Ozone catalysed with solids as an advanced oxidation process for landfill leachate treatment

Abstract

Heterogeneous catalytic ozonation (HCO) of wastewater is gaining both research and industrial interests. It is proved to be an advanced oxidation process since it involves hydroxyl radicals as oxidation species. Few studies have been carried out to test HCO in the treatment of landfill leachates. This work has been carried out to test three types of catalysts: activated carbon (AC), expanded perlite (EP) and titanium dioxide (TiO2) combined with ozone at 80 g/m3 gas concentration for the treatment of a leachate generated by Jebel Chakir landfill site near Tunis-capital of Tunisia. The work has shown a reduction in COD of about 45% and an increase in biodegradability (BOD5/COD) from 0.1 to 0.34. A catalyst concentration of 0.7 g/L was found optimal for the treatment of the leachate.

Landfill leachate treatment with ozone and ozone/hydrogen peroxide systems

“…For example heterogeneous catalytic ozonation (HCO) was successful to reduce COD by 89% at an ozone consumption of 1.5 g O 3 /g COD [34] and by 75% at an ozone consumption of 1.7 g O 3 /g COD removed [35]. In a previous work that employed HCO to treat the leachate used in this study, a decrease in COD by about 45% at an ozone consumption of 1.7 g O 3 /g COD removed was obtained [36]. In addition, Fig.…”

“…6 shows that the leachate presented low biodegradability (BOD 5 /COD = 0.1), which was not enhanced when both systems were used except for O 3 /H 2 O 2 system at [H 2 O 2 ] = 2 g/L that gave a biodegradability value of 0.7. Several studies have also shown improvement in biodegradability following treatment of leachates with AOPs particularly those based on ozone [5,17,[35][36][37]. Bila et al [17] used ozone in conjunction with a physicochemical and biological systems and found that ozonation alone was capable to enhance biodegradability from 0.05 to 0.3 at an ozone dose of 3 g/L and reduce COD by about 50%.…”

“…This small lowering in pH may be attributed to hydrogen peroxide, which is a weak acid (H 2 O 2 ⇔ HO 2 − + H + , pK a = 11.6). Several studies have also shown small changes in pH following ozonation of a leachate [5,29,36].…”

“…leachate age, pH, organic composition, • OH scavengers, etc.). Typically for intermediate COD removal (about 50%), when ozone-based AOPs are used, ozone consumption values are about 1.5 kg O 3 /kg COD [34][35][36], but they increase up to 3.5 kg O 3 /kg COD when the target COD removal is high (about 95%) [33].…”

Advanced Oxidation Processes for Wastewater Treatment: State of the Art

“…When the iron ion concentration was increased to 90 mg/L, the removal performance decreased. Tizaoui et al (2007) tested the effect of various catalysts for the treatment of a leachate before its deposit at a dedicated treatment facility. The catalysts studied were activated carbon, expanded perlite, and titanium dioxide, combined with ozone at 80 g/m 3 .…”