Treatment of landfill leachate using different configurations of ultrasonic reactors combined with advanced oxidation processes

Treatment of leachate generated from municipal solid waste using different configurations of ultrasonic (US) reactors in combination with advanced oxidation processes based on ozone, hydrogen peroxide (H2O2) and Fenton has been investigated in the present work. US configurations investigated were US horn, US flow cell and US bath with variation in mode of irradiation, operating volume and power consumption. The different approaches investigated were only US, US combined with ozone at fixed flow rate as 500 mg/h (US/O3), US/H2O2 and US/Fenton at different loadings of oxidants. For the case of US horn, the obtained extents of COD removal were 6, 24.5, 42 and 73% for different approaches of only US, US+ ozone, US+ H2O2 (5 g/L as the best loading) and US+ Fenton (Fe2+/H2O2 molar ratio as 1:10) respectively. US flow cell gave extent of COD removal as 44, 50, 72 and 92% when operated in different approaches as only US, US+ Ozone, US+ H2O2 (5 g/L as the loading) and US+ Fenton (Fe2+/H2O2 molar ratio as 1:10) respectively. US bath operated under optimized parameters established from studies in US flow cell as H2O2 loading of 5 g/L and Fe2+/H2O2 ratio of 1:10 resulted in COD removal of 90%. Synergetic coefficient and biodegradability index (BI) were also calculated and the most effective process established was US flow cell+ Fenton yielding maximum COD removal of 92% with increased BI from 0.36 to 0.55 and synergetic coefficient of 3.17. Energy efficiency and cost calculations for the US flow cell and US bath with Fenton established that treatment cost was 28.7 and 25 US$/m3 respectively. Overall the combination of US flow cell with Fenton has been established as the most viable approach for leachate treatment.