| In this study,compost experiments for 60 days were conducted with rice straw,bran and sewage sludge from Guangzhou Lijiao waste water treatment plant after dewatered as main raw material.Four kinds of disposal methods were designed: compost without white-rot fungi and adding 3%,6% and 15% white-rot fungi to the compost.This study aimed at passivating toxic heavy metal Ni,Zn and Cu in sewage sludge,reducing the risks of agricultural utilization of sewage sludge and providing method for reclamation of sewage sludge.During the experiments,it analyzed the impact of white-rot fungi on maturity progress of sewage sludge,quality of compost and bacterial community in compost with the changes in physic-chemical parameters and structures of bacterial community as the main indicators,such as temperature,organic matter,pH and humic acid et al.Lately,it estimated the passivation of heavy metals influenced by white-rot fungi based on the changes in the form of Ni,Zn and Cu.The effect of passivation of heavy metal Ni,Zn and Cu was verified by the germination index,root elongation inhibition rate and pot experiment.Meanwhile,it also explored the optimal dose of white-rot fungi for the best effect of maturity of sewage sludge and passivation of heavy metals in sewage sludge.The main research results are as follows:White-rot fungi could decomposed non-degradable substance like lignin directly,enhancing the decomposition of organic matter in sewage sludge.Compared to the non-inoculation compost of which organic matter decreased from 80% to 60.2%,the organic matter in compost inoculated 3%,6% and 15% white-rot fungi dropped to 49.4%,49.3% and 48%,respectively.The white-rot fungi help increase the content of humic acid rather than impact on fulvic acid.Simultaneously,white-rot fungi could improve the structures of bacterial community,promote the appearance of actinomycetes and increase the abundance of metabolism of carbohydrate and amino acid,enhancing the maturity of sewage sludge indirectly.And the optimal dose of white-rot fungi for the best effect of maturity of sewage sludge was 6%.The white-rot fungi could produce organic acid like oxalic acid to deal with the heavy metal contained environment.The percentage of acid exchangeable fraction and reducible fraction of Ni,Zn and Cu could be decreased and the percentage oxidization fraction and residual fraction could be increased by inoculating white-rot fungi.The passivation rate of Ni,Zn and Cu in inoculationg compost was much higher than non-inoculation.When the fermentation time was 40 days and the dose of white-rot fungi was 6%,the passivation rate of Ni,Zn and Cu reached the peak value of 73085%,62.80% and 88.21%,respectively.The organic matter was stabilized more thoroughly in sewage sludge composted with white-rot fungi.The content of humic acid in inoculating compost was higher than that in non-inoculation though nitrogen lost by decomposition.The content of total Ni,Zn and Cu was within the national standard.The sewage sludge repaired by white-rot fungi showed less inhibiting effect of heavy metals on the germination indexes of cabbage mustard and lettuces.The content of Ni,Zn and Cu in Edible parts of cabbage mustard and lettuces were below the national vegetable health standard,indicating that sewage sludge composted with white-rot fungi showed low risks in agricultural utilization of sewage sludge. |
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