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Potential of granulated modified nanozeolites Y for MTBE removal from aqueous solutions: Kinetic and isotherm studiesAdsorption of methyl tert-butyl ether (MTBE) from aqueous solutions by granulated modified nanozeolites Y was investigated. Nanozeolite Y powders were converted into granulated zeolites and subsequently modified with two cationic surfactants (20 mmol/dm3), to be used as adsorbent. Granulated nanozeolites were characterized by BET surface area analysis, elemental analysis and X-ray diffractometer. -Hexade-cyltrimethylammonium (HDTMA-Cl) modified granulated zeolite had more effective performance than N-cetylpyridinium bromide (CPB) modified granulated zeolite. The most conventional adsorption isotherms and kinetic models were applied to describe MTBE adsorption and reaction dynamic, respectively. The equilibrium sorption data fitted the Langmuir 2 isotherm model and the kinetic study was followed the pseudo-second-order model. The maximum adsorption capacities for HDTMA-Cl modified zeolite and CPB modified granulated zeolite were 333.33 and 142.8 mg/g, respectively as calculated by the Langmuir model. This study demonstrated that the removal of mtbe by granulated modified nanozeolites Y is a promising technique.

The performance of an aerated submerged fixed‐film reactor (ASFFR) under simultaneous organic and ammonium loading and its effect on nitrification was studied. Organic loadings varied in the range of 1.93 to 5.29 g chemical oxygen demand (COD) m−2d−1and NH4–N loadings were in the range of 116 to 318 mg NH4–N m−2d−1Increments of loading rates were obtained both by increasing the flow rate and increasing the influent substrate in individual pilot runs. Results showed that with organic loading rates up to 3.97 g COD m−2d−1, complete nitrification was achievable. Although high organic loading such as 5.29 g COD m−2d−1could cause nitrification to stop, shifting to lower organic loadings made nitrification start and set rapidly to its previous steady‐state concentrations. Comparison of results showed that in the ASFFR, nitrification would be severely affected by an organic loading rate of 5.29 g COD m−2d−1by increasing either the flow or the influent substrate. It should be noted that the average value of dissolved oxygen was 3.4 mg L−1with an air supply of 15 L min−1, and there was no indication of oxygen limitation. The results of this study show the flexibility of ASFFRs under changing organic loads. Furthermore, for achieving complete nitrification and optimum application of these reactors for protecting receiving water from the environmental hazards of ammonium, the maximum organic loading that would present complete nitrification should be considered.

A cross-sectional survey was conducted through Tehran city and a field study was conducted to prepare main and accessory drainage channels map. Three main drainage channels were identified for this research and some sampling stations were chosen. Three stations selected in south of Tehran. The reason for selecting these stations is that all urban surface runoff completelypass through these points and samples taken from these points are representative of all kinds of pollutants that transit from city surface. Another Three stations were selected in center and further three stations were selected at north of Tehran. Surface runoff flow in three main channels, from north to south of Tehran, converge at south of Rey city and finally end up to Ghom Salt lake. The stations were chosen at three trajectories, Sorkhe Hesar, Emad Avard, Kan. At each month two samples were prepared from nine different stations. After collection of samples with respect to standard methods, they were dissolved in nitric acid and then analyzed by atomic absorption device. The results show that the concentrations of pollutants increased from north to south. For instance, Zinc had most concentration with monthly average of 0.98 mg/l and Nickel had the lowest amount with 0.02 mg/l in southern stations. Average concentration of Zn, Pb, Cd, Cu and Ni were: 0.638, 0.097, 0.04 and 0.035 mg/l respectively. Total average concentrations of heavy metals at three main channels were of 0.177, 0.176 and 0.145 mg/l. Emad Avard was the most polluted channel.

Concern over agricultural diffuse pollution sources in integrated water quality management has been growing recently. High nitrogen fertilizers application rates may increase the potential groundwater pollution. These effects were investigated in Andimeshk and Susa plains that cover an area of 1100 km2between the Dez and Karkhe rivers in north of Khozestan-Iran. This region divided to 4 sub-regions A, B, C, and D. Additionally 168 groundwater samples were collected from 42 water wells during the months April, May, August, and September of 2004. The Hackspectrophotometer nitrate test was used to measure the NO3−concentration in water samples. Information about further nitrate data was obtained. A questionnaire procedure was used for collection N-fertilizers application rate data in studied area. The results demonstrated that all of the groundwater samples have NO3t-concentration below the EPA MCL (44.27 mg/l) and WHO guideline (50 mg/l). The mean nitrate concentrations are 16.1, 19.5, 13.3, and 7.9 mg/l in sub-regions A, B, C, and D respectively. There are different amount of N-fertilizers applied in sub-regions A, B, C, and D. Correlation between NO3t- concentrations and N-fertilizers rate suggests a inverse correlation between Nfertilizers application rate and ground waters nitrate concentrations in studied area (r=−0.69).