Urban wastewater (Fez, Morocco): characterisation and coagulation-flocculation treatment

Abstract

In this work, characterisation of urban wastewater from Fez City, Morocco, consisting mainly of a mixture of industrial and urban discharges, and its treatment using the coagulation–flocculation (C-F) process were conducted. Three coagulants were used: lime (Ca(OH)2), ferric chloride (FeCl3) and alum (Al2(SO4)3). Ferric chloride achieved the highest reductions in turbidity, chemical oxygen demand (COD) and colour. Then, the Box–Behnken design was applied to optimise the amounts of the coagulant and flocculant and pH. The maximum response values were 78, 98 and 99% for COD, colour and turbidity, respectively, under the following optimal operating conditions: [FeCl3] = 720 mg/l, [flocculant] = 150 mg/l and pH = 7. The operational cost of C-F implemented in this study was estimated at US$0.52/m3, proving that it could be a competitive and cost-effective process for the treatment of wastewater. These results will contribute to the existing literature and would be valuable for scaling up the C-F process.