聚己內酯添加量對淡水養殖水體硝酸鹽氮處理效果的影響

侯志偉， 高錦芳， 羅國芝,2

(1上海水產養殖工程技術中心，上海海洋大學, 上海 201306; 2 農業部淡水水產種質資源重點實驗室，水產科學國際級實驗教學示范中心，上海海洋大學，上海 201306)

聚己內酯添加量對淡水養殖水體硝酸鹽氮處理效果的影響

侯志偉1， 高錦芳1， 羅國芝1,2

(1上海水產養殖工程技術中心，上海海洋大學, 上海 201306; 2 農業部淡水水產種質資源重點實驗室，水產科學國際級實驗教學示范中心，上海海洋大學，上海 201306)

聚己內酯；固相反硝化；循環水養殖系統；硝酸鹽氮

1 材料與方法

1.1材料

試驗所用PCL顆粒采購自深圳市光華偉業實業有限公司，為白色結晶性米狀顆粒，平均大小為2～3 mm，主要力學性能參數：密度1.12 kg/L，分子量 80 000，熔融指數1～4 g/10 min，熔點58℃～60℃，斷裂伸長率800%。試驗開始前清洗PCL以去除雜質，在35℃下烘干至恒重。

1.2試驗設計

1.3水質測定方法

1.4顯微鏡觀察

取未使用和使用后的PCL顆粒，清洗后固定在鋁制圓盤上，真空條件下在其表面噴金，利用電子掃描顯微鏡(S3400NII，日立有限公司，日本)進行掃描觀察并拍照。

1.5去除效率和去除率計算

RE=100%×(C進-C出)/C進

(1)

RR=(C進-C出)×Q/V

(2)

RA=RR×V×t

(3)

1.6PCL利用率計算

實驗結束后將PCL在超聲波振蕩器(KQ2200E，昆山超聲波儀器有限公司)中清洗，使生物膜與PCL完全剝離，清洗后的PCL在35℃下烘干稱重。根據公式4計算各添加量的PCL利用率。

UR=100%×(W始-W末)/RA

(4)

式中：UR—PCL利用率，%；W始—實驗開始時PCL的質量，kg；W末—實驗結束時PCL的質量，kg。

1.7數據分析

所有數據用 SPSS 17.0(SPSS, Inc., Chicago, IL, USA)分析。各種PCL添加量指標采用單因素方差分析方法(ANOVA) 。差異顯著性用Tukey 檢驗，P<0.05為差異顯著。

2 結果與分析

圖1 各組進出水硝酸鹽氮濃度Fig.1 Concentrations of nitrate nitrogen

試驗結束時，各組PCL的消耗量見圖2。消耗量5 g組最少，且5 g組與其余三組差異顯著，25 g組最大，10、15和20 g組和15、20、25和30 g組消耗量均無顯著性差異。

圖2 試驗結束時各組PCL的消耗量Fig.2 Consumptions of PCL at the end of in the influent water for each group the experiment for each group

表1 試驗條件下去除和PCL利用情況Tab.1 Removal situation of N-N VS utilization situation of PCL under experimental conditions

注: 上標“a”和“b”表示同一列中是否有差異顯著性。相同則差異不顯著(P>0.05)，不同則差異顯著(P<0.05)

2.2DOC積累

試驗中進水的DOC質量濃度為4～24 mg/L，但出水的濃度明顯高于進水，說明發生了明顯的DOC積累。反應過程中6個實驗組的DOC濃度變化基本一致。試驗期間6組出水的平均DOC濃度分別為：(57.27±59.25)、(84.07±60.17)、(112.82±62.98)、(111.14±38.86)、(126.99±47.82)和(123.77±79.45) mg/L，出水DOC的變化波動較大，但在進水相同的情況下，其溶出量明顯與添加量相關。

圖3 6個實驗組中出水溶解性有機碳(DOC)含量Fig.3 Concentrations of dissolved organic carbons in the effluent water for the six experimental groups

總體上，添加量越高，水中DOC濃度就越高。5 g 組沒有明顯的DOC產生，這表明PCL添加量是影響DOC剩余的因素之一。

即使在出水硝酸鹽氮濃度較低的情況下，出水DOC仍有明顯積累，尤其是高濃度組。這可能是因為本實驗中將裝有PCL顆粒的燒瓶放置在搖床上，水流晃動帶來的沖擊會導致DOC的釋放[13]。這說明非生物因素在某種條件下可能會成為BDPs釋放DOC的主要因素。BDPs的DOC釋放不僅是一個生物學過程，物理、化學因素也會影響DOC的釋放量和性質[13]。研究發現固相反硝化時都有一定濃度的DOC積累。Luo 等[14]以PBS為碳源時發現有 205 mg/L的DOC積累；Cameron等[17]、Shen等[18]發現啟動階段的DOC會積累，運行穩定時積累較少。目前關于未被利用的DOC成分分析尚未見報道。為了提高BDPs的利用效率，需要進一步開展相關研究。

圖4 反應器進出水質量濃度及TAN質量濃度的變化Fig.4 Changes in mass concentrations of N-N and TAN in the influent water and effluent water

2.4PCL表面變化

試驗發現，在馴化過程中，PCL表面會逐漸形成一層淡黃色的膜狀物，隨著實驗時間的延長，膜狀物的顏色會有所加深。顆粒和瓶壁上的膜狀物形成時間較長且較厚時會脫落到水體中。收集膜狀物并掃描電鏡下觀察，發現膜質較密，附著大量的桿狀菌(圖5)。

圖6為掃描電鏡下放大40倍的PCL顆粒。Y表示使用前的PCL顆粒，其表面光滑完整，使用后整體結構完整未被破壞，但表面變得粗糙，出現了很多大小不同的坑洞。其中，添加5 g PCL的實驗組最為明顯，這是因為高負荷的硝酸鹽氮進水沖擊掉該組部分微生物，之后又重新生長，所以其表面坑洞會比其他組更深、更明顯。

圖5 掃描電子顯微鏡下的生物膜Fig.5 Image of a biofilm under scanning electron microscope

圖6 未使用的PCL(Y)和試驗結束時各組PCL顆粒表面Fig.6 Image of the particle surfaces at the end of the experiment for each group

3 結論

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EffectofadditiveamountofPCLonthenitrate-nitrogenremovalintherecirculatingaquaculturefreshwater

HOUZhiwei1,GAOJinfang1,LUOGuozhi1,2

(1ResearchandDevelopmentCenterofAquaculturalEngineeringofShanghai,ShanghaiOceanUniversity,Shanghai201306,China; 2ShanghaiCollaborativeInnovationCenterforAquaticAnimalGeneticsandBreeding,NationalDemonstrationCenterforExperimentalFisheriesScienceEducation,Shanghai201306,China)

Multiple-time addition of carbon sources, and the shortages and overages of it can be avoided for a denitrification progress using biological degradable Polymers(BDPs) as organic carbon sources. It has been proven that Polycaprolactone(PCL) can act as organic carbon sources for the denitrification progress in the recirculating aquaculture freshwater. In this paper, the effect of additive amount of PCL on the nitrate-nitrogen removal in the recirculating aquaculture freshwater was studied. In a denitrification progress with a about 0.1 g/L load of nitrate nitrogen in the influent water, when the additive amount of PCL in a water body of 200ml increased from 5 g, 10 g, 15 g, 20 g, 25 g and 30 g, the removal efficiency of nitrate-nitrogen for each group showed no significant difference, but the concentration of the unused dissolved organic carbon (DOC) increased with the increasing of the additive amount of PCL. It showed that the change of additive amount of PCL did not affect the removal efficiency of nitrate-nitrogen, but had a significant effect on the accumulation of unused dissolved organic carbon (DOC). In conclusion, 5 g is the best suitable additive amount for PCL.

Polycaprolactone; solid phase denitrification; recirculating aquaculture system; nitrate-nitrogen

10.3969/j.issn.1007-9580.2017.05.003

2017-08-15

上海水產養殖工程技術研究中心項目(16DZ2281200)

侯志偉(1993—)，男，碩士，研究方向：循環水養殖和水處理。E-mail：houzw2016@163.comn

羅國芝(1974—)，女，教授，博士，研究方向：循環水養殖系統與工程。E-mail: gzhluo@shou.edu.cn

S959

A

1007-9580(2017)05-012-07