藻床淨水技術應用於水中磷之去除研究

Abstract

附生藻類具有高適應性，可附著在水域任何物體的表面上。即使群落組成容易受到流況、溫度、光照、營養鹽等條件影響而發生改變，附生藻類仍能繼續在原棲地生存繁衍。台灣地區生態工程之型態多屬於淨化高污染水質之人工濕地，然而藻床淨水技術所能應用之層面則更可從畜牧廢水延伸至低污染環境。近年來，許多研究人員利用附生藻類進行水質改善的實驗，並提出令人注目的研究報告。國內水庫優養化現象日益嚴重，然而目前僅有少數人工濕地生態工法應用於集水區溪流之水質淨化。本研究目的即透過翡翠水庫集水區內金瓜寮溪附生藻類進行生長箱實驗以及棲地環境調查，分析附生藻類將水中磷濃度降低的最低極限和應用藻床淨水技術於野外溪流之合適地點。 室內實驗在半封閉狀態下，以批次方式，即在實驗開始進行後便不再添加任何營養鹽。實驗初始正磷酸鹽濃度為4~136 μg/L，總磷濃度為27~168 μg/L。實驗結果顯示，當初始的正磷酸鹽磷濃度在35 μg/L以上，附生藻類族群以細絲型綠藻佔優勢。平均之藻乾重生產量為0.05~0.16 g/m2-day，其有機質重量為0.02~0.11 g/m2-day。在此情況下，藻類可使水中磷酸鹽降低至1~2 μg/L，總磷濃度亦不超過10 μg/L。整體實驗中，水體總磷去除百分比最高為95.17 ％。 進行野外調查時，沿金瓜寮溪設置28個採樣點，經過12日培養將附生藻類取回，分析藻類生物量與磷元素含量，並同時進行水質分析與棲地物理因子調查。各採樣點水質與物理環境共22個項目調查所得數據，配合生物指標：藻類磷吸收量，進行主成分分析，取得金瓜寮溪流域的6個主成分因子：鹽分因子、營養因子、溶氧因子、濁度因子、硫酸鹽因子、背景因子。根據第1、2主成份得點圖分析，第4、20、23採樣點為高營養因子區域。其中，第4採樣點為主要點源污染，最適合施用藻床淨水技術。由以上結果可知附生藻類具有降低營養鹽至貧養程度的能力，如在集水區溪流施用附生藻，可有效降低水庫優養化的發生。

With high adaptability, periphyton could adhere to any surface in the water. Although periphytic microcommunities are subject to various environmental factors, including current, temperature, light intensity, and nutrient, the flora remains thriving at habitat. Artificial wetlands are the commonest ecological engineering for highly polluted wastewater treatment in Taiwan. However, algal turf scrubber method could serve more wildly ranges from livestock industrial one to low contaminated water. Researches have been done on the algae-water treatment experiment with significant results in recent years. Eutrophication in water reservoir has become more and more severe in Taiwan. However, only few artificial wetlands have been built to clean up stream water in the watershed. The purpose of this study was to determine the degree of phosphorus removal by the periphyton incubated in a growth chamber and the proper sites to apply algal turf scrubber method at Jingualiao Creek in Feitsui Reservoir watershed. The laboratory experiment was conducted under semi-enclosed conditions with no further addition of nutrients except initial addition. The onset of initial phosphate concentration ranged from 4 to 136 μg/L, with total phosphorus concentration between 27 and 168 μg/L. After an incubation of 26 days, periphyton community was dominated by filamentous green algae when the initial phosphate concentration was higher than 35 μg/L. The biomass production of periphyton had been as high as 0.05~0.16 g dry weight/m2-day, with ash free dry weight ranging from 0.02~0.11 g/m2-day Under such conditions, phosphate concentration in each culture was reduced to 1~2 μg/L, with total phosphorus concentration lower than 10 μg/L. As a result, the maximum phosphorus removal efficiency has been up to 95.17％. The field research was conducted at Jingualiao Creek in Feitsui Reservoir watershed. After incubated for twelve days, periphyton communities were sampled at 28 sites by artificial substrate and analyzed for biomass and phosphorus content. Water analysis and surveying of habitat physical condition was conducted at the same time. Twenty two environmental variables and bio-index: periphyton phosphorus uptake rate were combined into a data matrix and subjected to the principle component analysis. Six principle components were extracted as salinity factor, nutrient factor, dissolved oxygen factor, turbidity factor, and background factor. With the scatter plot of the first two principle components, the fourth, twentieth, and twenty-third sample site were classified as high nutrient locations. The result suggests that the point source pollution: fourth sample site was the most suitable place to apply algal turf scrubber method because of its high pollution loading. The present study shows that periphyton can remarkably reduce the phosphorus in stream water and thus is able to prevent water reservoirs from eutrophication when it is applied in the watershed.