Solid-liquid Separation Research Articles

Evaluation of solid-liquid separation of dairy manure with different separator screen sizes on the resource recovery and greenhouse gas emissions reduction

Solid-liquid separation is a critical step for the treatment of dairy manure, and the separator screen size plays an important role in determining the separation. Despite its importance, the impact of screen size on subsequent resource recovery and greenhouse gas (GHG) emissions reduction remains largely undetermined and varied. In this study, the influence of separator screen size for solid-liquid separation on resources recovery (bedding materials, biogas and nutrients) and GHG emissions reduction was evaluated. Taking a dairy farm with a stock of 1000 cows as an example, with the increasing of separator screen size from 0.5 mm to 5 mm, the results show that the annual bedding materials production decreased from 987.0 tons to 597.6 tons (dry basis), the annual biogas production increased from 32.5 × 104 m³ to 50.9 × 104 m³, the annual total nitrogen (TN) recovery increased from 35.8 tons to 44.4 tons, and the annual total phosphorus (TP) recovery increased from 8.2 tons to 10.1 tons. The annual economic benefits from resource recovery ranged from 28.7 × 104 ¥ to 34.8 × 104 ¥. Annual total GHG emissions increased with the increasing separator screen size and reached approximately 0.7 t CO2 equivalent/cow·year. These findings provide guidance for the selection of separator screen size for the solid-liquid separation of dairy manure.

Dimensional analysis for sedimentation behavior of magnetorheological fluids

Magnetorheological fluids (MRFs) are primarily composed of magnetic particles suspended in carrier liquids, exhibiting a remarkable capacity to respond dynamically to external magnetic fields. However, the phenomenon of solid–liquid phase separation, attributable to particle sedimentation, represents a formidable barrier to the real-world application of MRFs in engineering contexts. As a result, it becomes critically imperative to conduct a thorough investigation into the sedimentation behavior of MRFs under static conditions, to significantly enhance their practical utility. In the study, computational analysis through COMSOL was utilized to elucidate the sedimentation dynamics of MRFs. The findings indicated that particle sedimentation harbored the potential to induce localized turbulence within the flow field, thereby significantly impacting the sedimentation dynamics of MRFs. The motion of particles consistently followed a pattern where sedimentation rates decreased as the viscosity of the carrier liquids increased. Moreover, the elucidation of the settling behavior of MRFs was facilitated by the introduction of two dimensionless numbers. These dimensionless numbers were employed to systematically characterize the temporal evolution of the supernatant height throughout the settling process. This investigation further explored the intricate interdependence between these dimensionless parameters via a comprehensive series of settling experiments. The outcomes of this research uncovered a unique pattern in the solid–liquid separation process of MRFs, marked by a phase of gradual initiation, followed by acceleration, and culminating in deceleration. However, as the viscosity of the carrier liquids increased, this pattern became less pronounced, gradually shifting toward a more uniform settling trajectory.

Optimized Solid–Liquid Separation of Phenolics from Lavender Waste and Properties of the Dried Extracts

Lavender distillation produces huge quantities of solid waste yearly. This waste is usually discarded, resulting in serious environmental issues. However, it still contains residual essential oil and other bioactive compounds. This research reports on the development and comparison of optimized solid–liquid separation methods, i.e., microwave- (MAE) and ultrasound-assisted extraction (UAE) of phenolic compounds from lavender distillation waste. The optimal pretreatment conditions, such as waste moisture content and particle size, were also determined. The extracts were spray- or freeze-dried and the resulting powders were characterized for their physicochemical properties. The majority of the original phenolic compounds in lavender were found in the leachate fraction after distillation (61%), whereas 43% was found in the solid waste. Drying of the solid waste before extraction affected the process efficiency. UAE led to a higher phenolic content and greater antioxidant properties compared to MAE. Drying (spray or freeze) the extracts did not significantly affect their phenolic content, whereas the use of maltodextrin as a drying agent improved the drying process yield, especially when using the freeze-drying method. It is concluded that valorization of lavender distillation wastes can be achieved via an integrated process consisting of a green extraction method and a consequent drying process that results in a stable bioactive powder.

Regression Metamodel-Based Digital Twin for an Industrial Dynamic Crossflow Filtration Process.

Dynamic crossflow filtration (DCF) is the state-of-the-art technology for solid-liquid separation from viscous and sensitive feed streams in the food and biopharma industry. Up to now, the potential of industrial processes is often not fully exploited, because fixed recipes are usually applied to run the processes. In order to take the varying properties of biological feed materials into account, we aim to develop a digital twin of an industrial brownfield DCF plant, allowing to optimize setpoint decisions in almost real time. The core of the digital twin is a mechanistic-empirical process model combining fundamental filtration laws with process expert knowledge. The effect of variation in the selected process and model parameters on plant productivity has been assessed using a model-based design-of-experiments approach, and a regression metamodel has been trained with the data. A cyclic program that bidirectionally communicates with the DCF asset serves as frame of the digital twin. It monitors the process dynamics membrane torque and transmembrane pressure and feeds back the optimum permeate flow rate setpoint to the physical asset in almost real-time during process runs. We considered a total of 24 industrial production batches from the filtration of grape juice from the years 2022 and 2023 in the study. After implementation of the digital twin on site, the campaign mean productivity increased by 15% over the course of the year 2023. The presented digital twin framework is a simple example how an industrial established process can be controlled by a hybrid model-based algorithm. With a digital process dynamics model at hand, the presented metamodel optimization approach can be easily transferred to other (bio)chemical processes.

A novel approach for purifying food waste anaerobic digestate through bio-conditioning dewatering followed by activated sludge process: A case study

Although anaerobic digestion is the mainstream technology for treating food waste (FW), the high pollutant concentration in the resultant food waste anaerobic digestate (FWAD) often poses challenges for the subsequent biochemical treatment such as activated sludge process. In this study, taking a typical FW treatment plant as an example, we analyzed the reasons behind the difficulties in treating FWAD and tested a novel process called as bio-conditioning dewatering followed by activated sludge process (BDAS) to purify FWAD. Results showed that high concentrations of suspended solids (SS) (16439 ± 475 mg/L), chemical oxygen demand (COD) (24642 ± 1301 mg/L), and ammonium nitrogen (NH4+-N) (2641 ± 52 mg/L) were main factors affecting the purification efficiency of FWAD by the conventional activated sludge process. By implementing bio-conditioning dewatering for solid-liquid separation, near 100% of SS and total phosphorus (TP), 90% of COD, 38% of total nitrogen (TN), and 37% of NH4+-N in the digestate could be effectively removed or recovered, consequently generating the transparent filtrate with relatively low pollution load and dry sludge cake (<60% of moisture content). Furthermore, after ammonia stripping and biochemical treatment, the effluent met the relevant discharge standards regulated by China, with the concentrations of COD, TN, NH4+-N, and TP ranging from 151 to 405, 10–56, 0.9–31, and 0.4–0.8 mg/L, respectively. This proposed BDAS approach exhibited stable performance and low operating costs, offering a promising solution to purify FWAD in practical engineering and simultaneously realize resource recovery.

Pilot test on acidic fluoride-containing wastewater treatment in the photovoltaic industry through induced crystallization with a focus on calcium fluoride recovery

The utilization of hydrofluoric acid in the photovoltaic (PV) industry results in the generation of substantial volumes of acidic fluoride-containing wastewater, emphasizing the significance of wastewater treatment and the reclamation of fluorine resources. In this study, a pilot test was conducted on acidic fluoride-containing wastewater from a PV cell manufacturer in Yangzhou City, Jiangsu Province, China, employing a combined process system integrating chemical crystallization circulating pellet fluidized bed (CrystPFB) and high-efficiency solid-liquid separation pellet fluidized bed (SepPFB). The pilot test outcomes indicate that utilizing CaF2 as a seed crystal and employing a joint addition of Ca(OH)2 and CaCl2 at a combined dosage of 2,300–3,700 mg/L, under conditions of influent fluoride concentration ranging from 800–3000 mg/L and a pH range of 2.23–3.20, reduces fluoride levels in the effluent to 20–30 mg/L. The combined process system achieves a turbidity in the effluent below 5 NTU, a fluoride recovery efficiency of 45–63 %, and an operational cost ranging from 1.68 to 2.46 RMB/m3. The physical analysis of the reclaimed crystalline calcium fluoride particles reveals a dominance of CaF2 on the particle surface, with a purity exceeding 90 %. This study provides essential data supporting the application of the CrystPFB + SepPFB combined process system for treating acidic fluoride-containing wastewater and recovering calcium fluoride in the PV industry, establishing a groundwork for subsequent projects.

Carbon source fate in lysozyme-assistant anaerobic fermentation process of excess sludge: interphase carbon migration, recovery and extraction

Lysozyme has been regarded as promising approach to enhance anaerobic fermentation of excess sludge. However, little investigation has revealed the specific patterns of interphase carbon source migration and recovery. This study demonstrated that the rising lysozyme dosages greatly improved the kinetics and performances of endogenous carbon source release and biotransformation, which mainly occurred within 48-h treatment. Considerable 146.66 mg C/g VSS particulate carbon sources were solubilized from sludge solid, composing of proteins, humic acids and metabolic intermediates. Meanwhile, almost 57.48 % of the originally released carbon sources were bio-transformed into short-chain fatty acids with accelerated sludge acidification, which were regarded as the recoverable carbon source. Correspondingly, considerable carbon recovery of 103.18 mg C/g VSS was achievable by lysozyme assistance in 96-h anaerobic fermentation. Such lysozyme catalysis strategy improved carbon migration and recovery by 5.38 and 6.21 times, respectively. The fermented sludge was easily dewatered after chemical conditioning, thereby the effective carbon source extraction was implemented by solid-liquid separation. Approximately 65.99–87.02 % of the recoverable carbon sources were remained in fermentative liquid. The high ratios of carbon sources to nutrients (nitrogen and phosphorus) suggested favorable bio-availability and utilizability of the recoverable carbon sources. The overall carbon flow and migration pathways in lysozyme-driven patterns were illustrated to directly clarify the carbon source fate in anaerobic fermentation process and carbon recovery benefits from excess sludge.

High-performance pneumatic solid–liquid triboelectric nanogenerator

In the field of blue energy harvesting, solid-liquid triboelectric nanogenerators (SL-TENG) show significant potential. However, their low output performance in energy applications is limited due to the relatively small contact area and slow separation speed during the friction process. To overcome these limitations, we develop a pneumatic solid-liquid triboelectric nanogenerator (PSL-TENG) with ultrahigh output performance based on pneumatic solid-liquid triboelectrification and electrostatic breakdown. The pneumatic design effectively increases the solid-liquid interface area and the solid-liquid contact and separation rate, which can enhance solid-liquid triboelectrification effect. The synergistic design of the horn and the bent pipe can converge positively charged mist into large droplets, which can enhance electrostatic breakdown effect. This innovative design approach has achieved outstanding output performance, with a peak instantaneous voltage of 6436 V and a peak instantaneous current of 3.05 mA. This exceptional output performance is sufficient to directly power 3000 LED lights or a 55 W commercial lamp. These research achievements provide new insights for SL-TENG in energy harvesting, as significant output can be generated by collecting the inherent charges of liquids themselves.

The effect of crystallographic orientation of α-Al2O3 on the wetting behavior and adhesion characteristics of aluminum droplets

To solve the problem of adhesion of aluminum fluid to the inner wall of the vacuum ladle in the aluminum electrolysis industry, molecular dynamics simulation is performed to research the wetting behavior of Al droplets on the surfaces of the α-Al2O3 substrates C (0001), M ( 11ˉ00 ), and R ( 11ˉ02 ) at 1073 K. Meanwhile, the adhesion characteristics of the Al droplet are evaluated by the potential of the mean force (PMF) for the separation of the Al droplets from different surfaces of the α-Al2O3 substrate. The results show that the wetting behavior of Al droplets on the α-Al2O3 substrate is influenced by the different crystallographic orientations. The diffusion of Al droplets in the x-o-y plane of the substrate exhibits isotropic. The PMF and the interfacial potential energy reveal that the magnitude of the adhesion work in the solid-liquid separation of Al droplets from α-Al2O3 substrates follows the order C (0001) > R ( 11ˉ02 ) > M ( 11ˉ00 ). These findings characterize the wetting properties and adhesion behavior of Al droplets on an atomic scale and provide a theoretical basis for the selection of materials for the inner wall of the vacuum ladle.

Removal of cesium and strontium ions with enhanced solid-liquid separation by combined ion exchange and BaSO4 co-precipitation

Treatment of cesium and strontium is critical in radioactive liquid waste management, where their ions are difficult to remove in single operations, owing to differences in valence state. Here, the efficacy of composite coagulants synthesised by combining fine clinoptilolite with co-precipitated barite (BaSO4) were investigated for the simultaneous removal of Cs+ and Sr2+ ions, producing aggregates with enhanced dewatering properties. Co-precipitated BaSO4 without clinoptilolite was found to be very effective in the removal of Sr2+ (>99 %) while only giving low-level Cs+ removal (~14 %) for solutions containing 25 ppm of Cs+ and Sr2. Conversely, pure clinoptilolite gave high Cs+ removal (>98 %) with rapid adsorption (<1 h) fitted to a Pseudo-Second Order (PSO) rate model. Composite coagulants were then produced using natural clinoptilolite combined with BaSO4 co-precipitation. Higher Sr2+ removal was obtained in all cases (>99.9 %), whereas Cs+ removal was reduced to <90 %, owing to exchange interactions with free Ba2+ ions. However, NaCl-preactivated clinoptilolite overcame low Cs+ removal efficiency, achieving >95 % removal. Their physical properties, sedimentation rates, and compressional yield stress were also studied to characterise the aggregates solid-liquid separation behaviour. The combined coagulates obtained settling rates almost twice that of pure BaSO4, and produced much greater consolidation, owing to increased aggregate density. Also, the combined systems had a higher gel point and lower specific compressive yield stress, suggesting less resistance to compression under centrifugal forces for dewatering. Overall, this study highlights that the use of composite coagulants can improve the removal efficiency of Cs+ and Sr2+ while also accelerating solid-liquid dewatering.

Adsorption Properties of Magnetic Phosphorous Camellia Oleifera Shells Biochar to Sulfamethoxazole in Water

Magnetic phosphorous biochar （MPBC） was prepared from Camellia oleifera shells using phosphoric acid activation and iron co-deposition. The materials were characterized and analyzed through scanning electron microscopy （SEM）， X-ray diffractometry （XRD）， specific surface area and pore size analysis （BET）， Fourier infrared spectroscopy （FT-IR）， and X-ray photoelectron spectroscopy （XPS）. MPBC had a high surface area （1 139.28 m2·g-1） and abundant surface functional groups， and it could achieve fast solid-liquid separation under the action of an external magnetic field. The adsorption behavior and influencing factors of sulfamethoxazole （SMX） in water were investigated. The adsorbent showed excellent adsorption properties for SMX under acidic and neutral conditions， and alkaline conditions and the presence of CO32- had obvious inhibition on adsorption. The adsorption process conformed to the quasi-second-order kinetics and Langmuir model. The adsorption rate was fast， and the maximum adsorption capacity reached 356.49 mg·g-1. The adsorption process was a spontaneous exothermic reaction， and low temperature was beneficial to the adsorption. The adsorption mechanism was mainly the chemisorption of pyrophosphate surface functional groups （C-O-P bond） between the SMX molecule and MPBC and also included hydrogen bonding， π-π electron donor-acceptor （π-πEDA） interaction， and a pore filling effect. The development of MPBC adsorbent provides an effective way for resource utilization of waste Camellia oleifera shells and treatment of sulfamethoxazole wastewater.

Microbial diversity in dairy manure environment under liquid-solid separation systems

ABSTRACT In dairy manure, a wide array of microorganisms, including many pathogens, survive and grow under suitable conditions. This microbial community offers a tremendous opportunity for studying animal health, the transport of microbes into the soil, air, and water, and consequential impacts on public health. The aim of this study was to assess the impacts of manure management practices on the microbial community of manure. The key novelty of this work is to identify the impacts of various stages of manure management on microbes living in dairy manure. In general, the majority of dairy farms in California use a flush system to manage dairy manure, which involves liquid-solid separations. To separate liquid and solid in manure, Multi-stage Alternate Dairy Effluent Management Systems (ADEMS) that use mechanical separation systems (MSS) or weeping wall separation systems (WWSS) are used. Thus, this study was conducted to understand how these manure management systems affect the microbial community. We studied the microbial communities in the WWSS and MSS separation systems, as well as in the four stages of the ADEMS. The 16S rRNA gene from the extracted genomic DNA of dairy manure was amplified using the NovoSeq Illumina next-generation sequencing platform. The sequencing data were used to perform the analysis of similarity (ANOSIM) and multi-response permutation procedure (MRRP) statistical tests, and the results showed that microbial communities among WWSS and MSS were significantly different (p < 0.05). These findings have significant practical implications for the design and implementation of manure management practices in dairy farms.

The Oil:Water Ratio in the Vertical Centrifuge Separator and Its Influence in Phenolic Compounds in the Virgin Olive Oil and the Olive Mill Wastewater (Alpechín)

The use of the vertical centrifuge in the olive oil production process is generally assumed to be habitual and necessary for the elimination of both the vegetation water and the small olive pulp particles that are not eliminated during solid–liquid separation (horizontal centrifugation). Trials were carried out with different oil:water ratios to study the influence of this variable on both the quality parameters of the olive oils obtained and the loss of oil with the olive wastewater. The trials were carried out at the industrial mill level with oil:water ratios between 0.6 and 5.5. While no differences were observed in the quality parameters of the oils obtained, correct adjustment of the oil:water flow rates reduced the loss of phenols present in the oils by around 30%. In addition, the results show a direct relationship between the soluble effluent and the conductivity of the olive mill wastewater (alpechín) with the loss of oil in the effluent. This work proves that both oil quality and the competitiveness of the olive oil value chain can be increased with energy savings, water consumption reduction, and environmental sustainability.

Estimating methane emissions from swine waste treatment lagoons and the reduction through solid-liquid separation: A multiscale case evaluation

With an estimated global warming potential of 27 to 30 over 100 years, methane (CH4) is a significant greenhouse gas emitted by livestock operations across the United States. In particular, the swine production industry of North Carolina where agglomeration of the production and the use of open-air lagoon systems for waste treatment, cause substantial emissions of CH4 and alter the environmental quality. Yet the possibility of reducing CH4 emissions from these lagoons represents an avenue to sustain environmental quality. However, quantitative estimates of methane emissions potentials at county, and regional levels are needed to envision effective emissions reduction initiatives. In this study, updated guidelines of the Intergovernmental Panel on Climate Change (IPCC) and fifteen-month full-scale data of two scenarios of waste treatment systems were used for a multiscale estimation of CH4 emissions from swine farms in North Carolina. Scenario 1 (baseline) was the conventional lagoon-based swine waste treatment system. Scenario 2 (project activity) was the conventional lagoon-based system retrofitted with a solid-liquid separation module that diverted organic compounds from reaching the anaerobic lagoon and processed with aerobic in-vessel composting. Both scenarios are feeder-to-finish swine operations and the related in-situ data utilized are monthly animal population and weight, liquid waste temperature, and 5-day biological oxygen demand (BOD5). The farm-scale estimates showed an annual emission of 332.2 kg CH4 per 1000 kg swine mass for scenario 1 and 114.7 kg CH4 per 1000 kg swine mass for scenario 2 sustaining an overall 65.5% CH4 abatement ascribable to the solid-liquid separation system. Methane emissions potentials were upscaled at the county, and state levels. The multiscale estimates highlighted hotspots of swine lagoons CH4 emissions in the North Carolina region. Two counties, Duplin and Sampson, contributed 49% of the state-level swine lagoon emissions estimated as 117,227 Mg CH4/year. However, the solid-liquid separation, as a mitigation practice, could reduce the total emissions at the state-level by 76,723 Mg CH4/year. Hence, the spatial disparities highlighted through the multiscale scenarios analyses could help to plan strategies for CH4 emission avoidance and abatement through technology improvement such as solid-liquid separation modules.

Thermally enhanced solid-liquid separation process in food waste biorefinery: modelling the anaerobic digestion of solid residues.

The biochemical valorization potential of food waste (FW) could be exploited by extracting decreasing added-value bio-based products and converting the final residues into energy. In this context, multi-purpose and versatile schemes integrating thermal and biochemical conversion processes will play a key role. An upstream thermal pretreatment + solid-liquid separation unit was here proposed to optimize the conversion of the liquid fraction of FW into valuable chemicals through semi-continuous fermentation process, and the conversion of the residual solid fraction into biomethane through anaerobic digestion. The solid residues obtained after thermal pretreatment presented a higher soluble COD fraction, which resulted in higher methane production with respect to the raw residues (0.33 vs. 0.29 Nm3CH4 kg-1VSfed) and higher risk of acidification and failure of methanogenesis when operating at lower HRT (20d). On the contrary, at HRT = 40 d, the pretreatment did not affect the methane conversion rates and both tests evidenced similar methane productions of 0.33 Nm3CH4 kg-1VSfed. In the reactor fed with pretreated residue, the association of hydrogenotrophic methanogens with syntrophic bacteria prevented the acidification of the system. Modelling proved the eligibility of the FW solid residues as substrates for anaerobic digestion, given their small inert fractions that ranged between 0% and 30% of the total COD content.

Soluble carbon source recovery using preconditioning coagulants for applicable short-term fermentation of waste activated sludge in WWTPs

A huge production of waste activated sludge (WAS) has been a burden for wastewater treatment plants (WWTPs) with high disposal cost and little benefit back to wastewater purification. The short-chain fatty acids (SCFAs) produced by a short-term acidogenic fermentation of WAS before methane production have been proven to be a high-quality carbon source available for microbial denitrification process. The dual purpose of full recovery of fermentation liquid products and facilitating disposal of residual solid waste necessitate an efficient solid-liquid separation process of short-term fermentation liquid. The transformation and loss of various soluble carbon sources between solid and liquid are very important issues for carbon recovery efficiency when combining short-term fermentation and sludge dewatering in WWTPs. Here we testified the three conventional preconditioning coagulants, Polyferric Sulfate (PFS), Poly Aluminum Chloride (PAC) and Polyacrylamide (PAM), to improve the efficiency of subsequent solid-liquid separation. The results show that conversion yield of SCFAs in the liquid phase of sludge after short-term fermentation was 195 mg COD/g VSS, when using the coagulants PFS, PAC, and PAM for recovery, the recovery ratio was 79.5%, 82.0%, and 85.9%, respectively, while the dewaterability could be improved after preconditioning short-term fermentation sludge. The complexation of Al3+/Fe3+ in metal coagulants with carboxyl groups of SCFA demonstrated by Density Functional Theory calculation led to small part of soluble carbons co-migration to the solid phase, mainly a loss of high molecular weight organic compounds (carbohydrate, proteins, humic acids), while the application of PAM had little impact on carbon recovery. Economic calculations further showed PAM preconditioning short-term fermentation liquid of WAS could achieve higher recovery benefits.

Developing a novel technology for slurry management by project-based learning

Farming is responsible for 30% of global anthropogenic emissions. A novel technology, aligning with current regulations of covering slurry stores, has been developed for processing anaerobic digestate liquor, which is obtained from the screw press stage. Instead of using hazardous chemicals, such as sulfuric acid, to capture ammonia and greenhouse gases, the artifact contains calcium chloride as deliquescent salt. Preliminary simulations in Aspen Plus® v12 showed that the absorption of NH3 and carbon dioxide during the solid–liquid separation was feasible and the resulting clean brine could be used as chemical amendment of untreated slurry. The characterization of the performance of the artifact was organized following a project-based learning active teaching method, for a group of 3 students (17-year-olds) of secondary education, as part of the In2ScienceUK program. The collection of empirical data allowed the contents of the curriculum to be contextualized, enhancing environmental awareness of participants. A titrimetric method was employed to determine the content of NH3 and CO2 in the brine, and the granulation of the dewatered liquor with the fibers of anaerobic digestate was investigated by determining the compression strength required to break the pellets. The operation capacity of the prototype was found to be 250 m3 of liquor per year, at a cost of £1/m3. The use of the filtered brine as chemical amendment also represented an additional 5.60 grams of ammoniacal nitrogen and 0.96 grams of inorganic carbon per cubic meter of unprocessed slurry. The concentrated liquor was a good binding agent that provided the pellets with a compressive strength of 207.00 ± 26.36 N, which was above the threshold value for commercialization purposes (50 N). The advances in the development of the prototype enhanced the suitability of the technology for industrial scale applications but hindered the adoption of subsequent editions of this pedagogic tool.

Unveiling the role of pore characteristics in sludge dewatering: Visualization by Nano-CT and micromodel study

The solid-liquid separation is an indispensable and primary link in the process of sludge treatment and disposal. The past research was focused primarily on the technique explorations of sludge dewatering and always disregarded the internal pore structure and water migration behavior in sludge. In this work, the real three-dimensional pore structure of sludge was obtained by Nano-CT. Based on this, a pore-scale heterogeneous sludge micromodel was firstly presented, and the water flooding experiment was carried out to visualize the water migration behavior. The results showed that the sludge structure transformed from sheet-like floc to microsphere particles, and then agglomerated into large globular granules during anaerobic ammonia oxidation. And the equivalent pore size increases from 342 μm to 617 μm, improving the sludge dewaterability characterized by capillary suction time (CST). The most significant implication of this work was revealing the critical role of invalid connected pore in sludge dewatering. Such pore was not contributed to fluid flow but the circulating vortex in it even induced energy dissipation, thus deteriorated the sludge dewaterability. This work may be helpful to understand the critical role of pore characteristic in water migration and shed light on the new dewatering techniques from the perspective of regulating sludge structure.

Controlling Crystal Growth of a Rare Earth Element Scandium Salt in Antisolvent Crystallization

Recovering scandium from hydrometallurgical residue bears the potential of a better supply of an industry depending on imports from countries with more mineral resources than Europe. To recover scandium from unused metal production residue, strip liquors from a solvent extraction process are treated with an antisolvent to crystallize the ammonium scandium fluoride salt (NH4)3ScF6 with high product yields. However, high local supersaturation leads to strong nucleation, resulting in small crystals, which are difficult to handle in the subsequent solid-liquid separation. Reducing local supersaturation makes it possible to reduce nucleation and control crystal growth. Key operation parameters are the concentration of ethanol in the feed and its addition rate. The concentration of the antisolvent in the feed causes a shorter mixing time in the proximity of the antisolvent inlet, which leads to a smaller local supersaturation and therefore less nucleation and more crystal growth. Lowering the antisolvent addition rate enhances this effect. The crystal size distribution during and at the end of the fed-batch process is analyzed by SEM imagery of sampled and dried crystals. To produce reproducible crystal size distribution from SEM images the neural network Mask R-CNN has been trained for the automated crystal detection and size analysis.

Full quantitative resource utilization of raw mustard waste through integrating a comprehensive approach for producing hydrogen and soil amendments

BackgroundPickled mustard, the largest cultivated vegetable in China, generates substantial waste annually, leading to significant environmental pollution due to challenges in timely disposal, leading to decomposition and sewage issues. Consequently, the imperative to address this concern centers on the reduction and comprehensive resource utilization of raw mustard waste (RMW). To achieve complete and quantitative resource utilization of RMW, this study employs novel technology integration for optimizing its higher-value applications.ResultsInitially, subcritical hydrothermal technology was applied for rapid decomposition, with subsequent ammonia nitrogen removal via zeolite. Thereafter, photosynthetic bacteria, Rhodopseudomonas palustris, were employed to maximize hydrogen and methane gas production using various fermentation enhancement agents. Subsequent solid-liquid separation yielded liquid fertilizer from the fermented liquid and soil amendment from solid fermentation remnants. Results indicate that the highest glucose yield (29.6 ± 0.14) was achieved at 165–173℃, with a total sugar content of 50.2 g/L and 64% glucose proportion. Optimal ammonia nitrogen removal occurred with 8 g/L zeolite and strain stable growth at 32℃, with the highest OD600 reaching 2.7. Several fermentation promoters, including FeSO4, Neutral red, Na2S, flavin mononucleotide, Nickel titanate, Nickel oxide, and Mixture C, were evaluated for hydrogen production. Notably, Mixture C resulted in the maximum hydrogen production (756 mL), a production rate of 14 mL/h, and a 5-day stable hydrogen production period. Composting experiments enhanced humic acid content and organic matter (OM) by 17% and 15%, respectively.ConclusionsThis innovative technology not only expedites RMW treatment and hydrogen yield but also substantially enriches soil fertility. Consequently, it offers a novel approach for low-carbon, zero-pollution RMW management. The study’s double outcomes extend to large-scale RMW treatment based on the aim of full quantitative resource utilization of RMW. Our method provides a valuable reference for waste management in similar perishable vegetable plantations.