Study on Nitrogen and Phosphorus Removal Effect of Substrate in Subsurface Constructed Wetland

N,P removal effect of subsurface conotracted wetland with three kinds of substrates(detritus,zeolite and quartz) at initial operation stage is investigated by testing analysis.Water flows in and flows out continuously and hydraulic load in the range is controlled between 4.95 cm/d～8.25cm/d in test process.The experiment results show that the effect of N、P removal with the detritus as treatment unit is the best,the zeolite is the next and the quartz is the poorest.TP removal ratio with these three kinds of substrates is 90.34%、83.24% and 71.02%,NH_3-N removal ratio is 70%、48.68% and 39.34% and TN removal ratio is 59.48%、42.65% and 30.26% respectively.The results also indicate that substrate of the wetland on Phosphorus removal is a most effective factor and choosing the substrate is very important to Phosphorus removal.The substrate of the wetland has great influence on Nitrogen removal too.