| In recent years, with the popularity of urban sewage treatment and increasing amout of sludge treatment, adopting mechanized and high-efficient reactor for rapid composting has become the research hotspot due to its high compost efficiency as well as easy controlling. The research group has been committed to sludge resource utilization of sludge as a resource for many years, in our research we have creatively brought forward the idea of doing aging experiments with degradable and composting. To achieve this goal, we design a suit of new reactor system which can both carry on both solid waste stabilization and material aging so as to study the effect of waste water and sludge aerobic and anaerobic composting after adding PASS and we did primary research on the composting materials aging test under the condition of being able to compost.This research used the sewage sludge from FuZhou Xiang ban waster water treatment plant to carry out the following research:First, we design a suit of new reactor system which can both carry on both solid waste stabilization and material aging. Beginning with the sludge characteristics, we demonstrate the design, calculating process and painting for following things in detail: system of the main reaction tank, insulation and controlling temperature, churning system, air-circulation and oxygen controlling system, supporting system of the material accelerating aging. Among them, the most creative point is the trinity unique temperature controlling and insulation system entitled "the trinity system of Blasting to heat-Polyurethane foaming to insulate-Temperature sensation to control". Till now we have applied two patents of this reactor.(one is for comprehensive reactor of sludge aerobic and anaerobic composting; utility model patent no.:ZL200920138759.0; the other is for the accelerating reactor for plastic film aging in the way of sludge composting; patent application number no.:2009101119619).Then, we use this new reactor to conduct experiment of aerobic sludge composting under the condition of adding PASS to sludge. It was found that aerobic composting experiment gone well with the reactor under a certain control parameters,, all indicators presented changes by strong regularity, pile body temperature rises rapidly, and could maintain above 55℃for more than 5d, and a cycle of composting could be done in just 13d, degradation rate of organic matter was up to 30%, the final seed germination index was higher than 0.9 and compost products had a good and stable quality.Thirdly, we used the new reactor to carry out anaerobic sludge composting experiment after adding PAAS to the sludge. It was found that after adding active dry yeast powder to accelerate fermentation and controlling systems' operating parameters and material ratio, the reactor run well, and we also found it could not only complete a quick cycle of anaerobic composting in the 20d, but also showed good effect of fermentation with all indicators changing by strong regularity.Fourth, we primarily studied the light-Ca-type degradable plastic'degradation regularity under the conditions of composting which was done by using the new reactor and aging system. It was found that, PE/CaO composite material showed very good characteristic of composting, under the composting conditions, CaO particles of the composite materials can absorb H2O and CO2 in the environment, which generated the corresponding products Ca(OH)2 or CaCO3, and this led to the particles swelling and then falling off, so a lot of holes located the PE/CaO composite materials surface evolved. Due to these holes, not only the contact area between materials with the environment increased, but also provides more degradation bacteria with channels to enter the inside of material and greatly accelerated the material degradation process as well.Finally, water-absorbent properties of composting products on the basis of adding PASS to the new reactor were studied. The study found that adding PAAS to compost product made the water absorbent reach 5.97mL/g, which was much larger than ordinary compost without adding PAAS. According to the proportion of composting products with adding PASS to the dry farmland (water absorbency of only 0.51mL/g), we mixed them and found the mixture's water absorbent could still achieve 3.38mL/g, which is far better than the mixture of ordinary compost and land.PAAS added compost products and the mixture of such products with land both showed good water-retention capacity in relatively high temperature. With decrease in the temperature, the water-retention time correspondingly extended. Using the dynamics prediction equation to predict water-retention process of the mixture of PASS added composting products with land; we found the results could match the experimental results.In this series of studies, the reactor design was reasonable, and it presented good operating property when being applied to aerobic and anaerobic composting of PAAS added sludge from waster water treatment plant as well as the light-Ca type biodegradable plastics degrading under the condition of composting. Results of the water-absorbent and water-retention properties testing of fertilizers produced by this new type of reactor showed that they were superior than ordinary compost product by a large margin in water-absorbent properties, and we carried out its kinetic studies, then obtained the water retention prediction equation in good agreement with the experimental data of. This study of high-value utilization of urban sludge had a certain reference value. Due to the time the tension, we did not study the composting material degradation under the conditions of composting the study deeply. Future research will focus on researching the degradation regularity of various composting materials in the reactor under the conditions of the composting and have such process universal and standardization; as for rapid composting reactor research, we can explore their industrial application, and this research is currently being undertaken. |
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