Analysis on the Cause of Higher Qualified Rate of Terminal Piped-water than Treated Water from Urban Water Supplies in a Province

Objective To explore the cause of higher qualified rate of terminal piped-water than treated water from urban water supplies in a province.

Methods Monitoring the water quality of urban centralized water supplies in a province in 2014. Based on the capacity of water supply, waterworks were divided into three categories: < 10 000 t/day, 10 000~50 000 t/day and ≥50 000 t/day. The qualified rate of treated water and terminal piped-water of each category was calculated.

Results The qualified rates of treated water were lower than those of terminal piped-water before the data was not divided into categories. When samples were divided into three categories according to the capacity of water supply, the qualified rates of treated water were higher than those of terminal piped-water in each category.

Conclusions When comparing the qualified rates of treated water with terminal piped-water, the calculation of results should be based on specific circumstances for classification, to eliminate the possible impact of the uncertainties from wrong sampling proportion.