Effective removal of chemical oxygen demand from sanitary landfill leachate using raw and chemically treated olive stones

Abstract

ABSTRACT The biosorption capacity of untreated olive stones (OS) and olive stones chemically treated (TOS) to remove COD's landfill leachate was investigated in this study. Characterization of the both biosorbents was performed using XRD, SEM, FTIR and 13C NMR techniques. Leachate was taken from Hassi Bounif Sanitary Landfill (HBSL) in Oran (Western Algeria). So, Hassi Bounif Leachate (HBL) exhibited a basic pH between 7.83 and 8.2, high COD level varying from 5,200 to 8,000 mg.L-1, low BOD5/COD ratio from 0.1 to 0.16, and high NH3-N concentrations ranged from 2,300 to 2,800 mg.L-1. Accordingly, this leachate can be classified as an intermediate leachate that is likely to stabilize. Biosorption studies were carried out in a batch system and the effects of contact time, media pH, and biosorbent mass on the removal efficiency of COD were explored. Based on results obtained at pH=11, contact times of 55 and 105 min were achieved for biosorbent masses of 0.1 g for TOS and 0.3 g for OS, respectively, and were found to be the optimal operating conditions for HBL treatment. Thus, the highest COD removal efficiencies of 79.94 and 67.04% were reached for TOS and OS, correspondently. The pseudo-second order model was the best fitted to our experimental data with high regression coefficients (R2 ≥ 0.98). The Langmuir isotherm model adequately represented the COD removal process, with a maximum adsorption capacity of 90.91 mg.g-1 for TOS and 31.25 mg.g-1 for OS at T=50°C and pH=11. The thermodynamic parameters indicated that the biosorption process was feasible, spontaneous, and endothermic. These findings suggested that TOS might be employed as an inexpensive and effective biosorbent for COD removal from stabilized leachate. They can also provide baseline information and design assistance for a leachate treatment plant at the HBSL site, as well as for any sanitary landfill in Algeria.