下水終末處理場 슬러지의 堆肥化 및 安定化 特性 硏究
Performance characteristics of sludge composting and chemical stabilization for municipal sewage treatment plant
iv, 67 p.
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In an attempt to seek the most effective method to treat the sewage sludge discharging from small and medium sized municipal sewage treatment plants in Korea, a pilot scheme activation tank system for sewage treatment has been set up and evaluated. The final stage plan of sewage sludge treatment has also been investigated through an extensive literature survey, and then the characteristics of sludge have been analyzed and compared with the data. Composting experiments utilizing sludge samples, which were received from a sewage treatment plant in monthly bases, had been carried out throughout the one year. A chemical stabilization method as one of the sludge recycling methods has been considered and then the use as cover soil has been suggested as a sludge recycling method. General characteristics such as the contents of organic (or volatile) substances, moisture and manure, and the contents of harmful substances such as heavy metal elements in the experimental sludge have been investigated in this study. The pH value was shown to be approximately 8.0, indicating mild alkaline property, and the concentrations of TKN and TP, composting componetns of manure, were shown to be in the ranges of 2.0∼3.0% and 1.0∼3.0%, respectively, which were in the possible composting range, suggested in relevant literatures. As the initial stage of composting experiment, the reaction range of VS(volatile substances) is usually broad and the reaction temperature should be elevated to above 65℃. However, it was shown that the reaction temperature were relatively low(35℃), and the reaction range were narrow as well in the final stage of sludge samples from Chung-Ju sewage treatment plant since organic (or volatile) substances such as lignin, which were difficult to decompose, were shown to be contained in a high fraction. Organic (or volatile) substances contain a lot of non-decomposing substances, and the biological exothermic reaction usually takes place at relatively low temperatures so that soil can be infected with germs or parasites in case of spreading them over the soil. Thus it has been suggested that the use of the sludge as a fertilizer is not suitable. However, it can be speculated that composting of sludge, mixing with livestock manure, manure cake, kitchen garbage and so on, might be a alternative processing route to solve the problem. Authorities of the reclamation site located in metropolitan area suffer from the cover soils when reclaiming sanitarily. It was proved that the sludge, which were mixed with 50∼60% of limestone and consequently chemically stabilized, could be used as the cover soil. The use of sludge mixture as cover soil s believed to lead to a cost reduction in long term operation due to the facts that not only the actual reclamation site can be reduced as much as the amount of the sludge, but the transportaion cost for cover soil can also be reduced. However, the use of sluge as a fertilizer or a soil reconditioner is not considered to be suitable, since excessive amount of limestone is needed, say over 75%, in order to satisfy the PFRP condition when chemically stabilized sludge is spreaded over farmland for soil reconditioning.