Research on treatment efficiency of deep sequence constructed wetlands

According to the problems that traditional constructed wetlands have low nitrogen removal performance and large areas, deep sequence constructed wetlands(DSCW) is proposed and the influences of depth of wetland, filler particle size and operational states of DSCW on treatment efficiency are investigated. The experimental results show that when the depth of wetland is increased from 0.5 m to 2 m, it has no significant influent on its treatment efficiency. The running condition has influence on its treatment efficiency. When the water temperature is 20~25 ℃ and operating condition of DSCW is inlet water 8 min-reaction 12 h-outlet water 8 min-idle 12 h, the removal rate of COD, NH+4-N, TN, PO3-4-P is 83.8%, 54.1%, 48.1%and 63.9% respectively by DSCW with the depth of 2 m. The area load for COD, TN, PO3-4-P is 128, 17.6, 1.49 g/(m2·d) respectively, raised 2.4 times, 2 times and 1.71 times respectively compared with traditional constructed wetlands. Land occupation for processing 1 m3 wastewater is 1.87 m2, decreasing 3~5 times commendably. Compared to DSCW system of particle size of gravel of 20~30 mm, the removal rate of COD, NH+4-N, TN and PO3-4-P of DSCW system of 5~10 mm is increased by 3.8%, 7.9%, 3.8% and 7% respectively. The filler particle size exhibits some influences on DSCW efficiency.

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