牡蛎壳作生物滞留填料对城市地表径流污染物去除效果研究

选择磷吸附性能最强的牡蛎壳作为填料,在实验室构建3个生物滞留模拟装置(A柱:养殖牡蛎壳;B柱:海滩牡蛎壳;C柱:养殖牡蛎壳存在淹没区),采用道路径流模拟配水作为进水,研究牡蛎壳作为填料对青岛市城市径流常见污染物氮磷及COD的处理效果,并对各污染物去除机理进行探讨。结果表明:3种牡蛎壳填料的生物滞留设施对总磷的去除效果最好,在进水磷浓度为0.57～1.83 mg/L条件下,无淹没区装置平均去除率为96.12%,存在淹没区的装置平均去除率为91.02%。养殖牡蛎壳与海滩牡蛎壳对磷的去除效果并无明显差异,淹没区不利于磷的去除。在前期进水过程中(前5次进水)3个模拟装置氨氮(NH_4~+)的出水浓度高于进水浓度,延长落干期后,装置的NH_4~+去除率均上升,B柱NH_4~+平均去除率(58.83%)相对于A柱(48.77%)及C柱(53.06%)更高,有无淹没区对NH_4~+去除并无明显影响。由于填料中有机物的渗沥,首次进水出现严重COD淋出,在随后的进水过程中,COD去除效果迅速上升并稳定,3个模拟柱去除率分别为50.34%,23.47%和47.75%。由于反硝化作用受阻,对硝氮(NO_3~-)的去除效果不佳。整体看来,养殖牡蛎壳可以应用于青岛市生物滞留设施的填料,为加强滞留设施NO_3~-的去除效果,还需要采用强化脱氮措施。

Effects of Bioretention with Oyster Shell as Filler on Pollutants Removal from Urban Surface Runoff

Selecting oyster shells with the best adsorption performance of phosphorus as the fillers, and three bio-retention simulation devices (column A:aquaculture oyster shell; column B:beach oyster shell; column C:aquaculture oyster shell with submergence area) were constructed in the laboratory. The effects of oyster shell as fillers on the removal of nitrogen, phosphorus and COD, which were common pollutants in urban runoff in Qingdao, were studied by using road runoff simulation as inflow, and the removal mechanism of pollutants was discussed. The results showed that the removal efficiency of total phosphorus was the best in three kinds of biological detention devices filled with oyster shell. Under the condition of influent phosphorus concentration of 0.57~1.83 mg/L, the average removal rates of the unsubmerged area and the submerged area were 96.12% and 91.02%, respectively. There was no significant difference in the phosphorus removal efficiency between aquaculture oyster shell and beach oyster shell, and the submergence area was not conducive to phosphorus removal. The effluent concentration of ammonia nitrogen (NH₄⁺) in the three simulation devices was higher than the influent concentration in the first five influents. Whereas, after extending the drying period, the NH₄⁺ removal rate of the devices all increased, and the average NH₄⁺ removal rate of B column (58.83%) was greater than that of A column (48.77%) and C column (53.06%), and the submergence area had no obvious effect on NH₄⁺ removal. Due to the leachate of organic matter in the filler, serious COD leaching occurred in the first influent. However, the removal efficiency of COD increased rapidly and stabilized in the subsequent influent process, and the removal rates of three columns were 50.34%, 23.47% and 47.75%, respectively. Because of the inhibition of denitrification, the removal efficiency of nitrate nitrogen (NO₃^-) was not good. Overall, the oyster shell could be used as filler in Qingdao biological detention facilities. In order to enhance the removal efficiency of NO₃ ^- in the detention facilities, it was necessary to adopt intensified nitrogen removal measures.