Greywater Treatment Using Single and Combined Adsorbents for Landscape Irrigation

摘要

Greywater reuse can be considered as an additional supply of water not only to protect water resources but also to reduce water shortage. Thus, the aim of this research is to examine the feasibility of three adsorbents (activated carbon (AC), Iranian natural zeolite (Z) and stabilized nano zero-valent iron (nZVI)) in single and combined forms to treat greywater for reuse in landscape irrigation. For this purpose, greywater samples were collected from student hostel of Fasa University and analyzed in a batch mode experiment. Also, the adsorption of COD was studied in terms of kinetic, isotherm and thermodynamic models. The results indicated that among the seven treatments, the combination of AC, Z and nZVI had the best performance in greywater treatment. 85.75% removal of COD, 91.81% of TDS and 98.1% of turbidity were achieved by triple combined treatment. In double combined adsorbents, the highest adsorption rate of COD, TDS and turbidity was accomplished when AC+nZVI, AC+Z and nZVI+Z were used, respectively. The results also indicate that single adsorbents alone are not adequate to guarantee a sufficient reduction of COD, TDS and turbidity. Kinetics of COD removal by all treatments obeyed to pseudo-second-order model and the Freundlich isotherm closely fitted the experimental data. The COD data demonstrated that the sorption process is spontaneous and endothermic. The results indicated that the triple combined adsorbents were able to reduce the COD, TDS, turbidity and pH level to the required reuse in landscape irrigation and the results were satisfactory according to Iranian standards.