Cleaning Cycle Research Articles

Automatic cleaning suggestion adapting to real-time soiling status of solar farms

Solar farms are subject to various environmental factors that can affect their performance and output. One of the major factors is soiling. Consequently, it is essential to monitor and mitigate the effects of soiling on solar panels to ensure optimal performance and maximum profitability of a solar farm. In this paper, we present a novel cleaning intervention strategy that adapts to the present solar panel performance status to detect cleaning requirements for maximizing profit. This algorithm works with onsite insolation and panel data to give live feedback on cleaning requirements. Moreover, unlike other models in the literature, this method does not require historical or a priori insolation, weather, or soiling data. We have comprehensively tested the algorithm through experiment and simulation under various conditions (i.e., seasonal rain, few annual rainfall or sandstorms, unpredictable dust accumulation). The results show that the adaptive cleaning algorithm, even with no historical insolation or soiling information, outperforms optimal periodic cleaning strategies in terms of net revenue. The adaptive cleaning suggestion system shows significant advantages especially in locations with high variability in weather and soiling conditions. The algorithm is also suitable for practical deployment in solar farms near industrial or construction zones where sudden dust accumulation can occur. Our adaptive model will maximize profit in such unpredictable soiling scenarios, while in comparison, it is not even possible to utilize historical information-based cleaning cycle model in such cases.

The environmental costs of clean cycles: Quantitative analysis for the case of PVC window profile recycling in Germany

AbstractRecycling schemes for long‐lived products are challenged by the presence of “legacy substances,” which have been used in production in the past, but are nowadays classified as substances of concern. This study quantitatively evaluates the trade‐offs between phasing out legacy substances, increasing circularity levels, and reducing life cycle impacts of polyvinylchloride (PVC) window profiles recycling in Germany based on a comprehensive dynamic material and substance flow analysis coupled with a prospective life cycle assessment. Scenario results indicate that although lead had been phased out in virgin PVC by 2015, lead concentrations in end‐of‐life PVC window profiles will remain above 0.3% until the end of the century without a restriction of lead in recycled PVC and will be by factor 3–5 higher compared to a restriction as stipulated by EU 2023/923. However, the latter is associated with lower recycling rates and higher life cycle environmental impacts of PVC window frame waste management, which cannot be fully compensated by the introduction of new waste treatment pathways using currently available technologies. The study serves to introduce a new comprehensive modeling framework, which allows for the consideration of trade‐offs between substance, material, and environmental impact dimensions as a basis for discussing and developing sustainable waste management strategies.

Ultrafiltration membrane modified via synergistic integration of quaternary ammonium compounds bactericidal activity and g-C3N4 photocatalysis: Toward superior antibiofouling and self-cleaning property

Fouling, particularly biofouling caused by microbial adhesion and subsequent biofilm formation, limits the widespread applications of membrane-based technologies. Although integrating contact-killing agents (i.e., quaternary ammonium compounds, QACs) to fabricate antibiofouling membranes has been proven as an effective approach to mitigate this issue, the long-term effectiveness of the modified membranes after foulants covering remains a challenge. Herein, hydrophilic photocatalyst nanosheet g-C3N4 (NCN) was introduced into QAC-modified ultrafiltration (UF) membranes to address this limitation. Results showed that the hydrophilic surface of NCN can improve the antiadhesion properties of hydrophobic QAC modified membranes. Moreover, NCN can degrade organic and inorganic pollutants on QAC modified membrane surface under visible light, thereby restoring the antibacterial ability of QAC. Furthermore, the composite QAC/NCN modified membrane demonstrated long-term stability with sustained remarkable antibacterial performance even after numerous fouling-chemical cleaning cycles. These findings underscore the efficacy of the synergistic integration of contact-killing bactericidal activity and photocatalysis as a versatile and promising solution for combating biofouling, thereby contributing to the advancement of membrane technology in environmental remediation applications.

A comparison study on membrane fouling in A/O-MBR and A/A-MBR at different mixed liquor-suspended solids concentrations

ABSTRACT Membrane fouling leads to decreased membrane flux, increases the frequency of membrane tissue replacement and membrane cleaning, and increases the operating cost of membrane bioreactor. In this study, the pollutant removal effects, membrane fouling differences and microbial characteristics of anaerobic/aerobic MBR (A/O-MBR) and anaerobic/anoxic MBR (A/A-MBR) were investigated at different mixed liquor suspended solids (MLSS) concentrations. The results showed that the chemical cleaning cycle of membrane contamination was 12, 28, 44 h and 24, 40, 104 h, respectively, and the cycle was prolonged with the increase of MLSS concentration (from 6000 to 9000 mg L−1). A/O-MBR was 1.4–2.4 times the rate of membrane fouling of A/A-MBR. In irreversible resistance, extracellular polymer substances (EPS) were the most significant contributors to membrane fouling. EPS concentration in A/A-MBR (118.33, 73.75, 54.26 mg/gMLSS) was lower than that in A/O-MBR (171.68, 91.92, 62.33 mg/gMLSS). Therefore, increasing MLSS concentration could mitigate membrane fouling. 16S rRNA high-throughput sequencing demonstrated that filamentous bacteria was the primary reason for the membrane fouling difference. Filamentous bacteria were more likely to be attached to the surface of the membrane, causing membrane fouling. The abundance percentage of filamentous bacteria in A/A-MBR was smaller than that in A/O-MBR. In summary, The excellent performance of A/A-MBR in membrane fouling behaviour, resistance analysis, EPS and microorganisms proved that A/A-MBR is more promising than A/O-MBR in wastewater nitrogen and phosphorus removal. This study can provide a theoretical basis for the application of MBR in the field of sewage treatment.

Spray-coated PDA-wrapped carboxylic CNT/PES membrane to augment fouling mitigation, organic removal, and membrane stability in electrochemical membrane filtration

This study introduces robust and conductive polydopamine (PDA)-wrapped carboxylic carbon nanotube (C-CNT)-coated polyethersulfone (PES) membrane for electrochemical membrane filtration to treat greywater. Self-polymerized dopamine was prepared directly under oxidative conditions on the CNT strands, followed by their immobilizations on the surface of the PES membrane through a novel spray-coating technique. The spraying coating technique improved both the durability of the coating layer and membrane permeability by 27 % higher than that prepared by the conventional vacuum filtration method. The spraying coating technique enhanced the electroactive properties of the PDA/C-CNT membrane so that the fouling rate was reduced more effectively than the C-CNT membrane or bare PES membrane. Fouling mitigation of the PDA/C-CNT membrane was attributed to the combined effect of electrostatic repulsions between the foulants and the conductive membrane surface along with degradation of organic compounds by electrochemical oxidation. The constant current density profile also confirmed the structural stability of the conductive layer on the membrane under both cathodic and anodic conditions. Furthermore, the fouling layer formed by membrane filtration was removed effectively by in-situ anodic cleaning. Over 80% of water permeability was recovered without losing the membrane integrity up to 3 consecutive anodic cleaning cycles.

Effects of Local Economy and Seasonal Cleaning Cycle on Yield and Profit of Soiled Solar Farms

Effects of Local Economy and Seasonal Cleaning Cycle on Yield and Profit of Soiled Solar Farms

A strategy based on statistical modelling and multi-objective optimization to design a dishwasher cleaning cycle

This study proposes a novel approach based on statistical learning and multi-objective optimization to reduce the need for experiments during the design phase of new cleaning cycles for household dishwashers. We first build regression models associated with the feature selection methods to predict the outputs of a dishwasher cleaning cycle by using the existing cleaning cycles’ program flows as input data and the results of the performance laboratory tests of the related cleaning cycles as output data. Then, a multi-objective optimization problem is defined by assigning the regression models and chosen features as objective functions and unknown decision variables, respectively. Obtained optimization problem is then solved by using evolutionary algorithms according to the designer’s preferences (or customers’ needs).

Role of tea polyphenols in enhancing the performance, sustainability, and catalytic cleaning capability of membrane separation for water-soluble pollutant removal

Tea polyphenols (TPs), like green tea polyphenol (GTP) and black tea polyphenol (BTP), with phenolic hydroxyl structures, form coordination and hydrogen bonds, making them effective for bridging inorganic catalysts and membranes. Here, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable catalytic cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m−2 h−1 bar−1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of catalytic cleaning GO membranes for water purification and separation processes.

Assessment and Mitigation of Bacterial and Fungal Contamination in Refrigerator Waterlines

Three experiments were conducted on the recovery of microorganisms associated with refrigerator water lines. In the first experiment, between 2 and 3 logs CFU/ml were recovered from 100 different refrigerators’ residential water and ice lines. In a second experiment, plastic tubing segments cut from commercial refrigerator waterline systems were inoculated with the bacterium Pseudomonas aeruginosa and a fungal strain of Aspergillus flavus. Either 0.02% peracetic acid (PAA) exposure for 2 min or 0.03% PAA exposure for 1 min resulted in no recoverable bacteria cells, however, 0.25% PAA contact for 2 min was needed to eliminate detection of fungal cells. The third experiment tested sanitation of a water system inoculated with a mixed culture of P. aeruginosa and A flavus with a water filter cartridge filled with 3.5% PAA. The 3.5% concentration was determined using a computer simulation for mixing during a cleaning cycle that would yield a minimum concentration of at least 0.25% throughout the water system. After loading a water filter cartridge containing 3.5% PAA, allowing water to flow into the system for 15 s, and then allowing the system to sit for 5 min, no viable P. aeruginosa or A flavus cells were recovered up to 10 days after treatment.

Pretreatment Method of Landfill Leachate for Lessening Membrane Fouling Effect

This experiment involved membrane pollution cycle experiments to identify the optimal pretreatment method, which was found to be raw water combined with PAC, effectively reducing membrane fouling. Following pretreatment, the first-stage recovery rate reaches 80%, the chemical cleaning cycle spans approximately 90 hours, and the conductivity of the concentrated water ranges between 35 ms/cm and 40 ms/cm.

Changes in Gloss Alteration, Surface Roughness, and Color of Direct Dental Restorative Materials after Professional Dental Prophylaxis.

In the context of optimizing dental care for patients who are elderly, the purpose of this in vitro study was to evaluate the surface gloss (with a micro-area gloss meter) of, surface roughness (with a compact surface roughness measuring instrument) of, and color change (with a dental colorimeter) in two commercially available injectable resin-based composites (Estelite Universal Flow (EUF) and Beautifil Flow Plus F00 (BFP)) as well as two glass-ionomer cements (GC Fuji II LC CAPSULE (FLC) and GC Fuji IX GP EXTRA CAPSULE (FGP)), before and after dental prophylaxis. After 24 h, the surfaces of each specimen were polished at 2500 rpm with a prophy brush (Mersage Brush, Shofu) and one-step prophylaxis paste (Prophy Paste Pro, Directa): under 100 or 300 gf load, and for 10 or 30 s, 4× cycles of cleaning. After mechanical cleaning, conditions were found for a significant reduction in the gloss level (EUF, BFP, or FLC; p < 0.05) and a significant increase in surface roughness (BFP; 300 gf load, 10 s × four cycles of cleaning). Overall, the longer time or higher prophylaxis load tended to decrease the surface gloss. However, the observed change in surface roughness varied between the restorative materials. There was no color change post-prophylaxis.

Polytetrafluoroethylene hollow fiber membranes with thru hydrophilic channels for enhancing water transfer and anti-oil-fouling properties

Herein, a feasible method for hydrophilic modification of polytetrafluoroethylene (PTFE) hollow fibers via interfacial polymerization (IP) was proposed. 1, 3-Diamino-2-propanol (DAP) and trimesoyl chloride (TMC) were selected as monomers and a three-time IP method was adopted to construct hydrophilic channels within the membrane pores, thus effectively improving the hydrophilicity and permeability of membranes. The solvent of aqueous phase in conventional IP process was replaced by ethanol for better introducing amine monomers into membrane pores. The characterization results of Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and water contact angle (WCA) tests indicated the successful formation of polyamide (PA) layer within the membrane pores. In comparison to the ethanol pre-wetted control membrane, the PTFE hollow fibers modified under optimal IP conditions exhibited higher water flux (from 136.8 to 1059.1 kg m−2 h−1) and showed better resistance to both BSA (FRR from 53.4% to 92.3%) and soybean oil (FRR 16.4% from to 78.1%) after four cycles of filtration and cleaning. Simultaneously, the modified membranes demonstrated a favorable oil removal capacity (≥ 92%), and still maintained good stability after 24 h ultrasonic treatment and 8 d immersion tests in acid, alkali and oxidation solutions. This membrane holds significant application value in the treatment of oily wastewater.

Surface modification of NF membrane via an environmentally friendly and rapid approach for desalination Process: Performance and stability evaluation

In this study, an environmentally friendly and rapid surface modification method known as surface mineralization was adopted to alter the polyamide (PA) layer of commercial NF270 thin film composite (TFC) membrane, aiming to improve its characteristics for enhanced desalination process. An alternate soaking process was applied on the membrane surface by using barium chloride solution and sodium sulfate solution at varying concentrations (0.01 M, 0.05 M and 0.1 M). The reaction of these two salts can form a layer of barium sulfate (BaSO4) minerals atop the PA layer via an ionic interaction. Our result revealed that the best-performing membrane could be developed using salt solutions at 0.05 M with its water contact angle descended to 33.5° compared to the pristine membrane of 46.4°. Furthermore, the surface roughness of the BaSO4-mineralized membrane was reported to be higher than the pristine membrane. The increase in surface roughness together with improved surface hydrophilicity yielded the BaSO4-mineralized membrane to exhibit 12% higher water flux than the pristine membrane. Nonetheless, the difference in Na2SO4 rejection before and after surface mineralization was not found to be statistically significant owing to the high Na2SO4 rejection of the control membrane. The BaSO4-mineralized membrane also achieved excellent performance in filtering solutions containing sodium alginate and showed very stable salt rejection for multiple cycle of combined chemical cleaning and water filtration process. These results highlighted the potential of the surface mineralization process in overcoming the trade-off effect between water flux and selectivity of TFC membrane.

PH-responsive polyacrylic acid chemical cross-linking for end-of-life reverse osmosis membrane rejuvenation

An in-situ chemical cross-linking rejuvenation technique for reverse osmosis (RO) membranes was developed and investigated utilizing pH-responsive polymer with multiple carboxyl groups to improve the salt rejection and performance stability of end-of-life RO membranes. Polyacrylic acid (PAA) was used as a rejuvenating agent to cross-link with amino groups on the degraded RO membrane through EDC/NHS activated reaction. Indicated by ATR-FTIR, XPS, Zeta potential and SEM analyses, the covalent bonds between carboxyl groups and amino groups were generated on the PAA-rejuvenated membrane. The end-of-life RO membrane elements with an average NaCl rejection of 92.68 % could be recovered to 97.26 % by PAA rejuvenation. As a result of pH responsivity, PAA-rejuvenated membranes exhibit excellent rejection stability after continuous 12 cycles of alkali and acid alternate cleaning. The adjustable salt rejection and the durability of PAA-rejuvenated membrane elements were validated in real water tests for 185 days at a coal mine water treatment plant, indicating the practical application potentiality. The effects of initial end-of-life RO membrane condition on PAA rejuvenation are also provided.

Optimization for the HP-CORD UV chemical decontamination process for AISI 304 stainless steel

The decontamination of stainless-steel surfaces in Light Water Reactors components, that may suffer from nuclear activation and contamination, is still a topic that deserves research and development studies. In this paper, the HP-CORD-UV chemical method for the removal of thin surface layers from AISI 304 stainless steel samples is addressed, considering multiple cycles of oxidation and cleaning. A procedure for the optimization of the oxidation phase considering in particular the pH of the solution, the ([KMnO4]/[H+] ratio), and the immersion time (oxidation time), was developed and is here presented. The experimental results show that 10 oxidation cycles at pH 3, [MnO4-] = [H+], for 2 h, followed by 30 min of cleaning in oxalic acid, allowed to reach a thickness of dissolved metal of about 3–4 μm. Despite the intrinsic localised morphology of the corrosion attack on AISI 304 sample surface, scanning electron microscopy showed good reproducibility of the process.

Synergistic enhancement of external electrical energy in PM filtration with Cu-HHTP@CuO nanowire arrays coated copper mesh

Developing multifunctional purification systems that combine air filtration and antibacterial functionality is a challenging task. However, in designing air filtration materials, achieving a balance between filtration efficiency and pressure drop remains a significant challenge. In this study, we developed a novel filtration material composed of hierarchically 3D Cu-HHTP nanowiskers coated CuO nanowires that were grown in-situ on a copper mesh. Benefitted from the intrinsically electrical conductivity of Cu-HHTP, we combined the composite material with external electrical energy for air filtration. By applying lower electric potential directly (voltage of 5 V), the 3D conductive mesh filter exhibited excellent performances in terms of the PM2.5 removal efficiency (∼99.7%), pressure drop (∼32 Pa at 2 cm s -1), and quality factor (0.187 at 2 cm s -1). Furthermore, after ten cycles of filtration and cleaning, the material maintained a high PM removal rate. In addition to its excellent filtration performance, the composite metal mesh also exhibited outstanding antibacterial activity against both E. coli and S. aureus. The electro-mechanical stability and recyclability of the composite filter make it a cost-effective and environmentally friendly solution for air purification, with promising potential for improving air quality.

PICKLING – PASSIVATION MECHANISM AND PROCESS OPTIMIZATION OF Q235 STEEL PIPELINE

Pipe cleaning is currently the most effective method to improve the cleanliness and corrosion resistance of pipes. In this paper, a new method of pipe cleaning is proposed, combining mechanical and chemical cleaning, offline tank cleaning and online cycle cleaning. Through experiments and characterization of the morphology changes, the mechanism of pickling and passivation of Q235 steel was explored, and the entire process of microstructure and morphology changes on the pipe wall’s surface was analyzed to verify the feasibility of this technology. The cleaning process was optimised using response surface analysis to determine the optimum cleaning conditions. This study is of great relevance to the effective operation of continuous-casting equipment over a long period of time.

Construction of antimicrobial peptides/alginate multilayers modified membrane: Antibiofouling performance and mechanisms

Biofouling remains to be one of major obstacles for membrane-based technology in water and wastewater treatment, calling for the development of antibiofouling membranes. For the traditional release-killing strategy, uncontrollable release of biocides and thus a short lifetime as well as the potentially environmental risk are thorny issues for the modified membranes. Herein, hydrophilic hydrogel multilayers with controllable thickness at nanometer scale on a poly(vinylidene fluoride) (PVDF) microfiltration membrane were constructed via layer-by-layer (LbL) self-assembly of non-drug-resistant antimicrobial peptides (AMPs) and alginate. The AMPs/alginate multilayers modified membranes exhibited enhanced hydrophilicity, well-controlled pore size distribution and prominent antimicrobial ability against Escherichia coli and Staphylococcus aureus. As the number of multilayers of alginate increased, both initial and steady release rate of Ponericin G1 reduced; in particular, the AMPs/alginate modified membranes with fifteen multilayers (MSA15) had the slowest release kinetics (i.e., an initial release rate of 1.79 ± 0.07 μg/cm2 d and a steady release rate of 0.55 ± 0.03 μg/cm2 d), resulting in about 60% less release compared with the AMPs/alginate modified membranes with five multilayers (MSA5). Long-term antibiofouling tests showed that the AMPs/alginate modified membranes with ten multilayers (MSA10) exhibited a significantly reduced transmembrane pressure increase rate of 0.81 ± 0.01 kPa/d which was much lower than that of the control membranes (1.80 ± 0.20 kPa/d), mainly attributed to the antibacterial activity imparted by the lasting release of AMPs and competing membrane basic properties. Furthermore, the AMPs/alginate multilayers modified membranes revealed high stability suffering from long-term operation and chemical cleaning cycles. The novel AMP/alginate-incorporated modifying method provides a new dimension to enhance antibiofouling performance of membranes for water and wastewater treatment.

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.

Surface modification of ITER-like mirrors after one hundred cleaning cycles using radio-frequency plasma

In ITER, the metallic first mirrors (FMs) will undergo erosion due to their proximity to the fusion plasma and deposition of materials originated from the first walls (mainly beryllium). In-situ plasma cleaning is a promising technique to conserve the FMs optical properties by means of ion sputtering. In this work, the evolution of the optical properties of single-crystal (Sc) and nanocrystalline (Nc) molybdenum (Mo) and rhodium (Rh) mirrors were investigated up to 100 cycles of consecutive contamination and cleaning. Aluminum oxide (Al2O3) was used as contaminant to replace the toxic beryllium. The plasma cleaning was carried out using a capacitively coupled argon (Ar) plasma excited by a 60 MHz radio-frequency generator resulting in the formation of a self-bias applied on the mirrors of -280 V. The plasma potential being around 30 V, the Ar ion energy was about 310 eV. The optical properties of the mirrors were assessed using ex-situ reflectivity measurements. Moreover, the surface topography was characterized by means of scanning electron microscopy (SEM), focused ion beam (FIB) and roughness measurements using atomic force microscopy (AFM). ScMo and ScRh mirrors formerly exposed to 80 successful cleaning cycles using aluminum/tungsten (Al/W) deposits and air storage exhibit drastic changes in their optical properties after being subject to cleaning cycles using Al2O3 as contaminant. Additionally, freshly polished ScRh were exposed to identical cleaning cycles. All Sc mirrors exhibited pits induced by the polishing procedure using diamond paste in addition of mounds/wavy patterns. The carbon incorporated during the polishing process was demonstrated to be responsible for the pitting of the surface. The Nc mirrors preserved their initial reflectivities after up to 100 cycles. The surface topography was systematically characterized and an average erosion rate for NcRh mirrors of about 59 nm per cycle has been estimated from FIB cross-sections. The optical properties of the Nc mirrors showed a superiority in the present study in comparison to the Sc materials due to the influence of their polishing procedures.