Aims: The purpose of this study was to determine the inhibition and anaerobic biodegradation of benz[a]anthracene-7, 12-dione (BaAQ) via the specific methanogenic activity (SMA) test. Materials and Methods: In this study, 120 mL vials were filled with given concentration of BaAQ, anaerobic biomass and substrate. Each batch experiment was lasted 13 to 26 days. The inhibition effects of BaAQ with concentrations of 0.5, 5, 25, 50, 100, 250 and 500 mg/L on the methanogenic process was investigated in the presence of volatile fatty acids including acetic, butyric and propionic acids. Results: In some eatch test, the gas production was stopped after 13 days (312 h). Therefore, 312 h was considered as compared base of gas production. After this time, methane production cumulative rate was calculated for the each SMA. After 13 days (312 h) the lowest and the highest cumulative methane has been produced (per mL) at the presence of concentrations of 250 and 0.5 mg/L of BaAQ, respectively. Conclusion: The results of this study showed that the BaAQ with concentration of 250 mg/L has more inhibition effect on methane production rather than other concentrations (even of 500 mg/L). Therefore, we should not always expect that higher concentrations of toxic compounds had more inhibitory effects than low concentrations of them.

Aims: In this study, the effectiveness of modified clay [montmorillonite (Mt)] with polyethylene glycol (PWG) and tetradecyl trimethyl ammonium bromide (TTAB) on the benzene, toluene, ethylbenzene and xylene (BTEX) removal from aqueous solution was investigated. Materials and Methods: The batch adsorption experiments including surfactant loading rates (0.2-4 cation exchange capacity [CEC] of the clay), contact time (0-24 h), pH (4-12) and adsorbate concentration (10-200 mg/L) were conducted at room temperature (25°C) with 100 mL of BTEX solution into a 200-mL conical flask and mixed by an orbital shaker (250 rpm for 24 h). Results: It was found that the optimum adsorption condition obtains for the surfactant loading rate of 200% clay CEC for both the adsorbents at the contact time of 24 h. The sorption capacity of BTEX by both the adsorbents was in order of benzene toluene ethylbenzene xylene. The results of both the adsorbents also showed that the pseudo-second-order kinetic model and Freundlich isotherm model fitted the experimental data better than of other kinetic and isotherm models, respectively. Conclusion: The adsorption capacity of TTAB-Mt (22.11 mg/g) was slightly higher than PEG-Mt (18.77 mg/g). With regard to lower toxic effects and lower cost of nonionic surfactants than the cationic type, using the nonionic modified Mt is preferred than cationic modified Mt for the removal of BTEX from aqueous solution.

Aims: The objective of this study was to evaluate phenol removal from a synthetic solution using modified zeolite (clinoptilolite) with FeCl ₃ as an adsorbent. Materials and Methods: The zeolite samples were crushed and granulated using standard ASTM sieves (mesh size of 20). The prepared zeolite then was modified by FeCl ₃ . The chemical composition and the surface area of the zeolite were analyzed using XRF and N ₂ gas via BET isotherm and Belsorb software. In this study, different parameters including pH (3, 7, and 12), initial concentration of phenol (25-200 mg/l), contact time (20-240 min) and the amount of modified zeolite (0.25-3 g/l) were examined in a batch reactor. The concentration of phenol was measured at wavelength of 500 nm by a spectrophotometer. Results: The results of this study showed that as the initial concentration of phenol, the adsorbent dose and the pH in the range of 3-12 increased the adsorption / removal of phenol increased. Phenol adsorption equilibrium was achieved within 100 min contact time and the optimum pH for adsorption of phenol using zeolite was found as 3. The adsorption data complied with Langmuir isotherm (r ² =0.98). Conclusions: The results showed that modified zeolite can be used effectively in removing phenol. The removal efficiency of phenol in lower pH was more than in higher pH. Also, due to the low price of the zeolite and its simple modification, it can be used for removing hazardous pollutants in water and wastewater.

Aim: This study aimed to evaluate effectiveness of the coagulation process for reactive blue 19 dye (RB19) removal from textile industry wastewater. Materials and Methods: In this research, coagulation process using three coagulants poly aluminum chloride (PACl), alum, and ferric chloride in the presence of anionic polyelectrolyte and kaolin as coagulants aid were studied for the removal of RB19 dye from synthetic wastewater. The influence of effective parameters such as pH, coagulant dose, initial dye concentration, and addition of coagulants aid was investigated. Results: The results showed that the best dye removal efficiency using three coagulants was archived in neutral pH. Under this condition, the optimum dose of PACl, alum, and ferric chloride was 200, 300, and 400 mg/L and corresponding to dye removal efficiency of 91%, 92%, and 81%, respectively. Addition of polyelectrolyte as a coagulant aid with ferric chloride slightly increased process efficiency, whereas adding polyelectrolyte with alum and PACl slightly decreased dye removal efficiency. By addition of kaolin as a coagulant aid with PACl increased dye removal efficiency about 5%, whereas adding kaolin with alum slightly decreased removal efficiency and can be ignored also, in the case of ferric chloride no significant effect on process efficiency observed in the presence of kaolin. Conclusion: Regarding to obtained results, coagulation can be a robust treatment method for the management of wastewater containing reactive dye.

Aims: In this study, the temporal variations of Benzene, Toluene, Ethyl benzene and Xylene (BTEX) in the atmosphere of Tehran city was investigated. Materials and Methods: Two air quality monitoring stations, Aghdasieh and Ray, in different locations of the city were selected. Sampling was carried out hourly from Nov 23, 2007 to Dec 22, 2007 in Aghdasieh air monitoring station and from Dec 10, 2007 to Jan 9, 2008, in Ray's air monitoring station by an online BTEX monitoring system. The correlations, repeated measures variance and regressions tests were used for statistical analysis. Results: Results indicated that, concentrations of these compounds were sometimes higher than standard limits and were significantly different in selected stations. However, an approximately similar increasing and decreasing trend was seen among them. In most cases, equations for concentration variations were sinusoidal or fourth-order. Conclusion: According to the results, sinusoidal and fourth-order are most suitable equations for BTEX concentration variations in the ambient air of the city, and the trends of variations are similar in different places of the city.