本研究主要以含高濃度水溶性氯離子之都市污水廠污泥與元素鐵進行共同堆肥，探討元素鐵對污泥中硝酸氮及水溶性氯離子溶出之影響。
實驗中所用之污泥樣品採集自台南市安平污水處理廠之脫水污泥餅，實驗過程控制不同元素鐵添加劑量 (0-30g Fe0/kg Sludge)與污泥充分攪拌並調整含水率為80%後，置入壓克力管柱 (內徑9.5cm，高35cm)中進行共同堆肥30天。於堆肥時間0、5、10、20及30天進行污泥採樣及含水率、元素組成 (C、H、N、S)、碳氮比 (C/N ratio)、硝酸氮 (NO3--N)、亞硝酸氮(NO2--N)、氨氮 (NH3-N)、有機氯、水溶性氯離子 (Cl-)、亞鐵 (Fe2+)、總鐵等分析，以瞭解堆肥時間、元素鐵添加量對污泥基本特性、硝酸氮與水溶性氯離子溶出特性之影響；另外，為瞭解酸性雨水對下水污泥中硝酸氮及水溶性氯離子溶出特性與元素鐵添加量效應之影響，特以硫酸配製pH= 4.0之酸性水進行淋洗，於30天堆肥過程中淋洗600mL，並於底部以燒杯收集污泥之滲出水，除分析堆肥過程中污泥之基本特性外並分析滲出水中硝酸氮、亞硝酸氮、氨氮及水溶性氯離子等。
實驗結果顯示，不添加元素鐵之下水污泥空白樣品於堆肥過程中基本特性未有顯著變動，碳氮比亦無明顯變化，僅在6.5-6.7範圍內變動，顯示於堆肥過程中，污泥中微生物反應遲緩；添加元素鐵之下水污泥，基本特性於堆肥過程中亦未有顯著變化，碳氮比變動範圍亦在6.5-6.7，顯示添加元素鐵於污泥中未改變生物反應情形；而於堆肥過程中添加元素鐵並未能有效降低污泥中硝酸氮濃度，硝酸氮濃度約在0.1-0.2g/kg範圍內變動；在水溶性氯離子方面，原污泥中濃度為19.1g/kg，經添加元素鐵於下水污泥共同堆肥30天後，可有效降低污泥中水溶性氯離子濃度，且降低量隨元素鐵添加量增加而提昇，元素鐵添加量為20-30g Fe0/kg Sludge之污泥經30天後，污泥中水溶性氯離子濃度可降低至15.1g/kg；另外，於添加酸性淋洗部分，酸性淋洗未能提昇元素鐵降低污泥中硝酸氮濃度，污泥中硝酸氮濃度30天變動範圍為0.1-0.4g/kg；而添加酸性淋洗於污泥對於降低污泥中水溶性氯離子則有顯著的助益，水溶性氯離子下降量亦隨元素鐵添加量增加而提昇，經30天共同堆肥後，元素鐵最大添加量 (20-30g Fe0/kg Sludge)之條件下，污泥中水溶性氯離子濃度可降低至9.6 g/kg。 The aim of this study is to examine the effect of zero-valent iron on the co-compost of zero-valent iron and sewage sludge. The leachability of nitrate and soluble chloride in sewage sludge was observed during the composting period.
Samples of sewage sludge were gathered from the An-Pin sewage treatment plan in Tainan City. The experimental parameters were designed as follows: Fe0/sludge mass ration :0-30g/kg, water content of compost: 80%, sampling time of compost: 0, 5, 10, 20 and 30 day.The sewage sludge was firstly completely mixed with Fe0 for 18 mins and the packed into plastic columns with a 9.5 cm inner diameter and 35 cm hight. To discuss the effect of acid precipitation on the sludge co-compost, acidified water with pH = 4.0 was prepared by spiking H2SO4 into D.I. water. The water content, elemental conpsition, C/N, nitrate, nitrite, amino-nitrogen, soluble chloride and ferrious ion in the sewage samples were determined. The leachate from the column were collected in a beaker and used for the analysis of NO3--N, NO2--N, NH3-N and soluble chloride.
Based on the results of experiments, it was found that zero-valent iron appeare to have no effect on the reduction of NO3- in the sewage sludge. On the other hand, Fe0 was found to reduce the soluble chloride in the sludge singnificantly.
