Remediation of real industrial hypersaline effluent using sequential approach of precipitation followed by cavitation based oxidative process

Abstract

The current study aims to develop a cost-effective and efficient treatment method for the remediation of amine-containing real industrial effluent. The method consists of a precipitation to remove chloride ions and TDS, followed by cavitation-based AOPs involving US and chemical oxidants as H2O2, O3, Fenton’s reagent, NaClO, and nTiO2. Different parameters including precipitating agent type and dosage, oxidant loading/flow rate, and time were assessed to determine optimal conditions for effective treatment. Treatment schemes were evaluated based on cavitational yield (mg/J), treatment cost (Rs/L), and COD reduction to select an industrially feasible design for amine-containing real effluent treatment. The optimum conditions elucidated were H2O2 loading of 3 g/L, NaClO loading of 3 g/L, O3 flowrate of 3 LPH, nTiO2 loading of 3 g/L, and Fenton’s reagent ratio (H2O2/Fe2+) as 6:1. Under the optimum conditions, US+nTiO2 (70%) treatment schemes were the most efficient, achieving a maximum COD reduction compared to US+Fenton (65%), US+H2O2 (36%), US+O3 (49%) and US+NaClO (53%) schemes. Additionally, impact of chloride and TDS on the oxidation process in terms of COD reduction was assessed. Using Rotavap instead of precipitation, and subsequent use of the best oxidation method (US/HC+Fenton+CaO) achieved COD and TDS levels below 250 mg/L (discharge limit) at optimum conditions, with minimal operating costs of 0.23 $/L and 0.15 $/L, respectively. Overall, the study concluded that the sequential approach of precipitation/Rotavap and cavitation-assisted oxidation is an effective and sustainable method, providing a promising solution for the wastewater treatment in the metallurgical industry.