Purification effect and pollutant removal mechanism of vertical subsurface-flow wetland for rural sewage treatment under different aeration strategies:
摘要
In this study, a composite wetland was constructed by introducing the efficient phosphorus adsorbent and activated sludge into the traditional wetland. At the same time, the aeration strategy was optimized by comparing the purification efficacy of various wetlands on actual rural sewage under different aeration strategies. The results of a 90-day experiment showed that nitrification and aerobic phosphorus uptake by phosphorus-accumulating organisms (PAOs) were inhibited at low aeration/non-aeration ratio and low air-water ratio. In contrast, at high aeration/non-aeration ratio and high air-water ratio, denitrification and anaerobic phosphorus release by PAOs were hindered. In addition, the hydraulic disturbance caused by excessive aeration accelerated biofilm detachment. The optimal aeration strategy was determined to be the aeration/non-aeration ratio of 2 h: 4 h, and the air-water ratio of 6: 1. Under the optimal aeration conditions, the vertical direction of the composite wetland formed the differences in oxygen distribution, inducing the proliferation of functional microorganisms such as Proteus Hauser, Thauera, Nitrobacter, Candidatus Paracaedibacter and Brevundimonas, which enhanced the simultaneous biological removal of multiple pollutants within the composite wetland. The average removal efficiencies for turbidity, TN, NH4⁺-N, TP, PO43⁻-P, TCOD, and TOC under the optimal aeration strategy reached 89.22%, 80.21%, 94.62%, 92.08%, 94.66%, 79.76%, and 82.23% respectively. Correspondingly, the wetland effluent consistently met the Class 1 A standard (GB18918-2002). Therefore, this study is anticipated to provide valuable reference and guidance for the scattered sewage treatment in rural area and stable operation of wetlands.