Study On Aerobic Fermentation Of Sediment And Solid Wastes For Usage As Plants Growth Substrates

In this study, the different ratios of dredging sediment and biomasses (corn stalks, peat) were used to make different substrates. After aerobic fermentation, the completely composted substrates were obtained, and then physicochemical properties and application in plant growth of trefoil and cosmos were analyzed, the results as follows:(1) The physiochemical properties of dredging sediment feature with high density (0.94 g/cm3) and low porosity (32.73%), which is unsuitable for plant growth directly. Sediments were first mixed at different ratios with biomasses (corn stalks, peat) achieving four different substrates with improved physiochemical properties, that is, S6 (80% sediment+ 10% corn stalks+10% peat), S7 (70% sediment+ 15% corn stalks+ 15% peat), S10 (80% sediment+ 13.3% corn stalks+ 6.7% peat) and S11 (70% sediment+ 20% corn stalks+ 10% peat). These four substrates are better than the dredging sediment (SO) based on physiochemical properties and application in trefoil growth.(2) We designed a new device for aerobic fermentation in this study (the patent. 2013. Temperature control aerobic fermentation device with bilayer and round shape. 201310478377.3). Then the aerobic fermentation of substrates S6, S7, S10 and S11 were performed on the device. Sixties days later, leachate’ seed germination index indicated that the four substrates completely composted. The physiochemical properties of composted substrates were as follows:density is 0.6g/cm3, porosity is 80%, EC is 0.4-0.65 ds/m, and CEC is> 10 cmol/kg. The composted substrates can be used for growth of trefoil and cosmos, but S7, S10 and S11 were better than S6.(3) N2 adsorption experiment indicated that, as compared to raw sediment, surface areas of nanoparticles in substrates were decreased, average diameter of nano-pores and average nano-particle size in substrates were increased. Especially, nano-micropore area and micro-pore volume in both S10 and S11 were increased significantly, however, nano-micropore area and micro-pore volume in S6 and S7 were decreased greatly, compared to raw sediment. FTIR spectrum indicated that, the intensities of Si-O-Si、Si-O-Al and Si-O-Mg in four substrates were changed when compared to raw sediment, suggesting that the addition of biomasses alternated the content of some chemical components in sediment.