Effect of Iron-Manganese Industrial Wastes on Composting Process of Wastewater Sludge and Analysis for Humification Characteristics
Iron-manganese industrial wastes are used to improve the humification degree of sludge composting and realize the synergetic treatment and resource utilization.After iron-manganese smelting residuals or iron-manganese tailings were added to sludge compost mixture,the process and characteristics of sludge humification were studied by composting exper-iments for 15 days.Adding iron-manganese slags increased the heating rate of the sludge pile,and the period of thermo-philic composting(≥50 ℃)reached 96 h.After 15 days,the ratio of HA/FA was not less than 1.0,and the seed germina-tion index GI were more than 100％.Except for As,the contents of other metals such as Cr and Ni were lower than the limits of the Grade A stipulated by the Agricultural Sludge Pollutant Control Standard(GB 4284-2018),and then the obtained compost products were suitable for garden,pasture,and cultivated land where crops are not planted.The highest activities of polyphenol oxidase and dehydrogenase in the compost products with the addition of iron-manganese smelting slags were 2.2 μmol/(h·g)and 13.5 mg/(d·g),respectively,and water-soluble organic carbon increased significantly.Iron-manganese smelting slags was more conducive to the conversion of soluble organic carbon into macromolecular sub-stances such as humic acid,and it improved compost stability and maturity while retaining carbon and nitrogen.
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