Abstract:

Thiocyanate (SCN^-) is one of the main contaminants in coking wastewater and has non-neglectable contribution to COD, chroma and NH⁺₄-N value.The interactive inhibitory reaction of SCN^- with other pollutants would affect the selection of treatment technology and the draining water quality control.In this study, the SCN- degradation kinetics was investigated using activated sludge of coking wastewater.Effects of phenol on SCN- degradation and SCN^- on nitrification were also studied in order to assess the interaction of SCN^- with other pollutants.Under specified culture condition, the degradation rate of SCN- reached up to 20.15 mg SCN^-·(g MLSS)^-1·h^-1 and the sludge activity was not significantly affected by the initial concentration of SCN^-.The SCN^- degradation process follows the Michaelis-Menten model.Experiment results indicated that phenol has toxic inhibition on SCN- degradation, with 738 mg·L^-1 phenol, the complete degradation time of 108 mg·L^-1 SCN^- was delayed from 1.5 h to 20 h.On the other hand, SCN^- also inhibits the nitrification of NH⁺₄, especially for the conversion of nitrite to nitrate, which resulted in the accumulation of NO^-₂.Hence, the inhibitory interactions of thiocyanate with phenol and ammonia make the treatment of coking wastewater more complicated and difficult.Thus, for the pollution control of coking wastewater, it should identify the interaction effects among main contaminants, consider the adaptation of sludge activity with pollutants concentrations from the point of co-substrate effect or poisonous effect, which would give help in establishing an optimized biological treatment technology.

Key words:

焦化废水, 硫氰化物, 生物降解, 交互干扰

摘要：

硫氰化物（SCN^-）在焦化废水中的普遍出现，对COD、色度及NH⁺₄-N等指标构成贡献，且生物降解过程中还与其他污染物产生交互作用，影响工程工艺的选择和达标的控制。本研究采用实际工程不同单元工艺的活性污泥，在研究SCN-的基本降解特性与动力学基础上，重点考察苯酚对SCN^-降解及SCN^-对氨氮硝化过程的影响，评价SCN^-在焦化废水实际降解过程中与其他污染物的交互作用。研究发现，在特征活性污泥培养条件下，SCN^-的降解速率达20.15 mg SCN^-·（g MLSS）^-1·h^-1，污泥活性不受SCN^-底物浓度抑制，降解过程符合Michaelis-Menten动力学模型;苯酚对SCN^-的降解表现为毒性抑制且存在浓度阈值，高浓度苯酚可严重抑制SCN^-的降解，738 mg·L^-1苯酚使108 mg·L^-1SCN^-完全降解时间从1.5 h延长至20 h;SCN^-对硝化过程有抑制作用，可同时影响NH⁺₄的去除和NO^-₂的转化，导致硝化系统中NO^-₂浓度的积累。结果表明，生物过程中SCN^-与酚类、NH⁺₄之间的交互影响使焦化废水的处理变得复杂且难以控制，针对实际工程，需要明确各核心组分之间的相互作用，从共基质效应或毒性效应方面考虑污泥活性与浓度区间的适配，才能构建出各项污染指标得到优化控制的高效工艺。

关键词:

焦化废水, 硫氰化物, 生物降解, 交互干扰