Authors: 王允
清華大學環(huán)境系
Keywords: 地下水
反硝化
碳源材料
釋碳機制
groundwater
denitrification
carbon source material
carbon releasing mechanism
Issue Date: 2005
Abstract: 地下水硝酸鹽污染已成為世界范圍內(nèi)重要的環(huán)境問題，引起了各國廣泛關注。針對地下水原位生物反硝化治理技術中面臨缺乏合適的碳源材料，限制了反硝化過程的情況，本研究從可控碳源材料制備、結(jié)構(gòu)分析和性能測試出發(fā)，對材料加工工藝進行改進，并對其物化性能、釋碳機制及反硝化供碳性能進行分析，以判斷其作為反硝化碳源的適宜性。可控碳源材料以聚乙烯醇（PVA）為骨架，采用共混技術制備成型。通過對制備過程中的原料、添加劑和成型方法三方面進行改進，制備出PVAS、GPVAS、GEPVAS、GCPVAS和GPVAC五大類材料。電鏡掃描、拉曼光譜、比表面積及含水率測定結(jié)果表明，材料中淀粉（纖維素）與PVA存在分子間相互作用，并與水分子締合構(gòu)成均相體系；材料表面形態(tài)與性質(zhì)受組分影響。靜態(tài)碳釋放研究表明材料釋碳機制為擴散和凝膠層溶蝕協(xié)同作用，釋碳過程滿足二級動力學公式，即 。材料的組成、配比、添加劑等均能影響釋碳性能。纖維素材料Cm和K值均高于淀粉材料；40%淀粉材料的Cm和K值均最低。淀粉酶增加材料Cm值，降低K值；CaCO3降低材料的Cm和K值。因此，可通過改變材料組分實現(xiàn)釋碳的可控性。材料具有較高的可生化性，BOD5/COD高達0.55，具備作為反硝化碳源的能力，可被微生物有效利用，實現(xiàn)硝酸鹽的降解。試驗期間，NO3－－N濃度從45.36mg/L降低至7.15mg/L，降解效率高達84.2%；反硝化過程符合零級反應動力學公式。
Widespread pollution of groundwater by nitrate has become an important environmental problem, and has drawn wide attention in many parts of the world. As lack of carbon source materials limits denitrification process in in-situ treatment of groundwater, research on producing, structure analyzing and capability testing has been carried out. The producing technics had been improved, while analysis on physical and chemical performances, carbon releasing mechanism, and denitrification capability had been taken up to judge the applicability for in-situ denitrification of produced materials. With Poly Vinyl Alcohol (PVA) as the framework, five kinds of controllable carbon source materials have been produced, which were called PVAS, GPVAS, GEPVAS, GCPVAS and GPVAC, through improving the raw materials, additive and molding methods. Results of SEM, Raman Spectrum, Ratio Surface Area and Water Percentage showed that mutual molecular actions existed between starch (cellulose) and PVA, which would combine with water molecule and form homogeneous phase. The composition would affect the surface topography and structure. Through static releasing test, the mechanism was synergistic actions of diffusion and corrosion of gel layer, and the process followed the law of second order kinetics, which is the formula . The composition, content and additive could affect the carbon releasing capability. Cm and K of GPVAC were higher than GPVAS, among which Cm and K of GPVAS-40 are both the lowest. Amylase would increase Cm and decrease K while CaCO3 would decrease both Cm and K. The value and velocity of carbon release could be controlled by change of materials composition. The BOD5/COD can be up to 0.55, which meant the materials were easy to utilize by microorganism for nitrate degradation. During the experiments, NO3－－N fell to 7.15mg/L from 45.36mg/L, and the efficiency of degradation was up to 84.2%. The denitrification process followed the law of first order kinetics.