2차처리장 방류수 정화 부들습지셀의 초기운영단계 질산성질소 제거

Abstract

Nitrate removal was examined from May to October 2003 of a surface flow treatment wetla- nd cell, which was a part of a treatment wetland system composed of four wetland cells and a dist- ribution pond. The system was established on rice paddy near the Kohung Estuarine Lake located in the southern part of the Korean Peninsula. Effluent from a secondary-level night soil treatment plant was funn- eled into the system. The investigated cell, 87 m in length and 14 m in width, was created in April 2003. An open water was designed at its center, which was equivalent to 10 percent of its total area. Cattails (Typha angustifolia) were transplanted from natural wetlands into the cell and their stems were cut at about 40 cm height from their bottom ends. Average 25.0 m3/day of effluent from the treatment plant was funn- eled into the cell by gravity flow and average 24.1 m3/day of its treated effluent was discharged into the Sinyang Stream flowing into the lake. Its water depth was maintained about 0.2 m and its hydraulic detent- ion time averaged 5.2 days. Average height of the cattail stems was 42.5 cm in May 2003 and 117.7 cm in September 2003. The number of stems averaged 9.5 stems/m2 in May 2003 and 16.4 stems/m2 in September 2003. The growth of cattails was good. Temperature of influent and effluent averaged 25.9 and 26.7℃, respectively. NO3-N loading rate of influent and effluent averaged 176.67 and 88.09 mg/m2ㆍday, respectively. Removal of NO3-N averaged 89.58 mg/m2ㆍday and its removal rate by mass was about 50%. Considering its initial operating stage in which cattail rhizomes and litter layer on the bottom were not fully established, the NO3-N removal rate of the cell was rather good.