Ozonation as a pre-treatment of landfill leachate

Abstract Ozone is an oxidizing agent with a potential for removing complex molecules, including those of difficult microbiological decomposition, such as the molecules found in landfill leachates. This effluent presents high organic content, including recalcitrant molecules. Therefore, this study evaluated the efficiency of ozonation in the treatment of raw leachate at the Primavera landfill, located in Mato Grosso, Brazil. The experiments were carried out using the batch system. The leachate pH value was set at 7 and 10, and the contact times between the gas and the leachate were 20, 40, 60, 80, and 100 minutes. Throughout the study, we analyzed color, turbidity, pH value, chemical oxygen demand (COD), and ultraviolet absorbance at 254 nm (UV abs) of the leachate, both before and after ozonation. Results show that ozonation presented high removal of color, COD and UV abs when pH was 7. In contrast, turbidity removal was higher when the pH value was 10. Regarding contact time, we observed a high removal of color (between 80% and 90%) and UV abs (between 60% and 70%) at 40 minutes, depending on the pH value. Removal was also high for turbidity (approximately 75%) starting at 20 minutes with the pH value at 10, and at 70 minutes with pH at 7. The removal relation within all analyzed parameters (due to ozone consumption) decreased throughout the reaction time. Thus, we concluded that ozonation as a pre-treatment of leachate is indeed satisfactory because of its great capacity for organic material removal.

摘要：臭氧作为一种氧化剂，具备去除复杂分子的潜力，其中包括难生物降解的分子，例如垃圾渗滤液（landfill leachate）中含有的组分。该类渗滤液有机物含量较高，且含有难降解有机物。有鉴于此，本研究针对巴西马托格罗索州普里马韦拉（Primavera）垃圾填埋场的原渗滤液，评估臭氧氧化法的处理效能。本实验采用批式反应体系（batch system）开展，设置渗滤液pH值为7与10两个梯度，气液接触时间分别为20、40、60、80及100分钟。研究全程分析了臭氧氧化前后渗滤液的色度、浊度、pH值、化学需氧量(chemical oxygen demand, COD)以及254nm紫外吸光度(ultraviolet absorbance, UV abs)。实验结果显示，当pH值为7时，臭氧氧化对色度、COD及UV abs的去除效果优异；与之相对，当pH值为10时，浊度去除率更高。针对接触时间因素，研究发现在40分钟时，色度去除率可达80%~90%、UV abs去除率可达60%~70%，具体去除效果受pH值影响。浊度去除方面，当pH值为10时，仅需20分钟即可实现约75%的去除率；而当pH值为7时，则需70分钟方可达到相近去除效果。随着反应进程推进，所有待测参数的去除效能均呈下降趋势，该现象与臭氧消耗量的变化相关。综上，本研究认为臭氧氧化作为渗滤液预处理工艺具备良好的有机污染物去除能力，应用效果令人满意。