Experiment Studys On The Heavy Metal After Sludge Composting With Fly Ash And Leaching

Sewage sludge is good organic fertilizer resources with high yield and low utilization rate, contains a lot of nutrients and organic substance. As an effective biological resources, sludge is very suitable for used as a soil improver, especially for poor soil region loess. Land using has bright future for it can solve the disposal of sewage sludge and pollution problems.The heavy metals limited its utilization in agriculture. The mobility, the bioavailability and the toxicity of heavy metals in the soil depend on their specific chemical forms and on their binding state. This paper provide theoretical basis for land use of the sludge.This is also the purpose of this selected works.The sludge was chosen for aerobic composting after enhancing the heavy metals and adding different proportions of fly ash in this experiment. The transition of heavy metals Ni, Cd, Pb, Cu and Zn in municipal sewage sludge was studied after aerobic composting in this paper. The study analyzed the influence on the heavy metal forms of composting with and without adding fly ash., draw the appropriate amount of fly ash to add, and analyzed the profile distribution of the heavy metals in the soil column after leaching.The study showed that the aerobic composting without adding fly-ash has changed the distribution of the chemical forms of heavy metals, and reduced the the proportions of exchangeable form and the carbonate combination form of Ni by 12.01% and 3.74%, reduced the the proportions of exchangeable form of Cd by 10.61%, but increased the unstable state content of Cu Zn and Pb. By adding fly-ash composting, the total content of heavy metal decreased along with the increase of fly-ash, owing to the dilution of the fly ash. The composting with fly-ash could obviously decrease the biological activity of Ni, make its unstable state rate decrease 15.9%～20.52%, Adding fly ash was better than without fly ash to decrease the biological activity of Cd and Pb,but no obvious passivation effects for Cu and Zn; The appropriate proportion of fly ash was 21%～28%. The profile distribution of heavy metals after soil column leaching showed that the mobility of cadmium, nickel, lead, copper and zinc was poor, the heavy metals mainly accumulated in the surface of soil column(0～20cm), And the mobility of lead was the worst. Precscribed three times sludge of environmental quality standard into soil column satisfied Level 2 quality standards.