生活污水污泥炭化再利用於土壤之安全性

隨著科技水準的提升，都市生活污水的處理快速增加，都市公共下水道普及率增加，目前大部分的生活污水污泥主要以衛生掩埋處理，亦或是與垃圾焚化廠混燒等方式處理。污泥中存在大量重金屬，再利用於土壤的安全性為本次探討的主題。本研究使用台中市污水處理廠之脫水污泥，將其進行乾燥處理，並分析其重金屬含量。以不同溫度及時間進行污泥之碳化，分析污泥生物炭的重金屬含量、重金屬鍵結型態及生物有效性，並以不同比例添加污泥生物炭於土壤中，透過盆栽試驗了解污泥對植物生長及植體重金屬含量之影響。毒性特性溶出程序結果顯示污泥生物炭之Cd、Cr、Cu及Pb濃度皆未超過有害事業廢棄物認定標準，而污泥生物炭中Cd、Cr、Cu、Pb、Ni及Zn之含量皆超過國內食用作物農地管制標準；Cd、Cr、Cu、Pb及Ni在污泥生物炭中主要以殘留態含量最多，Zn則多以鐵錳氧化態、有機態及殘留態形式存在；生物有效性結果顯示污泥生物炭中Cd、Cr、Cu、Pb、Ni及Zn濃度會隨溫度升高而增加。盆栽試驗結果顯示，添加5%及10%的污泥生物炭，植體的鎘及鉛皆超出食用限量標準。

關鍵字

污泥；污泥生物炭；毒性特性溶出程序；生物有效性

並列摘要

With the advancement of science and technology, the treatment of urban sewage has rapidly increased, and the ubiquity of public sewers in urban areas has increased. Most of the sewage sludge are mainly disposed in sanitary landfills or treated in waste incineration plants. However, the sludge contains a large amount of heavy metals, and the safety of its reuse in soil is the subject of this study. This study used dewatered sludge from a sewage treatment plant in Taichung City to dry and analyze its heavy metal content. By using different temperatures and durations to carbonize the sludge, its heavy metal content and bonding types, as well as the bioavailability of sludge biochar were analyzed. After adding different proportions of the sludge biochar into soil, this study explored the impacts of sludge biochar on plant growth and plant heavy metal content through plant cultivation tests. The results of the Toxicity Characteristic Leaching Procedure showed that the concentrations of Cd, Cr, Cu, and Pb in sludge biochar have not exceeded the Taiwan hazardous waste certification standards. The contents of Cd, Cr, Cu, Pb, Ni, and Zn in the sludge biochar exceeded the Taiwan agricultural land control standards；Cd, Cr, Cu, Pb and Ni mainly existed as the residual fraction in the sludge biochar, while Zn existed in the Fe-Mn oxides fraction, the organic matter fraction and the residual fraction. The results of the bioavailability tests showed that the concentrations of Cd, Cr, Cu, Pb, Ni and Zn in sludge biochar increased with increasing temperature. The results of the plant cultivation tests showed that after addition of 5% and 10% sludge biochar, the plant's cadmium and lead levels exceeded the Taiwan consumption limit standards.