HAMASAKI TATSUHIDE

We have worked on the development of a biological filtration system utilizing indigenous bacteria to remove arsenite, arsenate, iron, manganese and ammonia from groundwater. Among various bacteria, iron bacteria (bacterial species that biologically oxidize dissolved Fe and/or Mn, and deposit them as oxides) together with nitrifiers play the most important role in our system. This report is a brief summary of our pilot study (started in 2004), treating groundwater by the biological filtration. The purpose is to determine the optimal operating conditions to achieve the most efficient removal of arsenic.

The purpose of this study is to remove pollution matter such as organic matter and nutrients from sewage using a bio film method with string media and then to recover the phosphorus from the used string media. The activated sludge method is the most popular method for sewage treatment. However this method produces a lot of excess sludge and increases the costs of the sewage treatment facility. The results of our experiments on removal of organic matter show that a bio film method using string bio film media can remove organic matters in sewage. Sewage also contains high concentrations of phosphorus, which should be removed to improve the treated water quality but is an important nutrient in agriculture. Since phosphorous becomes depleted in soil by agricultural activity, it must be added regularly to maintain soil fertility. This makes recovered phosphorous a valuable by-product of sewage treatment. This study therefore also evaluated phosphorus recovery from the used string media with hot water and confirmed the possibility of phosphorous recovery by that method.

In this study, we investigated the behavior of estrogens in the rhizosphere of white clover (Trifolium repens, clover hereafter) with two different pot tests, using soil and agar as growth media. In a pot test using agar spiked with estrogen, the estrogen concentration in the agar with clover decreased to non-detectable levels within one month, while in the agar without clover, 60% of initially added estrogen remained after one month. The half-lives of estrone (E1) and 17 -estradiol (E2) in the agar with clover were 2.4-3.8 and 13.2 d, respectively. The dissipation of E1 followed first-order rate law, while that of E2 fitted a zero-order reaction, indicating that they had different mechanisms of dissipation from agar. In the soil pot test, the behavior of E1 and E2 was not influenced by clover. An initial rapid decrease in the amount of estrogen extracted by methanol/acetic acid was followed by persistence for 1-3 months, regardless of presence of clover. Moreover, in three weeks E1 and E2 were only partly degraded by microbes extracted from the soil used in the pot test. In this study, abiotic degradation of estrogens and sorption of estrogen to soil, rather than the effects of soil microbes and clover, contributed to the initial rapid dissipation of estrogens in the soil. However, the results of the agar pot test suggested that vegetation such as clover may significantly contribute to removal of estrogens when estrogens in aqueous phase are discharged with surface runoff and preferential flow after heavy rain in agricultural fields, or when present in soils with low estrogen sorptivity.

加熱温度による吸着性の変化とともに、それぞれの素材の組成を詳細に分析し、吸着性と素材組成の関係について調べた。

特に園芸用赤玉土を製造する際に発生する微粉状の土を造粒したものを土壌浸透ろ過材として用いたパイロット試験を行って、造粒土の浄化性能および寿命について考察した。

高速土壌浸透法について、今までの研究成果をまとめ、高度排水処理システムの設計指針を作成した。

Dioxin pollution of aquatic sediments has been one of the important environmental problems in Japan. Grain size distribution and organic constituents may play important roles in dioxins contents in sediments, which have not been well investigated. This paper aims to quantify dioxins (PCDDs/Fs and coPCBs) in sieved surface sediment fractions obtained from Kizu and Sumiyoshi Rivers in Osaka, Japan. The samples were prepared and analyzed following the 'Manual of the Survey and Measurement of Dioxins in Sediment' (Environment Agency of Japan, 2000). The results showed that TEO concentrations of dioxins increased with decreasing grain size in sediment fractions. Sediment fractions with less than 20 mu m grain size showed the highest dioxin contents. Dioxins with five and six chlorine atoms dominated other congeners in less than 20 mu m fractions. The dioxin TEQ concentrations increased with total organic carbon (TOC), total carbon (TC), ignition loss (IL), total sulphur and nitrogen contents in the sediment fractions. Thus, reporting dioxin contents in sediments without considering grain size distribution may be erroneous and conventional, sedimentation and separation techniques might not be useful for treating contaminated sediments. This information can be useful for effective remediation of dioxin-contaminated sediments.

土壌浸透法の歴史と種類、現在の研究動向についてとりまとめた。

造粒と加熱処理を施したろ材を用いた高速土壌浸透システムを開発した。この方法の特徴や除去特性を明らかにしている。

新たに開発した浄化素材で、室内吸着試験およびカラム通水試験、ならびに現地通水試験を実施し、その結果を相互比較した。

これまでの研究によって、難分解性有機物およびリン酸の吸着除去につき有望な材料をいくつか見出すことができた。本研究では、見出した吸着材について、相異なる条件（液相のｐH、被吸着物質濃度オーダー、加熱、団粒）下で吸着等温式を求めた。

土壌浸透法の浄化素材として有望と判断した材料を加熱処理した場合のリン酸とフルボ酸の吸着能の変動を確認し、土壌浸透法をシステムとして構築するための基礎データを取得した。

溶解性リンならびに腐植質有機物の吸着性能の高い土壌浸透浄化素材を探索・選定するため、日本各地の土壌・鉱物・堆積物・堆肥・各種汚泥等の約40種についてバッチ吸着試験を実施した。リンおよび腐植質有機物の吸着がともに高い材料はアパタイト・褐鉄鉱・黒ボク土等であった。

天然素材を素材とし、形状を円筒型にした円筒型ろ布を用いて、環境中の浮遊物質のろ過と濃縮の特性についてまとめたものである。この円筒型ろ布を用いた簡易な濃縮方法は、今までに研究されていない方法である。本論文では、実験的にその分離・濃縮様状を明らかにした。