Study On The Treatment Process Of Wastewater Of TNT Ammunition Loading

TNT ammunition loading wastewater, due to the behaviours of high concentration, high colority and hardly biogradable, is considered as one of the most difficult wastewater to be treated. In this dissertation, the simulated wastewater with 140mg/L-170mg/L of TNT was prepared according to a really ammunition loading factory. First, the TNT concentration was reduced to an acceptable range for the biological degradation by pretreatment.Two kinds of pretreatment methods were investigated, Fenton's reagent oxidation and iron-carbon micro-electrolysis. Then, a combine process of hydrolytic acidification-biological contact oxidation was used, and the effluent meeting the emission standards was achieved.Single-factor method was used to determine the optimal pretreatment parameters. (1) For the pretreatment by Fenton oxidation, the optimal conditions were as follow:0.05mol/L of H2O2 concentration, FeSO4·7H2O:H2O2 of 1:7(mass ratio), pH of 3.5-4.5, reaction time of 4h. Under that condition, the concentration of TNT was reduced from 150mg/L to about 15mg/L, while COD removal efficiency was over 60%. (2) For the pretreatment by iron-carbon micro-electrolysis, the optimal conditions were as follow:10% in volume of the cast iron chip's, pH of 3, aeration rate of 7L/min, temperature of 25℃, reaction time of 1h. Under that condition, the concentration of TNT was reduced from 150mg/L to about 15mg/L, while COD removal efficiency was about 62%.The combine treatment process of hydrolytic acidification and biological contact oxidation was adopted to treat the wastewater coming from the pretreatment process. The optimal process parameters were investigated and the results were as following, (1) In the stage of hydrolytic acdification:IIRT=12h, temperature of 3O℃～35℃, pH=6.8-7.5. Under that condition, the effluent of TNT was below 2mg/L, COD removal ratio was about 84%, however, the effluent concentration of NH3-N didn't meet the emission standards; (2) In the stage of biological contact oxidation:HRT=8h, temperature of 15℃～20℃, pH=6.5～8.5. Under that condition, the effluent of TNT was below 1mg/L. COD removal ratio was about 84%, the effluent of NH3-N was below 3mg/L. The results showed that it was effect to degrade TNT by the combine treatment process of hydrolytic acidification and biological contact oxidation, while NJ3-N concentration could meet the emission standards.Two sets of combine treatment processes for the high concentration of TNT wastewater under continuous operation, namely, Fenton-hydrolytic acidification-contact oxidation, iron-carbon micro-elcctrolysis-acidilication-contact oxidation, were investigated in detail. For the former one, after being treated by Fenton, hydrolytic acidification and contact oxidation for 4h,12h and 8h, respectively, the effluent of TNT was about 15mg/L,1.6mg/L and below 0.5mg/L, and the final COD was below 31mg/L, NH3-N was less than 4 mg/L, removal ratio of colority was above 90%. For the later one, after being treated by iron-carbon micro-electrolysis, hydrolytic acidification and contact oxidation for 1h,12h and 8h, respectively, the effluent of TNT was about 15mg/L,1.6mg/L and below 0.5mg/L, and the final COD was below 30mg/L, NH3-N was less than 3 mg/L, removal ratio of colority was above 90%. In both of the two kinds of combine processes, the effluents could meet the emission standards, however, the later one should be more economical.