Chemical, physical and microbiological analyses of different drinking water sources among diverse governorates in Lebanon

The physico-chemical and bacterial properties of the total of collected drinking water samples are shown in Fig. 2. In terms of physical quality, the measured TDS values fell within the safe interval as per the LIBNOR drinking water standards (600 ppm). Regarding chemical quality, the concentrations of nitrate and sulfate in all samples were below the recommended threshold set by LIBNOR (nitrate: 45 mg/L; sulfate: 250 mg/L). However, the reported median of phosphate concentration exceeded the recommended limit (1.35). This data indicates that the overall physico-chemical quality of drinking water is satisfactory, except for phosphate contamination, which is a widespread issue across the country rather than being localized to specific regions.

In general, all the tested microorganisms were identified as contaminants in the drinking water samples when aggregated from various sources. The presence of FC indicates a fecal contamination of water. Otherwise, the Pseudomonas Aeruginosabacteria were identified. Even this minor level of contamination necessitates a rapid intervention to mitigate the health risks it poses to humans, as it can lead to a variety of infections and is a primary cause for sickness in immunocompromised individuals¹⁹.

Physico-chemical and bacterial qualities of drinking water according to their sampling sources

The physical and chemical characteristics of water gathered from diverse origins in Lebanon are illustrated in Fig. 3. Although the TDS, nitrate, and sulfate levels demonstrated satisfactory readings, the phosphate content surpassed the threshold in all drinking water sources (1.35 mg/L). Notably, the maximal concentration was detected in the water sourced from a treatment facility (Fig. 3, d). This finding underscores the critical need to enhance the efficiency and effectiveness of water treatment facilities throughout the country.

The microbial characteristics of water sourced from different locations in Lebanon are illustrated in Fig. 4. The documented findings indicated minimal contaminations of artesian wells, tap water, filtration water stations, potable water and spring water by TC, FC, Pseudomonas Aeruginosa and Streptococcus. Despite the generally low contamination levels, it is crucial for safe drinking water to be devoid of any pathogens. This information suggests a lack of adequate water treatment facilities and highlights the potential risks of consuming untreated tap or spring water by the public. While bottled water exhibited favorable outcomes in terms of TC, FC and Pseudomonas Aeruginosa, the presence of Streptococcusindicates that the sterilization and/or storage procedures may be ineffective or unsafe, respectively. Lately, there has been a rise in the consumption of bottled drinking water under the belief that it is more secure than tap water and can safeguard against waterborne illnesses²⁰. However, our data confirmed that bottled water could be a main contributor to the spread of water-borne diseases.

Comparison of physical parameters of drinking water in different Lebanese governorates

A comparative analysis was conducted among physical, chemical and bacterial parameters of drinking water in different Lebanese regions. The Beqaa governorate was excluded from this analysis due to its small sample size (n = 2). The comparative results of physical data were shown in Fig. 5. Interestingly, significant differences were observed in the conductivity and TDS measurements among the various regions (p < 0.001). Nabatieh exhibited the highest levels of conductivity and TDS, although they remained within the acceptable limits and did not exceed them.

Comparison of chemical parameters of drinking water in different Lebanese governorates

The comparison of the chemical profiles among the four regions is shown in Fig. 6. The results demonstrated significant variations in nitrate, magnesium and calcium concentrations (p < 0.001). The highest levels of contamination were observed in Baalbek-Hermel, followed by Nabatieh. This data should act as a benchmark to evaluate the efficacy of local treatment facilities.

Comparison of drinking water bacterial contaminations between Lebanese governorates

The average contamination levels of TC, FC, Streptococcus and Pseudomonas Aeruginosa in four different governorates are summarized in Fig. 7. A comparison of these outcomes revealed high contamination by TC and low levels of FC without significant variations, suggesting similar contamination levels of these bacteria in all areas. It is important to note that according to the Lebanese recommendations, the presence of these contaminants in drinking water is not permitted, indicating that this water is not safe for human consumption. The contamination of TC could be attributed to contact with soil in wells, springs and streams, while FC is likely originates from fecal materials discharged into rivers.

The presence of Pseudomonas Aeruginosa bacteria was also detected in the drinking water collected from the four governorates. Its prevalence ranged between 5% and 11% across these areas, with the highest percentage recorded in Nabatieh (11%).and Mount Lebanon (11%). A noteworthy significant difference in contamination levels among the examined regions was observed (p < 0.01). Nevertheless, even the small proportion of Pseudomonas Aeruginosa contamination in Baalbek-Hermel, similar to other Lebanese regions, warrants serious consideration. As per national and international guidelines, safe drinking water must be devoid of any pathogens.

Significant differences were noted in streptococcus contamination levels among samples collected from various areas (p < 0.001), with the highest levels found in South Lebanon and Baalbek-Hermel, while the lowest percentage of contaminated samples was observed in Nabatieh. Once again, the assessment of bacterial quality reaffirms that the majority of drinking water sources in various Lebanese governorates are unsuitable for consumption; this underscores the urgency to review and enhance the ineffective treatment procedures used in all examined regions.