To develop a method for screening ageing of water supply systems by analysing the supplied water's quality, water samples were collected from a water treatment plant, a delivery pump station, two distribution reservoirs and two feed pipes along a water pipe system. Principal component analysis of the water was conducted. In the first principal component, many elements exhibited high factor loadings, whereas the major contributor for the second principal component was iron (Fe). The unlined steel pipe, which was beyond its working lifetime, had a significantly high Fe content in suspended solids. X-ray absorption fine structure (XAFS) analysis showed differences in the abundance ratios of Fe3O4 and α-FeOOH among the sampling points. It was concluded that the concentration and speciation of Fe in supplied water can be a useful index for detecting the ageing of pipes.
To investigate the sources of suspended solids in lined water pipes and polyvinyl chloride pipes, the interior of the water pipes was observed, and the composition of surface-attached materials and corrosion as candidate matter and suspended solids were analyzed. As a result of the observation of the interior of lined water pipes using an underwater camera, brown surface-attached materials were noticed and corrosion was often observed in the seam joints of pipes. As a result of the analysis, the surface-attached materials and corrosion surfaces were found to have a wide variety of elements besides O, Al, Si, Mn and Fe. However, the component in the interior portion of corrosion was chiefl y iron oxide. The concentration and composition of three particle sizes ≤25 μm, 25-97 μm, ≥97 μm shows that the particles smaller than 25 μm had the highest total element concentration. This indicates that the suspended solids were concentrated on this particle size range both in number and in weight. The common feature was seen between the surface-attached material and corrosion surfaces and suspended solids was the high content rate of Al and Fe although they were of different origins.
Yellow and red metal oxides are commonly found on deteriorated water pipes and it has been reported that their main component is iron. X-ray absorption fine structure (XAFS) spectroscopy is an effective method which can be used to measure the chemical form of metals. However, when the iron concentration in water samples is extremely low, XAFS measurement and analysis can be difficult due to so much noise in the spectra. In this study, we examined various conditions related to XAFS measurements to analyze the chemical form of iron in water taken from water pipes. To optimize the XAFS measurement conditions, the energy range in pattern fitting was set at 7,100–7,140 eV. Piling up multiple pieces of filter paper was effective for improving the accuracy in the analysis of the XAFS spectra. The XAFS measurement of actual water samples was conducted and a low R factor was obtained from pattern fitting analysis. Differences were observed in the XAFS spectra depending on the chemical form of iron. These results showed that the chemical form of the iron of the actual water samples taken from the water pipes was able to be detected from the XAFS measurement.
懸濁物質は水道水質障害を招く場合があるため,配水管路における挙動の知見を得ることが重要である.本研究で は,わが国で多く使われているモルタルライニング管の管路にみられる懸濁物質の特徴を解析するとともに,その数 が懸濁態元素濃度と同様の挙動を示すことが報告されている細菌について存在状況を調査した. 懸濁態元素濃度を定 量し主成分分 析により解析すると,第一主成分は Al,Ca と強い相関を示す因子でありモルタルの影響を示している と考えられた.すなわち, ライニングのモルタルに由来する Al や Ca を含む粒子の水中への混入が懸濁物質の組成へ の影響要因となっていることが示された.また,既報におけるキノンプロファイル分析に基づく細菌数の推定では, 水道水質基準を上回ると報告されていたが,全ての地点で一般細菌はほとんど検出されず,死菌か標準寒天培地では 培養できない細菌であると考えられた. Key Word : water distribution pipe, suspended solid, chemical analysis, bacteria
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