Experimental Study On The Artificial Soil From Sewage Sludge, Fly Ash And Ferrous Tailing

Sewage sludge (SS), fly ash (FA) and Ferrous Tailing (FT) are three main solid wastes. A lot of land was occupied by the existence of these three solid wastes and it also resulted in water, soil, air pollution.On the basis of analyzing the properties and environmental hazard of the three solid wastes, artifitial soils were prepared by mixing of FA and SS at ratios of 3:1 (Ⅰ),2:1 (Ⅱ),1:1 (Ⅲ) and 0.5:1 (Ⅳ) respectively; the other was prepared by mixing of FA, SS and FT at ratio of 2:1:1 (Ⅴ). The basic properties and pollution elements activity of the artificial soil were researched.Though studying the basic properties, the main results were obtained as following. With the increasing of the fly ash content, the pH and CEC of the artificial soil increased, and the EC decreased. With the increasing of sewage sludge content, both the water-saturation coefficient and water-holding capacity of the artificial soil were increased. But water-holding capacity of artificial soil declined, when the ratio of SS to FA was 2:1.The organic C and nutrient were abundant in artificial soil and in high fertility level. Contents of trace elements in the artificial soil were obviously lower than the National Agriculture Standard, except the Ni content that was close to the national agriculture standard.Though constant moisture incubation, the main results were obtained as following. The fluctuation of pH and EC value of artificial soil was small, and it would not affect the soluble heavy metals and salt soluble ions. The TOC had been keeping at a high level and could meet the need of organic C for plant growth. Meanwhile, it could also adsorb part of toxicity element. With the going of constant moisture incubation, Ca2+, Mg2+, NO3- concentrations were increasing. And concentrations of SO42-,Cl- were gradually decreasing. Soluble Ni Cu, Cr Cd, Pb gradually declined during the incubation. And their concentrations were below National Groundwater Quality Standard 11(≤0.01mg/L) when they achieved a constant level. Except Ni, the concentrations of other elements were also below the EU Drinking Water Threshold (EU Directive 98/83). It can be concluded from this study that the artificial soilⅢ(Fly ash:Sewage sludge=1:1) andⅣ(Fly ash:Sewage sludg=1:2) could meet the need of nutrition for plant growth; Their heavy metal content was below National Agricultural Standard. Water-holding capacity was optimized. Groundwater would not be polluted by the leachate produced by artificial soil, Hence it could be used for further study. It is advised that artificial soilⅢand IV be used for laboratory pot experiment and outdoor experiment based on this study, and optimal ratio be determined.Compounding artificial soil by mixing fly ash and alkaline mine tailing with municipal sewage sludge has certain advantages, such as abundant local materials, convenient and economical transportation, besides it showed both environmental and ecological reconstruction effects. It could not only solve the environmental problems resulted from the pile of solid waste, but also could solve the problems of soil shortage.