WATER AND WASTEWATER
Year:2015 | Volume:26 | Issue:3 (97)|Papers Count:18

The main objective of the present study was to investigate Cd(II) adsorption by immobilized silica nanopowder within calcium alginate and to determine the isotherm, kinetics, and thermodynamics of the adsorption process. Batch flow mode reactors were used to investigate the effects of initial pH, contact time and metal ion concentration on Cd (II) adsorption. The optimal contact time and initial pH for Cd (II) adsorption were found to be 120 min and 4.0, respectively. Increasing Cd (II) ion concentration from 10 to 1000 mg/L led to increasing adsorbed Cd (II) ions from 5.71 to 100.65 mg/g. The results showed that the Langmuir isotherm model was the best model to describe the experimental data (R2=0.997). The maximum adsorption capacity (qm) for Cd(II) adsorption onto the adsorbent was estimated to be 72.99 mg/g. Based on the mean free energy of adsorption (E) obtained from Dubinin-Radushkevich (D–R) isotherm model, Cd(II) adsorption onto immobilized silica nanopowder follows a chemical mechanism (E=8.451 kJ/mol). The kinetic study indicated that the pseudo-second order model was a more suitable model than the pseudo-first order one for describing Cd (II) adsorption (R2=0.999). Additionally, the negative DHo and DGo values demonstrated an exothermic and spontaneous Cd (II) adsorption onto immobilized silica nanopowder.

The objective of this study was to determine the efficiency of lead removal from aqueous (both single- and multi-element) solutions using the nanostructured ash cedar absorbent. Nanostructured ash cedar was synthesized and the effects of pH, absorbent dosage, and contact time on lead removal efficiency were investigated in a batch system. The absorbent was characterized by SEM, PSA, XRF, and FTIR. SEM results showed that all the particles had diameters smaller than 207 nm. It was also found that the optimum pH values for lead adsorption were 6 and 5 for the single-element and the multi-element systems, respectively. The maximum removal efficiencies of 94% and 98% and maximum adsorption capacities of 27 mg/g and 21 mg/g were obtained for the single- and multi-element systems, respectively. Comparison of the Freundlich, Langmuir, and Sips isotherms showed that the Langmuir model with R2=0.99 and RMSE = 1.01 for the single element system described the adsorption data better than other models did. Also, this model with R2=0.99) and RMSE=0.024 better fitted the adsorption data in the multi-element system.

This study investigated the effect of EDTA as a hole scavenger on accelerating the photocatalytic decolorization of direct blue 71 as a non-degradable model pollutant with nano TiO2 powder immobilized on a cementitious bed. For this purpose, 75 mg/L of the dye was decolorized in 75 minutes with 0.03 M of EDTA at a pH level of 6 and under irradiation produced by a 60-W UV-C lamp. This is while decolorization under identical conditions but in the absence of EDTA had been accomplished in 225 minutes. The experiment, therefore, confirmed the accelerating effect of the scavenger on decolorization. The kinetics of the photocatalytic process with EDTA followed a first order reaction with a constant rate of 0.05 min-1, which is 2.5 times faster than the process without EDTA.

Aerobic treatment processes with fixed growths exhibit a high efficiency not only in the removal of organic materials and phosphorus but also in the nitrification process (conversion of ammonium to nitrate) in wastewater. The present study aims to evaluate the performance of activated sludge with a submerged fixed bed in the removal of phosphorus and nitrogen compounds from wastewater. For this purpose, a reactor was initially constructed and commissioned before the activated sludge with a submerged fixed bed was loaded. A total number of 225 samples were collected from the wastewater treatment plant at Farabi General Hospital in Kermanshah to evaluate the removal efficiency of ammonia nitrogen, total nitrogen, nitrite, nitrate, and phosphate over three different retention times (2.9 hours of aerobic and 1.1 hours of anaerobic operation; 3.6 hours of aerobic and 1.4 hours of anaerobic operation; and 4 hours of aerobic and 1.5 hours of anaerobic operation). Phosphorus, ammonia nitrogen, nitrite, and nitrate measurements were performed according to the Standard methods 4500-P, 4500-NH3, 4500-NO2, and 4500-NO3, respectively. Results showed that the highest phosphorus removal (53%) was achieved with Phase III of the system (i.e., 4 hours of aerobic plus 1.5 hours of anaerobic operation) while the highest ammonia nitrogen removal (97%) and TKN (96%) were achieved in Phase II of the system (i.e., 3.6 hours of aerobic and 1.4 hours of anaerobic operation). Significant differences (Pvalue<0.05) were observed among the mean values for the removal efficiencies of these parameters in the three retention times. The optimum time for the removal of ammonia nitrogen was estimated at 3.6 hours of aerobic and 1.4 hours of anaerobic operation and that for the removal of phosphorus was 4 hours of aerobic and 1.5 hours of anaerobic operation. Based on the results obtained, it may be claimed that the activated sludge process with the submerged fixed bed exhibits a high efficiency for the removal of phosphorus and nitrogen compounds from hospital wastewater only if the system is properly operated and maintained.

In the present study, the Box-Behnken design was used to investigate the effects of the four main parameters of initial Malachite green) MG (concentration, initial solution pH, algae content, and contact time on the efficiency of dye biosorption by the green microalgae Scenedesmus quadricauda and Chlorella vulgaris. The results showed that maximum dye removal efficiencies of S. quadricauda and C. vulgaris biomasses for the biosorption of MG were 76.23 and 91.32%, respectively. Under optimum conditions, the pseudo-second order fitted with the experimental data much better than other similar models (R2>0.99). The FT-IR spectroscopy method showed that several functional groups, especially carboxyl, hydroxyl, and amine groups, present on the surface of the S. quadricauda and C. vulgaris biomasses are responsible for binding of MG ions in the biosorption process. The differences observed in the MG biosorption efficiencies of algal biomasses may be attributed to differences in interactions between the dye molecules and the algal biomasses. Finally, the findings revealed that the algal biomasses used in this study are suitable as the biomaterial for MG biosrption from wastewaters.

Contamination of water resources with heavy metals has nowadays become a global problem that requires continuous monitoring and control. An annual quantity of about 25,000 tons of cadmium is normally discharged into the environment. The objective of this study was to investigate cadmium removal from aqueous environments with the natural Luffa sorbent using equilibrium experiments consisting of the batch flow mode and the continuous flow mode reactors with a fixed bed column. The effects of pH, contact time, adsorbent dosage, and initial solution concentration on the uptake of metal ions by the adsorbent in the batch operation were examined. Langmuir and Freundlich isotherm models were used to investigate the adsorption equilibrium. The adsorption behavior of Cd (II) ions fitted both isotherms but followed the Langmuir isotherm most precisely (R2=0.987), with a maximum adsorption capacity of 6.711 mg/g. Cadmium removal in the continuous flow mode using a fixed bed column was also studied. The effecte of operating parameters such as flow rate and inlet Cd (II) concentration on the sorption characteristics of Luffa were determined by assessing the breakthrough curve. The data confirmed that the total amount of sorbet Cd (II) and equilibrium Cd (II) uptakes decreased with increasing flow rate but increased with increasing inlet Cd (II) concentration. The Adams-Bohart model was applied to the experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. Results showed that the natural Luffa absorbent was capable of efficiently removing cadmium from water.

Adsorption is one of the major Processes for the removal of dyes from wastewater. This study investigates the removal of methylene blue dye, as an index color, using activated fly ash. For this purpose, fly ash from Zarand Power Plant was activated with formaldehyde in an acidic medium and used as the adsorbent. The parameters involved in the fly ash activation process (including temperature, time, formaldehyde content, as well as acid concentration and content) and those affecting the adsorption process were adjusted for optimized conditions. Experiments were performed with samples of real effluent from Baft Yazd Textile Plant. Preparation of activated fly ash was accomplished in a formaldehyde to fly ash ratio of 0.25, an acid concentration of 8%, and an acid to fly ash ratio of 6 over 5 hours. Maximum removal efficiency of methylene blue from synthetic samples (with a concentration of 50mg/L) under optimal conditions (pH: 9, contact time: 30 minutes, temperature: 35oC, and adsorbent dose: 3g/L) was equal to 99.07±0.112%. Under these same conditions, an adsorption capacity of 16.5±0.55 mg/g was achieved. The methylene blue removal efficiency from real samples under optimal conditions was 91.8±0.36%. Based on the findings of this study, modified fly ash from Zarand Power Plant may be recommended as an inexpensive adsorbent that can be used with a high removal efficiency for removing dyes from industrial effluents.

The aim of this study was to develop a model for estimation of major THMs produced as a result of river water disinfection. Experiments were designed for this purpose and different ratios of Cl2 to DOC were created in water samples to which were then added different concentrations of bromide ions. After the incubation period, analyzers were used to measure natural organic compounds, TOC, and DOC in the samples and the data thus obtained were fed into the SPSS software. Moreover, multivariate regression analysis was performed to extract the relevant statistical model. Four different formulas were obtained for predicting the rate of each of the THMs produced. Reaction time and bromide ion concentration were identified as the main factors involved in the production of THMs in the water supply investigated. In addition, the carcinogenicity of THMs in water samples reached its maximum with bromide concentrations between 207 and 246mg/l. The formulas obtained in this study can be used as a simple and accurate tool for the initial estimation of THMs production in different water supplies.

In this paper, the variations of dissolved inorganic and organic carbon (DIC, DOC) concentrations and their isotopic compositions (d13C - DIC, d13C - DOC) were evaluated in both surface and ground water resources in the Karde catchment area (with an area of about 547 Km2, located in the North of Mashhad). To identify the sources of the dissolved carbon (DIC and DOC), samples were collected in June 2011 from surface and ground water resources (river, dam’s lake, springs, wells, and Qanat) and from depths of 1, 5, 10, 15, and 20 meters of Karde dam lakeat a point located near the dam outlet. Field parameters (T, EC, and TDS) were measured during sampling. All measurements were performed in the G.G. Hatch Stable Isotope Laboratory at the University of Ottawa, Canada. The concentrations and isotopic compositions of DIC and DOC were determined using TCA and CF-IRMS instruments, respectively. Based on the results obtained, the average values of DIC are 54.1 mg/l and 66.8 mg/l in the surface and ground water resources in the Karde catchment area, respectively; the average values of DOC are 2.2 mg/l and 0.45 mg/l; the average values of d13C -DIC are -7‰ and -11 ‰; and the average values of d13C -DOC are -31.6‰ and -29.5 ‰, respectively. In general, the concentrations of DIC, DOC, and their isotopic compositions (d13C -DIC, d13C -DOC) are different in the various water resources (surface and ground water) in the catchment and the major source of dissolved carbon in the catchment area is believed to be due to the lithology (limestone and dolomite carbonate rocks) and partly due to the vegetation (plants C3) in the region.

Groundwater quality control is of great importance in (semi-)arid zones due to the water deficit in these regions. Geostatistical models are techniques commonly developed for the interpolation and spatial prediction of groundwater quality parameters. In this study, IDW, Kriging, and CoKriging methods were used in the geostatistical, LS-SVM, and MLP models to predict the spatial distribution of groundwater EC. The models were then compared in terms of their efficiency. For the purposes of this study, data were collected from 120 wells in the Mashhad plain. Variograms were then drawn after normalizing the data for application in the geostatistical models. In the next stage, the lowest RSS value was used for selecting the one model that was suitable for fitting the experimental variogram while cross-validation and RMSE were used to select the best method for interpolation. Comparison of the three models in question was accomplished by using 25% of the observation data and the statistical parameters of RMSE, R2, and MAE were determined. Results showed that the CoKriging method outperformed its Kriging counterpart in the geostatistic model for interpolating groundwater quality. Finally, the most accurate values for the quality parameters (i.e., R2=0.932, RMSE=367.9, MAE=265.78(mmos/cm) were obtained with the MLP model.

This paper studies the accuracy of hydraulic methods in determining environmental flow requirements. Despite the vital importance of deriving river cross sectional data for hydraulic methods, few studies have focused on the criteria for deriving this data. The present study shows that the depth of cross section has a meaningful effect on the results obtained from hydraulic methods and that, considering fish as the index species for river habitat analysis, an optimum depth of 1 m should be assumed for deriving information from cross sections. The second important parameter required for extracting the geometric and hydraulic properties of rivers is the selection of an appropriate depth increment; Dy. In the present research, this parameter was found to be equal to 1 cm. The uncertainty of the environmental discharge evaluation, when allocating water in areas with water scarcity, should be kept as low as possible. The Manning friction coefficient (n) is an important factor in river discharge calculation. Using a range of "n" equal to 3 times the standard deviation for the study area, it is shown that the influence of friction coefficient on the estimation of environmental flow is much less than that on the calculation of river discharge.

Groundwater resources are the most important sources of drinking water in many communities. The direct impact of water quality on public health warrants a thorough investigation of water quality and the factors involved from a hydrogeochemical viewpoint. In the present study, 25 villages of Sarab County in East Azerbayejan Province were selected and the quality of the drinking water supplied in the region was analyzed in terms of its physicochemical parameters along with heavy metals content including 20 different metals. The results were plotted using the Arc GIS for interpretation. The selected villages were subsequently categorized using the Principal Component Analysis (PCA) and the Hierarchical Cluster Analysis. Based on the result of study, the EC of the drinking water ranged over 220-2990ms/cm with an average value of 812. A remarkable finding was the high level of dissolved solids in the Western parts of the study area. Arsenic in two villages and mercury in one village were also high. PCA results showed that the drinking water in the pilot villages could be divided into three categories. Based on certain water quality problems observed ij the region, it is suggested that substitute water supplies should be identified for some of the villages while a comprehensive investigation is also carried out on the arsenic anomaly and its health effects on water consumers in the contaminated villages.

Condensation Irrigation (CI) is a combination of simultaneous desalination and irrigation/drinking water production. As saline water evaporates in a solar distiller and the hot and humid air is transferred into an underground pipeline, fresh water will condense on the inner pipe surface due to cooling of air by the ground. The water thus condensed infiltrates into the soil through pores in the perforated drainage pipes laid in the ground to transfer the humidified air. In this study, the CI system was developed using common buried pipes to determine the amount of water produced. In this setup, condensed water is collected at the end of the pipe to be used for drinking. Observations and calculations indicated a mean water production capacity of 4 liters every 8 hours along a pipe 25m long. Less water was produced on the first day because some of the water was lost to the wetting of the internal pipe walls. Finally, examination of temperature effects revealed that water production along the pipe reduces as we move farther away from the inlet part of the pipe.