A study on municipal leachate treatment through a combination of biological processes and ozonation

Abstract

Landfill is the most commonly method of municipal solid waste disposal in many countries. This practice has great potential to produce highly polluted leachate in massive quantities, which can cause environmental contamination. Biological processes are known as a common method to treat municipal leachate however this process alone in is less effective, especially in reducing the concentration of organic pollutants (BOD5/COD ratio). Leachate properties are site-specific and greatly influenced by landfill age. This study focuses on the investigation of treatment methods that can increase the extent of leachate biodegradability by applying an ozone concentration of 2.5 mg/L with up to 360 minutes of contact time. In this study, batch reactors were used and operated in anaerobic and aerobic conditions. The leachate used here represents both young and old leachate. Several treatment combinations were compared: Variation I (a combination of biologically aerobic and anaerobic process), Variation II (ozonation included as a pre-treatment process), and Variation III (ozonation was included as a post-treatment process). The results suggest that the BOD5/COD ratios of young and old leachates were 0.58 and 0.21, respectively. The COD removal for a young and old leachate treatment by biological process alone was 96.8% and 50.8%, respectively. Meanwhile, a combination of anaerobic-ozonation-aerobic processes gave better COD removal. Ozonation had a significant effect on the old leachate treatment, where the COD removal rose from 50.8% to 75%. Ozonation is a type of technology that can be applied to a subsequence treatment of biological processes in order to elevate the COD removal efficiency.