Applied sewage sludge compost to diesel-contaminated soil in-situ treatment
|關鍵字:||柴油;堆肥;中央合成設計法;一階反應動力模式;Diesel;compost;central composite design;first order reaction|
|摘要:||近幾年，石化產品之汽油、柴油及其他化學成品等高污染性的有機化合物在眝存和運輸方面十分頻繁而造成環境污染之事件層出不窮對於生態環境所造成的影響甚鉅。本研究所採用之生物復育技術是相當經濟且有效的油污染處理技術。利用污水廠之污泥予以堆肥後做為受柴油污染土壤的營養鹽和改良劑，模擬受柴油污染土壤現地復育之方式利用中央合成設計 (CCD) 與反應曲面法 (RSM) 作為實驗統計分析之工具，以摻合比 (濕重) 與水分含量作為實驗因子，再加上以溫度為正交區集設計，經由 MINITAB 統計軟體產生一反應曲面並探討獨立變數與反應變數之間的數學模式關係，探討其迴歸係數及變異數分析等相關數據並進行控制組之實驗分析。
由反應曲面結果可以知道生物降解最佳含水率範圍約在最大含水量之 20％-65％ 間，且可知摻合比分別在最高 (土壤和堆肥在濕基下，1:1 之重量摻合比例) 和最低 (土壤和堆肥在濕基下，1:0.1 之重量摻合比例) 摻合比中有最顯著之效果。而上述摻合比中可發現，在降解初期約 10 至 15 天中，產生較快的降解，降解率約 50至 55％，在最後20至30天，則有較緩慢之降解，降解率約 10 至 13％。由迴歸係數分析，可知含水率和摻合比無相互作用 (intereaction) 關係，但是溫度對生物之降解影響相當顯著，亦即在冬天進行現地復育時，降解效率會較差。從滅菌組實驗中可發現只有11％ 之降解效果，故可知本研究之降解過程，主要係生物降解所產生。由配適一階反應模式得知具有相當高之相關係數，故可知本研究之降解過程，可由一階反應模式表示，最適當之摻合比係為 1：0.1 (濕重)，且其動力常數 K 值大於未添加堆肥於土壤中之兩倍。|
In recent years ,leakage of various petroleum hydrocarbons from underground storage tanks primarily at automobile service stations and from pipelines has been experienced at an alarming rate. It would became a environmental pollution accident. Bioremediation with compost is the most cost-effective clean-up technology for the treatment of diesel-contaminated soil. Central composite design (CCD) and response surface method (RSM) of bioremediation experiments were used to construct second order response surfaces for the total petroleum hydrocarbons (TPH) degradation rate to investigate the effects of compost amendment. Fourteen fixed volume batch reactors were designed by central composite design (CCD). The CCD was applied with two design factors (mix ratio and water content) and a block orthogonally (temperature). The experiment data for the central composite design (CCD) was generated by MINITAB. Total cell counts in soil samples were stained by the dye, 4’, 6-diamidino-2-phenylindole (DAPI). The results showed that TPH of contaminated soil decreased in all treatments during bioremediation process. Addition of compost to contaminated soil showed a more rapid TPH reduction that occurred in the early stage (within about 10-15 days), i.e. 50-55％ of TPH can be degraded. The 10-13％ TPH reduction was obtained in the final stage (within about 20-30 days) with a slower degradation rate. By Estimated Regression Coefficients for TPH, the interaction of mix ratio and water content was insignificant (P=0.868). The biological reaction in bioremediation process of the diesel contaminated soil was the major reaction, since the biocide (control experiment) was only 11％ TPH reduction. The data of the bioremediation process were well described by a first order model. The degradation rate constant of TPH in the appropriate mix ratio was two times greater than that of contaminated soil only.The appropriate mix ratio (wet weight basis) of contaminated soil and compost was 1 to 0.1.
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