焦化废水中氨氮吹脱传质速率的影响因素研究

Research on Factors Eff ecting Mass Transfer Rate of Ammonia Nitrogen Stripping in Coking Wastewater

焦化废水是一种常见的工业废水,它不仅成分复杂,而且还含有高浓度的氨氮和COD。生物处理系统能有效去除废水中的COD,但由于氨氮的抑制作用,通常会使生物处理系统的效能降低,因此需要采用适当的预处理方法去除废水中的氨氮。选用空气吹脱法对某焦化厂产生的废水进行预处理,重点考察了废水初始pH、通气速度和废水温度三个关键操作因素对废水中氨氮去除率和总传质系数的影响。实验结果表明,废水在pH为12.00、通气速度为0.5 m^(3)/(h·L)、废水温度为40℃和反应时间为240 min的最适条件下,氨氮去除率和总传质系数分别能达到88.74%和0.00846/min,处理后出水中氨氮的剩余浓度低于25 mg/L,该浓度已满足《炼焦化学工业污染物排放标准》(GB 16171—2012)中规定的氨氮的间接排放标准。

Coking wastewater,a typical kind of industrial wastewater,can be considered complex effluent that often contains high concentrations of ammonia nitrogen and COD.Biological treatment systems are efficient to remove COD,but high concentration of ammonia nitrogen inhibit biological treatment systems.Therefore,pretreatment of ammonia nitrogen is very important.Air stripping was applied as a pretreatment method for the wastewater.The effects of pH,air flow rate and temperature on the removal of NH_(4)-N and total mass transfer coefficient were investigated.The results indicate that,the NH_(4)-N removal efficiency and total mass transfer coefficient can reach 88.74%and 0.00846/min,respectively,under the conditions of pH 12.00,air flow rate 0.5 m^(3)/(h·L),temperature 40℃and stripping time 240 min.The effluent quality could meet the indirect discharge criteria of Emission Standard of Pollutants for Coking Chemical Industry(GB 16171—2012).