Static aerobic composting of municipal sewage sludge with forced ventilation or air ventilation using matured compost as bulking conditioner was investigated. Physical and chemical parame ,eters, e.g., temperature, moisture content, VSS, CODcr, pH, and germination index （GI）, were analyzed to characterize the composting process. Fermentation starts quickly in both forced and air ventilation compost heaps and reaches high-temperature stage after 2 d, owing to the bulking function of matured compost. Compared to air ventilation, however, forced ventilation enables the high-temperature stage to last longer for approximately 7 d. The moisture content of both compost bodies decreases from 62% to about 50% as a result of evaporation, and it decreases slightly faster in forced ventilation compost heap after 13 d due to the higher temperature and better ventilation condition. Although no obvious differences of VSS and pH are observed between both compost heaps, the soluble CODcr and GI show differences during the second half period of fermentation. In forced ventilation compost, the soluble CODcr has a small rebound after 13 d, and GI decreases from 46% to 35% but then increases. These results show that in general, the matured compost is a good conditioner and force ventilation with a proper air supply strategy can be more efficient than air ventilation.
为了探讨生物表面活性剂鼠李糖脂对堆肥介质中水分下渗和保持性能的影响,通过下渗实验模拟堆肥,测定了添加表面活性剂后的堆肥样品的含水率。实验结果表明鼠李糖脂保持水分能力优于SDS和Triton X-100,且添加鼠李糖脂浓度越高,介质水分保持性能越好。不同浓度的鼠李糖脂对水在介质中下渗过程的影响各异,400 RE mg/L的鼠李糖脂促进了水的下渗,且效果优于两种化学表面活性剂,而浓度高于800 RE mg/L的鼠李糖脂阻碍了水的下渗。不同深度段的颗粒介质中水分含量和鼠李糖脂含量变化存在对应关系,浓度为400 RE mg/L鼠李糖脂可以提高介质中水的承载能力,这可能是由于鼠李糖脂能够显著降低溶液的表面张力,有效增强溶液在颗粒介质表面的铺展和向微孔中的扩散所致,而高浓度的鼠李糖脂形成的聚集体堵塞了扩散孔道,反而阻碍了介质中水的下渗和减弱了介质对水的承载能力。
Rhamnolipid production by Pseudomonas aeruginosa ATCC 9027 with waste frying oil as sole carbon source was studied using response surface method. Cultures were incubated in shaking flask with temperature, NO3- and Mg2+ concentrations as the variables. Meanwhile, fed-batch fermentation experiments were conducted. The results show that the three variables are closely related to rhamnolipid production. The optimal cultivation conditions are of 6.4 g/L NaNO3 , 3.1 g/L MgSO4 at 32 ℃, with the maximum rhamnolipid production of 6.6 g/L. The results of fed-batch fermentation experiments show that feeding the oil in two batches can enhance rhamnolipid production. The best time interval is 72 h with the maximum rhamnolipid production of 8.5 g/L. The data are potentially useful for mass production of rhamnolipid on oil waste with this bacterium.
