Response surface methodology approach to the optimization of oil hydrocarbon polluted soil remediation using enhanced soil washing

One of the environmental concerns in recent decades is the prevalence of different pollutants in soil. Hence, the importance of remediation has led to the development of various methods to remediate polluted soil. Among these methods, soil washing has gained significant attention to treat polluted soils. In this paper, the response surface methodology was applied in order to determine the optimal conditions for total petroleum hydrocarbon remediation using nonionic surfactant Brij35 in soil environment. The effect of different factors in soil washing process including surfactant solution concentration and volume, washing time, age of pollution and frequency of washing are evaluated. The predicted values for total petroleum hydrocarbon remediation efficiency by the response functions are in a very close agreement with experimental data [R[-2] = 98.75%]. The second order model was developed as experimented response and optimal conditions were obtained by analyzing the contour and surface plots and also by solving the regression equation using LINGO 9.0 software. The optimal concentrations [8 g/L], volume of surfactant solution [500 mL], washing time [75 min], age of pollution [29 days] and frequency of washing [three times] are determined. In this optimal condition, the removal efficiency has been observed to be 93.54% which conforms to the results of process optimization using response surface methodology. Based on the results, it can be concluded that the response surface methodology is a suitable approach to determine the optimal conditions of soil washing to remediate organic hydrophobic pollutants using the nonionic surfactant Brij35 from the soil

Decolorization of an acidic dye from synthetic wastewater by sludge of water treatment plant

In this research, sludge of Jalaliyeh water treatment plant in Tehran was used as an alternative coagulant for the removal of a specific type of acid dye [acid red 119 [AR119]]. For this purpose, the effect of initial pH, coagulant dose and initial dye concentration on dye removal efficiency were investigated. Results showed that the dye removal rates were largely dependent on pH. When the solution pH was increased from 3 to 8, the dye removal rates decreased from 96.3% to 2.3%. The removal efficiencies of the dye using 130-350 mg dried sludge/L were more than 90% at initial pH =3. With the increase of initial dye concentration in the range of 10-200 mg/L, the removal efficiency increased at first [from 10-40 mg/L] and then declined. So, sludge of Jalaliyeh water treatment plant may be considered as an appropriate coagulant for the removal of AR119 dye