saturated alkanes in aliphatics and naphthenes in alicyclics. This study provides a methodology for accurate assessment of the molecular level of treatment processes, new insights for process optimization in waste treatment plants, and data support for the detection of emerging contaminants. The environmental hazards of landfill leachate can be further evaluated in the future in conjunction with ecotoxicity assessment studies.

Occurrence, distribution, and behaviors of erythromycin A, production byproducts, transformation products, and resistance genes in a full-scale erythromycin A production wastewater treatment system

Antibiotic production wastewater from pharmaceutical manufacturing is a significant source of antibiotic and resistance gene pollution in the environment. Given that Erythromycin A (Ery-A) is a widely used antibiotic in both human clinical and livestock breeding, it is imperative to ascertain its presence, along with related compounds, in the biological treatment processes of production wastewater. In this study, the occurrence and behavior of Ery-A, its production byproducts, transformation products, and resistance genes were first systematically investigated in a full-scale anaerobic-aerobic system for treating Ery-A production wastewater. Simultaneously, residual antibacterial activity in wastewater and sludge was evaluated throughout the wastewater treatment process. Ery-A contributes only 24.2 – 36.0% to the antibacterial activities. Ery-A-derived compounds including production byproducts (erythromycin B and erythromycin C) and transformation products (anhydro erythromycin A, N-demethyl-erythromycin A, and erythromycin A enol ether), are determined to contribute to the antibacterial activities of the wastewater treatment system. High concentrations of antibiotics with antibacterial activity (up to 1,258.9 mg/kg·TS for erythromycin A enol ether) adsorbed in the sludge result in near collapse of the first-stage anaerobic sludge system. Sludge biodegradation in second-stage anaerobic and anoxic-aerobic tanks is essential in removing Ery-A-related compounds from wastewater. The Ery-A-related compounds in the secondary effluent and excess sludge are determined to be 44.5 g/h and 1.5 g/h through the mass balance analysis, respectively. The discharge of MLS resistance genes from the secondary effluent and excess sludge is 1.0 × 1016 copies/h and 7.1 × 1015 copies/h, respectively. These findings highlight the significant concern over the release of Ery-A-related compounds and MLS resistance genes from the Ery-A production wastewater treatment system. As a result, it is crucial to implement strategies for the removal of Ery-A-related compounds from production wastewater before biological processes. This study is the first to report the occurrence and behavior of Ery-A-related compounds and resistance genes along the full-scale wastewater treatment processes. Additionally, it sheds light on the importance of byproducts and transformation products with antibacterial activity from Ery-A in the Ery-A production wastewater treatment system.

Towards an automated framework for the finite element computational modelling of directed energy deposition

In the present work, a comprehensive framework for finite element-based computational modelling of Directed Energy Deposition (DED) process is presented. The proposed approach can be fully automated and implemented on a complex real-life part geometry to accurately predict a thermo-mechanical response during the full-scale deposition process. The discrete material deposition modelling in Finite Element Analysis (FEA) leads to artificial increases in temperature gradients in the melt pool domain. A new method is therefore proposed that aims to mitigate these gradients. Additionally, an easy-to-implement free-surface detection algorithm to accurately prescribe the evolving heat transfer boundary conditions is presented. A three-dimensional sequentially coupled thermo-mechanical model of the process is then validated against experimental data obtained in a deposition case study. The simulation results show good agreement with the in-situ temperature measurements taken during the actual deposition. In addition, result analysis showed that the largest tensile residual stresses form in the hoop and axial direction on the outer domain of the thin-wall cylindrical part near the base plate while the inward material is compressed.

Environmentally-viable utilization of chicken litter as energy recovery and electrode production: A machine learning approach

Waste-to-energy could eventually be a crucial role in new disposal strategy for organic waste like chicken litter. Herein, a pyrolysis-based process that fully utilize the pyrolysates of chicken litter as energy sources (gas and liquid fuels) and energy storage material (supercapacitor (SC) electrode), which significantly contributes to carbon neutrality, has been proposed. Feasibility and readiness of the proposed process were estimated by combining various approaches such as lab-scale experiment, full-scale process simulation, life cycle analysis, and machine learning. Pyrolytic products other than the SC electrode material, such as gas and liquid, could be considered as fuels given their higher heating values ranging from 6 to 7 MJ kg−1. The SC electrode is comprised of porous carbon and delivers a large specific capacitance of 90 F g−1 at a constant specific current of 0.1 A g−1, demonstrating a potential for use in energy storage. Compared with fossil-based electrode materials, the chicken litter-based electrode material had 49%–64% reduction in global warming potential (GWP) and 83% of abiotic depletion of fossil fuels. The implementation of an SC system using the chicken litter-derived electrode therefore has potential to reduce global warming and fossil resource depletion. In addition, a case study on Jeju Island in the Republic of Korea incorporating renewable energy networks was considered based on diverse samples and their forecasts from machine learning algorithms. The chicken litter-based SC system in Jeju Island could reduce 63,191 t CO2 eq. per year of GWP.

Sialylation and Sulfation of Anionic Glycoconjugates Are Common in the Extracellular Polymeric Substances of Both Aerobic and Anaerobic Granular Sludges.

Anaerobic and aerobic granular sludge processes are widely applied in wastewater treatment. In these systems, microorganisms grow in dense aggregates due to the production of extracellular polymeric substances (EPS). This study investigates the sialylation and sulfation of anionic glyconconjugates in anaerobic and aerobic granular sludges collected from full-scale wastewater treatment processes. Size exclusion chromatography revealed a wide molecular weight distribution (3.5 to >5500 kDa) of the alkaline-extracted EPS. The high-molecular weight fraction (>5500 kDa), comprising 16.9-27.4% of EPS, was dominant with glycoconjugates. Mass spectrometry analysis and quantification assays identified nonulosonic acids (NulOs, e.g., bacterial sialic acids) and sulfated groups contributing to the negative charge in all EPS fractions. NulOs were predominantly present in the high-molecular weight fraction (47.2-84.3% of all detected NulOs), while sulfated glycoconjugates were distributed across the molecular weight fractions. Microorganisms, closely related to genera found in the granular sludge communities, contained genes responsible for NulO and sulfate group synthesis or transfer. The similar distribution patterns of sialylation and sulfation of the anionic glycoconjugates in the EPS samples indicate that these two glycoconjugate modifications commonly occur in the EPS of aerobic and anaerobic granular sludges.

Molecular catalysed Guerbet reaction: Moving to the larger and the Greener through LCA and scale up simulation approaches

Efficient homologation of bio-ethanol can be performed under mild conditions exploiting a catalytic system based of a ruthenium molecular catalyst, benzoquinone and a base as a co-catalysts. Conversions and selectivity can be tuned by changing the head space of the reactor. On this basis, preliminary design of a full-scale process has been developed based on the experimental results. The process has been characterized with specific energy and performance indicators per unit of produced butanol, which have been used as input for the life cycle assessment analysis. The LCA was applied as scientific methodology to address potential burdens of the baseline configuration, 3X catalytic cycles, electricity from Italian grid and heat from natural gas. Hotspots were identified according to a multi-impact approach method (ReCiPe 2016). The usage of dedicated lignocellulosic biomass as a source of EtOH, the synthesis of the catalytic system and the energy requirements were addressed as the major contributors. Thus, further sensitivity scenarios were created. The best configuration was identified in the use of waste biomasses and in an integrated cogeneration unit. In addition, enabling the recovery of the catalytic system up to five cycles to scenario shows a reduction in the impacts higher than 50% for the categories of global warming potential, −41% for the mineral resource scarcity and around −16% for the fine particulate matter formation. The results were also confirmed by an uncertainty analysis with the Monte Carlo method, which demonstrated the major environmental sustainability of the Guerbet route compared to the oxo synthesis from propylene.

Challenges and Opportunities for Lithium Extraction from Geothermal Systems in Germany—Part 3: The Return of the Extraction Brine

Lithium (Li) is considered a crucial element for energy transition due to its current irreplaceability in Li-ion batteries, particularly in electric vehicles. Market analysis indicates that Germany’s future automotive sector and planned battery cell production will necessitate significant quantities of global lithium production. At the same time, only 1% of the world’s Li production is currently sourced from Europe. Recently, geothermal brines in Germany have gained attention as a potential local raw material source. These brines exhibit elevated Li concentrations and substantial flow rates in geothermal plants, suggesting the possibility of viable local production. However, a comprehensive full-scale Li extraction process from geothermal brines is yet to be established, and uncertainties persist regarding its long-term behavior. To address this, a generic model based on the geothermal settings of the Upper Rhine Graben was developed, simulating a 30-year operational period for Li extraction. The simulation revealed a 40% depletion of lithium during the observation period, while heat production remained constant. Nonetheless, the model also demonstrated a mean Li production of 231 t per year (equivalent to 1230 t per year of lithium carbonate equivalent), which could significantly enhance the economic prospects of a geothermal power plant and, if applied to multiple plants, reduce Germany’s dependence on global lithium imports. The primary factor influencing productivity is the achievable flow rate, as it directly impacts access to the raw material, hence, emphasizing the importance of detailed reservoir exploration and development in optimizing future lithium production from geothermal brines.

Dissolved Organic Matter Fractions and Their Removal in Full-Scale Drinking Water Treatment Process

Objectives:The objective of this study is to investigate characteristics about removal of dissolved organic matter (DOM) and its fraction for improving operation efficiency in an advanced water treatment plant. Methods:The monitoring of water quality was conducted at five processes such as raw water, pre-oxidation, after sedimentation, post-ozonation, after biological activated carbon (BAC) from July 2020 to August 2021 in advanced water treatment process (AWTP) supplying 180,000m<sup>3</sup>/day. The concentration of DOC (dissolved organic carbon) and number of algae were monitored and LC-OCD was used to fractionate DOC to four species, biopolymer (BP), humic substance (HS), building blocks (BB), and low molecular weights (LMWs). Results and Discussion:The characteristics of raw water showed that the concentration of DOC and the number of algae increased with an increase in water temperature. The portion of BP and HS significantly increased at low and high water temperature, respectively, while BB and LMWs maintained the similar portion. The removal efficiency of DOC in the AWTP was achieved at 59% with each species of BP, HS, BB, and LMWs obtaining removal efficiency of 87%, 65%, 26%, and 52%, respectively. Coagulation/sedimentation/filtration showed removal efficiency of 84%, 56%, 20%, and 18% for BP, HS, BB, and LMWs, respectively, corresponding to their molecular weight. The effect of post-ozonation would be negligible except for BP. In BAC, removal efficiency of 49% and 12% were obtained for LMWs and BB (low molecular weight, respectively. As a result, the BP portion significantly decreased due to high removal efficiency, while BB portion was increased in the final treated water compared to raw water. Conclusion:Most of DOM was removed in coagulation/sedimentation/filtration and BAC, whereas oxidation process such as pre-chlorination, pre-ozonation and post-oxidation did not have an effect on DOM removal. In coagulation/sedimentation/filtration, 84% and 54% of the BP and HS were removed, while BAC removed 49% and 12% of LMWs and BB, respectively. It has been recommended to improve the removal efficiency of BB, which obtained the lowest removal efficiency in AWTP, and to enhance the removal efficiency of LMWs in BAC to inhibit microbial regrowth in the distribution system.

Ultrafiltration with in-line coagulation (FeCl3) to enhance arsenic removal and improve drinking water quality: From bench to pilot-scale

There is a growing interest in advanced technologies to guarantee drinking water safety in scenarios of increasingly polluted water sources. Based on that, this paper discusses the use of ultrafiltration membranes aided by in-line coagulation with FeCl3 (0.086 – 0.172 mg/L) to improve the resilience of drinking water treatment plants. The process was considered after the settling units and was first studied on a bench scale, later validated in a pilot plant that operated continuously for approximately 31 days. In experiments without an in-line dose of FeCl3, the average flux values corresponded to 189.9 ± 11.8 L/m2h, compared with 193.4 ± 5.3 L/m2h for experiments when the coagulant was considered. The flux decay was lower in experiments with an in-line dose of FeCl3 (J/J0 > 0.95) and analysis of particle sizes revealed that the average diameter increased from 24.1 to 29.2 µm after the coagulant was added. Consequences related to a greater particle size were a fouling layer more porous permeable, and with a lower hydraulic resistance. The additional coagulant dosage also acts on the residual natural organic matter, monitored by excitation-emission matrices. Furthermore, the results show that the concentrate recirculation to the beginning of the water treatment plant did not affect its overall performance. In fact, concentrate recycling would increase the recovery rate of ultrafiltration membranes and reduce losses during water treatment. Similar observations were obtained in pilot-scale operations, that validated the in-line dose on a more representative system that is closer to the full-scale treatment process.

Occurrences and fates of per- and polyfluoralkyl substances in textile dyeing wastewater along full-scale treatment processes

Industrial wastewater is a substantial source of per- and polyfluoroalkyl substances (PFASs) in the environment. However, very limited information is available on the occurrences and fates of PFASs along industrial wastewater treatment processes, particularly for the textile dyeing industry where PFASs occur extensively. Herein, the occurrences and fates of 27 legacy and emerging PFASs were investigated along the processes of three full-scale textile dyeing wastewater treatment plants (WWTPs) based on UHPLC−MS/MS in combination with self-developed solid extraction protocol featuring selective enrichment for ultrasensitive analysis. The total PFASs ranged at 630-4268 ng L−1 in influents, 436-755 ng L−1 in effluents, and 91.5-1182 μg kg−1 in the resultant sludge. PFAS species distribution varied among WWTPs, with one WWTP dominated by legacy perfluorocarboxylic acids while the other two dominated by emerging PFASs. Perfluorooctane sulfonate (PFOS) was trivial in the effluents from all the three WWTPs, indicating its diminished use in textile industry. Various emerging PFASs were detected at different abundances, demonstrating their use as alternatives to legacy PFASs. Most conventional processes of the WWTPs were inefficient in removing PFASs, especially for the legacy PFASs. The microbial processes could remove the emerging PFASs to different extents, whereas commonly elevated the concentrations of legacy PFASs. Over 90% of most PFASs could be removed by reverse osmosis (RO) and was enriched into the RO concentrate accordingly. The total oxidizable precursors (TOP) assay revealed that the total concentration of PFASs was increased by 2.3-4.1 times after oxidation, accompanied by formation of terminal perfluoroalkyl acids (PFAAs) and degradation of emerging alternatives to various extents. This study is believed to shed new light on the monitoring and management of PFASs in industries.

Raw water biofiltration for surface water manganese control

Manganese (Mn) control in surface water systems is a challenge for the drinking water industry, especially through a sustainability framework. Current methods for removing manganese from surface water use strong oxidants that embed carbon and can be expensive and harmful to human health and the environment. In this study, we used a simple biofilter design to remove manganese from lake water, without conventional surface water pre-treatments. Biofilters with aerated influent removed manganese to concentrations below 10 µg/L when receiving influent water containing > 120 µg/L of dissolved manganese. Manganese removal was not inhibited by high iron loadings or poor ammonia removal, suggesting that removal mechanisms may differ from groundwater biofilters. Experimental biofilters also achieved lower effluent manganese concentrations than the full-scale conventional treatment process, while receiving higher manganese concentrations. This biological approach could help achieve sustainable development goals.

Predicting solvent degradation in absorption–based CO2 capture from industrial flue gases

This work aims to predict solvent degradation rates in absorption-based CO2 capture processes using a 30 wt% aqueous monoethanolamine (MEA) solvent. A degradation model for MEA is developed and used to predict solvent degradation in full-scale capture processes. Mass transfer resistances and the solubility of O2 are considered to obtain a generalized and consistent degradation model. Degradation is evaluated for the capture process for flue gases with typical industrial compositions; a natural gas-fired power plant, a waste-to-energy plant, a coal-fired– power plant, and a cement plant. The impact of process modifications, such as absorber intercooling, dissolved O2 removal, a reduction in solvent residence times, and increased stripper pressures on degradation is evaluated.The predicted degradation rate in the capture processes is approximately 90 to 150 g MEA/ton CO2 captured, and the composition of the flue gas was found to have a significant influence on the distribution of degradation throughout the process. Modifications to the process can significantly affect the overall degradation rate. Both absorber intercooling and removal of dissolved O2 may reduce the overall degradation by up to 40%, depending on the composition of the flue gas. A reduction in solvent residence times or pressure in the stripper has limited effects on the degradation in the case of MEA, because of the amine’s relatively low stability towards oxidative degradation. However, these process modifications look promising for more stable solvents.

Accumulating ammoniacal nitrogen instead of melanoidins determines the anaerobic digestibility of thermally hydrolyzed waste activated sludge

Full-scale thermal hydrolysis processes (THP) showed an increase in nutrients release and formation of melanoidins, which are considered to negatively impact methanogenesis during mesophilic anaerobic digestion (AD). In this research, fractionation of THP-sludge was performed to elucidate the distribution of nutrients and the formed melanoidins over the liquid and solid sludge matrix. Degradation of the different fractions in subsequent AD was assessed, and the results were compared with non-pre-treated waste activated sludge (WAS). Results showed that the THP-formed soluble melanoidins were partially biodegradable under AD, especially the fraction with molecular weight under 1.1 kDa, which was related to protein-like substances. The use of THP in WAS increased the non-biodegradable soluble chemical oxygen demand (sCOD) after AD, from 1.1% to 4.9% of the total COD. The total ammoniacal nitrogen (TAN) concentration only slightly increased during THP without AD. However, after AD, TAN released was 34% higher in the THP-treated WAS compared to non-treated WAS, i.e., 36.7 ± 0.7 compared to 27.4 ± 0.4 mgTANreleased/gCODsubstrate, respectively. Results from modified specific methanogenic activities (mSMAs) tests showed that the organics solubilised during THP, were not inhibitory for acetotrophic methanogens. However, after AD of THP-treated sludge and WAS, the mSMA showed that all analysed samples presented strong inhibition on methanogenesis due to the presence of TAN and associated free ammonia nitrogen (FAN). In specific methanogenic activities (SMAs) tests with incremental concentration of TAN/FAN and melanoidins, TAN/FAN induced strong inhibition on methanogens, halving the SMA at around 2.5 gTAN/L and 100 mgFAN/L. Conversely, melanoidins did not show inhibition on the methanogens. Our present results revealed that when applying THP-AD in full-scale, the increase in TAN/FAN remarkably had a greater impact on AD than the formation of melanoidins.

Separation mechanism and experimental investigation of pulsating high gradient magnetic separation

Pulsating high gradient magnetic separation (PHGMS) has been widely used for separating magnetic minerals in the past decades. In practice, magnetic field and flow field are the main factors that affect the capture of magnetic particles by medium wires. Therefore, an insight into the magnetic field distribution and the flow field distribution around the matrix would provide a crucial foundation for understanding the separating mechanism. In this investigation, the magnetic field and the flow field in the PHGMS process are simulated. Furthermore, the capture of hematite on matrix and its dependence on the key parameters of the PHGMS separator, i.e., wire diameter of rod matrix, particle size, magnetic induction and flow velocity are analyzed. The results indicate that the slurry forms a roundabout flow around the wire and the fluid velocity around the magnetic wire’s left and right sides is far greater than that of the upper and lower sides; with the increase of distance from the magnetic wire surface, the magnetic induction intensity around the magnetic wire decreases gradually. It all proves that the magnetic particles are mostly captured on the upper and lower surface of the magnetic wires in the matrix. The optimized parameters obtained from pilot-scale, the rod diameter of 2 mm, particle size of 60%, magnetic field intensity of 0.9 T and re-cleaning magnetic field intensity of 1.1 T. When all the parameters are optimized, a full-scale PHGMS process produced a magnetic concentrate assaying 63.24% Fe with 93.67% recovery from the hematite feed assaying 49.22% Fe.

Biotoxicity dynamic change and key toxic organics identification of coal chemical wastewater along a novel full-scale treatment process

It is particularly important to comprehensively assess the biotoxicity variation of industrial wastewater along the treatment process for ensuring the water environment security. However, intensive studies on the biotoxicity reduction of industrial wastewater are still limited. In this study, the toxic organics removal and biotoxicity reduction of coal chemical wastewater (CCW) along a novel full-scale treatment process based on the pretreatment process-anaerobic process-biological enhanced (BE) process-anoxic/oxic (A/O) process-advanced treatment process was evaluated. This process performed great removal efficiency of COD, total phenol, NH4+-N and total nitrogen. And the biotoxicity variation along the treatment units was analyzed from the perspective of acute biotoxicity, genotixicity and oxidative damage. The results indicated that the effluent of pretreatment process presented relatively high acute biotoxicity to Tetrahymena thermophila. But the acute biotoxicity was significantly reduced in BE-A/O process. And the genotoxicity and oxidative damage to Tetrahymena thermophila were significantly decreased after advanced treatment. The polar organics in CCW were identified as the main biotoxicity contributors. Phenols were positively correlated with acute biotoxicity, while the nitrogenous heterocyclic compounds and polycyclic aromatic hydrocarbons were positively correlated with genotoxicity. Although the biotoxicity was effectively reduced in the novel full-scale treatment process, the effluent still performed potential biotoxicity, which need to be further explored in order to reduce environmental risk.