| With the large-scale construction and operation of municipal sewage treatment plants, the production of sludge has been sharply increasing. The Water Pollution Prevention initiative("Ten Principals of Water") released in our country in February, 2015, clearly points out: the innocent treatment rate ratio of sludge in Chinese mainland should reach 90% above through 2020. Thus it can be seen that the treatment and disposition of sludge is imminent. There is a great deal of research that shows that the excessive sludge yielded by the process of waste water disposal is a valuable resource,which contains a lot of organic matters and nutrient elements. Therefore, developing the technologies of sludge disposal and treatment of low-carbon environmental is the research hotspot of the sewage treatment industry in home and abroad.In this review, the major methods of the sludge treatment and disposal are firstly analyzedat home and abroad, as well as their advantages and disadvantages. And then, based on the principles of the quantity reduction, harmlessness and reutilization of sludge disposal and treatment, as well as the ecological treatment function of earthworms, the sludge is disposedby choosing the excess sludge of sewage plants as main raw materials, mixing with a certain amount of chicken manure and straw, using the technique of ultrasonic disintegration coupled with the pretreatment of aerobic composting, combining with the earthworm treatment technology. In the experiment, these key indexes are tested, which mainly includes the basic property of sludge, the microbial quantity, nutritional components and heavy metal content.And then, the change laws and influential factors of sludge properties before and after treatment are analyzed. The main research contents and conclusions are listed as follows.The compost temperature of sludge composting is enhanced by the aerobic composting sludge. Besides, the high temperature produced by the aerobic composting can meet the basic requirement of sludge harmlessness. In the pretreatment process of Aerobic composting, the moisture content, EC (conductance Rate), organic matter, TOC, TN, C/N, fulvic acid (FA),pathogens content decrease with different degrees for all cases. However, the PH, TP, TK,humic acid (HA),the HA/FA values increase with different degrees for all cases. The degree of sludge humification and the degree of organic matter stabilization are preliminary improved by the pretreatment of sludge by the technique of ultrasonic disintegration coupled with the pretreatment of aerobic composting, which can create the favorable conditions for the sludge treatment by The earthworm in the next step. After the pretreatment sludge is disposed by Earthworms, the pH, TOC, C/N, FA and pathogens content in the sewage sludge decrease with different degrees for all cases, However, the EC value, TN, TP, TK, HA, available nitrogen,available phosphorus and available phosphorus increase with different degrees for all cases.Therefore, the organic matter can be further decomposed by the earthworm treatment.Meanwhile, the mineralization degree of the organic nitrogen is increased. The effectiveness and compost maturity of the compost product are improved obviously. In this way, the pathogens content in the sludge compost can be further reduced and it can meet the requirements of land utilization. When builds the system of ultrasonic disintegration coupled with the pretreatment of aerobic composting by Combining with earthworm treatment of residual sludge system, the dynamic model of the system is discussed and established in this paper by the time variation and The reduction rate of TOC.The organic matter in the reactor is decomposed continuously throughout the process by the synergy of microorganisms and earthworms. With the volatilization of the moisture, some poisonous and harmful gases, the quality loss of the pile body, the concentration effect is developed. Besides, After the heavy metals are disposed, The relative concentration of eight elements (including Zn?Cu?Pb?Cd?Cr?Hg?As) increased and the variation of total quantity is small. After the hierarchical classification of heavy metal morphology in the sludge by using the BCR method, the proportion of acetic acid extraction and reducible decreases and the proportion of better stability oxidizable and residual increases. Therefore, the immobility of all the researched heavy metals in the sludge is increased. Form The progress of absorption of heavy metals by earthworms, It is fully showed that earthworms can have good accumulation on heavy metals, such as Cd and Ni; and can have good bio-absorption on other heavy metals.Thus, the passivation and solidification of the heavy metals can be promoted and the biologic toxicity can be decreased by using the earthworm processing.After the sludge is treated with ultrasonic equipment, the hole effect appears in the sludge,the flocculate structure in the sludge can be effectively destroyed, the structure of the cell wall of sludge can be break up and the intra-cellular substances are released. And then, it can create favorable conditions for aerobic composting and earthworm processing of sludge. Therefore,many aspects by using ultrasound technology group are better than the control group with different extent, such as organic matters' decomposition rate, TN, TP, TK, available nutrient content and inactivation ratio of pathogens content. So the depth of sludge treatment can be improved by using the Ultrasonic technique.After the sludge is processed by earthworm, the average weight of the earthworm increases by 37.4%. According to the analysis of variance, it shows that both the ultrasonic technology and the earthworm stocking density have significant effects on the increasing of the earthworm weight. Besides, the stocking densities of earthworm has positive effect on many aspects, which mainly include the organic matter degradation rate, TP, TK, the accumulation of heavy metals. ?By the observation of sludge microstructure, it can see that the original compact structure of the sludge composting can be preferably destroyed, the flow efficiency of air can be improved, the compost viscosity can be reduced and the soil aggregate formation can be promoted by using the ultrasonic disintegration coupled with the pretreatment of aerobic composting and the earthworm processing. Besides, the recycling value of the sludge can be improved by transforming the sludge into the wormcast, which possesses the characteristic of the loose structure, rich clumpy structure and rich nutrient.The different indexes of the synthetic experimental shows that the operational parameters of the excess sludge system can be determined by using the ultrasonic disintegration coupled with the pretreatment of aerobic composting and the earthworm processing. For example, 10 minutes can be determined as the ultrasonic treatment time, 60% can be determined as the treatment capacity and 80 g/kg can be determined as the stocking density of earthworm. |
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