Sustainable Management Strategy for Taiwan's Constructed Wetlands

• Main Authors: Jung-Yi Lai, 賴榮一
• Other Authors: Kenji-Horigome
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/16440516190541356711

博士 === 中原大學 === 設計學博士學位學程 === 105 === Among the water-purification constructed wetlands along various local river basins subsidized by Environmental Protection Administration, Executive Yuan, R.O.C., nine of them are listed on "Important Wetland System" as determined by Construction and Planning Agency, Ministry of the Interior. The Environmental Protection Administration initiated the river clean-up remedies starting in 2002. Because of the slow development of public sewer systems, it decided to assist the local governments in building water purification systems on constructed wetlands along various polluted water sources and river tributaries. Constructed wetlands are a temporary water purification facility to slow down and to control the deterioration of pollution before the sewage treatment rate increases in neighboring areas. As this technology was introduced from developed countries in Europe and the United States to Taiwan, the early constructions were temporary, experimental and exemplary. Since 2003, the author has participated in the general planning of the "Zhudong Highland along the Hsinchu Touchien Riverside" project, which was one of the nine important national wetlands. In order to learn the effects on water purification after the construction of the wetlands, the author conducted the "Investigation and Research of Plant Transitions and Water Purification of Zhudong Highland along Hsinchu Touchien Riverside in the First and Second Stages of the Constructed Wetland Projects" and found positive results on water purification in 2009. In order to investigate the difference before and after starting maintenance management and the performance of water purification of the constructed wetland, the study has been continuously doing maintenance management, vegetation recording and water sampling in the monitoring area of the First and the Second Stages of Hsinchu Touchien Riverside Constructed Wetlands on the base of previous investigation. According to the natural water purification wetland operation guideline written by Environmental Protection Administration during the initial development stage of constructed wetlands, his study has thoroughly interviewed the competent authorities and the maintenance management units of the nine constructed wetlands for their performance since the operation started. Because the nine constructed wetlands locate in different river basins in the north, middle, south and east of Taiwan, the study will also refer to historical evaluation reports and studies of these constructed wetlands. Cross discussions will be conducted regarding common issues faced by constructed wetlands in different areas of Taiwan. Because years of deposit has made the river channel deformed and narrow, the study shows that the water capacities and hydraulic retention times of the First and the Second Stages of Hsinchu Touchien Riverside Constructed Wetlands are significantly different from the conditions when the construction was just completed. Three to seven purifying aquatic plant species have been extinct due to natural evolution and maintenance management. Among all of the water purification process and maintenance management of constructed wetlands, several common problems occur: low suspended solid (SS) removal rate, low biochemical oxygen demand (BOD5) removal rate, instable ammonia-nitrogen (NH3-N) removal rate, surplus or deficiency of aquatic plants, long dredging interval, disposal and coverage difficulties of removed plants at the scene and affected water purification rate by the river’s characteristics in Taiwan. For planning and operation issues, some common problems also occur: wetland site destructed by heavy rainfall, increasing extreme rainfall frequency, innate weakness of constructed wetland building and planting restriction along riverside. In this study, these problems would be individually discussed and recommendations would be given. When water stream which has been treated by a wastewater treatment plant or a gravel purification facility enters the constructed wetland for secondary purification, its RPI index would rise because the constructed wetland is a completely open environment. It is found that the RPI indices of independent gravel purification facilities presently operating in Taiwan are showing better purification results than the ones connected in series. Because the prevalence rate of sewage and the frequency of extreme rainfall are both expected to rise in the future, this study recommends that constructed wetlands shall be introduced into the green infrastructure concept, in order to identify, to reserve and to promote re-building them.