Intensified Biological Oxidation of Diclofenac Sodium Using Pretreatment With Acoustic Cavitation Coupled With Advanced Oxidation

ABSTRACT Pharmaceutical compounds, such as diclofenac (DCF) sodium, are being increasingly detected in aquatic environments due to poor removal by conventional processes, making the development of efficient treatment strategies critical. The present work explores acoustic cavitation (AC)‐based pretreatment as an intensification approach for improving the biological oxidation (BO) of synthetic effluent containing DCF sodium (equivalent chemical oxygen demand [COD] of 250 ± 15 ppm). AC was employed both as a standalone treatment and in combination with oxidants, including ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), Fenton's reagent, and sodium hypochlorite (NaOCl). The pretreated effluent was subsequently subjected to BO using cow dung‐based sludge acclimatized with the synthetic effluent at a sludge‐to‐effluent ratio of 1:3 with an 8 h treatment period. Conventional BO alone achieved only 4.36% reduction in COD, whereas COD reductions achieved after AC‐assisted pretreatment followed by BO were significantly higher at 14.55% (AC + O 3 ), 36.23% (AC + H 2 O 2 ), 56.63% (AC + Fenton), 48.55% (AC + Photo‐Fenton), and 8.55% (AC + NaOCl). Toxicity assays conducted using Staphylococcus aureus and Pseudomonas aeruginosa further confirmed improved biodegradability of the effluent by reducing inhibitory effects on microbial growth. Overall, the study establishes that combining AC with Fenton chemistry is the most effective strategy among those tested, achieving more than a tenfold improvement over conventional BO.