| Sewage sludge severely restricted on the disposal, for the persistence pollution in environment caused by heavy metals.In order to understand and control the pollution of heavy metals in sewage sludge, this paper investigate the gross and chemical fraction of As, Cd, Cr, Cu, Pb and Zn in sludge sample from five sewage treatment plant in hefei, analyzed their environmental pollution degree and risk grade;The change of bioavailable form in sewage sludge were study for apply the calcium magnesium phosphate fertilizer, hydroxyapatite,attapulgite three passivator and composted with cornstalk;The difference on biological effectiveness of Cr, Cu, Zn for apply calcium-magnesia phosphate fertilizer and hydroxyapatite judged by the uptaking of heavy metals in cabbage from sewage sludge.The experimental results show that:1.The amount of heavy metals in sludge samples : Zn>Cu>Cr>Pb>As>Cd.According to our country "urban sewage treatment plant sludge disposal farm argillaceous standard" regulation, content of some samples of As, Cd, and Zn are beyond class A standards;The content of Cd in the sludge from CTP is beyond class B standard, but the content of heavy metals in sludge samples are under "the urban sewage treatment plant sludge disposal landscaping with argillaceous standard ".bioavailable proportions of Cr, Cu and Pb are low; bioavailable form proportion of As is relatively high;Zn has the highest percentage of bioavailable form;distribution of Cd in Sludge sample is difference. Leaching of heavy metals in sludge concentration does not exceed the standard.The evaluate result of Nemerowindex is roughly same with potential ecological risk index method,integrated pollution of heavy metals in sewage sludge are serious and high potential ecological risk;The size of heavy metal pollution is: Cd>Cu>Pb>As>Cr(Zn).2.The mainly bioavailable proportion of As, Cd, Cr, Cu, Pb, Zn in sludge samples are all reduced by selected three kinds of passivator in experiment;Effect on three kinds of material are not identical,As: hydroxyapatite>attapulgite> calcium-magnesia phosphate fertilizer;Cd: attapulgite>hydroxyapatite>calcium-magnesia phosphate fertilizer;Cr: calcium-magnesia phosphate fertilizer>hydroxyapatite>attapulgite, calcium-magnesia phosphate fertilizer reduce iron and manganese oxidation state ratio from 3.60% to 1.20%;Cu: attapulgite>hydroxyapatite>calcium-magnesia phosphate fertilizer, of 3.67% attapulgite was reduced by 0.11%;Pb: calcium-magnesia phosphate fertilizer>hydroxyapatite>attapulgite;Zn : calcium-magnesia phosphate fertilizer> attapulgite>hydroxyapatite, calcium-magnesia phosphate fertilizer of proportion and the ions was reduced by 5.29% to 0.21%, carbonate combination state reduced from 22.71% to 22.71%.With the increasment of passivator on passivation effect more apparent.3.Temperature of sludge composted with maize straw sample rising quickly, reaching 49.7 in a week, the heat of pile body lasted for 11 days, normal temper? ature in 30 days slowly.Rape seed germination rate in the leaching liquid of sludge fresh samples was 31.67%, the germination rate in the initial stage of composting is slightly lower, while rised to 95.33% in 10 ~ 35 days gradually, when composts 50 days, rape seed germination rate up to 111.67%.Maize straw compost in the sludge samples reduce As, Cd, Cr, Cu, Pb, Zn mainly bioavailable proportion, the proportion of iron and manganese oxidation state on As in sludge samples from 38.44% down to 28.83%; The proportion of Cd ion was reduced from 23.22% to 0.12%;The proportion of iron and manganese oxidation state Cr from 3.60% down to 3.60%;Ion in Cu was reduced from 3.67% to 0.30%;carbonate combination state proportion in Pb reduced from 7.78% to 7.78%, iron and manganese oxidation state proportion reduce to 19.27% from 3.05%; proportion of ion in Zn was reduced from 5.29% to 0.04%, carbonate combination state proportion reduced from 22.71% to 22.71%.4.application of Calcium-magnesia phosphate fertilizer and hydroxyapatitein are all crease the total biomass of cabbage, as seems increased total biomass,promoting effect of calcium-magnesia phosphate fertilize is greater,average total biomass of cabbage in CK group is 204.35 g, 100 g calcium-magnesia phosphate fertilizer increased to 255.02 g.Groups of cabbage leaf and root of the average contents of Cr, Cu and Zn are lower than the average content of mixed soil matrix.The cabbage leaf to the average of each heavy metal uptake of size: Zn> Cu> Cr, the size of an average uptake of heavy metals by root: zinc> Cr> Cu.Calcium-magnesia phosphate fertilizer and hydroxyapatite are reduced to a certain extent Cu ? Cr ? Zn biological effectiveness;The ability of calcium-magnesia phosphate fertilizer to reduce biological effectiveness of a Cr and Zn is higher than that of hydroxyapatite. |
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