Abstract

Algal control and enhanced removal in drinking waters in Cairo, Egypt: A case study

Author(s): FaridaM.S.E.El-Dars, M.A.M.Abdel Rahman, OlfatM.A.Salem, El-SayedA.Abdel-Aal

Incidents of algal blooms targeting the major water treatment plants within the capital region have been reported by the Egyptian media since 2006. While previous studies focused upon the identification of algal types and its correlation to the disinfection byproducts formed, no correlation between the change in rawwater quality and this phenomenonwas explored. For this purpose, a survey of the Nile water quality parameters at one of the major water intakes at El-Maadi, South of Greater Cairo Urban Region was conducted during the period Dec 2011- Nov 2012. Bench-scale experiments were conducted to evaluate the effectivity of the conventional chloride/alum treatment relative to a combined Cl/permanganate preoxidation with Al and Fe coagulants during the algae outbreak period. The results showed that the addition of a permanganate dose of 0.5 mg/L significantly reduced the chlorine demand, the applied coagulant dose as well as the residual metal (aluminum/iron) concentration in the treated water. Multivariate analysis was used to identify the raw water parameters that contributed towards the reported algal population as well as to explain the impact of chemicals coagulants added upon the final water quality parameters.