Assessment of domestic water quality of households and schools in Nabatieh, Lebanon, and development of a new spectrophotometric method for the detection of Entamoeba spp. In tap water

Polluted resources of potable water are daily used for different purposes in Lebanon. The optical microscopy is the traditional method used for the detection of Entamoeba spp. in water despite its weak sensitivity. We aimed to characterize domestic water at Nabatieh district, South Lebanon, and to develop a simple method for Entamoeba spp. detection. A total of 70 water samples were collected from houses and schools and analyzed for physical (pH, total dissolved solids and temperature), chemical (nitrate, phosphate and sulfate) and bacterial (total and fecal coliforms) parameters. The contamination by Entamoeba spp. was examined using microscopy, then a spectrophotometric wavelength scan was recorded for 50 samples in order to determine the common peak between positive samples. High phosphate levels were detected in all the samples, with important bacterial and parasitological contaminations. The spectrophotometric analyses showed a peak repetition at the wavelength of 696 nm in the spectrum of the majority of positive samples. The number of cysts was significantly correlated to optical densities at 696 nm (R = 0.9087; p-value<0.0001). The regression analysis showed that the OD696 could statistically predict the concentration (F (1,48) = 267.02, p-value <0.001). In conclusion, potable water parameters at Nabatieh district did not meet the national and international guidelines of safe drinking water, and the detection of Entamoeba spp. cysts in potable water can be performed using a rapid spectrophotometric analysis, by the determination of the optical density at 696 nm and the application of a specific equation.