The effect of treatment stages on the coking wastewater hazardous compounds and their toxicity

► Organic compounds are main matters in coking wastewater exerting toxicity on maize. ► Aerobic treatment stage is the main process of toxicity reduction for the wastewater. ► Advanced treatment by photo-degradation can increase toxicity of the water on maize. ► Biodegradable and refractory organic in water both can act with amylase and protease. ► The wastewater treatment process cannot produce obvious new toxic organic materials.