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为了选择理想的农业废弃物作为优质碳源,同时作为生物膜载体应用于可渗透反应墙(PRB),通过反硝化作用去除地下水中的硝酸盐.选择小麦秸秆、玉米秸秆、稻秆、大豆秸秆、玉米棒、稻壳、甘蔗渣、杨树枝、木屑、芦苇共10种农业废弃物进行元素分析实验、浸溶实验和长效浸出实验研究.元素分析实验结果显示,10种农业废弃物的C、N、H元素含量分别为38%~48%、5%~7%、0.5%~2.5%.短效浸出实验表明,甘蔗浸出液的总有机碳(TOC)浓度最高,均值可达38.66 mg·g~(-1),大豆秸秆、水稻秸秆、玉米秸秆、稻壳、杨树枝和小麦秸秆为8.04~15.30 mg·g~(-1),其他均值约为2.36~6.33 mg·g~(-1).但是,大部分农业废弃物均释放一定量的含氮物质.其中,硝酸盐及亚硝酸盐释放量均低于0.05 mg·g~(-1),氨氮释放量低于0.30 mg·g~(-1),凯氏氮除木屑、玉米棒、杨树枝释放量较低,其余均高于0.80 mg·g~(-1),最高可达1.65 mg·g~(-1).同时,秸秆类材料浸出液具有一定的色度,其中稻杆的色度最高,其值为1025.选择浸出液TOC浓度较高的甘蔗渣、玉米秸秆、稻壳、小麦秸秆及凯氏氮浓度较低的玉米棒和木屑作为理想碳源材料,进行长效浸出实验.结果表明,6种材料的TOC能迅速达到高位平衡状态,且溶出速率稳定,浸出液的高效液相色谱(HPLC)和气-质谱联用仪(GC/MS)分析表明,其主要成分为有机酸、糖类、含氮有机物和酯类等物质.其中,有机酸主要为甲酸、乙酸、草酸、富马酸等小分子有机酸、糖类主要为纤维二糖、葡萄糖、果糖和木糖.脱氮效能实验表明,6种农业废弃物硝酸盐去除率均达到80%以上,脱氮速率均达到1.00~2.00 mg·cm~(-3)·d~(-1)(以N计).综上,这6种材料均可作为地下水硝酸盐污染原位修复的理想碳源填充材料.
In order to select the ideal agricultural waste as the high quality carbon source and at the same time as biofilm carrier applied to the permeable reaction wall (PRB), the nitrate in groundwater was removed by denitrification.Selection of wheat straw, corn stover, rice stalk, soybean stalk , 10 kinds of agricultural wastes including maize cobs, rice hulls, bagasse, poplar branches, sawdust and reed were studied by elemental analysis, leaching test and long-term leaching experiment.The results of elemental analysis showed that 10 kinds of agricultural wastes C , N and H were 38% -48%, 5% -7% and 0.5% -2.5%, respectively.The short-term leaching experiments showed that the total organic carbon (TOC) of sugarcane leachate reached the highest value with an average value of 38.66 mg · g ~ (-1), soybean straw, rice straw, corn stalk, rice husk, poplar branch and wheat straw were 8.04 ~ 15.30 mg · g -1, and the other average values were about 2.36 ~ 6.33 mg · g ~ 1). However, most agricultural wastes release a certain amount of nitrogenous substances, of which nitrate and nitrite emissions are less than 0.05 mg · g -1 and ammonia nitrogen is less than 0.30 mg · g ~ (-1), Kjeldahl nitrogen release except wood chips, corn cobs and poplar branches, the rest were higher than 0.80 mg · g ~ (-1), the highest 1.65 mg · g -1 .The same time, straw leaching solution has a certain color, of which the highest color rice stem, the value of 1025. Select leaching solution of higher TOC concentration of bagasse, corn stalks, rice husk , Wheat straw and Kjeldahl low concentration corn cob and sawdust were used as ideal carbon source materials for long-term leaching experiments.The results showed that the TOC of the six materials reached a high equilibrium rapidly and the dissolution rate was stable and the efficiency of the leachate Liquid chromatography (HPLC) and gas chromatography / mass spectrometry (GC / MS) analysis showed that the main components were organic acids, sugars, nitrogen-containing organic compounds and esters, among which organic acids were mainly formic acid, acetic acid, , Fumaric acid and other small organic acids, and the main carbohydrates are cellobiose, glucose, fructose and xylose.The experiment of denitrification efficiency shows that the removal rates of nitrate of the six kinds of agricultural wastes all reach more than 80% Reaching 1.00-2.00 mg · cm -3 · d -1 in N. In conclusion, all these six kinds of materials can be used as ideal carbon source in situ remediation of groundwater nitrate pollution.