Treatment of the pesticide industry effluent using hydrodynamic cavitation and its combination with process intensifying additives (H2O2 and ozone)

• Treatment of industrial effluent using hydrodynamic cavitation (HC) based processes.
• Biodegradability index of the effluent increased from 0.123 to 0.324 using HC + ozone.
• Higher rate of COD and TOC reduction obtained using HC + H2O2 as compared to HC alone.
• Cost estimation is done for individual HC and HC based hybrid processes.
• Combined HC and H2O2 process is the most effective and economical one.

Hydrodynamic cavitation (HC) and its combination with H2O2 and ozone have been applied in the present work for the treatment of industrial pesticide effluent. Initially, the effect of dilution of the effluent on the efficacy of hydrodynamic cavitation has been studied using circular venturi as a cavitator. Although an increase in the extent of dilution has not shown any beneficial effect on the actual moles of pollutant degraded, hybrid processes have been studied using 1:5 dilution due to very high TDS content of the effluent. Treatment of the industrial pesticide effluent using HC + ozone (3 g/h) process has demonstrated that the biodegradability index (BI) of the effluent increases from 0.123 to 0.324 after 2 h of operation. The rate of COD and TOC reduction has also increased by many folds by using HC in combination with ozone. In addition this, the treatment of industrial pesticide effluent using HC + H2O2 has also indicated that the rate of COD and TOC reduction increases significantly by using HC in combination with various loadings of H2O2. The study of interference of added H2O2 on the COD analysis has exhibited that the COD equivalence is 0.441 mg/L for 1 mg/L of H2O2. The energy efficiency and operating cost of various hybrid processes have been compared based on the cavitational yield and the cost of electricity. The combined process of HC and H2O2 has observed to be the most cost-effective one due to its higher cavitational yield and lower power consumption.