Assessment of the Efficiency of Commercial Reverse Osmosis Plants in Reducing Salts and Dissolved Constituents and Classifying Treated Water Quality Using the Water Quality Index in Bir al-Ashhab, Libya

Abstract

This study aimed to evaluate selected physicochemical characteristics of drinking water produced by commercial reverse osmosis (RO) plants in the Bir Al-Ashhab area, Libya; assess the efficiency of these plants in reducing salinity and dissolved constituents; and classify the quality of the treated water using the Water Quality Index (WQI). Six commercial plants were included in the study. Samples of raw groundwater and treated water were collected, with three replicates obtained for each sample. Twelve physicochemical parameters were measured: pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness (TH), sodium, calcium, magnesium, potassium, chloride, sulfate, nitrate, and bicarbonate. Removal efficiency and WQI values were also calculated. The data were analyzed using the paired-samples t-test and one-way analysis of variance at a significance level of 0.05. The results showed significant reductions in all physicochemical parameters after treatment compared with the raw groundwater (p < 0.001). The plants demonstrated high efficiency in reducing salinity and removing dissolved constituents, with overall removal efficiencies ranging from 64% to 99%, although performance varied among the plants. The pH values remained within the acceptable range for drinking water. WQI values ranged from 10 to 26; the water produced by four plants, representing 66.7% of the studied plants, was classified as excellent, whereas the water produced by two plants, representing 33.3%, was classified as good. These findings confirm the effectiveness of the investigated reverse osmosis plants in reducing salinity and improving water quality. However, periodic monitoring of the mineral content of the treated water is necessary, and remineralization should be considered when required. The study was limited to a single sampling period and to physicochemical parameters.