The Risk of Aluminum in Treated Water Containing Aluminum Sulphate

Water treatment using aluminum sulphate is a common process in water purification, primarily aimed at removing unwanted microorganisms. These inorganic coagulants are partially hydrolyzed salts, and their dissolution in water is highly pH-dependent. However, residual aluminum remains a concern as it often exceeds WHO standards. This study investigates the residual aluminum levels in treated water from a treatment plant, which were found to be 210 μg/L for an average dose of 40 mg/L of aluminum sulphate, surpassing the WHO's recommended maximum of 200 μg/L. Laboratory trials were conducted with flocculators to mimic treatment plant conditions, revealing a residual aluminum level of 182 mg/L, 13.33% less than WHO standards. An additional experiment employing a 40 mg/L alum dose and 3 mg/L of bentonite from M'Zila (Algeria) as an adjuvant resulted in a 20.48% reduction in residual aluminum, bringing it below recommended levels. The dry residues were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) to explore the aluminum spectra, while the raw bentonite was characterized through X-ray fluorescence to determine its elemental composition.