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The purpose of this study is to estimate the real water use for a person per day by analysing water use trend of respective metered data. To investigate the unit amount used and component ratio of residential water usage in households, 146 households nationwide were selected as ‘representative samples’, and each end‐use usage was monitored by actual metering from 2002 to 2006. From the results of analysing the acquired data, it was found that the unit amount used in a household was 165.8 litres per capita day (lpcd). Additionally, the unit amount used consisted of six end‐uses; toilet water was the greatest, at 25% (38.5 lpcd), laundry water represented 20% (30.8 lpcd), kitchen water was 19% (28.4 lpcd), bathtub water was 16% (24.7 lpcd), washbowl water was 10% (15.4 lpcd) and miscellaneous use of water represented 9% (13.5%). Comparing the unit amount used according to housing type, 141 lpcd was shown in the case of single houses, and 155 and 159 lpcd were derived in the cases of multi‐unit houses and apartments, respectively. Moreover, the proportions of the aged (50 and over) among the total number of members in single, multihouse and apartment houses were 68.2, 38.1 and 32.4%, respectively. In addition, comparing the amount used and the component ratio among United Kingdom, United States and Korea, the end‐use amount and component ratio in Korea are similar to those in the United States. The total amount of water use in the United Kingdom was less than that in both Korea and the United States.

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This study was conducted to suggest the hydraulic modification for improving evenness of inlet flow distribution into the manifold pipe having a structure in which the treated water flows in parallel arranged membrane modules using CFD (Computational Fluid Dynamics) simulation and experiment. From a result of CFD simulation, it was confirmed that the standard deviation of the inlet flows into each membrane module from the manifold pipe was reduced by about 76% by installing other orifice pipe inside header pipe (double piping header). In addition, the experimental results showed that the coefficient of variation was reduced by 50% in the case of double piping header compared to the case of single piping header. Consequently, the design concept of doubling header pipe with rough internal pipe is much effective to improve the evenness of the flow distribution rate in parallel arranged membrane modules.

In order to investigate the effect of mixer shape and mixing intensity on hydraulic turbulence and velocity field in a rapid mixer, and relate the results of the investigation to the performance of the rapid mixer with respect to coagulant dispersion and turbidity removal, this study conducted wet tests, CFD simulation and PIV analysis, using three different shapes of jar: a circular jar with squared baffles, a circular jar without baffles and a Hudson jar. From the results of the wet tests, it was observed that the performance of rapid mixing in the circular jar without baffles was better than in the other shapes of jar. Also, the shape of jar is found to be a factor affecting the performance of the rapid mixer and ultimately the efficiency of coagulation. The results of CFD simulation and PIV analysis confirmed this by showing that, since it forms moderate turbulence throughout the jar and minimizes localized dead zones, the circular jar without baffles produced the best mixing conditions among the jars. From all these results, this study concludes that turbulent fluid conditions in a rapid mixer, including distribution of turbulence and formation of dead zones, are important factors in determining performance of the rapid mixer. Furthermore, it is suggested that mixing intensity and mixer shape are determined considering those fluid conditions.

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Water service pipes made of galvanized steel were assessed by direct diagnosis according to major water basins, age of pipe, and their diameters. The tubercle growth and the hydraulic cross sectional area reduction rates from examination with the visual assessment showed that there was little difference among main water basins. However, comparing the results showed that their rates depended on the age of pipe indicating that as ages increase, their rates tend to decrease. Also, in the case of over 40 mm diameter, those rates tend to be higher than the case of less than 40 mm diameter. From the results of physical properties analysis, even though most of the sampled pipes satisfied Korea Standards (KS) of tensile strength and chemical composition, 90% of the sampled galvanized steel pipes could not satisfy KS of elongation. It could be thought that elongation was seriously effected by pipe deterioration in the view of physical properties and chemical compositions. In addition, the results of scale composition analysis revealed that the component ratio of Fe was highest, whose percentage was from 54.3 , 69.8%, and then that of Zn was 0.09 , 6.34%. In comparing corrosion rates on three water basins, the maximum corrosion rates of Nakdong-River basin was 0.064 mm/year (mmpy), higher than those of other basins. Also, the diameters of the sampled galvanized steel pipes increased the corrosion rates.