Abstract
In this study, the application of ozonation and ozonation with hydrogen peroxide processes for landfill leachate treatment was investigated. The effluents were characterized by COD 710 mgO2/dm3 and BOD5 72 mg O2/dm3. According to the adopted indicators, the determined BOD/COD ratio of 0.1 in raw leachates indicates a stabilized landfill. Ozone was applied at doses of 0.15 - 0.6 gO3/dm3, and hydrogen peroxide at such doses to keep the weight ratios of H2O2/O3 0.4 - 1.6. The maximum COD and UV absorbance removal was respectively 29% and 51% by applying a high ozone dose of 0.6 gO3/dm3. After oxidation, the ratio of BOD/COD was increased from 0.1 up to 0.3. It has been shown that by using hydrogen peroxide in ozonation, organic compounds expressed as COD can be efficiently removed from the effluents. The best conditions for the H2O2/O3 process were obtained with a H2O2/O3 ratio of 0.8 and ozone dose of 0.6 gO3/dm3. Under these conditions, the removal efficiency of COD was 46%.
Highlights
Ozone is a strong oxidant that reacts at ambient temperature with most organic compounds, either directly by electrophilic attack of the ozone molecule, or indirectly by generating OH radicals [1]
According to the adopted indicators, a BOD/chemical oxygen demand (COD) ratio below 0.12 in raw leachates indicates this type of landfill [18]
In studies using the ozonation process, the effectiveness of COD removal ranged from 20% to 20.9%
Summary
Ozone is a strong oxidant that reacts at ambient temperature with most organic compounds, either directly by electrophilic attack of the ozone molecule, or indirectly by generating OH radicals [1]. The ozonation process is used, among others, for the treatment of leachates from stabilized landfills in combination with sorption, coagulation, as well as biological processes, the operation time of which exceeds 5 years In these types of landfills, organic compounds that are harder to biodegrade prevail. As a result of ozone treatment, a part of organic compounds undergoes transformation into more readily biodegradable forms, which enables their further purification by biological methods. In this case, an increase in the BOD/COD ratio is observed, the share of biodegradable fractions in the effluents increases. In addition to removing the organic compounds, ozonation reduces the color of landfill leachates and eliminates odor nuisance [2]
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