Internal Electrolysis-Alkali Hydrolysis-Biological Integrated Technology For Efficient Treatment Of HNIW Production Wastewater

The explosives wastewater has complex components,high levels of refractory macromolecular organics,high biological toxicity,and poor biodegradability,so physical and chemical methods are often used for pretreatment.The biochemical method has the characteristics of stable treatment effect and rare secondary pollution.Therefore,it is of great significance to combine the physical method with the biochemical method and study the process suitable for treating the explosives wastewater.This article takes HNIW production wastewater as the research object,the main pollutants in HNIW production wastewater are composed of HNIW,ethyl acetate and chloroform.Firstly,we studied the effect of organic solvents on the degradation performance of anaerobic microorganisms.Secondly,the combined process of "internal electrolysis-alkaline hydrolysis-upflow anaerobic sludge reactor(UASB)-biological aerated filter(BAF)" was developed to realize efficient treatment of HNIW production wastewater.Finally,the HNIW production wastewater was treated by the combination process of "internal electrolysis-alkali-hydrolysis-UASB-BAF" for a long time,and the bioenhanced treatment section of "anaerobic-aerobic" was optimized.Organic solvent rebatch experiments results showed that anaerobic microorganisms had a certain ability to degrade low concentration of ethyl acetate.The activity of anaerobic microorganisms would be inhibited under high concentration of ethyl acetate and chloroform,especially for the strong toxic effect on Methanobrevibacter bacteria.It may reduce the p H of the system and exceed the adaptation range of anaerobic microorganisms.As a result,a large number of anaerobic microorganisms died gradually because of their poor adaptive capacity to the environment.The extracellular polymer(EPS)secreted by cells was reduced,resulting in the gradual cracking of sludge particles.In addition,the addition of organic solvents also increased the ORP of the system gradually,which was not conducive to the reduction and degradation of ethyl acetate and chloroform by anaerobic microorganisms.HNIW production wastewater was treated by the combined process of "internal electrolysis-alkalinity-UASB-BAF",the experimental results showed that HNIW in the wastewater could be completely removed after internal electrolysis reduction,and the ratio of BOD5/COD increased from 0.006 to 0.20.As for the alkali-hydrolysis section,under the best conditions: the removal rate of ethyl acetate and chloroform reaches about 99.7% and 97.5%,respectively under p H value 11 and HRT around 4 h.HNIW production wastewater was pretreated by "internal electrolysis-alkaline hydrolysis" and then flowed into "UASB-BAF" biological combination process.The experimental results showed that the residual ethyl acetate and chloroform could be completely degraded.The indexes of effluent,such as COD and aromatic compounds concentration were lower than that in the discharge standard for water pollutants from ordnance industry(GB14470.2-2002).The combined process of "internal electrolysis-alkalinity-UASB-BAF" was run under the best condition of the pretreatment section to explore the stability of the combined process.The experimental results show that the treatment effect is stable under low water retention time and high water inlet concentration.The toxicity of zebrafish in HNIW production wastewater was compared before and after treatment.When the HNIW production wastewater is treated by the combined process of "internal electrolysis-alkalinity-UASB-BAF",fish can survive for a long time.According to the above experiments,it proved that the combined process of "internal electrolysis-alkalinity-UASB-BAF" has good operation stability,and has a huge application prospect in the treatment of HNIW production wastewater.