Quantifying regional low flows under data scarce conditions.

Estimating low flow quantiles is essential for regulating minimum flow requirements and ensuring water availability, ecological health, and overall system sustainability. This study aims to quantify regional low flows by analyzing low-flow time series in data-limited environments. We utilized annual minimum 7-day instantaneous streamflow data collected from gaging stations. Discordancy measure assessments revealed that all sites were homogeneous, forming a single region. We employed Easy-Fit Statistical Software to select the best-fit probability distribution model and determine estimation parameter values. Through goodness-of-fit tests (GOFs), the Generalized Pareto model emerged as the most suitable, predicting low flow quantiles for 100-year returns. Rigorous application of GOFs ensures the statistical soundness of the model, capturing underlying data patterns. A correlation coefficient determination (R2) of 0.989 demonstrates the high satisfaction of the selected distribution model. The developed regression line for the region exhibited strong agreement between predicted low flows and catchment area. Thus, accurate estimation proves valuable in environmental and human-influenced decision-making processes, providing insights into low-flow behavior and mitigating drought effects on aquatic ecosystems.

Coagulation process for the removal of color and turbidity from wet coffee processing industry wastewater using bio-coagulant: Optimization through central composite design.

The growing problem of industrial pollution in developing countries, especially Ethiopia, has sparked serious issues about the quality of the water, particularly when it comes to the effluent from wet coffee processing industries. In response, this study investigates the potential of utilizing natural coagulants, Acanthus sennii C., Moringa stenopetala B., and Aloe vera L., either individually or in combination, for the treatment of coffee effluent. Methodologically, the study systematically varies operational parameters, including coagulant dose, pH levels, stirring speed, and stirring time, to evaluate their impact on coagulation efficiency. Experimental data undergo statistical analysis, employing ANOVA, while computational optimization techniques are employed using Design Expert software to determine optimal conditions. Notably, the blended form of the three coagulants emerges as particularly promising, yielding optimal conditions of 0.750 g/L coagulant dosage, pH 8.76, agitation speed of 80.73 rpm, and agitation time of 19.23 min. Under these optimized conditions, the blended coagulant achieves remarkable removal efficiencies, approximately 99.99% for color and 98.7% for turbidity. These findings underscore the efficiency of natural coagulants, particularly in blended form, for sustainable wastewater treatment in wet coffee processing.

Evaluating the effects of geochemical and anthropogenic factors on the concentration and treatability of heavy metals in Awash River and Lake Beseka, Ethiopia: arsenic and molybdenum issues.

In the Awash River basin (Ethiopia), massive urbanization and industrialization, driven by rapid development and human settlement, are detrimental to the environment and human health as pollutants such as heavy metals (HMs) find their way into water bodies without proper treatment. The purpose of this study was to assess the HMs content and pollution sources within the basin. In this context, a total of 205 samples were collected from 21 surface water sampling stations. Heavy metal concentrations were measured using the Perkin Elmer NexION 350 ICP-MS with inductively coupled plasma. Findings demonstrate that high levels of HMs, such as Al, Mn, Mo, As, V, Fe, and Ba were exhibited with the value of 1257 µg/L, 626.8 µg/L, 116.7 µg/L, 61.2 µg/L, 100.5 µg/L, 1082.7 µg/L, and 211.7 µg/L, respectively. Among 20 HMs analyzed, 20% of the parameters within the study area were above the WHO limit for drinking water; Al (157 µg/L), V (100.5 µg/L), Fe (1082.7 µg/L), Mn (626.8 µg/L), and Mo (103.8 µg/L) were exhibited at sites along the river system. Likewise, 57% of water samples showed high values of As at many stations down the river systems. In particular, high HM concentrations seen in the upper Awash are primarily controlled by anthropogenic activities such as untreated industrial, agricultural, and domestic discharges, while the high HM concentrations in the middle Awash samples were likely due to the influence from the Lake Beseka that has high HM concentrations due to geological process. In conclusion, securing potable water for the rapidly increasing population in Addis Ababa and in the watersheds of Awash is unsafe to sustain the environment and the human health.

Hydrothermal Synthesis of Heterostructured g-C3N4/Ag-TiO2 Nanocomposites for Enhanced Photocatalytic Degradation of Organic Pollutants.

In this study, heterostructured g-C3N4/Ag-TiO2 nanocomposites were successfully fabricated using an easily accessible hydrothermal route. Various analytical tools were employed to investigate the surface morphology, crystal structure, specific surface area, and optical properties of as-synthesized samples. XRD and TEM characterization results provided evidence of the successful fabrication of the ternary g-C3N4/Ag-TiO2 heterostructured nanocomposite. The heterostructured g-C3N4/Ag-TiO2 nanocomposite exhibited the best degradation efficiency of 98.04% against rhodamine B (RhB) within 180 min under visible LED light irradiation. The g-C3N4/Ag-TiO2 nanocomposite exhibited an apparent reaction rate constant 13.16, 4.7, and 1.33 times higher than that of TiO2, Ag-TiO2, and g-C3N4, respectively. The g-C3N4/Ag-TiO2 ternary composite demonstrated higher photocatalytic activity than pristine TiO2 and binary Ag-TiO2 photocatalysts for the degradation of RhB under visible LED light irradiation. The improved photocatalytic performance of the g-C3N4/Ag-TiO2 nanocomposite can be attributed to the formation of an excellent heterostructure between TiO2 and g-C3N4 as well as the incorporation of Ag nanoparticles, which promoted efficient charge carrier separation and transfer and suppressed the rate of recombination. Therefore, this study presents the development of heterostructured g-C3N4/Ag-TiO2 nanocomposites that exhibit excellent photocatalytic performance for the efficient degradation of harmful organic pollutants in wastewater, making them promising candidates for environmental remediation.

Assessment of Drinking Water Quality in Urban Water Supply Systems: The Case of Hawassa City, Ethiopia.

In many developing countries, such as Ethiopia, water quality and the risk of water-related diseases are serious public health issues. The present study goal was to assess the drinking water quality from source to household tap water. To characterize and analyze drinking water quality parameters, 21 water samples were collected, of which 11 water samples were collected from sources (spring, borehole, and river), 4 from service reservoirs, and 6 from tap water. The mean values of the parameters were as follows: total dissolved solids (TDS) (142.79 mg/L), temperature (22.08°C), turbidity (9.49 NTU), electrical conductivity (EC) (250.14°µS/cm), pH (7.45 mg/L), fluoride (1.15 mg/L), nitrate (NO3-) (2.91 mg/L), total hardness (TH) (57.45 mg/L), calcium (41.7 6 mg/l), magnesium (10.74 mg/L), phosphate (0.44 mg/L), sulfate (3.99 mg/L), residual chlorine (1.53 mg/L), alkalinity (196.39 mg/L), and microbiological (total coliform and coliform/CFU) which were the main physiochemical parameters analyzed for the study. The findings revealed that the majority of the water quality parameters tested were within the WHO and National Drinking Water Quality Standards (NDWQS). However, some of the parameters such as temperature, turbidity, fluoride, and residual chlorine did not meet the standards. The mean temperatures at the source, reservoir, and tap water were 22.01°C 22.5°C,and 21.83°C, respectively. Turbidity levels in source samples ranged from 10 to 45 NTU, with a mean of 24.5 NTU, exceeding the WHO's recommendation of less than 5 NTU. The Boko Alamura well had a high fluoride content (3.9 mg/l), which was above the WHO and NDWQS permissible limits. There was no free residual chlorine in the tap water sample. The results show that the Hawassa drinking water supply did not contain total or fecal coliform in any of the samples tested. The overall WQI for the water source, reservoir, and tap water was also determined to be 89, 71, and 69.7 points, respectively. Therefore, based on the WQI result, Hawassa drinking water quality is good for the source, reservoir, and tap water.

Fabrication of Enhanced UV Protective Cotton Fabric Using Activated Nano-Biocarbon Derived from Teff Hay Grafted by Polyaniline: RSM-Based Optimization and Characterization.

In the present study, a hybrid cotton fabric with an enhanced ultraviolet (UV) shielding property was developed by coating with functionally activated nanocarbon (FACN) which was grafted by polyaniline (PANI) using in situ polymerization. In light of this, Teff hay biomass was used to establish the activated nanocarbon (ANC), that was subsequently given a surface functionalization using a silane coupling agent. Using the response surface (RSM) statistical analysis, the study was optimized for the weight percent of ANC and PANI with respect to the cotton fabric that was found to offer remarkable UV protection, with an ultraviolet protection factor (UPF) of 64.563, roughly 17 times more than that of primitive cotton (UPF = 3.7). The different characterization techniques, such as UV absorption, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thermal behavior studies were investigated. In addition, the basic textile properties on optimized hybrid material were found to be appreciably increased. The results suggested that activated FACN made from Teff hay could be an effective alternative organic source material for developing UV protective hybrid cotton fabrics.

Water purification improvement using moringa oleifera seed extract pastes for coagulation follow scoria filtration.

Currently, millions of people are exposed to dangerous levels of chemical and biological water pollution in drinking water due to source contamination. The rising of populations and industrialization or agricultural wastewaters were causes of water contaminations. The aim of this study was to design, develop and performance evaluation of point of use drinking water purification technology using MoringaOleifera seed coupled followed by scoria coag-filtration media. Experimental laboratory based aquas solution of contaminated water was prepared for evaluations. Moringa Oleifera seed coagulation/flocculation and sedimentation tests were carried out using jar test with the batch experiment. The potential treatment of the sequential ordered unit process stages were evaluated by the determination of physicochemical parameters of the water; such as turbidity, Color, PO4-3, Fe+3 and F-concentration. The factor that affects the purification where coagulant doses, pH, and contact time. Based on this, the physicochemical parameter analysis indicated that turbidity from (150-8NTU), PO4-3 (20-5.95 mg/L), Fe+3 (7-2.93 mg/L) and F- (9-2.83 mg/L), Moringa Oleifera seed dose (10-40 mL/L) extract paste. The maximum pollutant removal efficiency was achieved at 35 mL/L of Moringa Oleifera seed extractdose, within 6.5-7.5 pH range. Then VSco filtration was conducted after jar test under small column experiment as a function of contact time (0, 2, 4 h s). The VSco removal capacity showed that the removal of turbidityfrom (8-2.54NTU), PO4-3 (5.95-1.07 mg/L), Fe+3 (2.93-0.43 mg/L) and F- (2.83-1.94 mg/L) were achieved after 4hr detention time. The percent removal of turbidity, PO4-3, Fe+3 and F- increases remarkably with increasing of their initial concentration. At an initial concentration of turbidity (150NTU), PO4-3 (20 mg/L), Fe+3 (7 mg/L) and F-(9 mg/L), the removal efficiency were 98%, 84%, 85% and 60% respectively. Therefore, we recommend Moringa Oleifera seed -Vscoas an economic, efficient and simple Point of Use drinking water treatment technology.

Spatio-temporal variability and potential health risks assessment of heavy metals in the surface water of Awash basin, Ethiopia.

Increasing urbanization and industrialization are impacting on water quality globally. In the Awash River basin, Ethiopia, these drivers are impacting on water quality with further impacts created due to changes in water management releasing geogenic contaminants. The resulting water quality has potential to cause significant ecological and human health impacts. The physicochemical and heavy metals saptio-temporal variability and their associated risks to human health and ecology were assessed across twenty sampling stations in the Awash River basin. Over twenty-two physicochemical and ten heavy metals parameters were analyzed using different instruments including inductively coupled plasma mass spectrometer (ICP-MS). Elevated levels of heavy metals (As, V, Mo, Mn, and Fe) were detected in the surface water, surpassing the drinking water quality standards set by the World Health Organization (WHO). Seasonal variation was evident with peak concentration of As, Ni, Hg, and Cr were recorded in the dry season. A water quality index, hazard quotient, hazard index, heavy metal pollution index and heavy metal evaluation index were formulated to assess the potential risks to both human health and the environment. The highest values of heavy metal pollution index (HPI) above the threshold (>100) were observed in stations at Lake Beseka with HPI values ranged from 105 to 177. Similarly, the highest values of the heavy metals evaluation index (HEI) were observed in stations situated at cluster 3. The evaluation of health risk that is not related to cancer through hazard quotient demonstrated that in the case of both dermal and ingestion contact, cluster C3 > C1 > C4 > C2 and C3 > C4 > C2 > C1 were observed in children and adults, respectively. Overall, measures to reduce potential pollution risks must be taken in accordance with the standards in the river basin. Nevertheless, further research on the toxicity of heavy metals that pose risks to human health is also necessary.

Single-Step Synthesis of Graphitic Carbon Nitride Nanomaterials by Directly Calcining the Mixture of Urea and Thiourea: Application for Rhodamine B (RhB) Dye Degradation.

Recently, polymeric graphitic carbon nitride (g-C3N4) has been explored as a potential catalytic material for the removal of organic pollutants in wastewater. In this work, graphitic carbon nitride (g-C3N4) photocatalysts were synthesized using mixtures of low-cost, environment-friendly urea and thiourea as precursors by varying calcination temperatures ranging from 500 to 650 °C for 3 h in an air medium. Different analytical methods were used to characterize prepared g-C3N4 samples. The effects of different calcination temperatures on the structural, morphological, optical, and physiochemical properties of g-C3N4 photocatalysts were investigated. The results showed that rhodamine B (RhB) dye removal efficiency of g-C3N4 prepared at a calcination temperature of 600 °C exhibited 94.83% within 180 min visible LED light irradiation. Photocatalytic activity of g-C3N4 was enhanced by calcination at higher temperatures, possibly by increasing crystallinity that ameliorated the separation of photoinduced charge carriers. Thus, controlling the type of precursors and calcination temperatures has a great impact on the photocatalytic performance of g-C3N4 towards the photodegradation of RhB dye. This investigation provides useful information about the synthesis of novel polymeric g-C3N4 photocatalysts using a mixture of two different environmentally benign precursors at high calcination temperatures for the photodegradation of organic pollutants.

Mobile trace elements in sediments from lakes Hawassa, Koka, and Ziway in the Ethiopian Rift Valley.

The present work focuses on total concentrations of trace elements such as chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) and their operationally defined speciation in surface sediments from three Ethiopian Rift Valley Lakes (Hawassa, Koka, and Ziway). Total concentrations were determined using inductively coupled plasma-mass spectrometer (ICP-MS). A six-step sequential extraction was also applied to evaluate the mobilization potential of these elements. Compared with the consensus-based sediment quality guidelines (SQGs) developed for freshwater ecosystems, the total Zn concentration in sediments from Lakes Hawassa and Ziway, as well as Cr, Ni, and Zn in sediments from Lake Koka, was higher than the probable effect concentration (PEC), suggesting that these elements could have a negative effect on benthic organisms. The sequential extraction results showed that Cd, Mn, and Se were to a certain extent associated with the reversible fractions (F1-F3) in sediments, and thereby more mobile than the other investigated trace elements. Predictions of mobility of trace elements using the distribution coefficients (Kd) values were also in agreement with the sequential extraction results. Furthermore, multivariate statistical analyses showed that redox-sensitive fractions (F4 and F6) and the residual fraction (F7) were the dominant factors controlling most trace element mobility. Finally, applying the Risk Assessment Code (RAC) classification system, results showed that Mn in Lake Koka could pose a high risk, while Cd and Mn in Lake Hawassa as well as Cd, Mn, and Se in Lake Ziway sediments could pose medium risk to benthic organisms.

Distillery industrial wastewater(DIW) treatment by the combination of sono(US), photo(UV) and electrocoagulation(EC) process.

The color and Chemical Oxygen Demand (COD) reduction in distillery industrial effluent (DIW) was investigated utilizing photo (UV), sono (US), electrocoagulation (EC), UV + US, UV + EC, US + EC, and US + UV + EC technologies. The empirical study demonstrated that the UV + US + EC process removed almost 100% of color and 95.63% of COD from DIW while consuming around 6.97 kWh m-3 of electrical energy at the current density of 0.175 A dm-2, COD of 3600 mg L-1, UV power of 32 W, US power of 100 W, electrode pairings of Fe/Fe, inter-electrode distance of 0.75 cm, pH of 7, and reaction time of 4 h, respectively. The values found were much greater than those produced using UV, US, EC, UV + US, UV + EC, and US + EC methods. The influence of various control variables such as treatment time (1-5 h), current density (0.075-2.0 A dm-2), COD (1800-6000 mg L-1), inter-electrode distance (0.75-3.0 cm), electrode pairings (Fe/Fe, Fe/Al, Al/Fe, Al/Al), UV (8-32 W), and US (20-100 W) on the color and COD reduction were investigated to determine the optimum operating conditions. It was observed that, an increase in treatment time, current density, UV and US power, decrease in the COD, and inter-electrode distance with Fe/Fe electrode combination improved the COD removal efficiency. The UV and US + EC processes' synergy index was investigated and reported. The results showed that, the US + UV + EC treatment combination was effective in treating industrial effluent and wastewater.

Development of electrocoagulation process for wastewater treatment: optimization by response surface methodology.

Electrocoagulation (EC) is a process used by supply of electric current with sacrificial electrodes for the removal of pollutant from wastewater. The study was experimentally investigated taking into account various factors such as pH (3-7.5), current (0.03-0.09 A), distance between the electrodes (1-2 cm), electrolytic concentration (1-3 g/L), and electrolysis time (20-60 min) which is impact on the % removal efficiency of color, chemical oxygen demand (COD), turbidity and determination of energy consumption used for aluminum (Al) electrode used. The surface response design process based on the central composite design (CCD) has been used to optimize different operational parameters for treatment of hospital wastewater using EC process. The % color, COD and turbidity removal, and energy consumption under different conditions were predicted with the aid of a quadratic model, as were the significance and their interaction with independent variables assessed by analysis of variance (ANOVA). The optimal conditions were obtained through mathematical and statistical methods to reach maximum % color, COD, and turbidity removal with minimum energy consumption. The results showed that the maximum removal of color (92.30%), COD (95.28%), and turbidity (83.33%) were achieved at pH-7.5, current-0.09A, electrolytic concentration-3g/L, distance between electrodes-2 cm and reaction time 60 min. This means that, the process of EC can remove pollutants from various types of wastewaters and industrial effluent under the various operating parameters.

Fixed-Bed Adsorption: Comparisons of Virgin and Zirconium Oxide-Coated Scoria for the Removal of Fluoride from Water.

Many people worldwide are exposed to extreme levels of fluoride in drinking water. It is, therefore, critical to develop inexpensive, locally available, and environmentally friendly adsorbents for fluoride-laden water defluoridation. In the current study, virgin scoria (volcanic rock) from Ethiopia, was modified with zirconium oxide and used as an adsorbent in a fixed-bed column aiming at the removal of fluoride from water. The adsorption capability of zirconium oxide-coated scoria (ZrOCSc) was compared with unmodified virgin scoria (VSco). XRD, FTIR, XRF, SEM, ICP-OES, and the pHPZC tests were evaluated to explore the adsorption mechanisms. Thermal analysis of VSco and ZrOCSc revealed lower total weight losses of 2.3 and 3.2 percent, respectively, owing to the removal of water molecules and OH species linked to metal oxides contained in the material. The effect of test conditions such as the pH of the solution and the influent flow rate on the adsorption capacity of the adsorbent was carefully studied. ZrOCSc exhibited the maximum removal capacity of 58 mg/kg, which was 4.46 times higher than the observations for VSco (13 mg/kg) at pH 2, and an initial flow rate of 1.25 mL/min. Breakthrough time increased with decreasing initial pH and flow rate. The adsorption experimental data under various test conditions were examined by the Thomas and Adams-Bohart models. Both models were found very effective in describing the experimental data with a correlation coefficient (R2) of ≥0.976 (ZrOCSc) and ≥0.967 (VSco). Generally, coating VSco with zirconium oxide improved the adsorption performance of VSco; hence, a ZrOCSc-packed fixed bed could be employed for the decontamination of high levels of fluoride from groundwater. However, further examination of the adsorbent using natural groundwater is advisable to produce a definitive conclusion.

Optimization of Fluoride Adsorption on Acid Modified Bentonite Clay Using Fixed-Bed Column by Response Surface Method.

Using small-scale batch tests, various researchers investigated the adsorptive removal of fluoride using low-cost clay minerals, such as Bentonite. In this study, Column adsorption studies were used to investigate the removal of fluoride from aqueous solution using acid-treated Bentonite (ATB). The effects of initial fluoride concentration, flow rates, and bed depth on fluoride removal efficiency (R) and adsorption capability (qe) in continuous settings were investigated, and the optimal operating condition was determined using central composite design (CCD). The model's suitability was determined by examining the relationship between experimental and expected response values. The analysis of variance was used to determine the importance of independent variables and their interactions. The optimal values were determined as the initial concentration of 5.51 mg/L, volumetric flow rate of 17.2 mL/min and adsorbent packed-bed depth of 8.88 cm, with % removal of 100, adsorptive capacity of 2.46 mg/g and desirability of 1.0. This output reveals that an acid activation of Bentonite has made the adsorbent successful for field application.

Evaluation of bentonite clay in modified and unmodified forms to remove fluoride from water.

The feasibility of fluoride adsorption from aqueous solutions using naturally available bentonite clay in both modified and unmodified forms is investigated in this report. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy analysis was applied to describe the structure and nature of modified and unmodified bentonite clay. The physicochemical characteristics of the adsorbent were also investigated for moisture content, pH, apparent density, specific surface area, cation exchange capacity and its point-of-zero charge. SEM images reveal particles are dispersed homogeneously and are irregular in shape. XRD and EDX analyses reveal that the bentonite is composed of seven materials: calcite, silica, alumina, hematite, bornite and green cinnabar, and chloride which are considered as impurities. Raw bentonite clays have shown very low fluoride removal efficiency (47.19%). Modification of the clay surface with HCl and aluminum oxide, on the other hand, increased fluoride removal efficiency to 79.77% and 94.38%, respectively. At 5 mg/L initial fluoride concentration, 10 cm bed depth packed dose of adsorbent, and 180 min breakthrough time, a 2.88 mg/g of fluoride removal capacity was observed. As a result, aluminum oxide modified bentonite clay was chosen for further investigation and the results are not presented here.

Enhanced Defluoridation of Water Using Zirconium-Coated Pumice in Fixed-Bed Adsorption Columns.

Millions of people across the globe suffer from health issues related to high fluoride levels in drinking water. The purpose of this study was to test modified pumice as an adsorbent for the purification of fluoride-containing waters. The adsorption of fluoride onto zirconium-coated pumice (Zr-Pu) adsorbent was examined in fixed-bed adsorption columns. The coating of zirconium on the surface of VPum was revealed by X-ray diffractometer (XRD), Inductively coupled plasma-optical emission spectroscopy (ICP-EOS), and X-ray fluorescence (XRF) techniques. The degree of surface modification with the enhanced porosity of Zr-Pu was evident from the recorded scanning electron microscope (SEM) micrographs. The Brunauer-Emmett-Teller (BET) analysis confirmed the enhancement of the specific surface area of VPum after modification. The Fourier transform infrared (FTIR) examinations of VPum and Zr-Pu before and after adsorption did not reveal any significant spectrum changes. The pH drift method showed that VPum and Zr-Pu have positive charges at pHPZC lower than 7.3 and 6.5, respectively. Zr-Pu yielded a higher adsorption capacity of 225 mg/kg (2.05 times the adsorption capacity of VPum: 110 mg/kg), at pH = 2 and volumetric flow rate (QO) of 1.25 mL/min. Breakthrough time increases with decreasing pH and flow rate. The experimental adsorption data was well-matched by the Thomas and Adams-Bohart models with correlation coefficients (R2) of ≥ 0.980 (Zr-Pu) and ≥ 0.897 (VPum), confirming that both models are suitable tools to design fixed-bed column systems using volcanic rock materials. Overall, coating pumice with zirconium improved the defluoridation capacity of pumice; hence, a Zr-Pu-packed fixed-bed can be applied for defluoridation of excess fluoride from groundwater. However, additional investigations on, for instance, the influences of competing ions are advisable to draw explicit conclusions.

Fixed-Bed Column Technique for the Removal of Phosphate from Water Using Leftover Coal.

The excessive discharge of phosphate from anthropogenic activities is a primary cause for the eutrophication of aquatic habitats. Several methodologies have been tested for the removal of phosphate from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce the nutrient loading of water. This research aimed to investigate the adsorption potential of leftover coal material to remove phosphate from a solution by using continuous flow fixed-bed column, and analyzes the obtained breakthrough curves. A series of column tests were performed to determine the phosphorus breakthrough characteristics by varying operational design parameters such as adsorbent bed height (5 to 8 cm), influent phosphate concentration (10-25 mg/L), and influent flow rate (1-2 mL/min). The amorphous and crystalline property of leftover coal material was studied using XRD technology. The FT-IR spectrum confirmed the interaction of adsorption sites with phosphate ions. Breakthrough time decreased with increasing flow rate and influent phosphate concentration, but increased with increasing adsorbent bed height. Breakthrough-curve analysis showed that phosphate adsorption onto the leftover coal material was most effective at a flow rate of 1 mL/min, influent phosphate concentration of 25 mg/L, and at a bed height of 8 cm. The maximal total phosphate adsorbed onto the coal material's surface was 243 mg/kg adsorbent. The Adams-Bohart model depicted the experimental breakthrough curve well, and overall performed better than the Thomas and Yoon-Nelson models did, with correlation values (R2) ranging from 0.92 to 0.98. Lastly, leftover coal could be used in the purification of phosphorus-laden water, and the Adams-Bohart model can be employed to design filter units at a technical scale.

Genetic diversity of Nile tilapia (Oreochromis niloticus) populations in Ethiopia: insights from nuclear DNA microsatellites and implications for conservation.

BACKGROUND: Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) is among the economically most important freshwater fish species in East Africa, and a major source of protein for local consumption. Human induced translocations of non-native stocks for aquaculture and fisheries have been found as a potential threat to the genetic diversity and integrity of local populations. In the present study, we investigate the genetic structure of O. niloticus from 16 waterbodies across Ethiopia using 37 microsatellite loci with SSR-GBAS techniques. RESULTS: The samples are structured into three main clusters shaped either by biogeographic factors or stocking activities. High FST values (Global FST = 0.438) between populations indicate a high level of genetic differentiation and may suggest long term isolation even within the same drainage systems. Natural populations of the Omo-Turkana system and the lakes in the Southern Main Ethiopian Rift showed the highest genetic variability while low variability was found in stocked populations of lakes Hora, Hashenge and Hayq. CONCLUSIONS: The results presented herein, may provide an essential basis for the management and conservation of the unique genetic resources in northern East Africa, and advance our understanding of biodiversity, phylogeny, evolution and development towards phylogenetically more accurate taxonomic classifications.

Bioaccumulation of trace elements in liver and kidney of fish species from three freshwater lakes in the Ethiopian Rift Valley.

The objective of the present work was to obtain scientific information on the ecological health of three freshwater lakes (Awassa, Koka, and Ziway) situated in the Ethiopian Rift Valley by investigating possible trace element contamination accumulated in fish. Accordingly, fish liver and kidney samples were collected from three commercially important fish species (Barbus intermedius, Clarias gariepinus, and Oreochromis niloticus) in the lakes to determine the concentrations of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb), using ICP-MS. Trace element concentrations were generally higher in O. niloticus compared with concentrations in B. intermedius and C. gariepinus. Compared to background values of most freshwater fish species, higher liver concentrations of Cu in C. gariepinus and O. niloticus, Mn in O. niloticus, Co in all except B. intermedius, and Zn in C. gariepinus from Lakes Ziway and Awassa were found. Cr, Co, Ni, Cd, and Pb were enriched in kidney, while Mn, Cu, Zn, As, and Se seems retained in the liver tissues. Assessment of transfer factors indicated that bioaccumulation from water and diet occurred, while uptake from sediments was low. Furthermore, the transfer factor values were generally higher for essential elements compared to the non-essential elements. Multivariate statistical analyses showed that the differences between the trace element levels were generally not significant among the lakes (p = 0.672), while significant differences were found between the fish species (p = 0.042), and between accumulation in kidney and liver (p = 0.002).