Comparative Assessment of Chloride Concentrations in Tap Water and Freshwater Bodies in Derbyshire, United Kingdom Using Ion Chromatography

Abstract

Chloride is a common inorganic anion in natural and treated waters and may indicate influences from geological processes and human activities. This study compared chloride concentrations in tap water and freshwater bodies at ten paired locations across Derbyshire, United Kingdom, using ion chromatography. Water temperature, air temperature, electrical conductivity and pH were also measured to characterise the sampled waters. Descriptive statistics summarised the observations, while the Shapiro–Wilk test assessed data normality and the Mann–Whitney U test evaluated differences between the two water categories. Mean chloride concentrations were 19.3 mg/L in freshwater and 19.1 mg/L in tap water. Freshwater concentrations ranged from 11.1 to 33.8 mg/L, whereas tap-water concentrations ranged from 9.6 to 36.4 mg/L. All measured chloride concentrations were substantially below the 250 mg/L acceptability benchmark applied in the study. Water temperature ranged from 12.4 to 18.1°C, air temperature from 17.5 to 32.5°C, electrical conductivity from 255 to 551 µS cm⁻¹ and pH from 6.8 to 8.0. The statistical analysis indicated no significant overall difference in chloride concentrations between freshwater and tap water (p > 0.05), although site-specific variation was observed. The findings provide baseline information for future environmental monitoring programmes and support continued surveillance of chloride concentrations to ensure sustainable management of freshwater resources.