Experimental Studies On The Effects Of Minerals On Anaerobic Degradation Of Organic Matters In Landfill Leachate

Batch experiments were designed to investigate the effects of minerals on the decomposition of organic matters in landfill leachate. During and after the experiments, concentrations of CH4, CO2, TOC, TIC, pH, ORP as well as COD were determined. Through analyzing the relationships between minerals and data derived from experiments, the mechanisms of mineral mediated organic matter decomposition were discussed. This study has potential significance of providing a new mineral way to improve the treatment efficiency of landfill leachate.The results showed that both carbonates (calcite and dolomite) and sulfate (gypsum and anhydrite) can promote the removal of COD. In experiments with and without mineral, the COD removal ratios are 75% and 60%, respectively. The effect of carbontes and sulfate is little on NH1+-N removal, while obvious on CH4 production. All the minerals used in this part of study can promote the producing of CH4, and dolomite is especially efficient. It is deduced that carbonates have the ability of buffering pH, and as a result they can promote the biological activities of microbes in landfill leachate (e. g. methane-producing bacteria). Furthermore, Ca and Mg in carbonates can act as elements which are necessary for microbial growth. Sulfates are potential electron acceptors and in landfill leachate they can promote the activities of anaerobic bacteria and the degradation of organic matters.Hematite, pyrite and pyrrhotite can promote the degradation of COD and production of CH4. Pyrrhotite is more efficient than the other two minerals. In pyrrhotite added experiment about 69% COD is removed, while that for control experiment is only 47%. It is inferred that more reactive site and conduction property make pyrrhotite to be more efficient in promoting microbial activities in landfill leachate. Pyrite is also a conductive mineral and this property helps promoting the activities of microbes and the degradation of COD. Acting as electron acceptor, hematite can promote the growth of microbes in landfill leachate.Clay minerals can promote the degradation of organic matters in landfill leachate, with the order of kaolite>montmorillolonite>palygorskite>illite>control. In experiments with clay minerals added, the organic matter removal ratios are about 80%, while that for control experiment is only 71%. The CH4 outputs are also kaolinite> montmorillonite>palygorskite>illite>control. Clay minerals can promote about 3.05, 2.78,2.78 and 2.55 times the output of CH4. It is believed that trace elements and high adsorption of clay minerals contribute to their high efficiencies in promoting organic matter degradation.In experiments with acetate as single substrate, pyrite, hematite and goethite can also promote the degradation of COD and production of CH4. The conversion ratio of organic matter to CH4 is high in acetate experiments and low in landfill leachate experiments, which means that substrate can impact the activities of microbes and end products.All the minerals used in this study can promote the anaerobic degradation of landfill leachate. However, different mineral has different promoting mechanism and efficiency. Resultantly, selecting a cheap and environment-friendly mineral for anaerobic treating landfill leachate deserves further investigation.