牡蛎壳改性及联合释氧复合材料修复地下水氨氮污染实验研究

为研究以牡蛎壳-释氧复合材料为填料的渗透反应格栅去除地下水氨氮污染的效果及其经济实用性,开展了相关室内实验:采用高温加热方式对牡蛎壳进行改性,通过测定牡蛎壳改性后的比表面积判定其吸附效果;以过氧化钙为释氧化合物,将其与水泥、石英砂/牡蛎壳粒、钙基膨润土以一定比例混合制成粒径约1.8 cm球型释氧材料,采用静态实验研究不同原料配比的释氧材料的释氧性能;最后研究了两种不同粒径牡蛎壳粒-释氧复合材料修复地下水氨氮的效果及不同供氧方式下不同吸附材料修复地下水氨氮的效果及其经济实用性。结果表明:对牡蛎壳粒进行高温改性,牡蛎壳粒高温条件下会产生团聚现象,比表面积随煅烧温度升高呈下降趋势,高温改性方式并不能有效改善牡蛎壳粒吸附性能;实验中制作的释氧材料在95天的实验期间,各实验柱的溶解氧量可以保持在18 mg/L左右,且在嗜碱菌作用下pH值得以有效降低,所制作的释氧材料可为硝化细菌长期在溶解氧低的地下水环境中生长提供氧气;以牡蛎壳-释氧复合材料为填料的渗透反应格栅通过耐碱硝化细菌的硝化作用可以将氨氮浓度从50 mg/L降至约35 mg/L,不同粒径牡蛎壳粒修复效果差异不明显。使用牡蛎壳-释氧复合材料渗透反应格栅长期修复地下水氨氮,不仅可以达到活性炭及沸石作为骨架的修复效果,而且更加具有经济实用性。

Experimental Study on Oyster Shell Modification and Combined Oxygen Release Composite Materials for Remediation of Ammonia Nitrogen Pollution in Groundwater

Laboratory experiments were carried out on the performance and economic applicability of permeable reactive barrier filled with modified oyster shell-oxygen releasing composite material, with the aim to mitigate groundwater ammonia nitrogen pollution. Calcium peroxide was used as the oxygen-releasing compound, and mixed with cement, quartz sand/oyster-shell grain and calcium bentonite in a certain proportion, in order to make a spherical oxygen-releasing material with about 1.8 cm particle size. Finally, we studied the groundwater ammonia nitrogen repairing effects and their economic feasibility of two different size oyster-shell oxygen-releasing composite materials, and those of different adsorbent materials under different oxygen supply modes. The results indicate that the high-temperature modification of oyster-shell particles could not improve the comparative area of oyster shell. The specific surface area of oyster shell decreases with increasing calcination temperature and aggregation occurred. During the 95-day experiment, the dissolved oxygen of each experimental column was maintained at about 18 mg/L, and the basophilic bacterial action reduced the pH effectively. The oxygen-releasing material produced could provide the oxygen for the nitrifying bacterial growth in groundwater with low dissolved-oxygen for a long period of time. By the nitrification of alkali-resistant nitrifying bacteria, the permeable reactive barrier filled with oyster shell oxygen-releasing composite material could reduce the ammonia nitrogen concentration from 50 to 35 mg/L, whilst the repairing effect by oyster shell particles of different sizes is unobvious. In the long term, it is more economical to use oyster shells as adsorbents, and to use oxygen-releasing materials as oxygen supply. The use of the permeable reactive barrier (filled with modified oyster shell-oxygen) releasing composite material for long-term groundwater ammonia nitrogen repair is both effective and economical with activated carbon and zeolite framework.