Keywords: 
• constructed wetland /
• vertical sub-flow /
• nitrogen /
• steel slag /
• limestone

Abstract: The purpose of this paper is to study the degradation effect of high concentration nitrogen in fecal sewage with steel slag-limestone constructed wetland. Different factors experiments impacting treatment effect were operated， such as fillings structure， surface filling and so on. The experimental results indicated that the NH3-N and TN concentration of constructed wetland effluent attained to 13.57 mg/L and 62.83 mg/L when the NH3-N and TN concentration ranges of raw water were 42.72～272.60 mg/L and 107.40～689.35 mg/，respentively . Then at the base of assuring effluent quality and improving quantity of treated wastewater， 60 h is the best intermittent inflow time. The bed structure having larger size difference which was mixed progressively-sized filling with anti-sized filling was more benefit for keeping long-time better degradation effect on nitrogen， and the surface filling mixed 40% soil and 60% washing sand was also the best choice because of its granularity penetrability， ability to restore oxygen. Steel slag can creat an environment which was not only benefit for adsorption and vaporizing ammonia nitrogen but also strengthen nitrification and denitrification. In addition， the calcium ion dissolved from limestone with steel slag assisting was helpful to exchanging ammonia nitrogen ion. At the same time， limestone was also a kind of carbon resource for autotrophic denitrifying bacteria including iron autotrophic bacteria and thiobacillus.