Feasibility of Reuse Filter Backwash Water as Primary/Aid Coagulant in Coagulation–Sedimentation Process for Tertiary Wastewater Treatment

Abstract

The purpose of this study is to evaluate the feasibility of reusing filter backwash water (FBWW) from the water treatment plant as a substitute for conventional coagulants (primary coagulant) and coagulant aid with aluminum sulfate (Al2(SO4)3) in the coagulation–sedimentation process as tertiary treatment urban effluents for reuse. The impact of reuse filter backwash water has been studied on the water quality in coagulation process. The analysis Fourier Transform Infrared showed the presence of Al(OH)3 in the filter backwash water. The results showed a very good performance of turbidity and organic matter removal by FBWW in both cases. For a dose of 22.5 mg Al/L of FBWW as primary coagulant, the removal of turbidity and UV254 absorbance was significant, with percentages of 65.8% and 31.7%, respectively, during the treatment of the secondary effluent. The best results were obtained for a neutral pH. With FBWW as coagulant aid, the optimal dose of Al2(SO4)3 decreased from 9.5 to 6.3 mg Al/L with better percentages of turbidity reduction and UV254 of 92.9 and 71.4%. This study permits to reduce the coagulant concentration.