報告書番号

U01067

タイトル（和文）

植生を用いた湖水直接浄化技術 ― 手賀沼における3方式の処理特性の比較 ―

タイトル（英文）

Lake water purification technique with Plant Bed Filter Systems: Evaluation of treating efficieny in Lake Teganuma

概要 （図表や脚注は「報告書全文」に掲載しております）

手賀沼湖水を原水に用いて，処理方式の異なる3種類の植生浄化水路について浄化特性を比較した。礫間接触酸化水路では1割未満であった全リン・全窒素除去率が，植生を用いた水路では3割程度みられた。植生による浄化を効果的におこなうためには，生長速度の大きな種を選択するのが有効であった。いずれの植生水路においても，植物の刈取りによって除去される窒素・リンは，植生水路で除去される窒素・リンの1～3割程度であった。流入流量を増やすと，植生水路で除去される窒素・リンも増えた。しかし，増加分は主に汚泥として堆積した窒素・リンであり，植物体への固定量に限界があることが明らかになった。

概要 （英文）

Treating efficiency of 3 different Plant Bed Filter Systems (PBFS) were investigated at a eutrophic lake, Lake Teganuma. The removal rates of TP and TN in PBFS were about 30%, though those in rock bed contact-purification systems were below 10%. It is more effective for water purification in PBFS to select plants that have high growth rate. The N and P amounts accumulated as plant biomass were below 30% of total amounts of removal N and P in PBFS. Especially when treating on high hydraulic load rate, N and P amounts in plant biomass were much smaller. The removal efficiencies of SS and COD in the rock bed contact-purification systems are higher than those in PBFS. But the rock bed contact-purification systems have lower removal efficiency of nutrients, such as N, so that phytoplankton re-increase in lake water is suggested. On the other hand, PBFS are more effective system for the removal of N from lake water. In summer, N is the main growth-limiting factor of blue green algae in Lake Teganuma. It is considered that PBFS are effective for purification of Lake Teganuma water.

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