Biodegradability Enhancement of Mature Landfill Leachate Using Fenton Process under Different COD Loading Factors

Abstract

The Fenton process is evaluated as a treatment method to reduce the total organic carbon (TOC) and increase biodegradability of the organic substrate in a mature landfill leachate. Biodegradability was quantified in terms of the ratios between biochemical oxygen demand after 5 days (BOD5) to chemical oxygen demand (COD) (after different Fenton reaction times), and BOD5 (after different Fenton reaction times) to initial BOD5 (original leachate sample), termed as BOD5,0, respectively. An increased TOC removal and improved BOD5/COD ratios were observed following the pH sequence of 3.5 > 6.0 > 2.0. The maximum TOC removal of 61 % and the highest BOD5/COD ratio from 0.11 to 0.37 were observed at pH 3.5. To quantify biodegradability enhancement at different COD loading factors (LCOD) by the Fenton process, the H2O2/Fe2+ ratio was fixed at 1.8 (w/w) and LCOD ranged from 0.22 to 1.19. Experimental results showed that higher TOC removal and biodegradability enhancement were obtained at lower LCOD. Quantitatively, two linear regression equations between LCOD and biodegradability (in terms of BOD5/COD and BOD5/BOD5,0) were established, as: BOD5/COD = 0.57–0.38 LCOD and BOD5/BOD5,0 = 1.40–0.40 LCOD with correlation coefficients (R 2 ) of 0.87 and 0.51, respectively. The experimental work described here, demonstrated that the Fenton process can be used as an effective pre-treatment strategy to increase leachate biodegradability within a short reaction time from 1 to 5 min.