| The organic waste had a potential threat to environment for its abundance and hard disposal,which has attracted the widespread attention by all over the world. As an environmental-friendly technique, the anaerobic digestion method can fully solve the difficulty and coupledwith producing biogas. However, the low biogas output was the common defect of the relevanttechniques, which has restricted the development of biogas industry in part. Thus, the biogasgenerating technique was optimized, using the surplus sludge as the experimental material,through regulating the substrate and external parameters in this dissertation, furthermore,anaerobic digested effluents were conducted to utilization. The results are as follows:(1) The biogas output changed significantly with the transformation of pH and carbon nitrogenratio(C/N), When the pH was varied from6.50to8.00, and C/N was varied from20to30. The unitbiogas output reached maximum338±6mL·g-1, at the pH of7.25and the C/N of25. CentralComposite Design(CCD) analysis showed that the quadratic equations modelR1=-2118.31+695.15689A-49.23690A2-0.033365B2could well imitate the relation amongC/N，pH and the biogas output.(2) La, Ce, Nd, Er, and Eu, at the ionic concentrations ranged from1×10-5g·L-1to1×10-9g·L-1, allcontributed to increasing the biogas output and the removal rate of CODCr.The promoting effectreduced following the decline of its concentration. The maximum unit biogas output reached294.182±19.799mL·g-1, and the maximum removal rate of CODCrreached86.1%, when theconcentration of lanthanum chloride was1×10-6g·L-1. The maximum unit biogas output reached272.545±8.228mL·g-1, and the maximum removal rate of CODCrreached87.4%, when theconcentration of cerium chloride was1×10-6g·L-1. When the concentration of erbium chloride was1×10-7g·L-1,the maximum unit biogas output reached285.100±7.778mL·g-1, only its maximumremoval rate of CODCrreached87.4%at the concentration of1×10-6g·L-1. When the concentrationof europium chloride was1×10-7g·L-1, the maximum unit biogas output reached277.100±4.667mL·g-1, and the maximum removal rate of CODCrreached83.1%. (3) Compared with the sludge, cow manure and sheep manure, the mushroom residue was moresuitable for anaerobic digestion, and its maximum biogas output reached325.78mL·g-1. Howeverthe proper mixed proportion of different substrates apparently promoted the anaerobic digestion.When the proportion of sludge: cow manure: sheep manure: mushroom residue was0:0.5:0:0.5,the maximum output reached348.75mL·g-1; When the proportion of sludge: cow manure: sheepmanure: mushroom residue was0.625:0.125:0.125:0.125, the output reached333.36mL·g-1,which were absolutely higher than the output of215.45mL·g-1produced by single slurry substratefermentation; The mathematic modelR1=215.84A+186.54B+176.24C+322.83D+299.7AB+370.49AC+355.79BC-372.64BD+4767.26ABD-4708.14BCDcan fully optimize the mixed proportion of multi substrates,such as sludge, cow manure, sheepmanure, and mushroom residue.(4)The tolerance of tomato seed to the concentration of biogas slurry declined along withlengthening the soaking time. When the soaking time was1hour, the optimum concentration thatcan promoting the germination of seed was75%, here its germination rate reached87.50±0.71%;When the soaking time was3hour, the optimum concentration was25%, and itsgermination rate reached79.00±1.41%; When the soaking time was5hour, the optimumconcentration was10%, and its germination rate reached80.00±1.41%.(5) The biogas slurry could promote wheat seed germination at the optimum concentration of10%,which germination rate was94±3.5%; when the optimum concentration of cow manure biogasslurry was25%, it also contributed to wheat seed germination which germination rate was96±4%;However, the mixed biogas slurry was only available to promote seeds germination at theconcentration of10%, here the germination rate was92.67±1.2%.The above mentioned results revealed that, the rare earth ion in appropriate concentration can notonly efficiently improve the output of anaerobic digestion, but also contribute to the removal effectof COD. Furthermore, mixed multi substrate fermentation can significantly promote the efficiencyof sludge anaerobic digestion. |
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