| Summary: | 碩士 === 中興大學 === 水土保持學系所 === 98 === Abstract
In order to figure out the feasibility to re-clarify the “Tripartite Composition Livestock Wastewater Treatment Point Pollution” by artificial wetland system, the research had conducted the whole process through a period of time, since December 2008 to August 2009. The water was sampled from a specific ranch which is located in Miaoli county and then clarifying water circularly and systematically by using soil and water conservation facilities, such as Flood Detention Pond ( area A and B), Farming Pond(area C), Gravel and Grassed Waterways(area D). These areas differ from their various dimensions and aquatic plants grow up rely on them. Water samples in each of area were collected under different climatic conditions, namely torrential rain (150mm and above per day), heavy rain (50-130mm per day), and light rain (50mm and below per day). Point contaminant removing efficiency was calculated for each operation of natural clarifying mechanism. RPI (River Pollution Index) were also calculated for the waste water in order to evaluate the degree of pollution. The results were compared with the livestock wastewater release standard.
Results of this research indicated that, livestock waste contaminant in the water was apparently decreased after going through the natural clarifying system. First, for BOD, system achieved the best performance (93.42%) during the heavy rain period, but performed worst during a torrential rain. Second, the removing efficiency of total phosphorous, ammonia nitrogen, and suspended solids, performed best under light rain ( 80.59%, 98.35%, and 99.03%), and worst under heavy and torrential rain (30.24%, 1.55%, and 69.61%). For DO, the increase rate was highest during the light rain (77.27%), and lowest during the heavy rain (33.33%).
Contamination of water from area B to area D was affected by the extent of rainfall. During the light rain period, natural clarifying mechanism was not activated owing to insufficient rainfall. RPI tended to rise because contaminant such as ammonia nitrogen and suspended solids was not diluted and gradually accumulated in water. Suggestion from The research suggested that, the natural clarifying system should be opened only limited to area A during the light rain period. By doing so, contaminant accumulation and double-contaminated situation would avoid. Natural clarifying mechanism usually works well during the heavy rainfall period. It is encouraged to open the whole clarifying system. In contrast, natural clarifying system is strongly urged to be closed during a torrential rain (especially with extraordinary rainfall or typhoon).
Statistics based on RPI classification indicated that contaminated index went down. We can conclude that natural clarifying mechanism does not burden or deteriorate the existing contamination. Related data of biological oxygen demand and suspended solids respecting to livestock wastewater release standard showed 70.6% and 99% rate of descent respectly.
Key word: Soil and water conservation facilities, Rainfall, Point contaminant removing efficiency, Deliver rate.
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