Hybrid Advanced Oxidative Pre-treatment of Complex Industrial Effluent for Biodegradability Enhancement Dr. (Ms) Kiran Paradkar CSIR-National Environmental Engineering Research Institute (NEERI) Nagpur, INDIA April 28, 2017

Genesis & Motivation Complex /recalcitrant effluents with high COD-color are generated from industries such as distillery, heterocyclic chemicals, API manufacturing (8-500 LWastewater/kgproduct) Advanced oxidation processes (AOPs) are mostly used for complete mineralization and are capital and energy intensive AOPs are set of chemical treatment procedures designed to remove organics by oxidation via hydroxyl radical mechanism Need for development of advanced oxidation based pretreatment process for selective biodegradability enhancement Hybrid combination (synergism) of AOPs can be a potential option for biodegradability enhancement and lowering energy requirements Biodegradability enhancement of complex effluent can facilitate integration with subsequent biological processes like anaerobic digestion for biogas generation and/or aerobic biooxidation April 28, 2017

Objectives Evaluation of Hydrodynamic-Cavitation, Wet air oxidation based Advanced Oxidation Processes for pretreatment of model complex effluent to enhance biodegradability Evaluation of the mechanism of pretreatment April 28, 2017 Cavn-Wetox......

Model Complex Wastewater- Biomethanated distillery wastewater Characteristics Raw complex waste water Desirable for anaerobic digestion pH 7.64 6.5-8 COD (mg/L) 40,000 >10,000 BOD (mg/L) 7015 - VFA: Alkalinity ratio 0.022 0.4-0.5 BOD: COD ratio 0.17 >0.4 April 28, 2017

Cavitation Cavitation is the generation, subsequent growth and collapse of cavities releasing large magnitudes of energy over a very small interval of time and over a small location In Hydrodynamic cavitation (HC) cavities are generated by passing liquid via a venturi/orifce resulting in conditions similar to acoustic cavitation/ultrasound but at comparatively much larger scale of operation and with much better energy efficiencies Important effects of cavitation phenomena are generation of very high temperatures & pressures locally with overall ambient operating conditions, release of highly reactive free radicals, generation of micro-turbulence and liquid circulation enhancing the rates of transport processes In water at 25oC, it is possible to achieve temp. as high as 5000K and pressures of 1000 bar by collapse of cavitation bubbles April 28, 2017

Wet Air Oxidation Wet air oxidation is aqueous phase oxidation of organic material at elevated temperature (120 - 320oC) and pressure (1 - 60 bar) Oxygen solubility in water decreases with temp to 0.85 ppm near 100oC under atm conditions and then increases with increasing temp to an infinite value at 374.1oC, the critical point of water. This enhanced solubility of oxygen in aqueous solutions provides a strong driving force for oxidation Longer molecules are oxidized to various intermediate products. Most of the initial intermediates formed are unstable except low molecular weight carboxylic acid which are resistant to further oxidation Complex molecules A + O2 C k1 k2 k3 B + O2 A : Unstable intermediates B : Carboxylic acids C : End products April 28, 2017

Abbreviations HYCA/HC: Hydrodynamic Cavitation WAO: Wet Air Oxidation VFA: Volatile Fatty Acids COD: Chemical Oxygen Demand BOD: Biochemical Oxygen Demand BI: Biodegradability Index; BOD5:COD ratio BDWW: Biomethanated Distillery Wastewater April 28, 2017

The CAVOX (HYCA+ WAO) Concept CAVOX is a recent hybrid technique and potential treatment/pre- treatment option for recalcitrant waste streams Advantage of hybrid technique is mainly due to identical controlling reaction mechanism leading to an enhanced generation of hydroxyl radicals, which eventually can result in higher oxidation rates Hybrid method can synergistically combine for higher energy efficiency and oxidation in comparison to standalone cavitation or wet oxidation Selective pretreatment targeting enhanced biodegradation and biogas recovery can be achieved by developing hybrid pretreatment process April 28, 2017

Summary of cavitation for complex model wastewater at various conditions April 28, 2017

Pretreatment of complex wastewater by Wet Air Oxidation 0.88 0.63 0.4 0.2 Original COD : 40,000 mg/L, BI : 0.17 April 28, 2017

Profile of VFA in WAO pretreated model wastewater April 28, 2017

Comparison of cavitation and WAO as stand alone and combined (CAVOX) pretreatment for biodegradability enhancement April 28, 2017

Biogas generation Post WAO Pretreatment April 28, 2017

Proposed Mechanism of Pretreatment FTIR analysis indicated the dissociation and reorientation of complex organic compounds in the untreated B-DWW to new and simpler organic compounds in comparison to the untreated sample Intense bands were found in the ranges 1600–1300,1200–1000 and 800–600 cm-1 which indicated that strong OH bonds are produced in treated sample over control investigation on 1H NMR spectrum of untreated and treated sample has shown signals at d 7.4 ppm d 8.0 ppm in only the untreated sample, indicative of presence of aromatic groups in the untreated sample which were not observed in WAO treated samples, probably because of breakdown of aromatic compounds by wet oxidation into simpler aliphatic compounds Important structural feature of Melanoidin (major coloring compound in original sample) is the peak of C=N and C=C conjugated bonds. The pretreatment aids in cleavage of the C=N (azomethane) and C=C(ethylinic) linkage producing more hydroxyl groups in (3400 cm-1) pretreated sample over the control This is indicative of conversion of complex molecules to simpler ones April 28, 2017

Summary & Conclusions Synergistic combination of Hydrodynamic Cavitation-Wet Air Oxidation is a potential high performance pretreatment concept Biodegradability Index > 0.4 favours anaerobic digestion for biogas generation WAO pretreatment indicated possibility to enhance BI greater than 0.4 for its utilization in biogas production Hybrid pretreatment could retain 50% COD with an BI of 0.55, indicating suitability of coupling with biological systems Hybrid pretreatment concept can be applied to similar complex wastes for enhancing biodegradability and biofuel recovery April 28, 2017

Future Needs Understanding Complete Mechanism and postulating possible pathway of pretreatment for application to similar complex effluents containing large number of complex (known and unknown) constituents April 28, 2017

Publications Wet Air oxidation as a Pretreatment Option for Selective Biodegradability Enhancement and Biogas Generation Potential from Complex Effluent. Bioresource Technology (2012) Cavitationally induced Biodegradability enhancement of a Distillery Wastewater. Journal of Hazardous materials (2012) Kinetics of Wet Air Oxidation Pretreatment and Biodegradability of a Complex Wastewater. J. of Environmental Chemical Engg. (2014) Wet Air Oxidation Induced Enhanced Biodegradability of Distillery Effluent. J. of Environmental Management (2014) Advanced Oxidative Pretreatment of Complex Effluents for Biodegradability Enhancement and Color Reduction. In: Advances in Biodegradation & Bioremediation of Industrial Waste, Taylor & Francis, CRC Press (2015)   April 28, 2017 Cavn-Wetox......

Thank You Acknowledgements Department of Science and Technology for Financial Support Thank You Dr.R.A.Pandey, CSIR-NEERI, Nagpur, India Prof.Dr.A.B.Pandit, ICT, Mumbai, India Dr.S.N.Mudliar, CSIR-CFTRI, Mysore, India April 28, 2017

Sample calculation for preliminary cost estimation of hydrodynamic cavitation treatment to facilitate biogas formation Biogas formed in the Cavitaionally pretreated B-DWW (13 bar, 25% Dilution, 50 minutes, BI: 0.32) = 400 ml in 2 L of pretreated B-DWW Biogas formed in the control system = 60 mL Additional biogas formed due to hydrodynamic cavitation pretreatment = (400-60) mL = 340 ml in 2 L of pretreated B-DWW Total Biogas formed in 6 lit of Cavitaionally pretreated B-DWW = 340 (mL) × (6/2) = 1.02L Total electrical energy consumed = pump power × total treatment time = 1.1 kW × (50/60) h = 0.92 kWh Biogas formed per unit energy consumed = 1.02 (L) / 0.92 kWh = 1.11 L/kWh Power cost in India for heavy industry = 0.13 US$/kWh Cost for the additional biogas formation = 1.11 (L/kWh) / 0.13 (US$/kWh) = 8.5 L/ US$ = 0.12 US$/L % COD reduction: Exp-70%, BI : 0.32, COD:19,000mgL-1 , Control-12%, BI:0.17, COD : 28,754 mgL-1 Duration: 40 days April 28, 2017 Cavn-Wetox......