臭氧预氧化强化煤气废水生化处理研究

煤气废水生物处理出水存在着色度、NH3-N和COD等指标超标的问题,需要进行深度处理。臭氧氧化是一种比较常用的深度处理方法,然而单独依靠臭氧氧化去除废水中的COD和NH3-N需要较高的臭氧投加量,处理成本很高。探讨了臭氧对煤气废水生物处理出水的预氧化效果及其对后续生物处理过程的强化作用。实验表明,臭氧对废水的色度去除很有效,投加<160mg/L的臭氧就可去除90%的色度,废水pH较低时色度去除效果较好;臭氧氧化对废水残留COD有一定的去除作用,不同的pH条件下去除率有差异,总体每mg臭氧可去除0.44～0.64mg的COD;臭氧有效投加质量浓度为240mg/L时,废水COD去除率降低,氧化后出水BOD上升,有利于后续生物处理;臭氧氧化对废水NH3-N的去除效果不明显。对比原水与臭氧氧化出水的分子质量分布特征,发现废水经臭氧氧化后其成分有两种变化趋势,既有一定量的小分子物质产生,又有大分子物质聚合生成,因此臭氧预氧化后续处理工艺应以生物处理为主,同时配合混凝处理工艺。

Ozonation of secondary effluent of coal gasification wastewater

Coal gasification wastewater is of high strength. It is difficult to obtain satisfactory effluent from the bio-treatment. Ozonation is an important way for the advanced wastewater treatment. But the removal of COD and NH3 - N by ozonation alone is too expensive. This research mainly focuses on the characteristics of wastewater under lower ozone doses. Experimental result shows that although pH value of wastewater affects the effectiveness, the wastewater can be decolored by low ozone dose (<160 mg/L). It is indicated that 0.44 ~ 0.64 mg COD can be removed by per mg O3. BOD, COD and pH show that 240 mg/L of O3 is the best dose for the following bio-treatment. Low ozone dose cannot removal NH3 - N whether the pH value of the wastewater is 7 or 9. From the analysis of molecular-weight distribution, it is found that low dose ozone have two effects include decomposition and polymer-ization on the wastewater composition. This characteristic is important for selecting the following treatment process.