Treatment of highly acidic wastewater containing high energetic compounds using dimensionally stable anode

Abstract

Highly acidic (pH < 2) wastewaters have toxic and carcinogenic properties and can’t be treated by conventional biological treatment methods. In the work presented, investigation of the treatment of very low pH, actual wastewater containing highly energetic materials was carried out using electro-oxidation method using a dimensionally stable anode (DSA) namely ruthenium oxide coated titanium (Ti/RuO2). Chemical oxygen demand (COD), current efficiency (CE) and specific energy consumption (SEC) were measured under various process conditions of current density (J) and time (t). Maximum COD removal efficiency of 41.83% was observed at J = 750A/m2, t=150min, and initial pH=0.4±0.1 with SEC=1.23kWh/kg COD. In the next phase, the addition of hydrogen peroxide (30%w/w) (H2O2) was done and COD degradation was evaluated by varying the dosage of H2O2. Maximum COD removal efficiencies of 48.83% was observed at J = 750A/m2, t=150min, pHo=0.3. This method produced very low or no amount of sludge and scum. The mechanistic study has been performed by carrying out scavenger study using terephthalic acid. Gas chromatography-mass spectroscopy (GC/MS), Fourier transform infrared spectroscopy and ion chromatography of the wastewater; and X-ray diffraction and Field emission scanning electron microscopy (FE/SEM) of electrodes were carried out for understanding the treatment mechanism. Operating cost analysis has been done based on the studies performed in laboratory scale EC reactor, and compared with those reported for other pollutant degradation.