The Research On The Treatment Of Landfill Leachate By Freeze-thawing

Landfill leachate is a kind of organic wastewater from the municipal solid waste landfill,with the volatile quality and quantity.Its components is very diverse and pollutants levels is high.Currently the treating technologies for the leachate are all operating-complicated and high-cost.If the leachate is not properly handled,it would be badly harmful to human being's health and the whole environment.Freeze-thawing is a kind of enrichment and separation method with simple operation and not causing secondary pollution.In recent years,it's gradually developed to treating the various wastewater,but it's hardly reported to treat the landfill leachate.This study is about the treatment of landfill leachate by the freeze-thawing.The effect of temperature,dilution ratio and the seed ice on the conductivity and CODCr variation during the freezing process is investigated.And then the conductivity and CODCr variation are explored during the melting stage.Next the comparison of the two stages,freezing and meling,during which the conductivity and CODCr variation is observed.Finally combining with barley toxicity test the quality of effluent by the freeze-thawing is evaluated.The results as follows:1.When the freezing temperature is-13?,the treating efficiency of landfill leachate by freeze-thawing is the best.Within the four dilution ratios to the raw water,twice,four times,eight times,there no great differences to the conductivity and CODCr variation.By the reaserch on the effect of the seed ice on the variation,we can conclude that no seed ice is more beneficial to the subsequent freezing process.2.The landfill leachate is completely frozen at-13?,and is melted at room temperature.It can be found that the variations of the conductivity and CODCr decay in forms of exponent.And to the raw water 15% of the volume can be discharged directly according to the national standard.By three groups of the same ices divided into pieces,we can find that the more fast the melting speed,the more smaller the ice piece is.Meanwhile for the largest ice piece,the distribution to the conductivity and CODCr is best during the melting process.3.Through the comparative study of the pollutants' variation at four temperatures,-6??-13??-20??-26?,it is concluded that the melting phase is better than the freezing phase to distributing the pollutants and the conductivity and CODCr are exponentially decline.4.The barley toxiticy experiments show that with the declining conductivity and CODCr of these melt waters,the inhibition of the leachate to the barley seed germination rate and seedling shoot wanes.And with the longer duration of contamination,the low concentration effluent show some toxicity to the barley seedlings.Taken together,as a simple and effective treatment method,the freeze-thawing has a good effect on the reduction of the landfill leachate,which is more obvious at the melting stage.