Departmental Bulletin Paper 帯水層内の水質混合を抑止する 単孔式二重揚水装置の作製と取水試験

石田, 聡  ,  白旗, 克志  ,  土原, 健雄  ,  吉本, 周平

(1)  , pp.11 - 17 , 2017-03-28 , 国立研究開発法人 農業・食品産業技術総合研究機構 , National Agriculture and Food Research Organization (NARO)
1 本の井戸の任意の深度を空気パッカーで遮断し,パッカーの上下2 深度から同時に揚水することで帯水層内の水質混合を抑止する単孔式二重揚水装置を作製した。この装置を用い,農村工学研究部門内の井戸の地下水面下2m にパッカーを設置して取水試験を行い,揚水中の水位,EC,pH,水温,DO,ORP をパッカー上段・下段それぞれについて測定した。その結果,揚水強度2L/min ではパッカー上段の水位は時間とともに低下した。これに対しパッカー下段の水位は殆ど変化せず,上段の水位変化の影響を受けなかった。また,揚水前のパッカー上段の地下水とパッカー下段の地下水にはEC,pH,DO,ORP それぞれについて差があったが,取水試験中もその差が保たれ,両者が同じ値に近づくことはなかった。これらの結果より,作製した装置により2 深度の地下水を混合させずに別々に揚水できることが示された。
We proposed a device made of air packing and installed as a partition in a borehole. The device had two pumps; one was set above the air packing and the other under it. The use of this air packing made possible the groundwaterpumping from two horizons. The device was set in a borehole with a 100-mm diameter drilled into a field in our laboratory, and then the groundwater was pumped into it. The length of the packing was 1 m, and the packing was set at 2 m below the groundwater table. The groundwater pumping rates of both pumps were 1-2 L/min. EC, pH, temperature, DO and ORP of the pumped groundwater were measured during the pumping. The groundwater level which was measured by a hydraulic pressure sensor at a pumping rate of 2 L/min was found to decrease with time at the upper side of the packing, but it was almost stable at the lower side. The EC of the groundwater drawn above the packing did not fluctuate so much. The difference between the EC of the groundwater above and below the packing remained unchanged; the same tendency was observed in other water quality parameters. These results showed that the groundwater from two horizons could be separately pumped by using this device without negatively affecting water quality.

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