Journal of Hazardous Materials 244–245 (2013) 403–411 Contents lists available at SciVerse ScienceDirect Journal of Hazardous Materials jou rn al h om epage: www.elsevier.com/loc ate/jhazmat Combined ultrasound and Fenton (US-Fenton) process for the treatment of ammunition wastewater Yangang Li a,b , Wen-Pin Hsieh b , Rovshan Mahmudov b , Xiaomei Wei a , C.P. Huang b,∗ a College of Water Resources and Architecture Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China b Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA h i g h l i g h t s ◮ Combined ultrasound-Fenton pro- cess was the most effective in TOC/COD/color removal. ◮ Initial TOC, [H 2 O 2 ]/[Fe 2+ ] ratio, pH, and temperature affected TOC/COD/color removal. ◮ Low pH and high US intensity improved TOC/COD/color removal. ◮ Optimal temperature for TOC/COD/color removal was 30 ◦ C. ◮ Optimal [H 2 O 2 ]/[Fe 2+ ] ratio for TOC/COD/color removal was 500. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 23 June 2012 Received in revised form 6 November 2012 Accepted 7 November 2012 Available online 10 December 2012 Keywords: Ammunition wastewater Ultrasound Fenton Total organic carbon (TOC) Chemical oxygen demand (COD) Toxicity a b s t r a c t A wastewater collected from a regional ammunition process site was treated with combined US-Fenton process. Factors such as pH, temperature, reaction time, US energy intensity, initial TOC concentration, and the molar ratio of iron to hydrogen peroxide that might affect the treatment efficiency were investi- gated. The removal of TOC, COD, and color increased with decreasing pH and increasing temperature and US intensity. Color was removed rapidly reaching 85% in 10 min; whereas TOC and COD were removed slowly, only about 20% for both in 10 min and approaching 65 and 92% removal in 120 min, respectively. The optimal molar ratio of Fe(II) to H 2 O 2 for TOC and COD removal was 500. The results showed that the change in the average carbon oxidation number (ACON) was parallel to that of the removal efficiency of TOC, COD, and color. The toxicity of treated wastewater was reduced as assessed by the respiration rate of Escherichia coli. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Ammunition wastewater generated during the manufactur- ing and demilitarization of ammunitions has rather complex chemical and physical characteristics. These chemicals include metals, nitroaromatic compounds, and various oxyanions that require proper treatment before discharge. In particular, nitroaro- matic compounds can cause serious soil and groundwater ∗ Corresponding author. Fax: +1 302 831 8428. E-mail address: huang@udel.edu (C.P. Huang). contamination. It is estimated that in the US alone over 1.2 mil- lion tons of soils have been contaminated by explosive materials [1,2]. In addition, transformation products of nitroaromatic com- pounds such as azoxy- and azo-compounds are similar to or more toxic than their parent nitro aromatics to the environment [3–5]. Therefore adequate treatment of these nitroaromatic compounds is necessary before discharge to the environment. A great deal of research efforts has focused on technology for effective treatment of ammunition wastewater. Yin et al. [6] studied reductive transformation of TNT using aerobically grown Escherichia coli cultures and reported that E. coli res- ting cells transformed TNT to hydroxylaminodinitrotoluenes, 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2012.11.022