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Being vulnerable to food shortage, tomatoes are dependent on nitrogen fertilizer for their growth and crop yields (Zomorrodi, 2006). In effect, there is a close relationship between the amount of nitrogen fertilizer consumed and the accumulation of nitrate, which poses a threat to consumer health (Mousavi Fazl, 2005). The accumulation of nitrate in tomatoes has a considerable negative effect on its quality and increase the amount of toxic substances in tomatoes (Malakuti et al., 2005). The results of many studies show that the appropriate combination of nitrogen fertilizer treatments and the irrigation regime in such a way that the plant encounters a certain level of water stress during a particular period or throughout the growing season may lead to the maximum efficiency of water usage in the plant (Bagheri et al., 2016). Zomorrodi (2006) examined the effect of deficit irrigation on the quantitative and qualitative characteristics of tomatoes. The results showed that the effects of irrigation water on vitamin C, acidity and soluble solids were significant. Khorramian (2015) also studied different levels of drip irrigation with the supply of 40, 70 and 100% water requirement on the yield and water use efficiency in tomatos. The findings of this study showed that maximum yield was obtained from drip irrigation with 100% water level, while 40% water level treatment had the highest water use efficiency.

Nitrate is a non-concentrated source of environmental pollution caused by fertilizer overdose in agricultural wastewater. These poisonous compounds are accumulated in aquatics tissues specially fishes and affect their reproduction and procreation ability. Generally, to eliminate nitrate from urban, agricultural, and industrial wastewater using of physical, chemical and biological methods is very complicated and expensive at industrial scales. Surface absorption method is one of the useful methods for removing nitrate compounds. Due to the high cost of activated carbon, researchers have always been searching for a more economic method alternatively to remove nitrate. Bagasse is one of the wastages of sugarcane industry which contains some amounts of cellulose, pentosane and lignin. In this research, efficiency of sugarcane bagasse absorbent for nitrate removal from agricultural drainage have been studied.

Nitaret is one of the stable components of nitrogen in the nature. Nitrate compounds are highly soluble and can easily imported to the surface and groundwaters and finally lead to be polluted of them. Denitrification is one of permanent removal methods of nitrate from terrestrial and aquatic ecosystems. In this study, denitrification process and nitrate removal rate changes with time in a column experimental study was evaluated on two types of denitrification beds, first type was a mixture of bagasse and soil (30 % of the volume of bagasse and 70 % of the volume of soil) and second type was only soil without bagasse. All experiments were performed under saturation conditions (anaerobic conditions). The influent nitrate concentraion to the all beds was considered an average of 45 mg/l. With sampling of inflow and outflow of the columns, nitrate removal changes were assessed over a period of three months. The maximum percentage of nitrate removal in columns with mixture of soil and bagasse were occurred in the end of the experiment (94%) and in columns without the bagasse were ocured in the first of the experiment (89%).The results showed that sugar cane bagasse as a carbonic source can be very useful in the design of carbonic filters and denitrification walls for nitrate favorable removal of inlet concentrated solutions. Overall, the results confirm that the denitrification process is one of the main mechanisms of biological nitrate removal from anaerobic enviroments.

Increased use of nitrogen fertilizers due to high dynamics of soil nitrate is a serious threat to groundwater and as a result for human health. The purpose of this study is evaluation of nitrate dispersivity values in the sandy soils of coarse, medium and fine-distance transmission at 80, 40 and 20 cm in laboratory conditions with three models including, Brigham, Fried-Combernous and CXTFIT code. For this purpose, pure potassium nitrate salt solution as sustainable contaminant under the steady regim with concentration of 160 was added to the soil column. In order to obtain the required parameters for the three models, output nitrat concentration were measured in the different nolum porosity and Breakthrough curves were plotted for each column. The results showed that in all three models with a moderate increase in transmission distance of medium and coarse sand, the amount of nitrate dispersivity increased. At various distance of transportation, dispersivity values were measured for fine sand from 0.09 to 3.06 cm,0.23 to 1.6 cm for medium sand and 0.43 to 2.18 cm for coarse sand, respectively. But the Brigham and CXTFIT models showed that the dispersivity of fine sand increases when the distance increases. It was also found that for the fine sand with reduction of transport distance, Brigham model and CXTFIT code showed better results.

In order to investigate the performance of sugarcane bagasse in the removal of nitrate from effluent subsurface drainage water, a study was conducted at the physical models laboratory of Water Sciences Engineering Faculty of Shahid Chamran University of Ahvaz, in the summer of 2013 till the summer of 2014. A physical model with the dimensions of , which simulated the drainage trench, was utilized in this experiment. Bagasse combined with soil by 3:7 volume ratio, the combination installed as a filter besides the drainage pipe. In this study, the influent nitrate concentration was 160 mg.L-1. Influent nitrate flow was continues. At first, every two days, and then every four days the drainage pipe was sampled. Input and output drainage model solution sampled with plastic bottles. Then some parameters like Nitrate, NH4, PH and EC measured. The presence of bagasse as a carbon material in the soil caused the amount of nitrate to reduce from 160 milligrams per liter to 60 milligrams per liter; a reduction of nearly more than 60 percent. The amount of ammonium increased very little in this study. The use of sugar cane bagasse as a filter drainage, reduces the acidity of the drainage outlet. It had no effect on the electrical conductivity. Physical model results show that the clogging of the filter in this period was relatively low and carbon filter had good performance. At first, the water output velocity was high but it decreased by time. According to analytics, the difference between input and output parameters in level of five percent were significant for acidity and electrical conductivity.

The aim of this study is the investigation of nitrate removal from aqueous solution using quartz sand – supported zero valent iron nano particles (Sa-Fe0). The synthesis of Sa-Fe0 was based on the reduction of ferrous iron with borohydride, in which quartz sand acted as a porous-based support material. The structure of adsorbent was characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET-N2) analysis. The SEM images revealed that nano zero valent iron particles (nZVI) immobilized on Sa-Fe0 were spherical and clearly discrete and uniformly dispersed on the surface of the stabilizer without any obvious aggregation. In the batch mode adsorption studies, the effects of the contact time, initial nitrate concentration of solution, sorbent dosage,temperature and initial pH on the nitrate adsorption by the Sa-Fe0 have been studied. The adsorption capacity decreased with increasing the Sa-Fe0 dosage and initial pH value of the solution but increased with the increase in the temperature and initial concentration of nitrate. Removal of nitrate using Sa-Fe0 was in accordance with the pseudo first order kinetic model. The initial phase with the rapid rise of the adsorption rate was about 8h and the removal efficincy in this time interval was about 85% for the initial nitrate concentrations of 100 mg/L. The equilibrium data fitted well to the Langmuir model. The maximum adsorption capacity of Sa-Fe0 for nitrate was 20.833 .

Groundwater in many parts of the world is the main source of drinking water. The Shahrekord aquifer (Iran) supplies the drinking water to the residents of Shahrekord. The aim of this research was to geostatistically analyze and map nitrate and phosphate concentrations in this aquifer. For this purpose, 100 agricultural wells, located in the Shahrekord plain, were sampled on three different dates during 2010 and water samples were analyzed for nitrate and phosphate. The results presented here are based on the average concentrations of the three samples. The mean concentrations of nitrate and phosphate were 25.9 and 0.09 mg/L, respectively. Comparison shows that these mean concentrations have increased since 2007. The spatial variability of nitrate and phosphate were better described by spherical semivariogram models. Examination of maps shows that the southeast of the aquifer had the highest concentrations of both nitrate and phosphate. In some wells, located in the southern part of the aquifer, the concentration of nitrate sometimes exceeded the permissible level of 45 mg/L. This may be attributed to the presence of the Shahrekord municipal wastewater treatment plant, the shallower water table in this part, and also due to the inflow of groundwater.

Nitrate leaching from the agricultural fields to the surface water via subsurface drainage systems is one of the disadvantages of these systems. As these nitrogen losses often lead to the pollution of both surface and groundwater, they are likely to result in environmental degradation that will be detrimental to aquatic life, plants, animals, and humans. There are some traditional methods for nitrogen removal such as biological processes, chemical processes and physical operation. Recently, the biological processes have proven to be the most economical, feasible and efficient method for nitrogen removal. Furthermore, this method is the most promising method available for removing nitrate from water in the saturation conditions. Since subsurface soils are generally limited in the amount of available organic carbon, most microbial denitrification processes require additional carbon sources to sustain these activities. In this study, barley straw was used as a carbon source to enhance the denitrification processes and the effect of that on effluent nitrate and ammonium were evaluated. Two forms of position of this biofilter near the drainage pipe to remove the nitrate form the drainage water were investigated in the laboratory study. The results showed 60% of influent nitrate was removed by these two forms of position over the study period. These biofilters also could remove more than 85% of influent nitrate after 8 weeks. Also, the results showed that this treatment had reduced the effluent nitrate concentrations below the USEPA maximum contaminant level for drinking water of 45 mg L-1 nitrate at the end of the study.

Nitrogen (N) loss from irrigated cropland, especially in rice paddies, results in low N-use efficiency and groundwater contamination. Soil conditions that increase ammonium and nitrate ion retention alleviate these problems. Clinoptilolite, a naturally occurring zeolite with high ion-exchange capacity, may be used to adsorb ammonium and retard excess leaching of nitrate. The objectives of this research were to determine the effects of different rates of Na-zeolite application (0, 2, 4, 8 and 16 g/kg soil) on pore water velocity and leaching of ammonium and nitrate applied as ammonium nitrate fertilizer to a silt loam soil at a rate of 350 kg N/ha under saturated conditions similar to that of a rice paddy. The results indicated that Na-zeolite applications of 2, 4 and 8 g/kg soil increase the pore water velocity by 5.0%, 19. 9, 68.0 and 58/6% compared with the control treatment, respectively. The maximum relative concentration (c/co) all treatments for the nitrate breakthrough curve (BTC) occurred at pore volume of about 0.5. When applying 39.1 cm of leaching water, leached nitrate by 86.9%, 66.00% and 48.5% of total applied nitrate at the soil surface with zeolite applications of 2, 4 and 8 g/kg soil, respectively. Although the ammonium discharged from all treatments was negligible (3.95, 3.48, 3.13 and 2.28 percent of total applied ammonium at the soil surface), the statistical analysis indicated significant differences among treatments that received zeolites. The relationship between the hydrodynamic dispersion coefficient (D) of nitrate and pore water velocity (v) was not linear and by increasing zeolite application to the soil, the value of D increased as well.

Nitrogen (N) loss from irrigated cropland, especially in rice paddies, results in low N-use efficiency and groundwater contamination. Soil conditions that increase ammonium and nitrate ion retention alleviate these problems. Clinoptilolite, a naturally occurring zeolite with high ion-exchange capacity, may be used to adsorb ammonium and retard excess leaching of nitrate. The objectives of this research were to determine the effects of different rates of Na-zeolite application (0, 2, 4, 8 and 16 g/kg soil) on pore water velocity and leaching of ammonium and nitrate applied as ammonium nitrate fertilizer to a siltyloam soil at a rate of 350 kg N/ha under saturated conditions similar to that of a rice paddy. The results indicated that Na-zeolite applications of 2, 4 and 8 g/kg soil increase the pore water velocity by 5.0%, 19. 9, 68.0 and 58/6% compared with the control treatment, respectively. The maximum relative concentration (c/co) all treatments for the nitrate breakthrough curve(BTC) occurred at pore volume of about 0.5. When applying 39.1 cm of leaching water, leached nitrate by 86.9%, 66.00% and 48.5% of total applied nitrate at the soil surface with zeolite applications of 2, 4 and 8 g/kg soil, respectively. Although the ammonium discharged from all treatments was negligible(3.95, 3.48, 3.13 and 2.28 percent of total applied ammonium at the soil surface), the statistic analysis indicated significant differences among treatments that received zeolites. The relationship between the hydrodynamic dispersion coefficient (D) of nitrate and pore water velocity (v) was not linear and by increasing zeolite application to the soil, the value of D increased as well.