Plant capacity affects some basic indices of treated water quality: multivariate statistical analysis of drinking water treatment plants in Japan

Abstract

The quality of treated water produced by a drinking water treatment plant (DWTP) is affected by many factors. Relative impacts of various factors that affect the following treated water quality indices—turbidity, color, aluminum concentration and aggregate organic constituents—were investigated. Multivariate statistical analysis based on Hayashi's Quantification Theory Type 1 was performed on a dataset comprised of statistics on raw and treated water quality collected from thousands of DWTPs throughout Japan. Explanatory factors were the source of the raw water, water treatment process employed, plant capacity, total plant capacity of the water supplier (TCWS), raw water quality and pH of treated water. The statistical analyses mainly revealed that not only did obvious factors such as raw water quality affect treated water quality, but also more obscure factors such as plant capacity and TCWS. The results also imply that the larger the water supplier a DWTP of a given size belongs to, the higher the quality of treated water will be.