Integrated membrane process (UF/RO/EDI) for treating a petrochemical wastewater to obtain ultrapure water for industrial reuse

Abstract

The scarcity and change in water quality reinforce the need to reuse effluents in water intensive industries as the petrochemical ones. In this article, the tertiary effluent from a Petrochemical Complex in Southern Brazil was used as feed water in a pilot unit with a capacity of 1 m³ .h−1 to produce industrial water to be reused as clarified or demineralized water (ultra-pure water). For the treatment, an integrated system composed of ultrafiltration (UF), reverse osmosis (RO) and electrodeionization (EDI) was used. The parameters evaluated were aluminum, calcium, chloride, electrical conductivity (EC), color, chemical oxygen demand (COD), iron, magnesium, pH, total suspended solids (TSS), sulfate and turbidity. The UF/RO system operated with average permeate fluxes of 6.6 and 6.7 L.h−1.m−2, respectively. For the EDI, the operational parameters (flow rate, electric current and EC in the feed water) were optimized, considering the percentage of conductivity removal (%RC) as a response, by using response surface methodology (RSM) based on a central composite design (CCD). The best predicted values of flow rate, electric current and conductivity of the feed water were 6.6 L.min−1, 1.27 A, and 22.2 µS.cm−1, respectively. The %RC predicted in the software was 98.2%, similar to the mean value at the midpoint 97.1%. The EDI system was operated with the model conditions, and the product water reached the necessary quality to be reused as demineralized water in the Southern Petrochemical Complex in Brazil. Industrial reuse can reduce 20% raw water collection and 70% of the effluent volume disposed in the soil, thus reducing the water footprint, and increasing the sustainability of the petrochemical industry.