周真明，劉啟迪，劉 彤，黃華山，馬紅芳，曾慶玲，苑寶玲

(華僑大學(xué)土木工程學(xué)院，廈門 361021)

生物沸石薄層覆蓋削減亞熱帶水源水庫氮負(fù)荷*

周真明，劉啟迪，劉 彤，黃華山，馬紅芳，曾慶玲，苑寶玲

(華僑大學(xué)土木工程學(xué)院，廈門 361021)

以福建泉州水源地山美水庫和惠女水庫的表層底泥和上覆水為研究對象，室內(nèi)靜態(tài)模擬試驗研究了生物沸石薄層覆蓋削減水源水庫氮負(fù)荷的效果及可行性，探討了上覆水體溶解氧(DO)濃度對削減氮負(fù)荷的影響，分析了削減氮負(fù)荷的作用機(jī)理. 結(jié)果表明，覆蓋強(qiáng)度為1 kg/m2的生物沸石覆蓋(厚度約1 mm)對上覆水中總氮的削減率為58.89%～65.75%，對底泥中總氮的削減率為10.39%～13.08%，對底泥中銨態(tài)氮的削減率為32.35%～44.56%，對底泥中有機(jī)氮的削減率為8.41%～11.04%；對于以硝態(tài)氮為主要形態(tài)氮的上覆水體，DO濃度越低，越有利于高效菌脫氮；可見，生物沸石薄層覆蓋能有效削減水源水庫氮負(fù)荷，利用生物沸石薄層覆蓋技術(shù)削減水源水庫氮負(fù)荷是可行的，但需要進(jìn)一步研究水源水庫底泥生物沸石薄層覆蓋修復(fù)過程中氮的遷移轉(zhuǎn)化機(jī)制.

底泥；薄層覆蓋；氮；生物沸石；水源水庫

水體富營養(yǎng)化是全球重要水質(zhì)難題之一[1]. 氮和磷是水體富營養(yǎng)化的主要限制因子，控制水體氮和磷濃度能有效抑制水體富營養(yǎng)化[2]. 水源水庫內(nèi)源(底泥)氮、磷釋放，是水庫氮、磷主要來源途徑之一，在外源氮和磷得到有效控制的條件下，削減底泥氮、磷釋放將成為控制水源水庫富營養(yǎng)化的有效方法之一[3]. 當(dāng)前，削減底泥氮、磷釋放的主要方法有清淤法和原位覆蓋法[4]，由于清淤法存在費用高、底泥再懸浮、運(yùn)輸和處置過程存在二次污染、破壞水底生態(tài)環(huán)境等不足[5]，使得原位覆蓋法成為國內(nèi)外學(xué)者研究熱點，并在歐美、日本等地得到廣泛工程應(yīng)用[4]. 原位覆蓋法由傳統(tǒng)物理厚層覆蓋[6-7]發(fā)展到當(dāng)今活性薄層覆蓋[8-12]，覆蓋層作用機(jī)理也從物理掩蔽[6-7]發(fā)展到物理化學(xué)吸附及生物化學(xué)轉(zhuǎn)化[8-15]. 目前研究和應(yīng)用中，針對水源水庫的污染底泥覆蓋材料主要有改性沸石的磷鈍化劑(Z2G1)[10, 16]和鑭改性膨潤土(鎖磷劑phoslock?)[12, 17-18]；實驗室研究表明[16]，Z2G1覆蓋不僅能完全抑制底泥氮和磷釋放，而且還削減了上覆水中氮和磷，但在新西蘭Okaro水庫實際應(yīng)用中表明，投加0.35 kg/m2的Z2G1后，水庫中氮、磷負(fù)荷削減不明顯[10]，有待進(jìn)一步開發(fā)研究. 鎖磷劑phoslock?是澳洲工業(yè)科學(xué)研究協(xié)會于1990年研發(fā)的，于2002年商品化的，到目前為止，鎖磷劑廣泛應(yīng)用于澳洲、歐洲、美國、加拿大、新西蘭等水庫和湖泊[18]，大規(guī)模應(yīng)用案例超過120處，但鎖磷劑主要針對削減水源水庫磷負(fù)荷，針對削減水源水庫氮負(fù)荷的底泥原位覆蓋法研究不多，對底泥不同形態(tài)氮削減效果鮮見報道.

1 材料與方法

1.1 試驗材料

表1 上覆水和底泥間隙水的水質(zhì)指標(biāo)*

*ND表示低于檢測限值.

表2 底泥物理化學(xué)性質(zhì)及礦物成份

試驗所用的生物沸石是將天然斜發(fā)沸石浸置在由2株高效異養(yǎng)硝化細(xì)菌(WGX10和WGX18，均為芽孢桿菌屬，Bacillussp.)和2株高效好氧反硝化菌(HF3和HF7，均為不動桿菌屬，Acinetobactersp.)組成的混合菌液中，通過連續(xù)曝氣掛膜方法制備而成；4株菌的生理生化特性及生物沸石制備過程詳見參考文獻(xiàn)[13, 22].

1.2 試驗裝置與方法

試驗在容積為10 L、直徑為200 mm的廣口玻璃瓶中進(jìn)行；上覆水水深為20 cm，底泥厚度為5 cm，生物沸石的覆蓋強(qiáng)度為1 kg/m2(覆蓋厚度約1 mm).

試驗共有16個廣口玻璃瓶，分為8組，每組2個平行，編號為1#～8#，其中，1#為山美水庫底泥，無覆蓋，廣口瓶敞開，命名為“SM-NC”；2#為山美水庫底泥，生物沸石覆蓋，廣口瓶敞開，命名為“SM-C”；3#為山美水庫底泥，無覆蓋，廣口瓶密封，密封前，先將加入瓶中的上覆水充N2，使其DO濃度<0.1 mg/L，然后加入玻璃瓶中，再充N2，使玻璃瓶中上覆水DO濃度<0.1 mg/L(下同)，命名為“SM-NC-A”；4#為山美水庫底泥，生物沸石覆蓋，廣口瓶密封，命名為“SM-C-A”；5#為惠女水庫底泥，無覆蓋，廣口瓶敞開，命名為“HN-NC”；6#為惠女水庫底泥，生物沸石覆蓋，廣口瓶敞開，命名為“HN-C”；7#為惠女水庫底泥，無覆蓋，廣口瓶密封，命名為“HN-NC-A”；8#為惠女水庫底泥，生物沸石覆蓋，廣口瓶密封，命名為“HN-C-A”.

1.3 測定方法

1.4 數(shù)據(jù)處理

上覆水體和底泥中不同形態(tài)氮削減率(P)的計算公式為：

(1)

式中，CCi為取樣時生物沸石覆蓋系統(tǒng)上覆水或底泥中不同形態(tài)氮濃度(mg/L或mg/kg)；CNCi為取樣時未覆蓋系統(tǒng)上覆水或底泥中不同形態(tài)氮濃度(mg/L或mg/kg)；i為取樣次數(shù).

采用Excel軟件對生物沸石覆蓋系統(tǒng)與未覆蓋系統(tǒng)之間削減氮污染物效果的差異進(jìn)行方差分析.

2 結(jié)果與討論

2.1 削減上覆水體中氮負(fù)荷的能力

圖1 山美水庫(a)和惠女水庫(b)各系統(tǒng)上覆水中濃度ü Reservoir(b)

SM-C系統(tǒng)對TN的削減率為37.38%～80.28%，平均值為58.89%；SM-C-A系統(tǒng)對TN的削減率為39.03%～75.06%，平均值為62.22%；HN-C系統(tǒng)對TN的削減率為52.96%～88.04%，平均值為65.75%；HN-C-A系統(tǒng)對TN的削減率為28.33%～78.92%，平均值為62.64%(圖2). 方差分析表明，SM-NC和SM-C、SM-NC-A和SM-C-A、HN-NC和HN-C、HN-NC-A和HN-C-A系統(tǒng)中TN濃度均存在明顯差異(P<0.01)，可見，在不同實驗條件下，生物沸石覆蓋均能有效削減上覆水中氮負(fù)荷，說明通過生物沸石覆蓋削減水源水庫氮負(fù)荷是可行的.

圖2 山美水庫(a)和惠女水庫(b)各系統(tǒng)上覆水中TN濃度Fig.2 TN concentration of overlying water in each system from Shanmei Reservoir(a) and Huinü Reservoir(b)

2.2 削減底泥中氮負(fù)荷的能力

表3 試驗前后各系統(tǒng)底泥中不同形態(tài)氮含量

2.3 上覆水體DO濃度對削減氮負(fù)荷效果的影響

2.4 削減氮負(fù)荷的作用機(jī)理分析

2.5 野外原位應(yīng)用時生物沸石覆蓋厚度討論

污染底泥原位生物沸石薄層覆蓋技術(shù)在野外原位應(yīng)用時，存在的實際問題有：1)薄層覆蓋厚度太小，實際投加時，很難均勻覆蓋，會有部分底泥表面未被生物沸石覆蓋，影響生物沸石覆蓋削減氮負(fù)荷效果，例如?zkundakci等[11]開發(fā)了一種以沸石改性的磷鈍化劑(Z2G1或Aqual-PTM)，以Z2G1為活性層覆蓋材料原位控制沉積物氮和磷釋放，富營養(yǎng)化Okaro湖實際應(yīng)用結(jié)果表明：投加Z2G1后，湖泊中氮、磷負(fù)荷降低不明顯，歸因于Z2G1覆蓋不均勻(Z2G1堆積密度為2 g/cm3，覆蓋強(qiáng)度為0.35 kg/m2，水下攝像機(jī)顯示實際覆蓋強(qiáng)度為0.115～1.52 kg/m2)，且部分沉積物表層未被覆蓋；2)若水下底泥有機(jī)腐殖質(zhì)較多，底泥表層較為松散，生物沸石也會容易沉入表層浮泥中，減弱生物沸石覆蓋削減氮負(fù)荷的效果；3)加上野外風(fēng)浪擾動，生物沸石薄層覆蓋層很難完全阻止底泥再懸浮. 因此，建議通過如下措施來消除或緩解上述問題：1)若底泥表層浮泥較多，可先通過清淤方式將表層浮泥清除掉，或先覆蓋5～10 cm厚度的干凈沙子，再覆蓋生物沸石；2)在經(jīng)濟(jì)條件允許情況下，適當(dāng)增加生物沸石覆蓋厚度，如2～5 mm；3)采用多層覆蓋方式，即下層覆蓋沙子，中層覆蓋生物沸石，上層覆蓋沙子.

3 結(jié)論

3)水源水庫底泥生物沸石薄層覆蓋修復(fù)過程中氮遷移轉(zhuǎn)化機(jī)制需要進(jìn)一步試驗研究，可借助于微生物分子生態(tài)學(xué)技術(shù)及氮平衡原理討論分析，同時需要考察其他因素的影響，如碳源、上覆水氮負(fù)荷等.

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Thin-layer capping with biozeolite for nitrogen load reduction in the water-supply source reservoirs， subtropical China

ZHOU Zhenming, LIU Qidi, LIU Tong, HUANG Huashan, MA Hongfang, ZENG Qingling & YUAN Baoling

(CollegeofCivilEngineering,HuaqiaoUniversity,Xiamen361021,P.R.China)

In this study, samples were collected from overlying water and surface sediment in Shanmei Reservoir and Huinü Reservoir in Quanzhou City, Fujian Province. The efficiency of nitrogen load reduction by thin-layer capping with biozeolite in the source water reservoirs was investigated through a series of laboratory-scale static simulating experiments. The effect of dissolve oxygen concentration in overlying water on reducing nitrogen load was discussed and the mechanism to reduce nitrogen load by thin-layer capping with biozeolite was also explored. The results showed that the reduction efficiency of total nitrogen in overlying water ranged from 58.89% to 65.75% by thin-layer capping with biozeolite at a dose rate of 1 kg/m2(the thickness of 1 mm), and the reduction efficiencies of total nitrogen, ammonium nitrogen and organic nitrogen in sediments were in the range of 10.39%-13.08%, 32.35%-44.56% and 8.41%-11.04%, respectively. To overlying water of the main form of nitrate, the lower the dissolve oxygen concentration of overlying water, the better the efficiency of biological denitrogenation by high efficient bacteria. Therefore, thin-layer capping with biozeolite is efficient and feasible to reduce nitrogen load in the source water reservoirs. However, it is urgent to understand the mechanisms of nitrogen transportation and transformation in remediation process of sediment using thin-layer capping with biozeolite.

Sediment; thin-layer capping; nitrogen; biozeolite; water-supply source reservoir

*國家自然科學(xué)基金項目(51408243)、福建省自然科學(xué)基金項目(2015J01213)、福建省科技計劃對外合作重點項目(2014I0013)、中央高?；究蒲袠I(yè)務(wù)費專項資金項目(11QZR07)和華僑大學(xué)中青年教師科研提升資助計劃項目(ZQN-PY313)聯(lián)合資助. 2016-03-09收稿；2016-08-08收修改稿. 周真明(1981～)，男，博士，副教授；E-mail: zhenming@hqu.edu.cn.