Integration of coagulation–flocculation and photolysis processes for treating reverse osmosis concentrate (ROC) of pharmaceutical wastewater management

Abstract

ABSTRACT This study provides novel insights into optimizing the integral treatment process, contributing to ROC treatment strategies. A comprehensive treatment approach for reverse osmosis concentrate (ROC) from pharmaceutical wastewater was investigated using an integral system consisting of a coagulation-flocculation and photolysis process. Ferric chloride (FC) and poly-aluminum chloride (PAC) are examined as coagulants within the range (0.1–1) gL−1, focusing on turbidity, chemical oxygen demand (COD), and total organic carbon (TOC) removal. The findings show that the optimal FeCl3 dosage is 0.4 gL−1, achieving significant turbidity reduction to 1 NTU. PAC at 0.2 gL−1 is optimal, reducing turbidity to 1 NTU and exhibiting non-linear behavior in COD and TOC removal, introducing them as a starting point to the post-treatment. Photolysis of treated samples at pH 7 yields COD reductions of 60.5% for PAC and 79.5% for FC, with respective TOC reductions of 79.5% and 75.23% over 360 min. At (pH 3.5) showed a significant reduction in the COD and TOC of treated ROC. The FC coagulant could decrease the COD from 261 to 5 mgL−1 (98% COD removal) and the TOC from 143.9 to 5 mgL−1 (74.8% TOC removal). The FAC coagulant could decrease the COD from 675 to 39 mgL−1 (93% COD removal) and the TOC from 186 to 13.1 mgL−1 (69.7% TOC removal). The conventional oxidant (H2O2) at optimal dosages enhanced COD and TOC removal at pH 7, with treated PAC and FeCl3 achieving 81.8% and 97.2% COD reduction and 89% and 98% TOC reduction at 360 minutes. These results were supported by the cost analysis in which this system was cost effective manner. This system can offer a solution for the efficient treatment of other types of industrial wastewater and open the door to new applications for water reuse on a broad scale, contributing to global water sustainability.