High Turbidity Research Articles

Design parameters of water intake chambers on water supply channels of pumping stations

The research is devoted to improving the working conditions of chamber water intakes of pumping stations (PS) on water supply channels, which is one of the main factors determining the efficiency of operation of pumping units and stations. An analysis of the current state of the operating conditions of chamber water intakes according to field surveys and literary sources shows that the dimensions of the water intake chambers were assigned based on the minimum energy loss in the suction pipeline of the pump, which, in conditions of high turbidity of water, leads to siltation and complicates the operation of pumping stations. When the water intake chambers are silted, its hydraulic resistance increases, air vortex funnels are formed, the water supply of the pump decreases and the likelihood of cavitation phenomena increases. A significant amount of work has been devoted to the issues of improving the hydraulic characteristics of the flow in the fore chamber and water intake chambers. Therefore, without duplicating them, we conducted research to establish the effect of silting of the chambers on the value of the hydraulic resistance of the suction pipeline and to develop measures to improve the hydraulic characteristics of the intake chamber under conditions of operation in a suspension-carrying flow. To solve the problem, a laboratory stand was made that simulates hydraulic processes in natural conditions based on modeling methods, taking into account the preservation of the constancy of the main similarity criteria.

Assessment of the Impacts of Converting Natural Wetlands to Agricultural Farms. Case of Nyabugogo, Kigali City, Rwanda

The assessment of the impacts of converting natural wetlands to agricultural farms in Nyabugogo wetland was the main objective for this research. Considering the efficiency of agricultural activities management, operation and their maintenance in Kigali is essential to reduce the increasing environmental pollution, to raise production and to search for a sustainable method of environmental conservation, this research assesses the pollutant removal efficiency of agriculture such as crops and animal residues in order to enhance the sustainable agriculture development mainly physico-chemical characteristics and some biological characteristics and based on the preliminary assessment and review of existing literature on agriculture management systems for water resources and other environmental conservation concerns in Kigali, the research aims at contributing to the search of an appropriate agriculture management that is more efficient in terms of the increase in productivity, hence contributing to environmental sustainability. Six sampling sites were chosen in Nyabugogo wetland that is Nyabugogo, Karuruma, Kabuye (2 destinations), and Nyacyonga (2 destinations). Nyabugogo and Karuruma in the rural area, and Nyacyonga in the urban area, were chosen for the investigation of fecal coliforms. On the two first locations, Nyabugogo (80 cfu/100ml) and Karuruma (40 cfu/100ml), the study found low but not insignificant results. This is related to the dispersion of habitation in rural areas. Total Dissolved Solid (TDS) ranged from 178.1 mg/l to 179.9 mg/l at Site 1 (dry season) and subsequent test (rainy season) results ranged from 178 to 200 mg/l. The results showed different TDS in different test areas. The TDS was as low as 145.4 mg/l in the surface water of SP4 and as high as 179.9 mg/l in SP1, and in the second survey, the minimum value was 140.3 mg/l and the maximum value was 285 mg/l in SP3. Because the high turbidity levels seen along the river, in the Nyabugogo catchment, erosion protection measures should be implemented, including the use of terraces where there is agricultural activity and tree plantations, particularly at Nyabugogo sites. As a result, the Nyabugogo Riverbanks must be preserved. It would cut down on the quantity of sediment that ends up in waterways.

Evaluation of the Feasibility of Foam Glass as Filter Media in Rain Garden

Objectives:In order to recycle and resource waste glass, the feasibility of foam glass as filter media was evaluated, and column experiments using foam glass media were conducted to confirm the applicability as filter media in rain garden. Through this experiment, various design factors to be considered can be derived in application of foam glass media in the rain garden.Methods:Sieve analysis and SEM/EDS analysis were conducted to confirm the physicochemical properties of the foam glass. Column experiments filled with only foam glass and mixtures of sand and foam glass were conducted to simulate rain garden to evaluate the removal efficiency of suspended solids and turbidity using the foam glass media, head difference (<i>Δh</i>) and hydraulic conductivity (<i>K</i>) changes, and calculation of filtered suspended solids loading using both discrete and cumulative mass approach. Finally, comparison of filtration performance with various filter media used in LID facilities was performed to evaluate the feasibility of foam glass media in rain garden.Results and Discussion:Since foam glass media has a lower density than water, homogeneous particle size, and smooth surface with pores of various sizes, foam glass media effectively induces internal capture and external adsorption of suspended solids. Foam glass media has been applied to high suspended solids and turbidity removal efficiency. As the suspended solids inflow load increased, clogging occurred in the pores and the removal efficiency gradually decreased, but the foam glass media with lower density than water was continuously disturbed and rearranged due to the head difference energy, and some clogging were alleviated by rearrangement of pores and channels. The load of suspended solids in precipitated, adsorbed, and retained on the foam glass was calculated using the effluent sample (discrete) collected at regular time intervals and the continuously accumulated sample (cumulative) from the output. The filtered suspended solids load calculated using the cumulative mass approach was higher due to the estimation of the amounts of suspended solids remaining in the filtration column is lower because the samples (discrete) collected at regular time intervals from the output do not reflect the amount of suspended solids that change over time. Thus, the amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples. Finally, when comparing the removal efficiency with other filter media, foam glass can be used as excellent filter media with higher removal efficiency and greater lifespan.Conclusion:Foam glass media with smooth surface, pores of various sizes, and lower density than water can rearrange and regenerate pores to alleviate some clogging, resulting in high suspended solids and turbidity removal efficiency for a long period of time. Considering that the amount of suspended solids filtered is determined by various factors such as particle size and distribution, porosity, depth, linear velocity, and inflow load of the suspended solids, the feasibility test using foam glass media through long-term field experiments is warranted. The amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples.

Assessment of the current trophic state and water quality of Lake Naivasha, Kenya using multivariate techniques

AbstractLake Naivasha is a tropical freshwater body in Kenya, providing a source of livelihoods to the surrounding communities. The lake ecosystem, however, has become degraded over time because of increasing pollutant loads from multiple sources, including human settlements and agricultural and surface runoff in its basin. Thus, it is vital to study the lake's water quality to determine its current status to inform appropriate management measures. Accordingly, the present study analysed water quality parameters and the trophic state of Lake Naivasha on the basis of water samples collected at eight sampling sites during the dry and wet seasons from December 2019 to May 2020. The physico‐chemical parameters were measured in situ, while nutrients were analysed in the laboratory. The results indicated high turbidity, total nitrogen (TN), ammonium‐nitrogen (NH4+‐N), nitrate‐N (NO3‐N) and total phosphorus (TP) levels during the wet season, and at the Malewa and Karati River mouths, while pH, electrical conductivity (EC) and chlorophyll‐a values were relatively high during the dry season. The water temperature and dissolved oxygen (DO) concentration, however, did not vary between sampling sites or seasons. Cluster analysis (CA) classified the sites into three clusters based on water quality spatial and seasonal variations. Cluster 1 was comprised of the isolated region (Crescent), while clusters 2 and 3 mainly comprised sites sampled during wet and dry seasons, respectively. Similarly, principal component analysis (PCA) revealed spatial and seasonal physico‐chemical variations, indicating nutrient parameters (TN, TP, NO3‐N and NH4+‐N), pH, Secchi depth and turbidity are the major variables influencing water quality variations. Furthermore, factor analysis (FA) identified nutrients, sediment and organic sources as the main lake pollution sources. The trophic state index (TSI = 60–72) indicated the lake varied from a eutrophic to hypertrophic state during the study period. The lake was found to be more eutrophic than reported in previous studies, indicating a progressive deterioration of its water quality. The overall results demonstrated some of the sampling sites in the lake are heavily contaminated with pollutants from various sources, attributable primarily to land use patterns and anthropogenic activities. The results of the present study are useful to inform decisions regarding management of the lake water quality.

Innovative Remote Sensing Identification of Cyanobacterial Blooms Inspired from Pseudo Water Color

The identification and monitoring of cyanobacterial blooms (CBs) is critical for ensuring water security. However, traditional methods are time-consuming and labor-intensive and are not ideal for large-scale monitoring. In operational monitoring, the existing remote sensing methods are also not ideal due to complex surface features, unstable models, and poor robustness thresholds. Here, a novel algorithm, the pseudo-Forel-Ule index (P-FUI), is developed and validated to identify cyanobacterial blooms based on Terra MODIS, Landsat-8 OLI, Sentinel-2 MSI, and Sentinel-3 OLCI sensors. First, three parameters of P-FUI, that is, brightness Y, saturation s, and hue angle α, were calculated based on remote sensing reflectance. Then, the robustness thresholds of the parameters were determined by statistical analysis for a frequency distribution histogram. We validated the accuracy of our approach using high-spatial-resolution satellite data with the aid of field investigations. Considerable results were obtained by using water color differences directly. The overall classification accuracy is more than 93.76%, and the user’s accuracy and producer’s accuracy are more than 94.60% and 94.00%, respectively, with a kappa coefficient of 0.91. The identified cyanobacterial blooms’ spatial distribution with high, medium, and low intensity produced consistent results compared to those based on satellite data. Impact factors were also discussed, and the algorithm was shown to be tolerant of perturbations by clouds and high turbidity. This new approach enables operational monitoring of cyanobacterial blooms in eutrophic lakes.

Monitoring of River Estuary Turbidity using Satellite Image Analysis and Its Correlation to Rainfall (A Case Study of the Krueng River in Aceh, Indonesia)

Activities along the Krueng Aceh river such as port activities, fisheries, ship breeding, tourist attractions, market activities and settlements cause a lot of domestic waste in the environment around the river and affect river clarity and increase the concentration of turbidity. High turbidity in rivers can affect the entry of light into the waters because light has an important role in the photosynthesis process. The method of monitoring water quality can be done by remote sensing because it has several advantages such as being able to carry out measurements on a larger scale for a long time, relatively quickly, and reducing the amount of costs incurred. Monitoring the Krueng Aceh River is carried out using remote sensing technology using Sentinel-2 imagery. This study aims to obtain the value of the distribution of turbidity by analyzing satellite imagery and its correlation with rainfall, and to determine the value of the distribution of turbidity, Total Suspended Solid (TSS), Total Dissolved Solid (TDS), and Power of Hydrogen (pH) in the Krueng Aceh River. The results showed that sentinel-2 image analysis got the lowest turbidity on September 6, 2021, which was -0.992424, and the highest on October 5, 2019 which was 0.248641. The distribution of water quality is known to have the highest turbidity concentration obtained at sampling location point 1, which was 107.9 NTU. The highest concentration of TSS was found at sampling locations 1, 4, and 7, which was 400 mg/l. The highest TDS concentration was found at point location 1, which was 1,413 mg/l. The pH concentration at the Krueng Aceh River sampling location has met the quality standards set in PP No. 82 of 2021

Monitoring threatened species with environmental DNA and open ecological data: Local distribution and habitat preferences of scalloped hammerhead sharks (Sphyrna lewini)

Evidence-based environmental management is urgently required to enable progress towards global conservation commitments. To fill large-scale biodiversity knowledge gaps, governments, organisations and communities must adopt innovative ecological monitoring techniques. The emergence of environmental DNA (eDNA) survey methods, as well as the increased availability of in situ ocean observation and satellite remote sensing data, offers opportunities to overcome significant logistic and financial challenges previously associated with traditional biodiversity monitoring. Here, a 1.5 year-long eDNA survey reveals the spatial and temporal presence of ‘critically endangered’ scalloped hammerhead sharks (Sphyrna lewini) in Apra Harbor, Guam. The survey confirms the presence of S. lewini in the region, and shows eDNA detections are most frequent at the beginning of the dry season, in January. Combined analysis of eDNA results with open (freely available) ecological data identifies that S. lewini presence is associated with increases in water velocity, turbidity and wind direction, as well as decreases in temperature and wind speed. Additionally, the data indicate S. lewini are most frequent at sampling sites characterised by high turbidity, shallow depths, and large distances from the harbor entrance. Information on local distribution and habitat preferences generated here is fundamental to the establishment of management protocols that aim to minimise negative anthropogenic impacts on S. lewini in Apra Harbor. The work provides an example of contemporary marine monitoring for the efficient generation of biodiversity data; an approach that will enable informed management decisions and help to reduce the risk and rate of species extinctions throughout the next decade.

Microalgal treatment of high-nutrient wastewater using twin layer cultivation system

High-nutrient wastewater such as solid waste leachate, anaerobic digestate, and poultry wastewater has high turbidity, dark color, and high concentration of nutrients. Therefore, it cannot be treated using microalgae directly and needs to be diluted prior to treatment. This study assessed the potential of Tetradesmus obliquus for the treatment of high-nutrient wastewater using a twin-layer cultivation system. Prior to microalgal treatment of high-nutrient wastewater, it was diluted by wetland treated municipal wastewater. Results showed Tetradesmus obliquus can efficiently treat and grow in all types of diluted high-nutrient wastewater using a twin-layer cultivation system. However, microalgae cultivated in poultry wastewater gave the highest average biomass productivity and carbon capture rate of 5.13 and 2.51 g m−2 d−1 respectively. Maximum nutrient removal rate of 6.15, 7.64, and 0.69 mg L−1 d−1 for NH4+-N, TKN, and PO4−3-P were achieved from poultry wastewater. In contrast, the highest lipid content of 30.3% was observed in microalgae cultivated in municipal wastewater due to its low nitrogen content. Thus, successful microalgal treatment of different high-nutrient wastewater can be performed through its prior dilution.

A novel remote sensing index for brine shrimp (Artemia) slick detection in salt lakes

Artemia (brine shrimp) are a widely distributed zooplankton in inland salt lakes and artificial ponds throughout the tropical, subtropical, and temperate zones. Notably, they are of great importance to fishery production and salt lake ecosystem health. Recently, Artemia resources have been threatened by habitat deterioration and overfishing, which mandate adequate monitoring; however, advanced methods for detecting Artemia from remote sensing images have rarely been discussed. Accordingly, this study explored the possibility of detecting the adult Artemia (Artemia) slicks using multispectral optical sensors by analyzing their unique aggregation patterns and consistent optical properties. After measuring Artemia spectra in the field, reflectance troughs were observed at ∼431 nm and ∼ 560 nm, which were deemed likely related to the absorption of β-carotene and heme, respectively, resulting in their reddish color. These characteristics could also be used to differentiate Artemia from other confounding features, including clean water and chlorophyll-a (Chl-a)- or suspended particulate matter (SPM)- dominated water. Based on these spectral signatures, a brine shrimp index (BSI) was developed using the difference between the reflectance at NIR band and a linear baseline between green and SWIR1 bands of Landsat-8 Operational Land Imager (OLI) imagery. Further, a BSI-based Artemia slick pixel extraction method was proposed. Using observation geometry information in conjunction with the BSI value of entire lakes, the BSI thresholds for the Artemia-containing pixels were automatically determined, and > 80% overall accuracy was achieved. The index performance was affected by the presence of residual cloud shadows, high water turbidity, and mixed pixels with low Artemia density. Moreover, BSI values were found to be relatively insensitive to atmospheric signals. It was shown here that the BSI detection limit was >0.53% Artemia subpixel coverage under clean water conditions; whereas a higher coverage was required to separate Artemia from Chl-a- or SPM- dominated water. The mean absolute percentage difference of BSI values calculated from Rayleigh-corrected and top-of-atmosphere (TOA) reflectance was <4% compared with surface reflectance derived BSI, and the relative difference in coverage area was < ±10%. Lastly, time series analyses of Lake Aibi in northwest China and the Great Salt Lake in North America revealed that the annual areal coverage estimation of Artemia slicks based on BSI was a positive indicator of Artemia harvesting, which can facilitate the Artemia resource management.

Macronutrients, iron and humic substances summer cycling over the extended continental shelf of the South Brazil Bight

We surveyed macronutrients and dissolved iron (DFe) concentrations and speciation in a transect over the shelf of the South Brazil Bight (SBB) at Santa Marta Grande Cape (SE Brazil) during a coastal downwelling episode. Driven by dominant NE winds, coastal downwelling is a common feature during the austral summer and force after water convergence, with contribution of internal wave breaking at the shelf edge, upwelling of macronutrients into the nutrient-depleted waters of the southbound Brazil Current at ~100 km from the coastline. As a result, we found a plume of high turbidity that reached the euphotic layer, a deepening of the silicate, nitrate, and phosphate isolines over the shelf and a bulging of the nitrate and phosphate isolines over the shelf edge and the slope. Our first measurements of DFe concentration and speciation in the area revealed that against prior findings in other coastal areas, macronutrients, DFe, and iron ligand cycles were disentangled. Higher DFe concentrations were often found at the surface indicating aerial deposition. Secondary DFe maxima over the sediment-water interface and in the upwelled plume indicated DFe fluxes from the sediment and from resuspended instable colloids. Iron ligand concentrations were higher than DFe concentrations in most stations with a clear land-to-ocean gradient. Subtraction of HS iron ligands revealed that except in upwelled water, the bulk of surface ligands was the result of local biological processes. The analysis of the concentrations of Fe-HS complexes showed that the contribution of HS to DFe was dominant in upwelled waters, significant in waters close to the coast, but nearly negligible in the rest of the studied area. We hypothesize that the injection of iron-humic complexes into the euphotic layer during summer upwelling episodes is the key to understanding the persistent high chlorophyll meanders found over the shelf edge of the SBB coast.

Assessment of heavy metal pollution in seawater, benthic flora and fauna and their ability to survive under stressors along the northern Red Sea, Egypt

The purpose of this study was to assess the north coasts of the Egyptian Red Sea, including Ras Gharieb, Hurghada, Safaga and Qusier, by evaluating the heavy metal pollution in seawater and benthic flora and fauna in the winter and summer of 2016. The concentrations of heavy metals (Fe, Mn, Zn, Cu, Ni, Cd and Pb) were analysed with an atomic absorption spectrophotometer. The results revealed that the Fe levels in the seawater ranged from 7.86 and 27.95 µg l-1, while the Zn concentrations fell between 1.83 and 5.63 µg l-1. In contrast, the recorded values of Mn, Cu, Ni, Pb and Cd in the seawater were minimal at the study sites. Regarding the biota samples, Porifera species were more adaptable than others to an accumulation of most metals in their tissues. Furthermore, seaweeds and seagrasses demonstrated remarkable adaptation in highly polluted regions, especially those with high turbidity, landfilling, sedimentation and high eutrophication rates – much more than the benthic fauna. Our research highlights the critical need for strict regulation of metal emissions in these coastal regions.

Restrictions in water treatment by conventional processes (coagulation, flocculation, and sand-filtration) following scenarios of dam failure

Dam failure events can result in a high suspended solids concentration in surface waters. To understand the impact of high suspended solids concentration on the treatment process of water treatment plants, this study investigated coagulation-flocculation stages using different coagulants (ferric chloride and a polymeric coagulant – CAT-FLOC 8799 Plus) and solids concentrations (2000–46,000 mg/L), and how they impacted on the mean diameter (d50), density (ρs), and settling velocity (vs) of the agglomerates formed. After the sedimentation process, the turbidity values varied between 201–26 NTU when FeCl3 was used as a coagulant, and 36–11 NTU when using the organic coagulant. The study reinforces the effect of particle diameter on sedimentation velocity, which is lower for cases involving smaller average diameters. Even so, solids removal was high regardless of the initial conditions and characteristics of the agglomerated particles, starting early in flocculators with removals >80 %. The results point to the need for frequent maintenance of these units to remove the sludge settled, which could compromise the operation of water treatment plants. In this sense, two alternatives were proposed as pre- and post-treatment. Under high total solids concentration (>20,000 mg/L), pre-treatment with thickeners becomes mandatory, and ultrafiltration comes as an additional barrier that will prevent high turbidity values in drinking water. In this study, the use of ultrafiltration membranes in partial or total replacement of sand filters showed stable performance (permeate flow: 130–136 L/m2h) with no tendency to fouling and guaranteeing a residual turbidity value <0.3 NTU. Future studies should prove the technical and operational feasibility of the strategies proposed, which until then showed promising results to guarantee the operation of water treatment plants in adverse scenarios.

Flow visualization simulation of cemented tailings backfill slurry by particle tracking technology

AbstractPipeline flow visualization of cemented tailings backfill slurry (CTBS) improves the safety and stability of transportation. High turbidity and low resolution make it difficult for conventional methods to monitor the particle distribution state of CTBS in a short period of time. Particle tracking technology (PTT) is used to simulate and investigate the flow characteristics of CTBS pipeline, combine with theoretical analysis to construct a CTBS pipeline visualization model, elaborate the particle distribution state when CTBS flows in the pipeline, and explore the effects of pipe diameter (PD), flow velocity (FV) and tailings gradation (TG) on the particle distribution. The results show that particle tracking technology is better applied to investigate the particle transport distribution characteristics of CTBS tailings. Three concepts of particle accumulated gravity Ga, static friction angle θ and diameter dividing line are defined, and the transport pipe is divided into light wear zone, medium wear zone and heavy wear zone. The increase in pipe diameter increases the content of fine particles at the pipe wall and the thickness of the lubrication layer becomes larger, which improves the safety and stability of CTBS transport. The increased flow velocity reduces the settling phenomenon of large size particles and improves the transport efficiency, which increases the pipeline transport resistance. Under good tailings grading conditions, a wide range of tailings grading is more suitable as backfill material. The results of the study illustrate the flow characteristics of the backfill slurry in the pipeline from the particle perspective and provide a theoretical basis for pipeline transportation research.

Structural characterization, interfacial and emulsifying properties of soy protein hydrolysate-tannic acid complexes

With increasing awareness of health and sustainable dietary pattern, plant-based proteins have shown a growing interest as substitutes for animal proteins. Meanwhile, the non-covalent interaction of protein with natural phenolic compounds can be used to develop functional ingredients. In this work, Alcalase hydrolysates of soy protein isolate (HSPI) were used to fabricate complexes with tannic acid (TA), and their physicochemical properties were investigated and compared with soy protein isolate (SPI) and sodium caseinate (SC) to get insights into the advantage of polyphenol modification. The complex solution showed reduced particle size, higher turbidity, and higher surface charge with increasing TA concentration. The interaction mainly occurred through hydrogen bond and hydrophobic interaction, leading to the unfolding of protein molecular structure. The complexes displayed lower interfacial adsorption activity and reduced interfacial viscoelastic modulus upon increasing TA concentration possibly because of the interference of TA on the diffusion and molecule interaction of protein hydrolysates to form elastic films. Nonetheless, the complex-based emulsion showed enhanced emulsifying stability with small droplet size, superior oxidation stability, high physical stability against heat and freeze-thaw treatment due to the higher surface charge and formation of particle-stabilized interfacial membrane. These findings provide insights for developing plant-based protein with excellent emulsifying properties, which show great potential for application as SC substitute in dairy-free emulsified products.

Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale.

Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two-three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries.

The Thores Lake proglacial system: remnant stability in the rapidly changing Canadian High Arctic

We describe limnological data sets from Thores Lake, a large ice-contact proglacial lake in northern Ellesmere Island, Nunavut (82.65°N), including longitudinal and cross transects (vertical resolution 0.03 m, horizontal resolution 100–200 m). The lake is formed due to damming by Thores Glacier at its northwest margin, has multi-year ice cover and a cold (&lt;1.54 °C) fresh water column with a bottom layer of &lt;0 °C, high-conductivity water in the deepest basin. Thores Lake is ultraoligotrophic, with low nutrient and phytoplankton stocks. Accessory pigment data and metagenomics were used to describe the eukaryotic microbial community. Diversity and taxonomic composition in the water column were homogeneous down to a depth of 40 m, consistent with density profiles. Surface water at the glacier interface was characterized by high turbidity and total phosphorus concentrations, and a distinct phytoplankton community dominated by chlorophytes, whereas the lake water column had higher relative abundances of chrysophytes and photosynthetic dinoflagellates. Thores Lake has a contracted pelagic food web, with the highest trophic level occupied by phytoplankton-feeding rotifers, and no crustacean zooplankton; profiles showed that omega-3 fatty acids (FAs) ranged from &lt;1% (glacier interface) to 3.6% (central lake) of total seston FAs. Given the stability of the Thores Glacier ice dam and the persistence of cold water capped by perennial ice, Thores Lake provides a baseline to assess the impact of climate change on far northern lakes.

An electrical- and chemical-free approach using microfilter and Ag-based catalysts for emergency drinking water treatment

ABSTRACT In emergency cases such as disasters, supplying enough safe drinking water is one of the most urgent needs for human life. This research aimed to develop a chemical- and electricity-free drinking water treatment system based on microfiltration and catalysts of Ag and Ag-TiO2-SiO2 coated on glass spheres in both dark and sunlight conditions. The system was applied to treat raw water samples taken from five rivers in Vietnam, simulated floodwater samples with high turbidity and E. coli concentration, and real flooding water samples. The results showed the filtration unit fed with simulated floodwater generated lower fluxes and shorter working durations before chemical cleaning than that fed with normal river water. However, filtrate quality was not significantly different for these five water samples with very low values of turbidity (0–0.66 NTU), total coliform (5–19 CFU (100 mL)−1), and E. coli (0–17 CFU (100 mL)−1). The catalyst units using glass spheres coated with either Ag in dark and sunlight or Ag-TiO2-SiO2 under sunlight can completely remove E. coli and coliform as well as additionally mitigate natural organic matters. This study hence suggests the combination of microfiltration and Ag-based catalytic treatment for safe drinking water supply in emergencies, especially for flooding conditions.

HIGH TURBIDITY AND COD REMOVAL IN RIVER WATER USING LOW DOSAGE PLANT-BASED TACCA LEONTOPETALOIDES FLOCCULANT (TBPF) FOLLOWED BY ACTIVATED CARBON TREATMENT

Pollution in river water affects human, plant and animal health and activities, and its removal using chemical coagulants is a huge concern. This study aims to reduce turbidity and COD pollutants in river water through coagulation-adsorption process by using Tacca leontopetaloides biopolymer flocculant (TBPF) and powder activated carbon (PAC). In coagulation experiment, TBPF dosages were varied to evaluate the effect on turbidity and COD removal in river water by using Bioblock flocculator followed by adsorption process by adding PAC. The results found that at 200 mg/L of TBPF dosage with 2000 mg/L of PAC, the maximum turbidity and COD removal were obtained at 49% and 81%, respectively. The final turbidity and COD loads were 4.2 NTU and 9.3 mg/L, respectively, which were below the standard limit set for CLASS IIB provided by the National Water Quality Standards of Malaysia (NWQSM). High turbidity and COD removal using low dosage of environmental friendly plant-based TBPF-PAC through coagulation-adsorption process in this study has a great potential for river water treatment, particularly at the domestic area.

Bias-Correction of Diffuse Solar Irradiance Modeled Through Parametric Models

Abstract In this paper, a bias-correction of clear-sky models in prediction of the diffuse solar irradiance is presented. High quality ground date from two networks is used for model input and validation: aerosol optical depth from AERONET and diffuse solar irradiance from BSRN. Four established clear-sky models are tested: REST2, Yang, PS and MAC2. Two types of bias-corrections are developed: i) a correction for multiple aerosol scattering (MSC), accounting for extinction at high turbidity, and ii) a general regression on the model errors as a function of Sun elevation angle (h) and turbidity (β) correction (MOS). While the impact of MSC proves marginal, the MOS correction shows good results. Two versions of MOS are developed, one on the global dataset and a site-specific adaptation. Both versions bring significant improvements over the original implementation of the models, while the site-specific version reduces the errors with a few additional percentage points. The aggregate nRMSE of the REST2 model is reduced from 17.8% (no correction) to 11.3% (global MOS) and 9.4% (site-specific MOS).

UCRNet: Underwater color image restoration via a polarization-guided convolutional neural network

Underwater images always suffer from low contrast and color distortion due to the wavelength-dependent scattering and absorption effects caused by particles existing in turbid water, especially in high turbidity conditions. Based on the polarization properties of the backscattering light, polarimetric methods can estimate the intensity level of the backscattering and the transmittance of the media. Accordingly, they can separate the target signal from the undesired ones to achieve high-quality imaging. In addition, learning-based polarimetric methods are effective for gray-model image restoration, but the learning-based polarimetric technique for color image restoration has yet to be considered. In this paper, we propose a 3- dimensional convolutional neural network, which maintains the correlation of polarization information among different polarization channel images as well as embodies polarization constraints, for underwater color image restoration. The experimental results verify that the proposed solution improves the image quality (i.e., the image contrast, details, and color) and outperforms other existing methods, especially when the turbidity of scattering media is high. The proposed solution can be readily applied to practical applications and potentially realize the clear vision in other scattering media, including biomedical imaging and remote sensing.