Influence of physical-chemical parameters on the composition of toxic constituents in landfill leachate

ABSTRACT The characterization of leachate generated in landfills can clarify the degradation phenomena that occur inside the waste cells and indirectly indicate their toxic potential. The objective of this study was to evaluate the influence of physical and chemical parameters on toxic components, such as metals and total ammonia nitrogen (TAN), found in the leachate generated by a cell from the Sanitary Landfill in Campina Grande, Paraíba. pH, volatile fatty acids (VFA), total alkalinity (AT), chlorides, chemical oxygen demand (COD), TAN and metals (Pb, Cr, Co, Ni, Fe and Mn) were investigated. The results showed that during the acid fermentation phase a high production of VFA occurred in the landfilled waste mass, which maintained the values of pH below neutrality and contributed for high concentrations of COD, chlorides and a higher toxicity in the leachate compared with the analyzed metals. However, in the case of methanogenic conditions, a decrease in the VFA contents was observed and, with this, the pH tended to be basicity, making the medium more alkaline, favoring the precipitation of the studied metals, but contributing to the high levels of TAN. It is possible to conclude that pH and VFA had a strong influence on the metals (Pb, Cr, Co, Ni, Fe and Mn) and TAN during the 150 days of evaluation.

摘要 对垃圾填埋场产生的渗滤液进行表征，可明确垃圾填埋单元内部发生的降解过程，并间接反映其毒性潜力。本研究旨在探究理化参数对帕拉伊巴州坎皮纳格兰德市某卫生填埋场填埋单元产生的渗滤液中有毒组分（包括金属与总氨氮(TAN)）的影响。本次研究测定了pH值、挥发性脂肪酸(VFA)、总碱度(AT)、氯化物、化学需氧量(COD)、总氨氮(TAN)以及金属（铅(Pb)、铬(Cr)、钴(Co)、镍(Ni)、铁(Fe)和锰(Mn)）。研究结果显示，在酸性发酵阶段，填埋垃圾体内会大量产生挥发性脂肪酸(VFA)，使渗滤液pH值维持在中性以下，同时使得渗滤液中COD、氯化物浓度升高，且相较于所分析的金属组分，其毒性更强。而在产甲烷条件下，挥发性脂肪酸(VFA)含量出现下降，渗滤液pH值逐渐趋向碱性，环境碱度提升，促进了所研究金属组分的沉淀，但同时导致总氨氮(TAN)浓度升高。综上可得出结论：在为期150天的评估周期内，pH值与挥发性脂肪酸(VFA)对所研究的金属（铅(Pb)、铬(Cr)、钴(Co)、镍(Ni)、铁(Fe)和锰(Mn)）以及总氨氮(TAN)均具有显著影响。