Bag Filter Research Articles

Bioactive profile and microbiological safety of Coffea arabica and Coffea canephora beverages obtained by innovative cold extraction methods (cold brews)

Coffee cold brews have been gaining prominence and popularity among consumers worldwide. However, only a few studies have systematically analyzed their chemical composition or evaluated microbiological safety aspects. This study aimed to evaluate the survival of Bacillus cereus and Escherichia coli in cold brews prepared from roasted and ground Coffea arabica and C. canephora seeds using the following preparation methods: immersion without filter (INF), immersion in a cotton filter bag (ICF), vacuum (Vac.) and cold dripping (Drip.). Traditional hot dripping methods using filter paper (HDFP) and cotton filter (HDCF) were also tested for comparison. Water at 4 °C or 25 °C was intentionally contaminated (105 CFU/mL) with cells of Escherichia coli ATCC 25922 (EC) and Bacillus cereus F4433 (BC) before coffee extraction and refrigeration at 4 °C. Coffee concentrations of 5, 10, and 15% were tested. Analyses of pH, soluble solids, nine chlorogenic acids and two lactones (CGA), caffeine, trigonelline, and melanoidins were performed. Results were compared by ANOVA, followed by the Fisher’s test, Pearson correlation, Variable Importance in Projection (VIP), and Cluster analyses, with a significance level of 5%. EC and BC were not detected (<10 CFU/mL and < 1 CFU/mL, respectively) after preparing C. arabica and C. canephora hot brews. In cold brews, the higher the extraction of soluble solids and bioactive compounds (with the highest occurring at 25 °C), the lower the counts of inoculated microorganisms during 24 h of storage. BC was not detected after 24 h of extraction and/or storage in the drinks obtained by ICF and Drip. at 5%, 10%, and 15% and INF and Vac. at 15%. EC was not detected in ICF and Drip. at 10 and 15%, and in INF at 15%. C. canephora brews exhibited higher levels of soluble solids, CGA, caffeine, and melanoidins than C. arabica brews. Based on these results, it can be concluded that in the absence of thermal processing as in hot brews, more concentrated cold brews, such as 15%, produced at 25 °C by dripping and immersion methods, are preferable for later dilution due to the higher content of soluble solids and bioactive compounds that contribute reducing the number of microorganisms in the beverage.

Analisa Partikulat Debu, SO Dan NO2 Pada Industri Manufaktur Di Surabaya

This study aims to determine how much dust, SO2 and NO2 concentrations are in the air and to know the description of the distribution of air in the study site. In addition, this research also aims to design air pollution control devices that can be used to control the emissions produced. The method in this research uses the Gausse method in modeling and uses AERMOD software and Google Earth to complete the model description. It is known that the farthest distance the highest concentration of dust spread is 0.071 km with a dust concentration of 101.3 µg/m3. The farthest distance the highest concentration of SO2 spread was at a distance of 0.051 km with a value of SO2 concentration of 6753.3 µg/m3. The farthest distance the highest concentration of NO2 spread was at a distance of 0.051 km with a value of NO2 concentration of 91.45 µg/m3. The air controller uses a bag filter with 6 compartments for dust control and uses silica absorbent and activated charcoal for controlling NO2 and the Flue-Gas Desulfurization (FGD) method for SO2.

Development of the technology for the production of a medicinal product from fennel (Foeniculum vulgare) fruits in a filter bag

Aim. To develop the technology of a medicinal product with a dry extract of fennel (Foeniculum vulgare) fruits in a filter bag with carminative, antispasmodic, analgesic, anti-inflammatory, antimicrobial and mild diuretic effects, which improves digestion, the motor evacuation function and the functional state of the gastrointestinal tract. Materials and methods. To solve the tasks set in the work, such research methods as bibliosemantic, analytical and logical, generally accepted organoleptic (appearance, color, odor, etc.), biopharmaceutical (the study of the effect of the degree of grinding of the substance and excipients on the quality of the finished product), pharmacotechnological (description, weight of the contents of the container) and mathematical (statistical processing of results according to the requirements of the State Pharmacopoeia of Ukraine, using Statistica (StatSoft, USA) and Excel (Microsoft, USA) programs) were used. Results and discussion. One of the biopharmaceutical indicators is a properly selected primary packaging, which will deliver the drug in a timely manner, ensuring the patient’s safety. Based on a complex of preliminary pharmacotechnological studies, the technology of the drug under the conditional name “Fenelmet, filter bags” has been developed. Conclusions. Based on the research conducted, the technological process has been developed. The technology for the production of the medicinal product “Fenelmet, filter bags” and the draft technological regulations have been developed. Critical stages of the technological process have been identified; control parameters of critical stages and acceptance criteria that affect the quality indicators have been determined.

Turning waste into treasure: Effects of waste polyphenylene sulfide (PPS) microfibers as potential synergists on flame retardancy and mechanical property of polylactic acid

In this work, we prepare flame-retardant and toughened PLA using waste PPS microfibers prepared from waste PPS filter bags. Waste PPS microfibers not only act as synergists to improve the impact properties and flame retardancy of PLA composites, but also act as heterogeneous nucleating agents to promote PLA crystallization. Specifically, when only 5 wt% waste PPS microfibers are added, the crystallinity of the AP/PLA system increases from 3.6% of 15AP PLA to 44.06% of 15AP5PPS PLA. When 10 wt% waste PPS microfibers are added, the UL-94 rating of 15AP10PPS PLA increases to V-0 rating, which is significantly improved compared to the V-1 rating of 15AP PLA. Under the premise of passing the UL-94 V-0 rating, the impact properties of 15AP10PPS PLA and 10AP15PPS PLA are significantly better than 20AP PLA, with an increase of 34.8% and 50.6%, respectively. This study provides a new strategy for polymer flame retardant and toughening modification and waste recycling.

Troubleshooting dioxins stack emissions in an industrial waste gas incinerator

An important source of dioxins and furans at present is waste incineration, utmost formed during combustion processes and emitted to the environment without being fully captured by waste-gas treatment equipment. In this study, monitoring campaign of International Toxic Equivalents for dioxins and furans (I-TEQDF), was carried out at pharmaceutical industrial waste incinerator to find a correlation between combustion parameters and feed composition with potential emission. Principal Component Analysis (PCA) shows that high values of dioxin emission correlate with short residence time of the flue gas in the furnace as well as low oxygen concentration. These operating conditions were further investigated, using COMSOL Computational Fluid Dynamics (CFD) simulation to calculate the temperature profiles along the furnace. The results suggest that the flame temperature profile is anticipated to exhibit cold areas (cold spots), which may be used as a proxy for dioxin formation due to incomplete combustion. Additionally, the calculated congeners furan to dioxin concentration ratio, points to their formation via de novo mechanism. SEM-EDS analysis preformed on the bag filter upstream the feed following its filtration, have shown large amount of iron, which may have served as a metal catalytic source for dioxin formation. The iron origin is most likely from corrosion of the feeding pipe, drifted with the waste gas and trapped on the bag filter. The results of this study provide a better understanding of the parameters controlling dioxin formation and emission from the plant and may assist a planning of process optimization in such a plant.

Fluoride and Aluminium in Tea (Camellia sinensis L.)-Tea Quality Indicators and Risk Factors for Consumers.

In recent years, the quality and sourcing of tea have gained importance in Europe, but information remains scarce. The aim of this study was to determine the concentrations of fluoride (F-) and total aluminium (Al) species in infusions of commercially available teas in Slovenia, and thus in Europe, and to relate them to tea quality and their impact on consumer safety. F- concentrations were determined using a fluoride-ion-selective electrode and Al concentrations using inductively coupled plasma optical emission spectroscopy. A comparison of the results obtained for four selected tea samples using the calibration curve and a standard addition technique showed good agreement, with no interferences caused by the sample matrix. The concentrations of 35 commercial teas ranged from 0.34 to 4.79 and 0.51 to 8.90 mg/L for F- and Al, respectively. The average concentrations of the two elements followed the same descending order: black filter > green filter > black leaves ≈ green leaves. Single and multivariate statistical methods supported the categorisation of teas by packaging but not by type, with tea in filter bags being more expensive than loose tea. The linear relationship between F- and Al concentrations in infusions (C(Al) = 1.2134 · C(F-)) allows for the determination of one element and estimation of the other, leading to a significant reduction in laboratory effort and cost. This research advances tea assessment by proposing Al concentration alongside F- as a quality indicator and provides the basis for tea-monitoring protocols. Finally, the daily consumption of larger quantities of tea (≈1 L) with elevated F- and Al concentrations could potentially pose a health risk.

A multiway spectral analysis model to monitor the kinetic chlorination reaction of caffeine and determine its content in commercial liquid and solid drinks.

A multiway data analysis model, namely parallel factor analysis (PARAFAC) was proposed to decompose a three-way array of second-order kinetic UV measurements, for the chlorination reaction of caffeine with NaOCl, into a set of the spectra, time, and concentration matrices. The multiway resolution provided the simultaneous estimation of spectral, kinetic, and quantitative analysis of caffeine. The ability of the PARAFAC tool was checked by analyzing the validation samples in the presence of interferences. The added recovery and relative standard deviations for caffeine in the spiked samples were calculated as 99.1%-99.5% and 0.52%-1.34% for Iced Coffee Black liquid coffee (ICB), 99.5%-103.0% and 0.42%-1.03% for Jacobs Monarch Gold 100% Instant Coffee (JMG) and 99.5%-101.4% and 0.11%-0.13% for Çaykur Black Filter (Süzen) Bag Tea (BTB). Caffeine in commercial drinks was analyzed using the concentration matrices of the PARAFAC application. The PARAFAC results were statistically compared to those obtained by the developed UPLC method.

Production of drip bag coffee filled with blended arabica and robusta coffee beans by ohmic fermentation technology

To produce the highest quality brewed coffee based on consumer preferences, it is required to conduct a cupping test before to determining the ideal blending formula. The greatest blended formulations created by ohmic fermentation technology and the use of a drip bag filter during the brewing process can produce a high-quality coffee fragrance and flavor. The purpose of this study was to identify the optimal blending formulation based on the results of the cupping test and to assess the caffeine content, pH value, and organoleptic test results of Arabica and Robusta ohmic drip bag coffee. Fully Randomized Design (CRD) was employed for the study with four treatment ratios of Arabica: Robusta coffee blending (20%:80%; 40%:60%; 60%:40%; 80%:20%). Based on the findings of the cupping test, the optimal ratio of Arabica to Robusta was 80%:20%. The variance analysis revealed that the mixing of Arabica and Robusta coffee had a highly significant (P0.05) effect on the overall. The variance analysis of brewing coffee with the best treatment revealed that the treatment had no significant influence (P>0.05) on the overall. The average caffeine concentration measured using UV-Vis spectrophotometry was 0.25. The second test resulted in the lowest caffeine value, 0.16, whereas the first test resulted in the highest caffeine value, 0.31. The mean pH level was 0.93. The first test yielded the lowest pH value, which was 4.86, whereas the third test yielded the highest pH value. The organoleptic test results for the blended ohmic drip bag coffee based on the cupping test yielded a cupping score of o>84, which corresponds to an overall score of 85 for a ratio of 80% Arabica: 20% Robusta (cup of excellence coffee). In contrast, the cupping score of 15 grams of coffee powder without a drip bag filter was greater than 80, totaling 84.06 points (specialty coffee).

Experimental Study of the Combustion of and Emissions from Olive and Citrus Pellets in a Small Boiler

Agro-industrial activities generate a great amount of bioproducts as biomass residues containing energy and with potentially useful applications in the thermochemical conversion process. The management of this feedstock as uncontrolled combustion (“open burning”) can often be a problem within the supply chain for disposal practices, both in environmental and economic aspects. The residual matrices from agroforestry biomass processing can be treated to increase their energy levels and economic value. A widespread practice for sustainable disposal is the production of pellets from residual biomass, such as pruning. The aim of this study is to explore the combustion of pellets obtained from olive and citrus pruning, and their emissions into the atmosphere. This study confirms the possibility of using waste biomass to obtain a high-energy biofuel that is usable in a controlled combustion system and to monitor the process and its related emissions (CO, CO2, NOx, SO2, PM). Three different pellets (olive pellet, citrus pellet and a pellet obtained from a mix of olive and citrus) were characterized to determine their physicochemical properties and burned in an 80 kWth boiler equipped with multicyclone filter bags as an abatement system to evaluate relative emission. The characterization results show that citrus pellet has a higher ash content, moisture content and lower energy value than mixtures of olive pellet. The emission results suggest that, during combustion, higher emissions of CO and SO2 were monitored from mixtures of citrus pellet compared to burning only olive pellet.

In‐situ leakage detection of single bag filter in baghouse based on the resistance change of conductive polymer fibers

AbstractBaghouse is effective for controlling the particles emitted from industrial production, and the in‐situ leakage detection of a single bag filter is essential for maintaining the high filtration performance of the whole baghouse. In the present study, the changes of PM emission concentration induced by the leakage of the bag filter materials was studied. The results showed that the concentration of particles in the size range of 20–1000 nm significantly increased when the bag filter sample had three holes with a diameter of ~500 μm. In order to prevent the loss induced by the leakage of bag filter, a resistance sensing method was developed to detect the early leakage of single bag filter. The effectiveness of proposed sensing method was verified by detecting the leakage of polymethyl methacrylate (PMMA) bag filter. A sensing grid made of PMMA conductive threads was embedded in the PMMA bag filter, and the resistance change (ΔR) induced by the broken of sensing grid was used as sensing signal. The ΔR of sensing grid was 3.24, 3.31, and 3.05 Ω, respectively, when the bag filter failed due to the mechanical stress, chemical corrosion, and thermal erosion. Moreover, a model was proposed to predict the numbers of broken conductive PMMA threads that could indicate the damage area of the failed bag filter.

Digital Twin Based on Historical Data and Simulation Results: Fault Detection and Estimation of the Remaining Useful Life of a Cyclone Bag Filter

This study deals with the development of a digital twin for monitoring the operating conditions of a cyclone bag filter installed on the suction system of a wheat mill. The model aims to be used for fault identification and real-time prediction of the remaining useful life (RUL). Computational fluid dynamics simulations were performed to characterize in detail the fluid-dynamic behavior of the airflow inside the system under different conditions of filter sleeve clogging. Furthermore, the simulation results were used to identify a location for the installation of a new velocity sensor that would allow, together with the pressure drop measured at the ends of the filter, monitoring of the systems’ conditions. A model able to assess the filter’s operating state, identify failure events or operating anomalies, and make a prediction of the RUL was then developed. A possible implementation of the developed model, based on the simulation results that aimed to optimize the management of the sleeve cleaning cycles was also proposed. The developed digital model was then tested on a working cycle lasting one year, in which a sleeve failure was simulated. It was shown how the simultaneous monitoring of the two identified quantities allows for the correct identification of the failure and the accurate prediction of the RUL.

Research on modelling and stability of seamless dust removal system based on generalized system

The dedusting system is the parameter selection and the degree of cooperation between several dust collector components. The stability of the system plays a decisive role in the dust removal efficiency of the whole system. The existing dust removal system model is a mechanism model, and the bag size, filter bag distribution and other parameters are optimized by simulation results. It cannot provide a model reference for the use of a new filter bag. In this research, the generalized model of the dust removal system is established by MATLAB. The factors affecting the service life of filter bag and dust removal efficiency of dust removal system are analysed. A differential equation is used to describe the influence of these factors. The dynamic model of the dust removal system is established. When considering the problem of flue gas emission, the algebraic equation with dust is constructed. The model of the bag-type dust removal system is described by a generalized system. Finally, the model’s stability is analysed using the method of generalized system analysis, and the necessary and sufficient conditions for the stability of the model are obtained. Given the advantages of a seamless filter bag in filtration efficiency and mechanical properties, the stability of the system is studied. The results show that the system stability increases by 55.4% and 41.9% respectively. The performance of the filter bag is introduced into the modelling of the dust removal system, which plays a key role in the overall evaluation of the filter bag.

Design and implementation of a novel dust collector controller for powder production industry

Industries those work with powder either in production or processing always left a portion of industrial dust in the air. By releasing this air directly in the surrounding environment of the industry pollution occurs. Therefore air filtration system is mandatory in these industries and usually bag filter dust collector controller is used. To control and maintain the proper functionality of the bag filtration system PLC based control system or a modular control board is used. In this paper, a novel dust collector controller is designed which can be installed by any user without having any programming knowledge. The main control keys of the control board are the pulse duration and pulse interval which drive the solenoid valves to release air pressure on the filter bags sequentially. Pulse duration can be controlled in the range of 0.01-0.9 seconds and pulse interval can be varied in the range of 1-99 seconds to control 10 rows of pulse jet simultaneously connected with the solenoid valve. The Number of rows can be adjusted and expanded if required. Moreover, noiseless switching provides silent operational functionalities and switching durability as well as the addition of surge controller ensures a complete protection from any sudden high electrical surge. The finally developed prototype was tested in different industries and provides maximum operational efficiency, which can effectively control online bag filter dust collector to separate micro dust particles from the polluted air.

Assessment of the Costs of Implementing the Best Available Ash Collection Technologies at Coal-fired Thermal Power Plants

According to existing plans, the environmental situation in Russia is going to be improved by modernizing or replacing outdated equipment at industrial enterprises and making a shift to the best available technologies. The thermal power industry is commonly referred to industrial sectors featuring the greatest negative impact on the environment. Emissions of fly ash with flue gases from coal-fired thermal power plants are of much significance from the viewpoint of atmospheric air pollution. Various ash removal technologies are used to reduce them, but a number of them are no longer able to provide the required quality of atmospheric air in areas experiencing a negative impact of thermal power plants. The aim of this work was to assess the possibility of using different types of ash collectors to fulfill the technological indicators of solid fuel ash emissions. For this purpose, the technical and environmental characteristics of various technologies for removing solid fuel ash from the flue gases of thermal power plants were compared, and their main indicators, advantages, and disadvantages were considered. The choice of the most effective ash collection technologies -- electrostatic precipitators and bag filters — to fulfill the technological indicators of ash emissions according to GOST R 50831-95 as the best available technologies is justified. A comparative technical and economic assessment of using electrostatic precipitators (EP) and bag filters (BF) downstream of the boilers of combined heat and power plants (CHPPs) and condensing thermal power plants (CTPPs) combusting the main Russian coals: grade SS Ekibastuz coal, grade SS Kuznetsk coal, grade 2B Irsha-Borodino coal, and Donetsk anthracite culm was carried out. The total capital and operating costs for the implementation, the specific costs for the removal of one ton of ash from different coals in EF and BF for pessimistic and optimistic inflation forecasts are determined. It is shown that an increase in inflation will have a very negative impact on the introduction pace of BATs at Russian thermal power plants and may slow down the introduction of bag filters, which are the most efficient BAT for ash collection. Recommendations on the use of electrostatic precipitators and bag filters at CHPPs and CTPPs for different types of coals have been formed. It is proposed to use bag filters in combusting high-ash coals, the ash of which is characterized by high electrical resistivity. Electrostatic precipitators should be used in combusting low- and medium-ash coals, because the difference in the mass of captured ash in the EF and BF for the same coal is small, whereas the cost of implementing EF is significantly lower. The specific cost of the ash removed differs little for the boilers of CHPPs and CTPPs operating on the same coal; however, it depends strongly on the level of inflation, the growth of which increases significantly the operating costs.

Comparison of alternative neutral detergent fiber methods to the AOAC definitive method

Neutral detergent fiber (NDF) is the most commonly reported metric for fiber in dairy cattle nutrition. An empirical method, NDF is defined by the procedure used to measure it. The current definitive method for NDF treated with amylase (aNDF) is AOAC Official Method 2002.04 performed on dried samples ground through the 1-mm screen of a cutting mill with refluxing and then filtration through Gooch crucibles without (AOAC-; reference method) or with (AOAC+) a glass fiber filter filtration aid. Other methods in use include grinding materials through the 1-mm screen of an abrasion mill, using filtration through a Buchner funnel with a glass fiber filter (Buch), and use of the ANKOM system (ANKOM Technology, Macedon, NY) that simultaneously extracts and filters samples through filter bags with larger (F57) or smaller (F58) particle size retentions. Our objective was to compare the AOAC and alternative methods using samples ground through the 1-mm screens of cutting or abrasion mills. Materials analyzed were 2 alfalfa silages, 2 corn silages, dry ground and high-moisture corn grains, mixed grass hay, ryegrass silage, soybean hulls, calf starter, and sugar beet pulp. Samples were run in duplicate in replicate analytical runs performed on different days by experienced technicians. Compared with cutting mill-ground samples, the aNDF% of dry matter results from abrasion mill-ground samples were or tended to be lower for 8 of 11 samples. Method affected aNDF% results for all materials, with method × grind interactions for 6 of 11 samples. For ash-free aNDF% assessed with cutting mill-ground materials, a priori selected contrasts showed that the number of materials for which methods differed or tended to differ from the AOAC methods were 4 (Buch), 8 (F57), and 3 (F58); and 3 for AOAC- versus AOAC+. However, statistically different does not necessarily mean substantially different. For a given feed and grind, a positive value for the absolute difference between the AOAC- mean and an alternative method mean minus 2 times the standard deviation of AOAC- suggests that values for the alternative method fall outside of the range of results likely to be observed for the reference method. The number of observed positive values for materials processed with cutting and abrasion mills, respectively, were 0 and 2 (AOAC+); 2 and 2 (Buch); 8 and 10 (F57); 4 and 7 (F58); and 0 and 4 (AOAC-). With the materials tested, methods in order of agreement with the reference method were Buch, F58, and F57, which often gave lower values. The AOAC+ gave results similar to AOAC-, substantiating it as an allowed modification of AOAC-. Best agreement between the reference method and variant NDF methods was achieved with the 1-mm screen cutting mill grind. The 1-mm abrasion mill grind produced more aNDF% results that were lower than the reference method but with fewer differences when filter particle retention size was smaller. The use of filters that retain finer particles could be explored to improve comparability of variant NDF methods and grinds. Further evaluation with an expanded set of materials is warranted.

Chemical Speciation Distribution and Thermal Stability of Heavy Metals along Flue Gas Cleaning Systems in a Hazardous Waste Incinerator

Hazardous heavy metals may release from incineration residues in the utilization concerning heat treatment or landfills, which would cause great harm on the environment. The evaluation of chemical speciation and thermal stability of heavy metals are of great significance for the control of heavy metal pollution during heat treatments. In this study, chemical speciation distribution and thermal stability of heavy metals (As, Cd, Cr, Cu, Pb, Se, Zn, and Hg) along flue gas cleaning systems were investigated in a hazardous waste incinerator located in Zhejiang, China. The chemical speciation and thermal stability of heavy metals, environmental risk evaluation, and morphological and mineralogical characteristics of incineration residues were assessed before and after heat treatments. Results indicated that the chemical speciation of heavy metals in the bottom slag, burn-out chamber ash, boiler ash, and bag filter ash varied significantly. The thermal stability of heavy metals in the incineration residues was significantly influenced by chemical speciation, and the thermal stability of the chemical speciation decreased basically in the order of residual form > reducible form > oxidizable form > acid soluble form. As, Cr, and Se showed high thermal stability due to the fact that they were involved in the crystallization reaction, and heat treatment would promote the transformation from mobile fractions into the residual fraction. Hg and Cd displayed the worst thermal stability, and high-temperature heat treatment would contribute to secondary volatilization from the incineration residues. More attention should be paid to the secondary volatilization of Hg and Cd during thermal disposal. Cu, Pb, and Zn had moderate thermal stability, and heat treatment would cause the volatilization of mobile fractions and the transformation from mobile fractions into the residual fraction. Pretreatments such as water-washing or adding a chemical stabilizer would be conducive to reducing the volatilization of heavy metals during thermal disposal.

Optimization Method Based on Hybrid Surrogate Model for Pulse-Jet Cleaning Performance of Bag Filter

The pulse-jet cleaning process is a critical part of the bag filter workflow. The dust-cleaning effect has a significant impact on the operating stability of bag filters. Aiming at the multi-parameter optimization problem involved in the pulse-jet cleaning process of bag filters, the construction method of hybrid surrogate models based on second-order polynomial response surface models (PRSMs), radial basis functions (RBFs), and Kriging sub-surrogate models is investigated. With four sub-surrogate model hybrid modes, the corresponding hybrid surrogate models, namely PR-HSM, PK-HSM, RK-HSM, and PRK-HSM, are constructed for the multi-parameter optimization involved in the pulse-jet cleaning process of bag filters, and their objective function is the average pressure on the inner side wall of the filter bag at 1 m from the bag bottom. The genetic algorithm is applied to search for the optimal parameter combination of the pulse-jet cleaning process. The results of simulation experiments and optimization calculations show that compared with the sub-surrogate model PRSM, the evaluation indices RMSE, R2, and RAAE of the hybrid surrogate model RK-HSM are 9.91%, 4.41%, and 15.60% better, respectively, which greatly enhances the reliability and practicability of the hybrid surrogate model. After using the RK-HSM, the optimized average pressure F on the inner side wall of the filter bag at 1 m from the bag bottom is −1205.1605 Pa, which is 1321.4543 Pa higher than the average pressure value under the initial parameter condition set by experience, and 58.4012 Pa to 515.2836 Pa higher than using the three sub-surrogate models, verifying its usefulness.

A sustainable and low pollutive strategy for the recycling of waste hot-gas filter bags: The development of filter reinforced epoxy composites

The fast accumulation of waste hot-gas filter bags has become a growing public concern considering its difficulty in degradation, severe pollution elicited by landfill and incineration, high energy consumption during burning or complicated recycling and low margin of regenerative products. Herein, we provide a new feasible recycling strategy by directly employing the cleaned polyphenylene sulfide (PPS) /polytetrafluoroethylene (PTFE) waste filters in their fabric state as the reinforcement of epoxy composites. Merely two layers of filters could produce composites with flexural strength and modulus sufficient for many applications and the additional carbon fiber fabric (CFF) covering could further strengthen the composites (295 to 1010 % increments). The filters also showed a bonding promotion function between CFF and polymethacrylimide foam in lightweight composites. After hydrothermal treatment, the composites reinforced by the recycled filters displayed 97.2 % and 90.9 % retention rate for flexural strength and modulus, respectively. Compared to the pure epoxy, the composites could achieve a limiting oxygen index of 27.6 %, and display 24 % decline in thermal energy release and 20.0 to 31.0 % reduction in the generation rate of combustion products, indicating strengthened flame-retardancy. With shortened processes and elevated properties of composites, the approach established for recycling waste filters in this work showed far-reaching implications in carbon emission reduction, environmental pollution diminishing and commercialization potential.

Service-lines as major contributor to water quality deterioration at customer ends

Biofilm detachment contributes to water quality deterioration. However, the contributions of biofilm detachment from different pipes have not been quantified or compared. Following the introduction of partial reverse osmosis (RO) in drinking water production, this study analyzed particles at customers’ ends and tracked their origins to water distribution mains and service lines. For doing so, filter bags were installed in front of water meters to capture upstream detached particles, while biofilm from water main and service line were sampled by cutting pipe specimens. The results showed that elemental concentrations of the biofilm in mains were higher than those of service lines (54.3–268.5 vs. 27.1–44.4 μg/cm2), both dominated by Ca. Differently, filter bags were dominated by Fe/Mn (77.5–98.1%). After introducing RO, Ca significantly decreased in biofilms of mains but not service lines, but the released Fe/Mn rather than Ca arrived at customers’ ends. The ATP concentrations of service lines were higher than mains, which decreased on mains but increased in service lines after introducing RO. For the core ASVs, 13/24 were shared by service lines (17), mains (21), and filter bags (17), which were assigned mainly to Nitrospira spp., Methylomagnum spp., Methylocytis spp., and IheB2–23 spp. According to source tracking results, service lines contributed more than mains to the particulate material collected by filter bags (57.6 ± 13.2% vs. 13.0 ± 11.6%). To the best of our knowledge, the present study provides the first evidence of service lines’ direct and quantitative contributions to potential water quality deterioration at customers’ ends. This highlights the need for the appropriate management of long-neglected service line pipes, e.g., regarding material selection, length optimization, and proper regulation.

Enhanced filtration characteristics of a PTFE foam-coated filter using PTFE nanofibers

Polytetrafluoroethylene (PTFE) is a bag filter material with limited options for fiber production methods because of its high melt viscosity. In this study, a new method for fabricating a PTFE composite filter with high filtration performance was proposed. PTFE nanofibers produced by electrospinning, were coated on the surface of the PTFE foam-coated filter, and heat-treated, resulting in the fabrication of PTFE composite filter. The optimal conditions for preparing PTFE nanofibers with a uniform fiber distribution were determined using a systematic approach. A uniform fiber morphology of the electrospun fibers was prepared by controlling the PTFE-Polyvinyl alcohol (PVA) mixing ratio and the electric field strength, and pure PTFE fibers were obtained by heat-treatment at an optimal temperature based on TGA, DSC, and FT-IR analyses. The filter quality factor of the resultant PTFE composite filter, which represents the filtration performance, was approximately twice that of the PTFE foam-coated filter for all particle sizes. Furthermore, the cleaning cycle and cleaning efficiency of the PTFE composite filter improved by 9% and 3.9–5.4%, respectively, compared to those of the PTFE foam-coated filter, which was closely related to high contact angles of water and oil.