Prediction on contaminant migration in aquifer of fractured granite substrata of landfill

Nowadays,a certain amount of landfills in China were constructed without horizontal liner system.The research conducted focuses mainly on the contaminants from landfill leachate migrating in the aquifer of a fractured granite area,and pollution predictions for groundwater were made by establishing numerical model with Visual Modflow combining field investigation like geological surveys,drilling,geophysical explorations,hydrogeological experiments,water quality analysis.The transportation of the chloride ion from landfill in the aquifer was simulated in the model with time frames of 2 555,3 650,5 475 and7 300 d.The model shows that from 2 555 d to 7 300 d starting from 2003,the chloride ion migrated from 900 m to 1 300 m,respectively,along the groundwater flow.The results indicate that as leachate plume migrated in the aquifer,the concentration of the pollutants can be up to 19.74 to 251.76 times that of background value.The research proves that the leachate poses a threat to the local water body and offers a reference towards groundwater pollution prevention for fractured granite landfill sites.

Investigation of migration of pollutant at the base of Suzhou Qizishan landfill without a liner system

We investigated migration of pollutant at the base of the Suzhou landfill after it had been operated for 13 years. The investigation was carried out by performing chemical analyses on the soil samples taken from the silty clay deposit. Concentrations of chloride, chemical oxygen demand （COD） and the heavy metals in the soil samples were determined using the standard methods. The experimental data showed that the maximum migration depth of chloride was more than 10 m, while the maximum migration depth of COD varied between 1 and 3.5 m. It is believed that the difference is attributed to the variation in diffusion rate and leachate-soil interaction. The chloride profiles also indicated that adveetion may be the dominant contaminant transport mechanism at this site. The total contents ofCu, Pb and Cr are very close to the background levels and the concentration values of these metals mainly are lower than the threshold values specified by the Chinese soil quality standard and the European one. The water-extractable concentrations of COD in the surface of the silty clay generally exceed the limit value specified by the Chinese standard. The concentrations of copper and chromium in pore water are 1-2 orders of magnitude less than the total concentrations of these heavy metals within the soils, implying that heavy metals are mainly adsorbed by the soil particles. Finally, remediation methods were suggested for this landfill site.

Evaluation of zeolite-sand mixtures as reactive materials protecting groundwater at waste disposal sites

To recognize properties of a mixture of Vistula sand （medium sand acc. to USCS） with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment in vicinity of old landfills comprehensive laboratory investigations were performed. The present study investigates the removal of contaminants specific for landfill leachates onto zeolite-sand mixtures containing 20%, 50% and 80% of zeolite （ZS20, ZS50 and ZS80）. Taking into account the results of batch tests it was concluded that the Langmuir isotherm best fitted the data. It was observed that the presence of ammonium, calcium and magnesium decreases the removal efficiency of copper by 32%. Column tests of contaminant migration through the attenuation zone of the reactive materials were interpreted using the software package CXTFIT, which solves a one-dimensional advection-dispersion equation. Column test results also indicate the strong influence of the presence of interfering substances on copper immobilisation; dynamic sorption capacities decrees twofold. Throughout the landfill leachate flow through ZS80 sample, a constant reduction of NH＋4 （at 100%）, K＋ （at 93%） and Fe total （at an average of 86%） were observed. There was no reduction in chemical oxygen demand and biochemical oxygen demand.