| Soil utilization of sewage sludge is an important international method of treating sewage sludge, and how to prevent the pollution of heavy metal is always the most important problem. According to the composting principle and the correlation between the forms of heavy metals and biological efficiency, combining with the controlling means of heavy metals' activity, this test studied the effect of passivation reagents including fly ash, phosphorate rock, zeolite, peat and lime on the forms and the biological efficiency of heavy metals; and the different perception of different passivation reagents were screened and optimized. Basing on the study, the adsorption mechanism of passivation reagents on heavy metals in sewage sludge composting was discussed, and the transformation mechanism of organic forms of heavy metals was also studied through some methods including dialysis and G-75 gel chromatogram separation etc. The study supported some theoretical foundation for the application of sewage sludge composting and fertilizer in agricultural produce. The result of the study indicated:In the sewage sludge composting, the fly ash (FA20) to passivate Cu had the best passivation effect, remarkably better than control experiment; to Zn, the adding fly ash and phosphorate rock (FA20, PRIO) had the best effect, remarkably better than control experiment; to Mn, the best treating is addition of phosphorate rock and lime (PR15, CL10); to Pb, the best is fly ash and phosphorate rock (FA10, PRIO); to Cd, the best is fly ash and peat (FA20, PT10). So according to the passivation effect on available forms of heavy metals, fly ash, phosphorate rock and peat are effective passivation reagents, and the appropriate proportion of addition is respectively 20%,15% and 10% (FA20, PR15, PT10).To zeolite and peat, the larger addition concentration of heavy metals (Cu2+ Mn2+ Zn2+ Pb2+ Cd2+), the adsorption is more of passivation reagents on ions of heavy metals; the adsorption ability of different passivation reagents on ions of heavy metals has a little difference, peat > zeolite; the adsorption appetency order of peat on heavy metals: Zn2+>Mn2+>Cu2+>Cd2+>Pb2+; the order of zeolite: Zn2+>Cu2+>Mn2+>Cd2+>Pb2+; the both adsorption isotherm had better inosculation with Freundlich and Temkin formula, Langmuir formula is unfit to describe the isothermal adsorption of both passivation reagents on heavy metals, their isotherm fit the Freundlich isothermal adsorption model.For the combination of humus to heavy metals, through composting the giant molecule substance combined more Mn, the little molecule substance easily combined Zn; HA not only combined plentiful Mn, but also combined very tightly; although FA combined more Zn but the combination of FA and Zn was not tightly;Along with the increase of sewage sludge compost using, the total dry heavy of potted lettuce increased, but the content of heavy metals in soil and the top tissue of lettuce plot also increased remarkably, when using quantity >10%, the content of heavy metals in the top tissue was over national criterion of food sanitation; using sewage sludge fertilizer the content of heavy metals in the top tissue wasn't over national criterion, but in different reaping time the content was different, reaping aptly could decrease the content of heavy metals in the top tissue;Using inactivated sewage sludge, sewage sludge compost and fertilizer a year, the wheat and corn increased production evidently than comparison, and the total microorganism and the activity of soil enzyme increased, no obvious heavy metal effect to soil and crops, this showed that inactivated sewage sludge, sewage sludge compost and fertilizer were a kind of common effective fertilizer as chemical fertilizer and other organic fertilizer, but the long effect on soil and groundwater should be studied ulteriorly.
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