Treatment of real time textile effluent containing azo reactive dyes via ozonation, modified pulsed low frequency ultrasound cavitation, and integrated reactor

•KINFRA, India needs to replace stage-1 facility of CETP to avoid sludge formation.•COD removal > 90% with the final COD level < 150 mg L − 1 are the major criteria.•Ozonation provides COD removal of 90% with the final COD level of 29 mg L − 1.•Stand-alone ozonation process can replace stage-1 facility of CETP, KINFRA, India.•For ozonation process, COD removal is achieved via possible attack of •OOH.