This study aimed to investigate the effect of anthropogenic factors, including land use, environmental factors, and topography at a radius of 400 m around the wells on nitrate concentration so as to assess the health risk from nitrate concentration and accordingly analyze its sensitivity using field and software surveys. In this study, 70 samples of drinking water were taken from 35 wells in two seasons: low rainfall and high rainfall in 2017 and the concentration of nitrate was determined using spectrophotometry. The area of four types of land use in a radius of wells was determined using Google Earth and GIS software. Pearson correlation and t-test were employed to determine the effect of the above factors on nitrate concentration by SPSS. Health risk assessment was performed for three age groups and analyzed by a sensitivity analysis using Monte Carlo. The results showed that eight samples (11.4%) exceeded the recommended. limit of 50 mg/L. The concentration of nitrate in wells without sanitary protection area was 51.1 ± 11.01. The wells at the bottom of the groundwater flow have an average nitrate concentration of 41.39 ± 11.85. The highest CDI (0.98 mg/kg) and HQ (0.75) values were belonged to age group of 0–6 years; approximately 90% of this age group was at high risk during this high rainfall season. Nitrate concentration was recognized as the most effective factor in the non-carcinogenicity risk of nitrates.

Electrocoagulation is a widely used method for treating leachate since it is cost effective and eco-friendly. In the present study, the electrocoagulation process was employed to remove chemical oxygen demand (COD), NH₄⁺, total dissolved solids (TDS), total suspended solids (TSS), turbidity, and color from landfill leachate. At first, lime was used as a pretreatment, then the Fe/Gr and Ti/PbO₂/steel electrodes were used, and the optimum electrode was selected. Afterwards, the effects of some variables, including pH, current density, temperature, the inter-electrode distance, and the type of electrolyte were investigated. Results showed that COD, NH₄⁺, TSS, TDS, electrical conductivity (EC), turbidity, color, and pH of effluent pretreatment chemical reached 22,371, 385, 884, 21,820 (mg/L), 13.8 (ms/cm³), 1355 (NTU), 8500 (TCU) and 10, respectively (the removal efficiency was 0, 20.37, 32.4, 61.99, 59.18, and 56.6 percent). With the Fe/Gr electrode, the optimal condition was observed as follows: pH of 7.5, current density of 64 mA/cm², inter-electrode distance was equal to 1.5 cm, temperature at 20 °C, and retention time 2–4 h. Overall, the electrocoagulation with the Fe/Gr electrode was a suitable technology for landfill leachate treatment due to its effectiveness for the removal of both COD and NH₄⁺, with advantageous performance indicators.

Iran's most important iron ore mine is located in the central region, and because of the water shortage in this area, the need to reuse the effluent from this mine is essential. On the other hand, there are no suitable conditions for treating large effluent volumes in iron mine in central Iran. For this reason, produced effluent should be reduced and returned to the consumption cycle by using appropriate technology. This study aimed to investigate the ozonation/lime effect on polymer consumption reduction and evaluate the treatment and economic efficiency compared to the currently used treatment method (coagulation-flocculation without ozonation/lime).The use of ozonation along with the coagulation and flocculation process has been an effective factor in reducing all the studied indicators, which has been a much more significant reduction effect for turbidity (95%), decreasing from 374-350NTU in the non-ozonation process to 110-160NTU, and Chemical oxygen demand (37%). In addition to increasing the treatment efficiency, the hybrid ozonation/coagulation and flocculation process reduced operation costs. The ozonation process caused the high-level conversion of Fe²⁺ and Al²⁺ to Fe³⁺ and Al³⁺ (> 90%), thus it improved wastewater treatment and increased cost benefit. The hybrid process was affected in improving the effluent quality and reducing the produced sludge volume. The ozonation process caused sludge volume reduction or has photocatalytic effect on it. It effected the micro-sized bubbles production reduction in sludge volume unit. However, estimating the cost–benefit of using this method can be beneficial in making the final decision on whether to use it or not.

MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it is expected that its interference in the photocatalytic removal of organic matter includes MTBE. Nevertheless, there is a lack of observation of this effect. In this study, the effect of arsenic on the photocatalytic removal of MTBE using an Fe₂O₃/MgO catalyst under UV radiation was investigated. Using an experimental design, modeling, and optimizing operational parameters, such as the arsenic and MTBE concentrations, catalyst dosage, pH, and reaction time, were studied. The synthesized nanocatalyst had a uniform and spherical morphological structure and contained 33.06% Fe₂O₃ and 45.06% MgO. The results indicate that the best model is related to the quadratic (p-value < 0.0001, R² = 0.97) and that the effect of the MTBE concentration is greater than the others. The highest removal efficiency was taken in an initial concentration of 37.5 mg/L MTBE, 1.58 mg/L Fe₂O₃/MgO, pH 5, and a reaction time of 21.41 min without any As. The removal efficiency was negatively correlated with the initial MTBE concentration and pH, but it was positively associated with the Fe₂O₃/MgO dosage and reaction time. Finally, the presence of arsenic decreased the removal efficiency remarkably (90.90% As = 0.25 μg/L and 61% As = 500 μg/L). Consequently, MTBE was removed by the photocatalytic process caused by Fe₂O₃/MgO, but the presence of arsenic was introduced as a limiting factor. Therefore, pretreatment for the removal of arsenic and more details of this interference effect are suggested.