Mechanical Separation Of Aged Refuse And Characterization Of Humic Substances In Leachate

As aged refuse is considered to be a reusable resource, the excavation of aged refuse can not only alleviate the pressure of increasingly limited landfill site, but also recycle the materials in it. In this work, the aged refuse was used as the substrate to make an aged-refuse-based bioreactor (ARB) to treat refuse leachate. Meanwhile, the humic substances in leachate were characterized, especially on the interaction between humic substances and heavy metals in leachate, aiming to improve the leachate treatment by ARB and the assessment of leachate's environmental impact as well. The main findings were listed below.(1) The high proportion of recyclable and reusable materials in aged refuse makes it a favorable waste for water treatment and resource reuse. The results of screening tests showed that the optimum operation parameters for the trammel screener with a pore size of 40 mm could be obtained when a v/V_max (where v revolution speed and V_max maximum revolution speed) and a roller angle ranged from 0.51 to 0.60, 4.5°to 6.5°, respectively. In the large-scale practice at Shanghai Laogang Refuse Landfill, the trommel screener with a v/V_max of 0.73 was applied, achieving a separation efficiency of over 90%.(2) The humic substances extracted from leachate at Shanghai Laogang Refuse Landfill accounted for 30.2% of the leachate's COD and 41.1% of TOC. After treatment using ARB, 62.3% and 35.7% of the humic acids and fulvic acids in leachate can be reduced respectively. In terms of FTIR, A negligible difference between the humic substances extracted from ARB's influent and effluent was observed. While the humic acids with large molecular size in can be reduced greatly using ARB. In addition, C content, C/H and C/O of HA and FA in the effluents were higher than those in the influents.(3) Though the concentrations of individual heavy metals in leachate may be relatively low, however, the total amount of heavy metals may be quite high and exert combined pollution to the environment, especially when released from refuse subjected to the environment changes. It was found that the concentrations of Hg both in leachate and refuse seemed to be high, and the metal (Cu and Hg) bound with the humic substance in the effluents should be stronger than those from the influent.