Through the test of two sand columns for comparing,the effect on removal of pollutants in landfill leachate by biological effect in sand layer of vadose zone was studied.

Different kinds of chromium disposition and distribution in soil and groundwater are summarized, including adsorption, redox and biological effects.

Using the biological effect of the microorganism such as nitrifying bacteria carried in the effluent of biological pretreatment process and biological sludge recirculation,the biological effect of the sedimentation tank can be enhanced.

Because the cooperating action of the chemical and biological function, the removal efficiencies of the chemical-biological flocculation process were higher than that of the chemical flocculation process at the same flocculant dosage.

Diatoms biological functions on subaerial Karst sedimentation are studied chiefly in this paper,including assimilation,tapping and felting effects,encrustation,cementation.