Authors: 王允
清华大学环境系
Keywords: 地下水
反硝化
碳源材料
释碳机制
groundwater
denitrification
carbon source material
carbon releasing mechanism
Issue Date: 2005
Abstract: 地下水硝酸盐污染已成为世界范围内重要的环境问题，引起了各国广泛关注。针对地下水原位生物反硝化治理技术中面临缺乏合适的碳源材料，限制了反硝化过程的情况，本研究从可控碳源材料制备、结构分析和性能测试出发，对材料加工工艺进行改进，并对其物化性能、释碳机制及反硝化供碳性能进行分析，以判断其作为反硝化碳源的适宜性。可控碳源材料以聚乙烯醇（PVA）为骨架，采用共混技术制备成型。通过对制备过程中的原料、添加剂和成型方法三方面进行改进，制备出PVAS、GPVAS、GEPVAS、GCPVAS和GPVAC五大类材料。电镜扫描、拉曼光谱、比表面积及含水率测定结果表明，材料中淀粉（纤维素）与PVA存在分子间相互作用，并与水分子缔合构成均相体系；材料表面形态与性质受组分影响。静态碳释放研究表明材料释碳机制为扩散和凝胶层溶蚀协同作用，释碳过程满足二级动力学公式，即 。材料的组成、配比、添加剂等均能影响释碳性能。纤维素材料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，可通过改变材料组分实现释碳的可控性。材料具有较高的可生化性，BOD5/COD高达0.55，具备作为反硝化碳源的能力，可被微生物有效利用，实现硝酸盐的降解。试验期间，NO3－－N浓度从45.36mg/L降低至7.15mg/L，降解效率高达84.2%；反硝化过程符合零级反应动力学公式。
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.