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Recycling of waste materials plays a significant role in waste management strategies, but the interactive properties of recycled aggregates in concrete have been considered by only a few researchers. The experimental study reported in this paper focused on the effects of recycled concrete aggregate (RCA) and waste glass (WG) on the properties of concrete. The response surface methodology was used to optimise and model the results of tests for compressive strength, tensile strength, slump, water absorption, electrical resistivity and hardened unit weight. The effective variables of the experiment were RCA (0–65%) as coarse aggregate replacement and WG (0–40%) as fine aggregate replacement. The results obtained indicate that high volumes of waste materials could be used in concrete without a significant reduction in the mechanical and durability (namely water absorption and electrical resistivity) properties of the concrete. Moreover, when WG was substituted in the mixture, the water absorption, electrical resistivity and workability of the concrete improved and the use of RCA had a significant influence on the mechanical properties of the concrete. Based on statistical analysis, all the proposed models were adequate, with coefficients of determination above 0·95. The optimum condition in which all response targets performed properly was found to be 17% of RCA and 35% of WG.

Background and Purpose: Elevated nitrate concentrations in drinking water can cause methemoglobinemia in infants, stomach cancer in adults and nitrate poisoning in animals as well. Modeling of nitrate fate and transport in groundwater to minimize nitrate concentration in groundwater has been studied by numerous researchers. Materials and Methods: In order to determine the potential nitrate and nitrite ions contamination of groundwater, 93 groundwater samples were collected. All the observation wells were located in agricultural areas. In order to measure the amount of nitrogen in the soil, 45 samples from the entire region were randomly selected and analyzed. Results: The results showed that in 82% of groundwater samples nitrate concentration has exceeded the standard level of 10 mg/l as N. Water level in orchard fields were between 1m to 3.7 m below the ground surface. Nitrate concentration in all samples from the citrus orchard fell within the standard levels. Simulation of potential nitrate movement was performed in 4 different areas. Results indicated that in the rice field nitrate penetrated to the depth of 3.2 m that was the deepest nitrate seepage between four areas. Probable reasons of different results in these areas are discussed. Conclusion: The simulated and observed measured data showed that the model was able to predict the groundwater quality changes within the soil profile and the aquifer.

Background and purpose: Excessive amount of heavy metals in industrial wastewater is a seriously crucial issue and requires efficient methods to be introduced and dealt with. Meanwhile, steel making plants as productive units in every country release large amounts of fluid into surface and underground sources. Typically, this wastewater contains heavy metals in minor amounts, while this amount could cause severe damages to the living organisms. Materials and methods: In this study, removing iron, manganese, zinc and total dissolved solid in a typical wastewater resulted from steel making plant was considered using reverse osmosis (RO) and nanofiltration (NF) membranes. At first, different pH values and operating pressures were applied to the wastewater. Then, these parameters were evaluated for a wastewater only containing iron to compare the interaction of other elements in iron removal. Results:The results indicated that RO and NF membranes could successfully treat industrial wastewater containing several heavy metals with high concentrations of Fe, Zn and Mn, especially at optimum pH and pressure. Moreover, the interaction of other heavy metals and components in the influent decreased the efficiency of RO but improved the NF efficiency to remove iron. To have a better image, a formula was proposed for each method to represent the influence of the parameters on removal rates. Finally, cost estimation for both procedures showed that RO was not economicallytechnically efficient in comparison with NF. Conclusion: NF showed an acceptable performance with high water flow which made it more suitable for industries. At the end, the relative cost analysis showed that even if the initial price of NF is high, the energy consumption and total cost of RO will be higher.