連続オゾン発生反応処理装置を用いた逆浸透膜（RO）・ナノろ過（NF）濃縮浸出水からの腐植物質の除去

Removal of humic substances from reverse osmosis (RO) and nanofiltration (NF) concentrated leachate using continuously ozone generation-reaction treatment equipment.

• Huawei Wang
• Ya-Nan Wang
• Xiaoyue Li
• Yingjie Sun
• Hao Wu
• Dali Chen

抄録

膜処理プロセスからの濃縮浸出水は、分解困難な腐植物質を多量に含んでおり、生態環境に悪影響を及ぼす可能性がある。本研究では、逆浸透膜(RO)及びナノろ過(NF)の濃縮浸出液を連続オゾン発生反応一体型装置で処理し、ゲルろ過クロマトグラフィー(GFC)、励起電子マトリックス蛍光分光法(EEM)、XAD-8樹脂分画法、フーリエ変換赤外分光法(FTIR)を用いて腐植物質の除去特性を分析した。ＸＲＤ-８分画、ＳＵＶＡ２５４の結果から、オゾン処理時の芳香族炭化水素の分解と腐植度の低下とともに、フミン酸（ＨＡ）、フルボ酸（ＦＡ）を含む腐植物質が効果的に除去されていることがわかった。反応時間110分後には、両濃縮浸出液中のHAは完全に除去された。GFC分析の結果、両濃縮浸出液の分解後の分布は、より広範囲であることがわかった。高分子量(MW)有機物は10kDa以下の低分子量に変換された。NF濃縮物の高分子量有機物の大部分は10kDa〜1kDaの低分子量に変換されたが、RO濃縮物の高分子量有機物は1kDa未満の低分子量に分解された。EEM分析の結果から、HAとFAの分解により蛍光強度が大幅に低下していることが示唆された。2つの濃縮浸出水の排水は、中国における浸出水の直接または間接排出基準の最大許容基準を満たしていなかったが、濃縮浸出水中の有機物の組成と特性は、さらなる生物処理や他の高度な処理に資するであろう、全体のオゾン反応後に大きく変化した。

Concentrated leachate from membrane treatment process, which contains large amount of difficult-to-degrade humic substances, can induce potential hazards to ecological environment. In this study, the concentrated leachates from reverse osmosis (RO) and nanofiltration (NF) were treated by continuous ozone generating-reaction integrated equipment, and the removal characteristics of humic substances were analyzed using gel filtration chromatography (GFC), excitation-emission matrix fluorescence spectroscopy (EEM), XAD-8 resin fractionation, and Fourier transform infrared spectroscopy (FTIR). The results of XRD-8 fractionation and SUVA254 showed that the humic substances including humic acid (HA) and fulvic acid (FA), were effectively removed along with the breakdown of aromatic hydrocarbons and decrease in the degree of humification during the ozonation process. After 110min of reaction, HA in both concentrated leachates was completely removed. GFC analysis indicated that both concentrated leachates had much broader distribution after the degradation. The high molecular weight (MW) organic matter was transformed into low molecular weight of <10kDa. The majority of high MW organics in NF concentrate were converted to low MW molecules of 10kDa-1kDa, while those in RO concentrate were decomposed to small MW molecules of <1kDa. The results of EEM analysis implied that the degradation of HA and FA led to a significant decrease in the fluorescence intensity. Though the effluent of two concentrated leachate did not meet the maximum allowable criterion for leachate direct or indirect discharge standard in China, the composition and properties of organic matters in concentrated leachate were changed significantly after entire ozonation reaction, which would be conducive to the further biological treatment or other advanced treatment.

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