Eutrophication Of Water Bodies Research Articles

"Needle" hidden in silk floss: Inactivation effect and mechanism of melamine sponge loaded bismuth oxide composite copper-metal organic framework (MS/Bi2O3@Cu-MOF) as floating photocatalyst on Microcystis aeruginosa

Photocatalytic technology showed significant potential for addressing the issue of cyanobacterial blooms resulting from eutrophication in bodies of water. However, the traditional powder materials were easy to agglomerate and settle, which led to the decrease of photocatalytic activity. The emergence of floating photocatalyst was important for the practical application of controlling harmful algal blooms. This study was based on the efficient powder photocatalyst bismuth oxide composite copper-metal organic framework (Bi2O3 @Cu-MOF), which was successfully loaded onto melamine sponge (MS) by sodium alginate immobilization to prepare a floating photocatalyst MS/Bi2O3 @Cu-MOF for the inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. When the capacity was 0.4 g (CA0.4), MS/Bi2O3 @Cu-MOF showed good photocatalytic activity, and the inactivation rate of M. aeruginosa reached 74.462% after 120 h. MS/Bi2O3 @Cu-MOF-CA0.4 showed a large specific surface area of 30.490 m2/g and an average pore size of 22.862 nm, belonging to mesoporous materials. After 120 h of treatment, the content of soluble protein in the MS/Bi2O3 @Cu-MOF-CA0.4 treatment group decreased to 0.365 mg/L, the content of chlorophyll a (chla) was 0.023 mg/L, the content of malondialdehyde (MDA) increased to 3.168 nmol/mgprot, and the contents of various antioxidant enzymes experienced drastic changes, first increasing and then decreasing. The photocatalytic process generated·OH and·O2-, which played key role in inactivating the algae cells. Additionally, the release of Cu2+ and adsorption of the material also contributed to the process.

Phosphorus Threshold for the Growth of Microcystis wesenbergii, Microcystis aeruginosa, and Chlorella vulgaris Based on the Monod Formula

The outbreak of algae in freshwater bodies poses an important threat to aquatic ecosystems, making finding an effective method for controlling algal blooms imperative. Numerous key factors influence algal bloom outbreaks, with nutrient levels in the water body being the decisive factor. Current research regarding the effect of nutrient levels on algal growth shows that phosphorus is a nutrient that influences algal blooms. Herein, we propose the concept of a modified Monod model for the relationship between algal specific growth rate and phosphorus concentration. Through this improved Monod model, we inferred that the phosphorus concentration at a specific growth rate of zero is the lower threshold of phosphorus concentration that limits algal growth and can effectively control algal outbreaks. This lower threshold is denoted as S′. On the basis of this concept, we designed algal growth experiments. Our results provided an equation that effectively describes the relationship between algal growth and nutrient concentration. When three algal species grow under phosphorus-limited conditions, the corresponding phosphorus concentrations at which they maintain a growth rate of 0 are 0.0565, 0.0386, and 0.0205 mg/L as reflected by the following order of their S′ values: Microcystis wesenbergii S′ < Microcystis aeruginosa S′ < Chlorella vulgaris S′. Furthermore, with the increase in phosphorus concentration, the growth of M. aeruginosa becomes faster than that of M. wesenbergii and C. vulgaris. Consequently, M. aeruginosa becomes the dominant population in the water, leading to its predominance in algal blooms. This situation explains the common occurrence of cyanobacterial blooms. Our findings provide a theoretical basis for regulating the concentration of phosphorus to control algal outbreaks. Therefore, our study is of great importance for controlling the eutrophication of water bodies.

Assessment of agricultural water protection strategies at a catchment scale: case of Finland

For decades, water quality monitoring programmes, agri-environment schemes and environmental permits for animal farms have targeted a decrease in agricultural loads. These have been supplemented with more recent policies related to nutrient recycling and a circular economy. However, eutrophication of surface water bodies remains a widespread problem. In this paper, we focus on the nutrient loading and recycling in the catchment of Eurajoki River, Finland. We statistically examine the generation of nutrient loading and its variation on a sub-catchment scale. We extend this examination to the factors behind the loading and estimate the impact of nutrient recycling on it. Our analysis reveals shortcomings in the availability and collection of data on the agricultural nutrient loadings and the parcel-specific data on the presence and application of manure and fertilisers. Nine sub-catchments were responsible for roughly half of the TP loading from the 46 sub-catchments studied. To reveal such hot spots and to better target agricultural water protection measures, we recommend short-term water quality sampling campaigns. Judging from our data, the rate of manure recycling is not high enough to reduce the regional P surplus to manageable levels. Therefore, we suggest facilitated collaboration between animal and crop farms to decrease the nutrient surplus. We also propose setting up a national database containing parcel-specific information, for example, on soil P content, manure and fertiliser application, agricultural practices and the presence of acid sulphate soils. We also suggest an independent soil fertility sampling to provide valid baseline soil P data for field parcels.

Homogenization of Functional Diversity of Rotifer Communities in Relation to Eutrophication in an Urban River of North China.

Rapid urbanization has triggered nutrient loading, which will inevitably lead to the eutrophication of water bodies and further affect the structure of aquatic populations. At present, eutrophication is a significant challenge for urban aquatic ecosystems. However, we still know little about the correlation between eutrophication in urban rivers and the composition of aquatic functional groups. The effects of urban river eutrophication on rotifer communities were investigated using an annual field survey of the Jinan section of the Xiaoqing River, a typical urban river in northern China. Using functional diversity (FD) and beta diversity, the spatiotemporal variation of the aquatic biological functional groups regime along stretches subject to different eutrophication was investigated. The functional evenness (FEve) and functional divergence (FDiv) decreased significantly with the increment of the trophic level index. Functional diversity exhibits an extremely low level across functional groups, with the richness difference (RichDiff) being an important component. The results indicate that eutrophication led to the homogenization of rotifer communities. This can be attributed to the functional homogenization of the rotifer community in the Jinan section of the Xiaoqing River. The observed homogenization may be due to widely distributed species complementing the ecological niche space. Our findings provide valuable information on the conservation of the urban river under the threat of eutrophication caused by high-intensity human activities.

Exploring shared adsorption capacity and thermodynamics for simultaneous removal of microcystin and phosphorus via green sorption media in eutrophic water

The recurrent events of harmful algal blooms due to an increase of nutrients in eutrophic water bodies have augmented concerns over the presence of cyanobacterial toxins, especially Microcystin. Microcystin-LR (MC-LR) is the most common cyanobacteria toxin, gaining focus in the literature for its effect on human health. The aim of this study is to investigate the simultaneous removal of MC-LR and phosphate via four green sorption media is the presence or absence of phosphorus or calcium ions and their shared adsorption capacity and thermodynamics to mimic eutrophic water condition in a karst environment (South Florida). The four green sorption media are known as: (1) CPS (clay, perlite, and sand), (2) ZIPGEM (Zero-valent-Iron and Perlite-Based Green Environmental Media), (3) BIPGEM-1 (Biochar-Zero-valent-Iron and Perlite-Based Green Environmental Media-1), and (4) BIPGEM-2 (Biochar-Zero-valent-Iron and Perlite-Based Green Environmental Media-2). Based on the MC-LR removal efficiency, BIPGEM-2 has the best performance, followed by BIPGEM-1, ZIPGEM, and CPS. In terms of simultaneous removal of phosphate ions and MC-LR, ZIPGEM achieves higher removals, ranging from 55 to 60%, followed by BIPGEM-2, BIPGEM-1, and CPS. The MC-LR adsorption capacity of BIPGEM-2 ranges from 16.9 to 29.49 μg·g−1 based on the Langmuir isotherm model under different influent conditions, whereas the MC-LR adsorption capacity of BIPGEM-1 in a dynamic environment is 1.19 μg·g−1 based on the Modified Dose Response model. The decrease in the adsorption capacity of BIPGEM-1 in a dynamic environment can be attributed to the presence of dissolved organic matter and inorganic ions, present in the influent water matrix. The influence of the water matrix is also observed in the isotherm studies because the presence of PO43− negatively impacts the removal efficiencies of MC-LR, whereas Ca2+ positively impacts the removal efficiencies of MC-LR. Similarly, the presence of MC-LR affects the PO43− adsorption capacity of the sorption media.

New insights into endocrine reproductive toxicity of Microcystis aeruginosa combined with ammonia exposure in zebrafish

The ecological risk posed by MCs-producing M. aeruginosa and elevated ammonia to fish in actual aquatic environments remains uncertain. To address this knowledge gap, we conducted simulations to investigate the endocrine-reproductive toxicity of prolonged exposure (45 d) to Microcystis aeruginosa (2 × 10^6 cells/mL) and 30 mg/L total ammonia nitrogen (TAN) in zebrafish under environmentally relevant conditions. Our results showed that exposure to M. aeruginosa significantly inhibited the body weight, increased gonadosomatic index (GSI), delayed oocyte development, and disrupted endocrine hormonal balance (reduced gonadotropin-releasing hormone (GnRH), and increased estradiol (E2) and testosterone (T)). Mechanistically, it should be attributed to the over-expression of hypothalamic-pituitary-gonadal-liver (HPGL) axis-related genes (cyp11a and cyp17) induced by M. aeruginosa. On the other hand, TAN exposure caused mild damage to zebrafish ovarian tissue and promoted an increase of T levels by inducing the upregulation of steroid hormone synthesis gene (3βhsd) expression in the ovary. It is worth noting that the dysregulation of E2/T ratio in zebrafish ovaries may be attributed to the inhibition of cyp19a1a by both M. aeruginosa and TAN. These results were further confirmed by changes in steroidogenic enzymes activities in the M. aeruginosa or TAN treated groups. Our findings indicated that exposure to M. aeruginosa and TAN had adverse impacts on the reproductive system of zebrafish. And the combined exposure of M. aeruginosa and TAN had more severe effects on the body weight, GSI, pathological changes, hormone levels and HPGL-axis related gene expression in female zebrafish. These results provide compelling evidence regarding the potential risks for reproductive health associated with M. aeruginosa and TAN in eutrophic water bodies experiencing M. aeruginosa blooms, and contribute to the development of effective strategies for monitoring and managing these toxins in aquatic ecosystems.

Optimization of the adsorption performance of herbal residues as lanthanide ion-modified carriers for phosphate by fly ash and its application

In order to mitigate the harmful effects of eutrophication in water bodies, the applications of lanthanum-modified materials for phosphate removal from wastewater have attracted much attention. Unlike conventional adsorbents, plant wastes usually have poor adsorption abilities and are difficult to be reused for desorption of phosphate due to their small pore sizes and ununiform loading of modified ions. In this paper, a composite adsorbent (LC-MM) was synthesized by hydrothermal treatment of waste traditional Chinese medical materials (MMs) with load of lanthanum carbonate and co-heating treatment with coal fly ash (CFA), which was applied to remove phosphate from water. The results showed that maximum adsorption capacity of LC-MM was 52 mg g−1, and the LC-MM showed appreciable adsorption capacity of phosphate for agricultural wastewater in the presence of complex interfering ions and for urban surface waters with low phosphate concentrations. Five adsorption-desorption cycles showed good reusability. The mechanism study showed that the La3+ ions were more uniformly distributed on the surface of the absorbents with the introduction of Fe3+, Al3+, Mg2+ and Ca2+ ions in CFA. The ligand exchange between phosphate and carbonate, the internal spherical complexation formed by lanthanum ion and phosphate, and surface chemical precipitation attachment are the main reasons why the adsorption capacity of LC-MM approached or even surpassed that of conventional lanthanum-modified adsorbents. In conclusions, this work proposed an effective method for the modification of plant materials.

Investigating the applicability of waste foam concrete for phosphorus recovery in real pig wastewater based on the effect of organic matter on the HAP crystallisation method

HAP crystallization use waste foam concrete as a calcium source, studied the impact of typical organic compounds in simulated pig wastewater on phosphorus recovery, and applied them to actual wastewater. Energy dispersive X-ray spectrometer(EDS) and SEM indicate: citric acid had a stronger inhibitory effect on crystallization compared to humic acid. Citric acid chelated Ca2+ ions, competing with crystallization ions and interfering with crystal nucleation. Humic acid hindered crystal growth through adsorption and ion exchange mechanisms. When citric acid and humic acid were added together, they competitively interacted, reducing the inhibition of phosphorus recovery. HAP crystallization alone reduced phosphorus content and turbidity in secondary pig wastewater, while combining 2 mL(5 g/L)PAM yielded favorable outcomes. Effluent phosphorus concentration was only 1.0 mg/L, with turbidity below 25. here was a noticeable reduction in Pseudomonas pathogenic bacteria from the Aspergillus phylum, along with a significant downward trend in the CL500_29_marine_group, which represents water body eutrophication. The combined method cost RMB 1.15 yuan/ton of water treated, a 26 % decrease compared to the original treatment plant. This method is suitable as an add-on unit for secondary pig wastewater treatment.

Aluminium dross waste utilization for phosphate removal and recovery from aqueous environment: Operational feasibility development

The need to minimize eutrophication in water bodies and the shortage of phosphate rock reserves has stimulated the search for sequestration and recovery of phosphate from alternative sources, including wastewater. In this study, aluminium dross (AD), a smelting industry waste/by-product, was converted to high-value material by encapsulation in calcium alginate (Ca-Alg) beads, viz. Ca-Alg-AD and utilized for adsorptive/uptake removal and phosphate recovery from an aqueous environment. Encapsulation of AD in alginate beads solves serious operational difficulties of using raw AD material directly due to density difference constraining efficient contact of AD with pollutants present in water and post-treatment recovery of AD material. The phosphate removal was evaluated in both batch and continuous flow operation modes. The batch adsorption study revealed 96.86% phosphate removal from 10 mg L−1 of initial phosphate concentration in 70 min of optimal contact time. Further, the phosphate removal potential of Ca-Alg-AD beads turned out to be independent of solution pH, with an average of 95.93 ± 1.40 % phosphate removal in the 2–9 pH range. The result reflects phosphate adsorption on Ca-Alg-AD beads following a second-order pseudo-kinetic model. Ca-Alg-AD beads-based adsorption followed Freundlich and Langmuir isotherm models. Further, a continuous packed bed column study revealed a total phosphate adsorption capacity of 1.089 mg g−1. The chemical composition, physical stability, and surface properties of Ca-Alg-AD beads were analyzed by means of state-of-the-art analytical techniques, such as Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetry/Differential Thermal Analysis (TG/DTA). These characterization techniques comprehend the mechanism and influence of surface properties and morphology on the phosphate adsorption behaviour, which induce the involvement of multiple mechanisms such as ligand complexation, ion exchange, and electrostatic attraction for phosphate adsorption on Ca-Alg-AD beads.

Cyanobacterial effects on an aquatic keystone grazer are reshaped by presence of the herbicide atrazine

Abstract As cyanobacterial blooms and herbicide pollution, which are often detected in eutrophic waters, can separately jeopardise zooplankton populations, there is an urgent and on‐going need to understand the strength and direction of their interactive effects. This is a crucial step toward realistic risk‐evaluation of agricultural pollution in eutrophic waterbodies. In this study, we evaluated how the herbicide, atrazine (ATZ), alters the effects of cyanobacterial food on the zooplankter, Daphnia magna. We found survival time of Daphnia decreased with increasing amounts of Microcystis in their diets, and the magnitude of this cyanobacterial effect was independent of ATZ. In contrast, ATZ exposure triggered faster growth and larger body size in Daphnia fed diets containing Microcystis compared to those fed the good‐food diet. Although toxic Microcystis reduced the overall reproductive output of Daphnia, the presence of ATZ, regardless of the type of food treatment, exhibited a masking effect by further significantly decreasing Daphnia's overall reproductive output, resulting in a low level of reproduction. Finally, we found an expression trade‐off at the molecular scale between growth and reproduction genes on one side, and antioxidation gene on the other, which could account in part for ATZ's influence on Microcystis toxicity to Daphnia at maturation stage. These results demonstrated that ATZ can reshape Daphnia's responses to Microcystis, predominantly with effects on growth and reproductive traits. These trait‐dependent responses were found to be closely linked to the regulation of key metabolic pathways. Collectively, our study enhances current knowledge regarding the potential interaction between fundamental trophic levels in cyanobacteria‐dominated lakes around farmlands, and is helpful to achieve more realistic environmental risk management of agricultural pollution in eutrophic waterbodies.

Simultaneous removal of nitrogen and phosphorus nutrients from secondary effluent by magnetic resin containing two types of quaternary ammonium adsorption sites: Preparation, characterization, and application

The direct discharge of secondary effluent (SE) from wastewater treatment plants without proper nitrogen and phosphorus treatments can result in the eutrophication of landscape water bodies. The primary objective of advanced treatment should focus on the removal of NO3− and PO43− as the optimal approach. In this study, magnetic resin microspheres known as MGE (derived from the initials of the three organic monomers used, namely methyl methacrylate, glycidyl methacrylate, and 3,4-epoxy-1-butene) were successfully prepared through suspension polymerization. MGE incorporated two types of sites specifically designed for the removal of anionic nitrogen and phosphorus nutrients. The removal of NO3−, PO43−, and humic acid (HA) by MGE fit well with the pseudo-second-order kinetic and Freundlich adsorption isotherm models (R2 = 0.884–0.993 and 0.918–0.969, respectively). The removal efficiencies of ultraviolet absorbance at 254 nm, total nitrogen, total phosphorus, NO3−, PO43−, and total fluorescence in SE by MGE were 50.4 %, 20.9 %, 27.1 %, 21.5 %, 30.2 %, and 42.0 %, respectively, which were significantly higher than those achieved by commercially available MIEX® and D201. The molecular dynamic simulation results indicated that the increased removal of NH4+ by resin after adsorption of HA can be attributed to the aggregation effect of HA and NH4+ caused by H-bonds. The nitrogen and phosphorus indicators of the MGE effluent met the GB/T 18921-2019 water quality standard for scenic environmental use in China. MGE exhibited exceptional adsorption capacity and rapid achievement of adsorption equilibrium, making it a potential adsorbent for the removal of anionic nitrogen and phosphorus nutrients in engineering applications.

Enriched microbial fuel cells; Enhancing anode fillers to purify eutrophic water

Microbial Fuel Cells (MFCs) play a crucial role in both contaminant removal and energy generation. This study focuses on developing a novel anode material composed of Poly3-hydroxybutyrate-co-3‑hydroxy, activated carbon, pyrite, and sponge iron particles. The aim is to effectively remove various pollutants, including nitrite-nitrogen, ammonium-nitrogen, nitrate-nitrogen, total inorganic nitrogen, algae, chemical oxygen demand and total phosphorus while generating bioelectricity. The MFC design involves connecting the anode carbon felt and cathode wire using externally insulated titanium, along with a fixed resistance. The anaerobic reactor column is filled with different proportions of the four particles. The results show that total inorganic nitrogen (TIN) removal rates are impressive, with 93 % in Box 2 (B2), 91 % in Box 3 (B3), 86 % in Box 1 (B1), and 66 % in Box 4 (B4). Additionally, the enhanced anode material achieved a high-power output of 959.9 mW/m3 and a current density of 6.989 A/m3. In conclusion, this study demonstrates the potential of the enriched bio-bed structure for purifying eutrophic water bodies, making it a promising method for contaminant removal and energy generation.

Biodegradation of microcystin using free and alginate-immobilized Stenotrophomonas geniculate DMC-X3 bacterium

The eutrophication of water bodies and global warming have led to frequent cyanobacterial blooms, producing large quantities of algal toxins, which are released into water bodies, posing a threat to human health. Among known algal toxins, microcystin (MC) is the most harmful and most commonly detected. Because of its stable chemical structure, it is difficult to degrade MC though chemical and physical methods. Hence, effectively removing MC from water and ensuring water safety have become urgent issues. In this study, strain DMC-X3, which could rapidly and efficiently degrade MC, was isolated from a reservoir affected by a Microcystis aeruginosa bloom and identified as Stenotrophomonas geniculate. Inoculated at OD600 = 0.1, strain DMC-X3 degraded 70 % of 1000 μg/L MC in 24 h, and over 90 % within 48 h. When the inoculation density was increased to OD600 = 0.35, this bacterial strain completely degraded 1000 μg/L MC in 16 h and 5000 μg/L MC in 96 h. DMC-X3 maintained its MC degradation ability under the environmental conditions of pH 5–11 and 15–35 °C. After 60 d of storage at room temperature, DMC-X3 embedded and immobilized on sodium alginate pellets showed 90 % degradation of 200 μg/L MC in 48 h, and the pellets could be used for at least three cycles. Sustained-release pellets made by embedding and immobilizing both the degradation bacteria DMC-X3 and algicidal substance prodigiosin on sodium alginate effectively eradicated M. aeruginosa cells and degraded MC, promising a good application prospect in controlling M. aeruginosa blooms.

Assessment of pathogen removal efficiency of vertical flow constructed wetland treating septage

Septage refers to the semi-liquid waste material that accumulates in septic tanks and other onsite sanitation systems. It is composed of a complex mixture of human excreta, wastewater, and various solid particles. Septage is a potential source of water pollution owing to presence of high organic content, significant pathogen concentrations, and a range of nutrients like nitrogen and phosphorus. The harmful impacts of septage pollution poses significant risks to public health through the contamination of drinking water sources, eutrophication of water bodies and spread of water borne diseases. Conventional septage treatment technologies often face limitations such as high operational costs, energy requirements, and the need for extensive infrastructure. Therefore, with an aim to treat septage through an alternative cost effective and energy-efficient technology, a laboratory-scale constructed wetland (CW) system (0.99 m2) consisting of a sludge drying bed and a vertical flow wetland bed was utilized for the treatment of septage. The sludge drying bed and vertical flow beds were connected in series and filled with a combination of gravel with varying sizes (ranging from 5 to 40 mm) and washed sand. Canna indica plants were cultivated on both beds to facilitate phytoremediation process. The system was operated with intermittent dosing of 30 Ltrs of septage every day for 2 months. The HRT of the system was fixed at 48 h. The average inlet loads of Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS) were measured as 150 ± 65.7 g m−2 day−1, 713 ± 443.9 g m−2 day−1, and 309 ± 66.3 g m−2 day−1, respectively. After treatment, the final effluent had an average load of 6 g m−2 day−1 for BOD5, 15 g m−2 day−1 for COD, and 51 g m−2 day−1 for TSS, indicating that the CW system achieved an average removal efficiency of 88% for BOD, 87% for COD, and 65% for TSS. The average load of total coliforms and helminthes eggs in the influent was recorded as 4 × 108 Colony-Forming Units (CFU) m−2 day−1 and 3 × 107 eggs m−2 day−1, respectively. However, the CW system demonstrated significant effectiveness in reducing microbial contamination, with an average removal efficiency of 99% for both total coliforms and helminthes eggs. The vertical flow constructed wetland system, equipped with pretreatment by sludge drying bed, has proven to be efficient in treatment of septage.

One health implications of fur farming

Fur farming involves the captive-breeding, rearing, and killing of between 85 – 100 million animals annually for their pelts. The purpose of this report is to summarise key areas of significance and concern regarding fur farming, and discuss these matters and their one-health considerations. We conducted primary literature searches using Google Scholar and PubMed that focused on issues of animal welfare, zoonoses and public health, and environmental impacts of fur farming, and examined 280 reports. We identified that at least 15 species are farmed for fur across at least 19 countries. We found 16 categories of animal welfare concern (e.g., deprivation, stress, abnormal behaviours, insanitary conditions, forced obesity, and high morbidity and mortality), 18 reported endemic pathogens and diseases with confirmed or potential zoonotic and cross-species implications (e.g., bacterial n = 6, viral n = 5, and parasitic n = 7), and four main categories of environmental concern (e.g., greenhouse gas emissions, invasive alien species, toxic chemicals, and eutrophication) associated with fur farming. Despite numerous efforts to systematically monitor and control animal welfare at fur farms, practices continue to fail to meet normal scientific principles and models used in other animal welfare situations. In our view, limited available data does not currently indicate that fur farms are major sources of zoonotic epidemics and pandemics. The environmental problems caused by fur farming are significant, and relate mainly to invasive species, toxic chemical release and eutrophication of water bodies. We offer some recommendations for monitoring and controlling particular fur farming practices, in line with many governments and other investigators we conclude that inherent problems are essentially unresolvable and advocate complete prohibitions on the sector.

Emerging algal organic matter from simulated on-line chemical cleaning of ultrafiltration membranes treating algae-containing water

Massive reproduction of algae due to the eutrophication of water body poses a new challenge to the water ecosystem. Despite ultrafiltration (UF) acting as an effective method to treat algae-containing waters, on-line chemical cleaning is frequently utilized to sustain the permeability of UF membranes. However, little attention is currently paid on the side-effects of practical on-line chemical cleaning on aqueous environments. Therefore, this work evaluated the generation of algae organic matter triggered by diverse membrane cleaning reagents (i.e., HCl, NaOH, NaClO, SDS and CA), and their subsequent fate in terms of biodegradation and membrane retention. The results indicated that NaOH, HCl and NaClO caused serious damage and lysis of algal cells, leading to the significant release of dissolved organic matter (DOM), while CA and SDS induced negligible DOM release. The occurrence of DOM release was able to cause extra biofouling, thus deteriorating the UF permeability. Furthermore, DOM was characterized in terms of three molecular weight ranges, i.e., high molecular weight (HMW, > 3400 Da), medium molecular weight (MMW, 150–3400 Da), and low molecular weight (LMW, <150 Da). Protein-related substances in the range of HMW and MMW were primarily produced under HCl and NaOH exposures. In contrast, NaClO led to an obvious release of humic-like materials with MMW. During the next round of UF operation, roughly 17 % to 31 % of these released DOM could be removed by via the joint actions of suspended algae biodegradation and fouling layer retention. Nevertheless, roughly 69 % to 83 % of these produced DOM eventually entered into the UF permeate, resulting in the deterioration of permeate quality. Consequently, the detailed mechanisms of DOM generation and subsequent removal by UF were proposed, which re-examined the origins of emerging contaminants in aqueous environment and shed new light on the strategies to ameliorate current practice of on-line membrane chemical cleaning.

Dependence of element composition of bile of freshwater and marine fishes on some abiotic and biotic factors

IntroductionThe elemental composition and physical properties of fish bile is a very important marker for ecotoxicological and physiological studies as bile is able to accumulate elements from environmental compartments. In the present study we focused on the effects of long term (seasons and years) and spatial distance (different water bodies) as well as other biotic (feeding habits, fish species, gut morphology) and abiotic (water salinity) factors on element composition of bile of 429 individuals belonging to 22 forms/species of fishes.MethodsElement composition was determined using an inductively coupled plasma optical emission spectrometry. The fishes were analyzed from one marine (the Kandalaksha Gulf of the White Sea), two freshwater oligotrophic (Teletskoye and Baunt lakes), and one freshwater eutrophic water body (Chany Lake). In parallel, we have estimated the volume and density of bile from the same fishes using an automatic pipette and electronic balance.Results and discussionBased on fish bile density and volume data, we hypothesize that gastric fish species (those fishes that have a stomach) require a low volume of bile, but with higher density if compared to agastric fish species (those lacking a stomach) that mainly possessed large volumes of bile, but with a lower density. We have found that the concentrations of the following Na, K, Ca, Mg, S, P (major elements) and Al, Cu, Fe, Sr, Zn (trace elements) were the highest among the 28 elements studied. There were significant findings to contribute to a better understanding of the physiology of bile. First, we have determined the conditions formed in a water body in a given year (season) are more important for element composition of fish bile rather than other tested factors (feeding habits, gut morphology, etc.). Second, the feeding habits of fishes (carnivorous compared to non-carnivorous) had a significant effect based on differences among several elements. Third, the clear distinction between marine and freshwater fishes was found only for K and Na. Understanding which elements are produced as part of waste elimination and those that are present as a consequence of vital biological functions could improve the ecotoxicological study of bile as a marker of heavy metal contamination.

Magnetically recyclable Cu2+ doped Fe3O4@biochar for in-situ inactivation of Microcystis aeruginosa: Performance and reusability

Harmful cyanobacterial blooms in eutrophic water bodies have frequently occurred worldwide and become a major environmental concern. Therefore, it is imperative to develop a stable and efficient algaecide to solve this issue. In this study, our purpose was to investigate the efficacy and mechanism of a newly developed Cu2+ doped Fe3O4@Biochar magnetic composite (Cu-Mag-BC) in in-situ inactivation of Microcystis aeruginosa (M. aeruginosa). We successfully synthesized the Cu-Mag-BC by coating Cu2+ onto Fe3O4@Biochar. Cu-Mag-BC exhibited superparamagnetic behavior and was uniformly impregnated by Cu2+. Cu-Mag-BC (5 mg/L), rapidly inactivated chlorophyll-a (Chl-a) in M. aeruginosa with low Fe and Cu leaching, during which time the OD264 value and malondialdehyde (MDA) content increased, while the activities of superoxide dismutase (SOD) and catalase (CAT) first increased and then decreased, due to oxidative stress induced by over-generated reactive oxygen species (ROS). Quantitative results showed that ·O2− and ·OH were the main ROS species produced from Cu-Mag-BC. Inactivation efficiency was maintained at approximately 80 % after three consecutive runs and total Chl-a removal efficiency reached 2.84 g/g, indicating good reusability and stability. A possible inactivation mechanism is proposed; amino groups and adipose chain were the primary oxidation sites. Thus, Cu-Mag-BC shows potential as a candidate for simultaneously inactivating harmful cyanobacteria and preventing secondary pollution.

Visualization of microcystin-LR and sulfides in plateau lakes

In eutrophic water bodies, sulfides are closely related to the growth of cyanobacteria and the production of microcystin-LR (MC-LR). To date, the underlying interaction mechanism between a sulfides and MC-LR remains controversial. Thus, visually presenting the distribution characteristics of sulfides and MC-LR in contaminated water is crucial. Here, we propose a novel and expeditious practical approach, utilizing fluorescence probe technology, to assess the distribution characteristics of MC-LR and sulfur in natural lakes. We have developed novel probes, pib2, to detect HSO3– and HS–, and pib18, to simultaneously identify MC-LR and sulfides. Through correlation analysis of fluorescence data and physicochemical indicators at sampling points, it is found that fluorescence data has good correlation with sulfides and MC-LR, and speculated that pib2 and pib18 may be able to detect sulfides and MC-LR in lakes. Using this method, we rapidly obtained the distribution of MC-LR and sulfur in Qilu and Erhai Lakes. Notably, for the first time, we rapidly displayed the distributions of sulfides and MC-LR across lakes by the fluorescent probe technology.

Detection and mapping of water and chlorophyll-a spread using Sentinel-2 satellite imagery for water quality assessment of inland water bodies.

Water quality monitoring of reservoirs is currently a significant challenge in the tropical regions of the world due to limited monitoring stations and hydrological data. Remote sensing techniques have proven to be a powerful tool for continuous real-time monitoring and assessment of tropical reservoirs water quality. Although many studies have detected chlorophyll-a (Chl-a) concentrations as a proxy to represent nutrient contamination, using Sentinel 2 for eutrophic or hypereutrophic inland water bodies, mainly reservoirs, minimal efforts have been made for oligotrophic and mesotrophic reservoirs. The present study aimed to develop a modeling framework to map and estimate spatio-temporal variability of Chl-a levels and associated water spread using the Modified Normalized Difference Water Index (MNDWI) and Maximum Chlorophyll Index (MCI). Moreover, the impact of land use/land cover type of the contributing watershed in the oligo-mesotrophic reservoir, Bhadra (tropical reservoir), for 2018 and 2019 using Sentinel 2 satellite data was analyzed. The results show that the water spread area was higher in the post-monsoon months and lower in the summer months. This was further validated by the correlation with reservoir storage, which showed a strong relationship (R2 = 0.97, 2018; R2 = 0.93, 2019). The estimated Chl-a spread was higher in the winter season, because the reservoir catchment was dominated by deciduous forest, producing a large amount of leaf litter in tropical regions, which leads to an increase in the level of Chl-a. It was found that Chl-a spread in the reservoir, specifically at the inlet sources and near agricultural land practices (western parts of the Bhadra reservoir). Based on the findings of this study, the MCI spectral index derived from Sentinel 2 data can be used to accurately map the spread of Chl-a in diverse water bodies, thereby offering a robust scientific basis for effective reservoir management.