JWSS - Journal of Water and Soil Science

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Rice husk, an agricultural waste, is produced about 100 million tons annually in the world and 0.5 million tons in Iran. Due to growing environmental concerns about disposal of these wastes, efforts are required to apply the wastes in industry. In this research, the mechanical properties of concrete incorporating rice husk ash (RHA) in sulfate environments (such as irrigation canals) were investigated and the increase in concrete strength was compared with control samples. In order to burn the husks at a controlled temperature to obtain a highly reactive pozzolanic RHA, a furnace was designed and built. The experiments included 405 samples of cubical (707070-mm) and cylindrical (50.8101.6-mm) concrete samples (105 samples for A, B and C treatments, respectively) which were stored in different ages (7, 28, 60, 180 days) under three different conditions (solutions of magnesium, calcium and sodium sulfates). The portions of RHA as cement replacement were 20 and 30 percents for B and C treatments. The results showed that the samples of concrete containing 20 percent RHA as cement replacement had higher compressive and tensile strengths in sulfate environments at 180 days compared with those of control concretes. The concrete samples containing RHA showed sharper gradients compared to control samples of up to 180 days under sulfate conditions. The best portion of RHA in concrete was determined to be 20 percent by weight.

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Water crisis is an important issue in arid and semi-arid regions like Iran. The situation has been getting more worse over recent years drought. Hence, there is a growing need to utilize low quality water where freshwater is scarce. In this regard, urban wastewater is a promising source but there are concerns about the environmental and health aspects of using such water. The main problem regarding the performance of trickle irrigation system utilizing wastewater effluents is clogging of the emitters. In this study, field trials at pilot scale were carried out to investigate the hydraulic properties of emitters using two types of water including treated wastewater and groundwater. The trickle irrigation system consisted of three 16 mm lateral tubes placed at 300 mm spacing in the main tube and each lateral tube had 16 emitters at 300-mm spacing. The designed discharge of the emitters was 4 L/h. The hydraulic properties of the different commercial emitters (micro flapper, long path, turbo plus and Eurokey) were assessed at different time periods. The results indicated that the Eurokey and long path emitters had the maximum and minimum emission uniformity, respectively, when applying wastewater. using groundwater, the Eurokey and turbo plus emitters had the maximum and minimum emission uniformity, respectively, during the initial phase of the study. However, the Eurokey and long path emitters had the maximum and minimum uniformity values, respectively, at the end of the study. The turbo plus emitters are regulated and, as a result, showed no evidence of sensitivity to pressure variations hence, they can be used on uneven lands and where the trickle irrigation system has long lateral tubes.

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A field study was conducted at the Zabol Agricultural Research Center during the years (2003-2004) to investigate the effect of irrigation with treated municipal wastewater on the yield and quality of wheat and some soil properties. Irrigation treatments were: T₁: Irrigation of wheat with well water during entire period of growing season T₂: Irrigation of wheat with well water until the begging of flowering stage, and irrigation with wastewater in every other turns of irrigation T₃: Irrigation of wheat with well water until the beginning of booting stage, and irrigation with wastewater in every other turns of irrigation T₄: Irrigation of wheat with well water until the begging of tilling stage, and irrigation with wastewater in every other turns of irrigation and T₅: Irrigation of wheat with wastewater during entire period of growing season. A complete randomized block design with four replications was adopted for this experiment. The soil was sandy loam with no limitation for internal drainage. Chemical and physical aspects of soil were measured during the experiment. Grain yield, yield components and chemical composition of wheat grain were also measured. The results showed that yield of wheat and total biomass production were statistically significant in T₃, T₄ and T₅ compared with the control treatment. Plant height, width and length of flag leaf, numbers of fertile tillers, length of panicle, numbers of grains per panicle and weight of 1000 grains were also statistically significant with the control treatment. Percentages of protein were statistically different among various irrigation treatments. No significant changes in accumulation of heavy metals in soil and plant grains were observed. The increase of SAR, ECe, O.C% and total nitrogen in the T₄ and T₅ were statistical significant compared with the control treatment. In summary, for sustainable use of Zabol municipal wastewater, the growth stages of wheat should be irrigated with municipal wastewater and other growth stages should be irrigated with nonsalinty water, so that the maximum yield is obtained and soil salinitisation and sodication is prevented.

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To optimize the use of water for agriculture, knowledge of the seepage of the channel is required. Although there are many empirical equations for estimating canal seepage, the coefficients of these equations are different from Iranian conditions and these equations vary in different areas. In this research, the ability of the SEEP model was studied to estimate the seepage from earth canals in downstream of Zayandehrud dam. Seepage from seven different earth canals (degrees of 3 and 4) was simulated with the model of SEEP and the results were compared to the water balance studies. Also, four empirical equations, Davis-Wilson, Moles worth and Yenni dumia, Moritz and Ingham were used to estimate seepage from these canals. The determination coefficients for these methods and SEEP model were obtained 9.3%, 6.7%, 37.3%, 18.3% and 87.9%, respectively. In contrast with empirical models, SEEP model has a proper ability to simulate seepage from degree 3 canals. The empirical models must be calibrated for local conditions.

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Due to the important role of climatic parameters such as radiation, temperature, precipitation and evaporation rate in water resources management, this study employed time series modeling to forecast climatic parameters. After normality test of the parameters, nonparametric Mann-Kendall test was used in order to do trend analysis of data at P-value<0.05. Relative humidity and evaporation (with significant trend, -0.348 and -0.42 cm, respectively), as well as air temperature, wind speed, and sunshine were selected for time series modeling. Considering the Autocorrelation function (ACF) and Partial Autocorrelation function (PACF) and trend of data, appropriate models were fitted. The significance of the parameters of the selected models was examined by SE and t statistics, and both stationarity and invertibility conditions of Autoregressive (AR) and Moving average (MA) were also tested. Then, model calibration was carried out using Kolmogorov-Smirnov, Anderson- Darling and Rayan-Joiner. The selected ARIMA models are ARIMA(0,0,11)*(0,0,1), ARIMA(2,0,4)*(1,1,0), ARIMA(4,0,0)*(0,1,1), ARIMA (1,0,1)*(0,1,1), ARIMA (1,0,0)*(0,1,1) for relative humidity, evaporation, air temperature, wind speed and sunshine, respectively. The fitted models were then used to forecast the parameters. Finally, trend analysis of forecasted data was done in order to investigate the climate change. This study emphasizes efficiency of time series modeling in water resources studies in order to forecast climatic parameters.

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The effect of sugarcane straw anion exchanger with Micro and Nanostructure scale as the adsorbent for contaminated water treatment was investigated. The effects of operating conditions such as adsorbent loading, initial anion concentration, pH and the presence of competitive ions on the adsorption performances were examined. Equilibrium time and pH and adsorbent dosage were 3h, 6 and 0.5g respectively. The effect of initial concentration on the adsorption of NO3- ions by sugarcane straw anion exchanger was investigated by varying solution concentrations (5-120 mg L-1) using 0.5g adsorbent dose. For micro and nanostructures, adsorption capacity was (0.38-6.94 mg g-1) and (0.44-7.51 mg g-1) respectively. In the column experiment, for micro and nanostructures with (15, 50 and 120 mg L-1) and 0.98 L hr-1 flow rate, adsorption capacity was (8.73, 25.71and 36.25 mg g-1) and (12, 27 and 48.15 mg g-1) respectively. The result of this study indicated that sugarcane straw anion exchanger with micro and nanostructure scale could be used for the removal of nitrate ions in the contaminated water treatment. sugarcane straw anion exchanger -nanostructure adsorbent had higher adsorption than micro adsorbent for nitrate removal.

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Crisis of quality and quantity of water resources is one of the most important problems in arid and semi-arid areas such as Iran. Wastewater treatment and reuse as a potential source of water can not only compensate for the water scarcity but also can prevent the hazardous pollutants from entering the groundwater and surface water resources. There are various methods to improve water quality, among which method of filtration is an effective and efficient method to remove elements. The most important issue for filter system is the selection of adsorbent materials. In this work, the tire chips were used as adsorbent. Column adsorption tests in a pilot system were conducted in two distinct steps using two types of water, including salt water and industrial effluents. Each test was conducted as a factorial experiment with three factors based on a completely randomized design with three replications. Three factors were studied including particle size (2-5 mm and 3-5 cm), filter thickness (10, 30 and 50 cm) and sorbent contact time with solution. The results showed that adsorption rate increased by increasing the thickness of the filter and sorbent contact time with solution. The best performance of reducing the salinity was observed in the treatment with 50 centimeter thickness and 24 contact hours. The salinity of this treatment was reduced by 20.3 percent (in the test with salt water) and 11.2 percent (in the test with industrial effluents). This filter reduced the heavy metals of lead, zinc and manganese up to 99, 72.1 and 41.4 percent, respectively. Also, the performance of millimeter and centimeter particles did not show a significant difference. Generally, the tire chips showed a proper performance to improve the water quality especially for industrial wastewater.

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Heavy metals in water resources are one of the most important environmental problems in most of countries. Up to now, various methods for removing these metals including using low price materials have been used. In this study, two new absorbents (zizyphus spinachristi leaf and its fly ash) were studied for adsorption of cadmium from aqueous solutions using batch experiments. The effect of contact time, pH, and amount of adsorbent on adsorption efficiency was evaluated and the best kinetic and isotherm model was determined. Results showed that optimal absorption of pH was 5 and 6 for zizyphus spinachristi leaf and its fly ash, respectively. The equilibrium time was 45 min for zizyphus spinachristi leaf and 30 min for ash. Adsorption efficiency was increased by increasing the adsorbent dose. By comparing the parameters of isotherm models, it was observed that the cadmium adsorption capacity of fly ash (4.27 mg/gr) was higher than that of zizyphus spinachristi (3.91 mg/gr).