植物-生物膜氧化沟中不同形态铁及根表铁膜与除磷的关系

针对传统氧化沟投资建造成本高,脱氮除磷效率较差的问题,在污染现场建设植物-生物膜氧化沟,通过室内曝气模拟试验和室外小试试验,研究了总磷(total phosphorus,TP)的去除与铁和曝气时间的关系以及美人蕉、茭白根表铁氧化物胶膜对污水中磷的吸附去除情况,了解不同形态铁和植物根表铁膜与除磷的关系。研究结果表明:不同形态铁及植物根表铁膜与污水中磷的去除密切相关。随着曝气时间的延长,污水中铁减少量呈现出逐级递增的趋势,当曝气时间为12 h时,铁减少量达到0.45 mg/L以上,铁减少量与曝气时间之间的相关性达到极显著水平(P0.01),而TP的减少量与铁减少量之间也呈现极显著的相关性(P0.01)。小试试验中,3个系统出水磷含量及全Fe、Fe2+含量均有所降低,降低量表现出茭白系统美人蕉系统对照系统的规律;同时,美人蕉、茭白根表铁氧化物的沉积量随运行时间的延长而增加,且茭白根表铁膜数量及其吸附磷的数量均要高于美人蕉。该研究为植物-生物膜氧化沟工艺的改进及应用和推广提供了理论和实践依据。

Relation of ferrum in different forms and ferric iron plaque of plant root with phosphorus removal in plant-biofilm oxide ditch

Abstract: Oxide ditch technology for wastewater treatment has been developed recently with such advantages as simple treatment flow, high stability, low capital construction investment and low operation cost. But the conventional oxide ditch still has many shortcomings as a type of deformation technology of activated sludge processes. For example sludge is easily suspending and expanding in the system, and single technology can bring lower removal efficiency on nitrogen and phosphorus (P). In order to solve these problems, a new type of oxidation ditch treatment system, plant-biofilm oxide ditch was developed in our laboratory, which combined the phytoremediation and biofilm technology with the oxidation ditch system and was applied to lake water surface for in-situ wastewater treatment. The simulation test and the plant-biofilm oxidation ditch small-scale experiment were carried out, and the removal of total phosphorus (TP), and the relationship between ferrum and aeration time, as well as the P absorption and removal by the ferric iron (Fe) plaque on the root surface of Canna generalis and Zizania cadaciflora in wastewater were investigated, in order to figure out the correlation between Fe in different forms and ferric iron plaque of plant root and P removal. Results showed that there was a close relationship between P removal and aerated time, Fe in different forms, ferric iron plaque of plant root in wastewater. The Fe3+ concentration of discharge water went up, but the P concentration descended after wastewater was treated by oxidation ditch system. When the aerated time was 1, 2, 4, 8, 12 and 24 h, the reduced amount of Fe increased by degrees on the whole with the extension of aeration time. When aerated for 12 h, the decline extent of Fe concentration in wastewater was very high, and the reduced amount of Fe was up to 0.45 mg/L. After the aerated time preponderated over 12 h, the decline extent of Fe concentration in wastewater was decreased. The relevance between the reduced amount of Fe and the aeration time reached a very significant level (P<0.01), while the correlation between the reduced amount of TP and the reduced amount of Fe also had a very significant correlation (P<0.01). In the small-scale test, the concentrations of P, Fe and Fe2+ in the effluent of 3 systems all decreased to some extent and the reduced amounts exhibited as Zizania cadaciflora system > Canna generalissy stem > control system. Additionally, the ferric iron plaque of Canna and Zizania root surface could absorb P. The deposition of iron oxide on the root surface of Canna generalis and Zizania cadaciflora increased with the operation time increasing, and the amounts of iron plaque and absorbed P on Zizania cadaciflora root surface both exceeded that of Canna generalis. The amounts of ferric iron plaque were up to 3096 and 1595 mg/kg respectively for Zizania cadaciflora and Canna generalis. The correlation analysis result showed that the relationship between P and ferric iron plaque on enrichment root surface had positive correlation (P<0.05). The experimental research provides theoretic and practical basis for the improvement, further application and generalization of plant-biofilm oxide ditch.