Self-cleaning Process Research Articles

Natural Self-Purification of Creek Ecosystems: The Role of Foam Formation in Pollutant Absorption and Microbial Decomposition

<p style="text-align:justify;text-indent:36.0pt;"><span style="font-family:"Times New Roman","serif";font-size:12.0pt;line-height:115%;" lang="EN">This study investigates the natural self-purification ability of a creek through the process of froth formation. The research focuses on the creek's capacity to clean itself by capturing and removing pollutants naturally. The problem addressed is the accumulation of organic and inorganic contaminants in the water, which poses a threat to the aquatic ecosystem. The proposed solution explores how naturally formed froth can act as an effective mechanism for trapping and eliminating a wide range of pollutants. The froth formation is driven by biological processes, including the decomposition of organic matter by fungi, bacteria, Archaea, Algae, Virsus, Protozoa and animal parasites. These processes release biological surfactants and biogas microbubbles, which, combined with dissolved air and pollutants, lead to the creation of froth enriched with contaminants. The findings confirm that the creek has a natural ability to purify itself, as the froth effectively absorbs and collects dissolved pollutants. This process reduces the organic load in the water, thereby improving water quality. The study demonstrates that froth formation is a vital subprocess in the self-purification of river ecosystems, particularly through microbial decomposition of organic material. This natural mechanism supports water treatment by enhancing the removal of contaminants. The research validates the hypothesis that the creek's froth formation plays a significant role in its self-cleaning process, offering insights into the potential for natural water purification methods.</span></p>

OH radical initiated oxidative degradation of imidacloprid in the environment: An assessment of breakdown kinetics and environmental hazards

Imidacloprid (IMI) is a common neonicotinoid pesticide that acts via a similar mechanism of action to nicotine, a naturally occurring insecticide. It is therefore important to understand its chemical fate in the environment. Hydroxyl radicals (HO) are significant oxidizing species in natural aquifers due to their strong reactivity towards organic substrates. Therefore, principal photo-oxidation products are expected to form with the involvement of HO in the self-cleaning process of water in nature. Here quantum chemical calculations are used to examine the reaction of IMI with HO in the atmosphere and aqueous environments. It was found that the principal mechanism of the HO + IMI reaction is the hydrogen transfer that, in a two-step process, produces stable cations in the gas phase. Within the atmospheric temperature range of 253–323 K, the overall rate constants for the HO + IMI reaction decreased from 4.35 × 1010 to 2.13 × 1010 M−1 s−1. Consequently, IMI can undergo rapid gaseous degradation within a comparatively brief period of 2.81 × 10−4 – 5.75 × 10−4 years. However, differences in environmental temperature and pH in aqueous environments influence the processes, rate constants, and products of IMI breakdown by the HO radical. The data indicate that IMI breakdown by OH radicals is strongly temperature and pH-dependent, resulting in the generation of different reaction products. The results imply that at all pH levels, the interaction between IMI and the ambient HO radical in water produces toxic chemical species. According to the computed data, it appears that IMI and the vast majority of degradation products present potentially carcinogenic and/or mutagenic hazards, and they also lack downstream biodegradability.

Surface with wettability gradient — A novel approach for crystallization fouling control on the horizontal falling film flow

To manage scaling on heat transfer surfaces, using chemical-based antifouling treatments takes a toll on the environment, and related maintenance costs are significant. A unique and environmentally friendly scale mitigation strategy is developed in this work. By manipulating the scale layer distribution using surface wettability gradients, stronger flow shear and weaker scaling adhesion are achieved, facilitating self-cleaning process. Experimental work utilizes a horizontal-tube falling-film evaporator to mimic multiple-effect distillation process. A millimetric wettability pattern – alternating hydrophilic and hydrophobic regions – is created by coating stainless steel tubes. The results show scale layers (calcium carbonate) were either thicker in hydrophilic regions and thinner in hydrophobic regions or had approximately uniform thickness in both regions but cracks in scale layers near wettability boundaries. Scale layers wash-off with flow is observed on patterned tubes, demonstrating self-cleaning process. In contrast to persistent deterioration in overall HTC (heat transfer coefficient) for baseline tube (77 % of initial HTC after 192 h), HTC on patterned tubes initially increases due to surface wetting effects, then maintains roughly constant (15 % higher than that of baseline after 192 h) along with lower scale mass. This work provides a novel scaling control method, a potential “green” alternative to current industry scale-control practices.

Kinetic monitoring of molecular interactions during surfactant-driven self-propelled droplet motion by high spatial resolution waveguide sensing

Hypothesis: Self-driven actions, like motion, are fundamental characteristics of life. Today, intense research focuses on the kinetics of droplet motion. Quantifying macroscopic motion and exploring the underlying mechanisms are crucial in self-structuring and self-healing materials, advancements in soft robotics, innovations in self-cleaning environmental processes, and progress within the pharmaceutical industry. Usually, the driving forces inducing macroscopic motion act at the molecular scale, making their real-time and high-resolution investigation challenging. Label-free surface sensitive measurements with high lateral resolution could in situ measure both molecular-scale interactions and microscopic motion.Experiments: We employ surface-sensitive label-free sensors to investigate the kinetic changes in a self-assembled monolayer of the trimethyl(octadecyl)azanium chloride surfactant on a substrate surface during the self-propelled motion of nitrobenzene droplets. The adsorption–desorption of the surfactant at various concentrations, its removal due to the moving organic droplet, and rebuilding mechanisms at droplet-visited areas are all investigated with excellent time, spatial, and surface mass density resolution.Findings: We discovered concentration dependent velocity fluctuations, estimated the adsorbed amount of surfactant molecules, and revealed multilayer coverage at high concentrations. The desorption rate of surfactant (18.4 s−1) during the microscopic motion of oil droplets was determined by in situ differentiating between droplet visited and non-visited areas.

Thermo-adaptive interfacial solar evaporation enhanced by dynamic water gating

Solar-driven evaporation offers a sustainable solution for water purification, but efficiency losses due to heat dissipation and fouling limit its scalability. Herein, we present a bilayer-structured solar evaporator (SDWE) with dynamic fluidic flow mechanism, designed to ensure a thin water supply and self-cleaning capability. The porous polydopamine (PDA) layer on a nickel skeleton provides photothermal functionality and water microchannels, while the thermo-responsive sporopollenin layer on the bottom acts as a switchable water gate. Using confocal laser microscopy and micro-CT, we demonstrate that this unique structure ensures a steady supply of thin water layers, enhancing evaporation by minimizing latent heat at high temperatures. Additionally, the system initiates a self-cleaning process through bulk water convection when temperature drops due to salt accumulation, thus maintaining increased evaporation efficiency. Therefore, the optimized p-SDWE sample achieved a high evaporation rate of 3.58 kg m−2 h−1 using 93.9% solar energy from 1 sun irradiation, and produces 18–22 liters of purified water per square meter of SDWE per day from brine water. This dynamic water transport mechanism surpasses traditional day-night cycles, offering inherent thermal adaptability for continuous, high-efficiency evaporation.

Facile synthesis of carbon black and sodium alginate based particles system for efficient solar desalination of highly concentrated brine

Interfacial solar desalination of seawater/wastewater is one of the most promising strategies to mitigate the crisis of freshwater shortage. Tremendous progress on improving the evaporation rate has been achieved over the past ten years, however, with the rapid evaporation at the interfacial region of water and air, salt simultaneously aggregates on the solar absorbers, reducing the stability of the evaporative performance. It is essential to design salt-resistant solar evaporators, especially for dealing with highly concentrated brine, in which salt clogging is more likely to occur. Here, we demonstrate a facile and scalable synthesis of self-cleaning particles system by coating carbon black (CB) onto expanded polystyrene (EPS), which can generate freshwater from high salinity brine. With sodium alginate (SA) as a binder, the EPS core-CB shell particles are fabricated by a simple ‘rolling rice dumpling’ strategy. These particles spontaneously gather to a system in water attributing to the surface tension, which function coordinatively to realize the self-cleaning process through rotating ascribed to the unbalanced force after salt crystallization. Benefiting from the low cost of materials, facile synthesis procedure, and good performance in high salinity water, our EPS-CB particles system opens up an avenue for the practical applications of interfacial solar desalination.

Sustainable control of organic-inorganic combined fouling of electroactive ultrafiltration membrane during electrocatalytic-driven self-cleaning process: Mechanism and implications

Organic-inorganic combined fouling of membrane is a tough problem that restrained its application in water treatment, which was insufficient and non-sustainable to be alleviated by conventional chemical cleaning. Herein, a facile and sustainable control strategy was developed to mitigate biopolymer-Ca2+ combined fouling for an electroactive metal-organic framework ultrafiltration membrane. Bovine serum albumin (BSA) and sodium alginate (SA) were selected as model biopolymer. The results showed BSA and SA fouling both accelerated with increasing Ca2+ concentration (0–1.0 mM) via calcium bridging action and hydraulic cleaning was insufficient to restore flux (flux recovery < 7 %). By comparison, flux can be fully recovered by applying electricity to all combined fouling, suggesting membrane presented outstanding self-cleaning performance. According to the free radical quenching test and physicochemical property of biopolymer, fouling control mechanism was revealed because in-situ electro-generated OH and O2− free radicals caused decomplexation of biopolymer and Ca2+, and then degraded biopolymer into smaller and less hydrophobic fragments that repulsed membrane. Extended Derjaguin–Landau–Verwey–Overbeek theory further unveiled the foulants-membrane interaction shifted from attraction to repulsion after self-cleaning. This strategy has the advantages of low chemical cleaning reagents and energy consumption, which may provide the guidance for sustainable control of organic-inorganic combined membrane fouling.

Assessment of surface water quality in the Siversky Donets river within Kharkiv region in 2023

Purpose. Provide an assessment of the quality of the massif of surface waters of the Siverskyi Donets River within the Kharkiv region in 2023 based on the determination of water quality indices. Methods. The methods of the modified water pollution index (WPI) and the combinatorial water pollution index (CWPI). Results. State of the river water at the observation point of the v. Pechenigy according to the method of the modified water pollution index WPIF is estimated as II class characterized as "clean", WPIH - I class, "very clean"; according to the method of the combinatorial index of water pollution CWPIF - class III a, "dirty", CWPIH - class I, "slightly polluted". State of the river water at the observation point of the v. Eschar according to the method of the modified water pollution index of WPIF is estimated as III class characterized as "moderately polluted", WPIH - II class, "clean"; according to the method of the combinatorial index of water pollution CWPIF - class III b, "dirty", CWPIH - class II, "polluted". State of the river water at the observation point of the v/ Zadonetskyi according to the method of the modified index of water pollution, WPIF is estimated as III class characterized as "moderately polluted", WPIH is II class, "clean"; according to the method of the combinatorial index of water pollution CWPIF - class III b, "dirty", CWPIH - class I, "slightly polluted". Conclusions. It was determined that there are changes in water quality along the watercourse of the Siverskyi Donets River within the Kharkiv Region in 2023. There is a deterioration of water quality after the confluence of the Uda River, by 1.69 times the magnitude of the index change, then the state of water quality improves by 1.25 times the magnitude index changes, probably due to self-cleaning processes and lower anthropogenic load. The quality of water according to WPI indicators varies from 0.25 to 1.47 (from "very clean" to "moderately polluted"). The quality of water according to the CWPI indicators varies from 1.0 to 3.83 (from "slightly polluted" to "dirty"). It was established that according to both assessment methods and both standards, the quality of water in the Pechenigy reservoir, p. Pechenegs the best, and the worst water quality in the Siverskyi Donets River below the mouth of the Uda River, village Eschar.

La0·8Mn0·2FeO3 impregnated ceramic membrane for membrane fouling elimination via peroxymonosulfate activation

To endow SiC ceramic membranes a catalytic self-cleaning capability, a pore-functionalized SiC ceramic membrane with impregnated a perovskite-type catalyst La0·8Mn0·2FeO3 was fabricated by a urea-assisted one-step combustion method. Diffraction of X-ray (XRD), canning electronic microscopy (SEM) with an energy dispersion X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed to investigate the effects of the impregnating of La0·8Mn0·2FeO3 on SiC membrane pore-structure (La0·8Mn0·2FeO3-CM). The catalytic self-cleaning performance of the as-prepared membranes was assessed through peroxymonosulfate (PMS) activation under a cross-flow filtration mode. Results indicate that La0·8Mn0·2FeO3 has been successfully impregnated into the macropores of SiC membranes without pore blocking, and 92.4 % of the flux recovery rate (FRR) was achieved when the PMS concentration was 70 mM and catalytic flushing time was 45 min. Therefore, the La0·8Mn0·2FeO3 impregnated SiC membrane exhibited excellent catalytic self-cleaning property, which can effectively avoid the environmental pollution and the deterioration of membrane materials caused by chemical cleaning for membrane fouling. In addition, the radical quenching experiment and electron spin resonance (EPR) tests were conducted in the catalytic self-cleaning process, and the results suggested that the hydroxyl radical (⋅OH) and sulfate radical (SO4•‾) are simultaneously captured and ⋅OH is the dominant active species. This study embarks on a novel and environmental friendly membrane cleaning approach for irreversible fouling eliminates in diverse membrane separation applications.

Integration of Ultrathin Hafnium Oxide with a Clean van der Waals Interface for Two-Dimensional Sandwich Heterostructure Electronics.

Integrating high-κ dielectrics with a small equivalent oxide thickness (EOT) with two-dimensional (2D) semiconductors for low-power consumption van der Waals (vdW) heterostructure electronics remains challenging in meeting both interface quality and dielectric property requirements. Here, we demonstrate the integration of ultrathin amorphous HfOx sandwiched within vdW heterostructures by the selective thermal oxidation of HfSe2 precursors. The self-cleaning process ensures a high-quality interface with a low interface state density of 1011-1012 cm-2 eV-1. The synthesized HfOx displays excellent dielectric properties with an EOT of ∼1.5 nm, i.e., a high κ of ∼16, an ultralow leakage current of 10-6 A/cm2, and an impressively high breakdown field of 9.5 MV/cm. This facilitates low-power consumption vdW heterostructure MoS2 transistors, demonstrating steep switching with a low subthreshold swing of 61 mV/decade. This one-step integration of high-κ dielectrics into vdW sandwich heterostructures holds immense potential for developing low-power consumption 2D electronics while meeting comprehensive dielectric requirements.

Bio-Inspired Magnetically Responsive Silicone Cilia: Fabrication Strategy and Interaction with Biological Mucus.

Cilia are biological structures essential to drive the mobility of secretions and maintain the proper function of the respiratory airways. However, this motile self-cleaning process is significantly compromised in the presence of silicone tracheal prosthesis, leading to biofilm growth and impeding effective treatment. To address this challenge and enhance the performance of these devices, we propose the fabrication of magnetic silicone cilia, with the prospect of their integration onto silicone prostheses. The present study presents a fabrication method based on magnetic self-assembly and assesses the interaction behavior of the cilia array with biological mucus. This protocol allows for the customization of cilia dimensions across a wide range of aspect ratios (from 6 to 85) and array densities (from 10 to 80 cilia/mm2) by adjusting the fabrication parameters, offering flexibility for adjustments according to their required characteristics. Furthermore, we evaluated the suitability of different cilia arrays for biomedical applications by analyzing their interaction with bullfrog mucus, simulating the airways environment. Our findings demonstrate that the fabricated cilia are mechanically resistant to the viscous fluid and still exhibit controlled movement under the influence of an external moving magnet. A correlation between cilia dimensions and mucus wettability profile suggests a potential role in facilitating mucus depuration, paving the way for further advancements aimed at enhancing the performance of silicone prostheses in clinical settings.

A Super Hydrophilic Material for Self-Cleaning by Cold Plasma of Zinc Selenite Nanostructure

This research is devoted to the fabrication of zinc selenide nanostructures using the pulsed laser deposition (PLD) technique in a vacuum under a pressure of [Formula: see text] mbar. The structure and structural properties were studied, as it was observed that it had polycrystalline structures and showed peaks for zinc and selenium and peaks belonging to the compound zinc selenide. As for the morphological characteristics of the nanostructures, the structures showed the nature of the surface and the roughness to identify its surface properties. Photocatalysis was carried out using several techniques (visible light, ultraviolet radiation and cold plasma), where a plasma jet system produced under normal atmospheric pressure was used in the treatment, with an exposure time of 4[Formula: see text]min and an argon gas flow rate of 3[Formula: see text]l/min. The hydrophilic properties were studied to apply these compositions in the self-cleaning process and photocatalytic activity. The results show that the ZnSe nanostructures have high wettability under UV light which has been shown to have excellent catalysis in the UV region, making its application as a self-cleaning material an attractive option.

Synergistic effects of PVDF membrane surface functionalization with polydopamine and titanium dioxide for enhanced oil/water separation and photocatalytic behavior

This study investigates the surface modification of poly(vinylidene fluoride) (PVDF) membranes using polydopamine (PDA) and titanium dioxide (TiO2) for effective separation of oily compounds and self-cleaning photocatalytic behavior. The aim was to improve the antifouling properties of the membrane, which was modified by varied PDA and TiO2 concentrations and evaluated regarding the water permeance, total organic carbon (TOC) rejection, and photocatalytic degradation activity. The results demonstrated considerable improvements in the membrane's antifouling properties, achieving a water permeance of 781 kg h−1 bar−1 m−2, TOC rejection of 87%, and methylene blue photocatalytic degradation of 97%, using dopamine (DA) and TiO2 concentration of 0.92 g L−1 and 1.4% (w/w), respectively, and a solution agitation speed of 106 rpm. Additionally, flux recovery reached 86% after the photocatalytic self-cleaning process, indicating that TiO2 improved the membrane's antifouling properties. These findings highlight the potential of PDA and TiO2 as effective surface modifiers for enhancing oil/water separation, reducing fouling, and promoting self-cleaning effect in photocatalytic PVDF membranes. This study’s outcomes provide valuable insights for developing efficient and sustainable membrane-based separation processes for oily wastewater treatment applications.

Cascaded Kerr beam self-cleaning in graded-index multimode fibers

Spatial beam self-cleaning has shown a nonlinear improvement in beam quality in multimode fibers (MMFs), proving its value in high-power fiber lasers and nonlinear biomedical imaging. In this Letter, we propose a novel cascaded Kerr beam self-cleaning scheme that combines multiple MMFs to further improve beam quality. Through this scheme, the initially speckled beam gradually evolves into a well-defined bell-shaped, primarily dominated by the fundamental mode, after undergoing two or three cascaded self-cleaning processes. Simulation results also suggest that an increased number of high-order modes (HOMs) with negligible energy along with a higher number of cascaded fibers contribute to superior beam quality. This phenomenon is attributed to the new excited HOMs acting as attractor and facilitating an energy cascade towards the fundamental mode.

Biodiversity in wetland+ system: a passive solution for HCH dump effluents.

The hexachlorocyclohexane isomers (HCH) are long-banned pesticides. Even though their use has been prohibited for decades, their presence in the environment is still reported worldwide. Wetland + is a registered trademark of the remedial treatment technology consisting of an aerobic sedimentary tank, a permeable reactive barrier, a biosorption system, and an aerobic wetland. This proven method combines a reductive treatment known from PRBs with the natural wetland self-cleaning processes. The average efficiency of the system is 96.8% for chlorobenzenes (ClB) and 81.7% for HCH, during the first 12 months of the system operation. The presence of the genes encoding enzymes involved in the degradation of the HCH compounds indicates that the removal of HCH and ClB occurs not only by chemical removal but also through aerobic and anaerobic combining biodegradation. Changes in abundance and the composition of the diatom community were found to be suitable indicators of the water quality and of the impact of the Wetland + operation on the water ecosystem. The system's annual operation exhibited a markedly higher number of diatom species in the closing profiles of the Ostrovský Creek, the Wetland + effluent recipient.

High performance photodegradation resistant PVA@TiO2/carboxyl-PES self-healing reactive ultrafiltration membrane

The occurrence of ultrafiltration (UF) membrane fouling frequently hampers the sustainable advancement of UF technology. Reactive self-cleaning UF membranes can effectively alleviate the problem of membrane fouling. Nevertheless, the self-cleaning process may accelerate membrane aging. Addressing these concerns, we present an innovative design concept for composite self-healing materials based on self-cleaning UF membranes. To begin, TiO2 nanoparticles were incorporated into the polymer molecular structure via molecular design, resulting in the synthesis of TiO2/carboxyl-polyether sulfone (PES) hybrid materials. Subsequently, the nonsolvent-induced phase inversion technique was employed to prepare a novel of UF membrane. Lastly, a polyvinyl alcohol (PVA) hydrogel coating was applied to the hybrid UF membrane surface to create PVA@TiO2/carboxyl-PES self-healing reactive UF membranes. By establishing a covalent bond, the TiO2 nanoparticles were effectively and uniformly dispersed within the UF membrane, leading to exceptional self-cleaning properties. Furthermore, the water-absorbing and swelling properties of PVA hydrogel, along with its capacity to form hydrogen bonds with water molecules, resulted in UF membranes with improved hydrophilicity and active self-healing abilities. The results demonstrated that the water contact angle of PVA@5%TiO2/carboxyl-PES UF membrane was 43.1°. Following a 1-h exposure to simulated solar exposure, the water flux recovery ratio increased from 48.16% to 81.03%. Moreover, even after undergoing five cycles of 12-h simulated sunlight exposure, the UF membranes exhibited a consistent retention rate of over 97%, thus fully demonstrating their exceptional self-cleaning, antifouling, and self-healing capabilities. We anticipate that the self-healing reactive UF membrane system will serve as a pioneering and comprehensive solution for the self-cleaning antifouling challenges encountered in UF membranes while also effectively mitigating the aging effects of reactive UF membranes.

Chitosan bimetallic particles with in-situ ROS driven self-cleaning performance for tetracycline elimination

Adsorption enrichment coupled with oxidative degradation is a promising technique for eliminating tetracycline (TC) from an aqueous environment. However, the high cost associated with this technique limits its applicability. Thus, in this study, we synthesized Cu2O and CuFe2O4 bimetallic-modified chitosan particles (Cu(I)–CuFe2O4@CS) with high adsorption efficiency and self-cleaning performance. The self-cleaning performance was driven by the in-situ generated reactive oxygen species (ROS). Batch experiments and characterization methods indicated that 97.39% of TC was rapidly adsorbed on the particles surface and subsequently degraded by in-situ generated ROS, to achieve a self-cleaning process. The Cu(I)–CuFe2O4@CS/TC system exhibited maximum O2•- and H2O2 concentration of 12.95 μmol/L and 42.05 μmol/L, respectively. Cu2O was the main source of the ROS generation, while CuFe2O4 effectively adsorbed TC and contributed to the synergistic accumulation of ROS. Moreover, the adsorbed TC with reductive functional properties facilitated the reduction of Fe(III)/Fe(II) and Cu(II)/Cu(I) cycles, thereby improving TC elimination efficiency.

Recent progress on transparent and self-cleaning surfaces by superhydrophobic coatings deposition to optimize the cleaning process of solar panels

Superhydrophobic transparent coatings have recently gained significant attention in the solar energy field due to their ease of preparation, low cost, self-cleaning process, and high effectiveness in reducing dust adhesion to the surface. However, very few journals have addressed the application of self-cleaning coatings for the solar energy field due to its complexity. The transparency and the roughness responsible for the self-cleaning feature are two contradictory parameters; Increasing one parameter strongly implies a decrease in the other, Moreover, the durability of the coatings is also considered as an essential parameter for their industrial-scale acceptance, as solar panels are exposed to highly aggressive environments. Therefore, studying superhydrophobic coatings oriented for solar applications can be challenging. Most reviews reported in the literature provided limited information on the choice of materials, deposition techniques, and synthesis protocols of transparent and superhydrophobic coatings. Several reviews have addressed the topic of superhydrophobic coatings, which have various applications such as water/oil separation, anti-ice, anti-biofouling, self-cleaning and more. However, there are not many reviews that specifically focus on the development of superhydrophobic coatings for solar applications. This is mainly due to the transparency constraint required for the solar applications, making this topic particularly challenging. In the past five years, only five reviews have been published on this subject. In this review, we discuss in detail the impact of solar panel dust accumulation and its impact on their efficiency. Then, we discuss the principle of superhydrophobicity and self-cleaning as well as the principle of transparent coatings. In this review, we aim to address this gap in knowledge by discussing in detail the impact of dust accumulation on solar panel efficiency, as well as the principles of superhydrophobicity, self-cleaning, and transparent coatings.

Self-purification monitoring of the Danube delta and Merlo river aquatic water according to microbiological indicators

Purpose. Analysis of self-purification monitoring of the water area of the Danube delta and the small Merlo river (tributary of the Vorskla) according to microbiological indicators. Methods. To evaluate the role of microorganisms in maintaining the homeostasis of aquatic ecosystems, to study the intensity of self-cleaning processes and bioindication of pollution, the qualitative and quantitative characteristics of various ecological and trophic groups were determined. The dynamics and intensity of self-cleaning processes were determined by the ratio indicator (Ri) of TBC of autochthonous and allochthonous saprophytic microorganisms. The level of trophicity and saprobity in the Merlo river was determined by phenomenological signs. Results. It was established that the most intensive processes of self-purification were observed in the water area of the Danube delta above Reni city and in the Bystry branch. The most polluted water areas among studied were in the Kiliya branch near the town of Izmail, below the town of Kiliya and above the town of Vylkove (9th km). Monitoring studies of the Merlo river, in the area of the wastewater discharge in it of the food industry enterprise, were carried out according to hydrobiological and microbiological indicators. It was established that the river is very polluted, is under a large anthropogenic load on the water ecosystem and has a low ratio indicator (Ri). It was determined that according to the degree of saprobity and trophicity, the river in the wastewater discharge zone is related to hypertrophic and polysaprobic. After reconstruction of the treatment facilities at the food industry enterprise, the situation at the wastewater discharge point changed: Ri has increased from 1.1 to 3.2, and the water area at the discharge point has been classified as a polysaprobic zone, with signs of a mesosaprobic zone, which indicates a tendency to self-purification. Conclusions. It was established that the degree of self-cleaning processes is affected by anthropogenic sources of pollution of water bodies. The water ecosystems of the Danube delta have more pronounced tendencies to self-recovery than the ecosystems of the small Merlo river (a tributary of the Vorskla river). The positive impact of effective treatment of industrial wastewater discharged into the river on Ri, as well as on the trophicity and saprobity of ecosystems, has been established.

Contaminant Removal from Nature's Self-Cleaning Surfaces.

Many organisms in nature have evolved superhydrophobic surfaces that leverage water droplets to clean themselves. While this ubiquitous self-cleaning process has substantial industrial promise, experiments have so far been unable to comprehend the underlying physics. With the aid of molecular simulations, here we rationalize and theoretically explain self-cleaning mechanisms by resolving the complex interplay between particle-droplet and particle-surface interactions, which originate at the nanoscale. We present a universal phase diagram that consolidates (a) observations from previous surface self-cleaning experiments conducted at micro-to-millimeter length scales and (b) our nanoscale particle-droplet simulations. Counterintuitively, our analysis shows that an upper limit for the radius of the droplet exists to remove contaminants of a particular size. We are now able to predict when and how particles of varying scale (from nano-to-micrometer) and adhesive strengths are removed from superhydrophobic surfaces.