畜牧業廢棄汙泥之資源化與再利用

Abstract

畜牧業污泥含大量有機物質及氮磷等營養成分, 可利用為農地肥料或是土壤改良劑, 除可達到資源回收目的, 亦有畜牧場減廢之功效.但由於畜牧方式的改良, 飼料中添加銅與鋅化學鹽類, 以作為豬隻生長之刺激劑與調理劑, 造成養豬廢水甚至污泥中含有過量的重金屬.但是, 污泥量增加、處理費用升高, 加上更嚴格管制要求, 未來污泥處理與處置技術必須脫離傳統方法重新調整, 始能因應實際之需要.以往於重金屬生物溶出法於污泥處理之過程中可以發現, 除有重金屬去除效果外, 若同時配合污泥本身中所存在之好氧異營菌, 則亦有污泥之好氧消化作用, 如此便同時具有污泥無害化及安定化之效用.因此, 本研究之主要目的在於建立經濟可行之同時污泥好氧消化與金屬溶出程序, 探討不同之操作條件下進行實驗, 以求得其最佳之處理效率, 以作為實際運用於污泥處理時之設計參考.計畫中將分為三個年度進行, 第一年度重點在於建立可行之畜牧業污泥同時好氧消化與金屬溶出程序, 進行硫氧化菌與異營菌對於污泥中重金屬溶出與有機物分解之影響因子探討.第二年之重點主要在於瞭解不同反應條件的改變, 對於畜牧業污泥中重金屬溶出與有機物分解之反應有何影響, 尋找出反應影響因子, 建立最佳化之操作參數.第三年的研究重點著重於, 畜牧業污泥同時好氧消化與金屬溶出程序在畜牧場之運用, 藉由連續式反應槽之設計, 最佳操作參數之探討, 及污泥上澄液重金屬回收處理技術之建立, 以期對於整個處理程序估算最經濟的處理效率, 增進畜牧業污泥同時好氧消化與金屬溶出程序之實用性.由此三年之成果, 可以對於畜牧業污泥同時好氧消化與金屬溶出技術, 在未來應用上及其所能達到之效果有研究成果可以依循參考.

The livestock sludge often contains high concentrations of organic matters and nutrients.The application of livestock sludges on the agricultural lands as the soil fertilizers has the benefits of resource recycling and waste minimization of livestock farm.However, the addition of metal salts in the pig fodder makes the high contents of metals in sludges produced from the livestock farm.Therefore, the presence of elevated heavy metals in livestock sludge will limit the land application of livestock sludge.In order to solve the above problems, it is important to develop the techniques for treatment of the large quantity of livestock sludge for reuse the sludge in land application or soil fertilizer.Several environmental problems were caused by the microbiological oxidation of sulfur or reduced-sulfur.In contrast, the acid-producing activity of this particular class of bacteria is useful in biotechnlolgy and environmental engineering.On the other hand, some of heavy metals in sludge are combined as sulfides and these metal sulfides are usually difficult to remove from the sludge by chemical extraction method.Recently, a bioleaching process that applies thiobacilli for removal of heavy metals from sludge is useful and economically feasible.If the acclimated indigenous bacteria are used as the inoculum in the bioleaching process, besides the reaction of metal leaching, the aerobic sludge digestion by indigenous heterotrophic bacteria in sludge will take place in this process.Therefore, a new process called simultaneous sludge digestion and metal leaching has been applied for sludge treatment.The purposes of this study are to develop the simultaneous aerobic digestion and metal leaching process for livestock sludge to simultaneously solubilize metals from sludge and digest the organic matters in sludge.This is a three-year project.In the first year, a comparison of a two-stage of aerobic digestion and metal leaching process and simultaneous aerobic digestion and metal leaching process for livestock sludge will be conducted.It is necessary for the development of the economically feasible simultaneous aerobic digestion and metal leaching process for livestock sludge.Besides, the effects of solid and sulfur contents on this process will be examined respectively.In the second year, the effects of process parameters ( temperature, aeration and inoculum )and kinetic of metal leaching and sludge digestion in simultaneous aerobic digestion and metal leaching process for livestock sludge will be investigated and developed.In the third year, simultaneous aerobic digestion and metal leaching process for livestock will be studied in a continuous air-lift reactor with recycling and the optimal parameters will be examined.On the other hand, the treatment and recycling of heavy metal in the supernatant of the treated sludge will be studied.