| It is being paid close attention to the disposal and utilization of sewage sludge. Land treatment is the best solution to dispose of them according to the condition of our country. We studied the effects of coal fly ash on forms of Zn, Cu, Mn, Pb in sewage sludge based on the analysis of physicochemical properties of sewage sludge from Hangzhou Sibao Sewage Treatment Plant. The soil column experiments and the pot experiments were performed to identify the effects of sewage sludge amended with coal fly ash at different ratio on environment and the feasibility of its application to green area,. The main results obtained were summarized as follows:1. Sewage sludge of Hangzhou Sibao Sewage Treatment Plant contained quite a lot of organic matter and plant nutrients such as nitrogen and phosphorus; however, sewage sludge also contained high heavy metal contents, especially the content of Zn exceeded severely to the controlling criterion of sludge in agriculture.2. The available content of Zn, Cu, Mn, Pb decreased significantly in sewage sludge amended with coal fly ash. With the increasing of coal fly ash amendment, the exchangeable, organic matter content of these four kinds of metals decreased, but the iron, manganese oxides and primary, secondary minerals content increased.3. The application of stabilized sewage sludge in soil can increase the content of Zn, Cu, Mn, Pb in topsoil, but have little effect on the content of these four kinds of metal in subsoil and infiltration. Even if in the circumstance of stabilized sewage sludge with soil at 1:1(V/V), the content of this four kinds of heavy metal in infiltration still did not exceed the criterion of water quality in farm irrigation. It was also found that groundwater could not be polluted by high nitrogen and phosphorus concentration if we Controlled the ratio of stabilized sewage sludge with soil at ^ 1:5(V/V).4. The application of stabilized sewage sludge improved significantly the soil physicochemical properties, for example, the content of organic matter and nitrogen, phosphorus, kalium, boron and porosity of soil increased, while bulk density decreased. But, if the ratio of coal fly ash amendment is too high, the pH and the content of water soluble boron of the soil will exceed the range of plant growth, then harm to plant. Thecontent of water soluble boron in mixture reached to that of controlling soil 10 times or above after sewage sludge amended with coal fly ash at 20% and 40% and then mixed with soil at 1:1 (V/V), so cockscomb appeared obviously toxic symptom.5. Pot experiments planted cockscomb and F. elata Keng sequentially was indicated that the plant height, dry biomass and chlorophyll of cockscomb was increased and florescence was ahead of time. Compared with controlling soil with fertility, there is no significant difference. The experiments also indicated that stabilized sewage sludge still had good aftereffects on the secondly stubble crop. The plant height, dry biomass and chlorophyll of F. elata Keng were excelled significantly to controlling soil and controlling soil with fertility. Besides, stabilized sewage sludge reduced the content of Zn, Cu, Mn, Pb in plants compared with sewage sludge. With the ratio of coal fly ash amendment increasing, the content of these four kinds of heavy metal were close to the content of controlling.6. The content of available Zn and Cu in soil after the second stubble corps (F. elata Keng) were harvested had no increase in contrast with that of the first stubble corps were harvested, but available Mn decreased distinctly and available Pb increased slightly. The results showed that heavy metals had not been activated by crops growth.7. From the biological and environmental effects of stabilized sewage sludge, it is the best management that sewage sludge was amended with coal fly ash at an application ratio of 10%~20%, mixture was then mixed with soil at 1:5(V/V).
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