(399a) Treatment of Ammunition Wastewater Using Ultrasound-Fenton Process (Invited Keynote Speaker)

Ammunition wastewater contain many harmful chemicals, such as 2,4,6 trinitrotoluene(TNT), 2,4 dinitroanisole(DNAN) , 3-nitro-1,2,4-triazol-5-one(NTO) and so on that are extremely difficult to treat by conventional treatment processes.  Among the various treatment technologies, advanced oxidation processes (AOP) are among the promising methods to deal with the ammunition wastewater.  Particularly, the combination of ultrasonic with Fenton reagent has evolved as a promising AOP for the treatment of ammunition wastewater.  In this study, the wastewater from washing of equipment after energetic operations to remove residual energetic materials and occasional sump out operations was collected for study.   Different treatment methods including photo (UV), Fenton, photo-Fenton and US-Fenton were compared for treatment efficiency. The results showed that US-Fenton was the best among all methods screened.  Moreover, the effect of pH, temperature, reaction time, US energy intensity, initial TOC concentration, and the ratio of iron to hydrogen peroxide were investigated. Results showed that the degradations of TOC, COD and color increased with decreasing pH value.  On the other hand, the removal rate TOC, COD and color increased with increasing temperature and US intensity.  Low pH value and high temperature and US intensity were favorable conditions for treating the ammunition wastewater. Color removal was very fast, reaching 80% in 10 minutes.  Comparing with color removal, TOC and COD removal rate were slower, only about 20% in 10 minutes. After 120 minutes, TOC and COD removal approach to 65% and 93%, respectively. The degradation rate increased with initial TOC concentration to a peak value then decreased upon further increase in TOC. However, the color removal was different from TOC and COD removal; with sample diluted the degradation became better. The optimal ratio of iron to hydrogen peroxide was 500. The oxidation carbon numbers under different effect factor were also calculated to analyze the average oxidation state of wastewater samples. Results clearly showed that the oxidation number of carbon molecule increased upon oxidation and that the combination of ultrasound and Fenton process appeared to be the most effective method for the treatment of the ammunition wastewater for the control of color, TOC and COD.