潜流水平湿地对农业灌溉径流氮磷的去除

 构建了潜流水平芦苇湿地,对农业灌溉径流(TN约为7mg/L,TP约为0.5mg/L)中氮磷进行了为期1年的去除研究.在水力停留时间(HRT)为2,4,6d时,TP和TN的去除率均大于87%和68%.湿地对TN、NH₄⁺-N和TP的去除受HRT的影响较大(P<0.05),对PO₄^3--P的去除受HRT的影响较小.在不同HRT情况下,NH₄⁺-N、NO₂^--N、NO3--N和PO₄^3--P的去除率均高于93%,出水浓度一般均小于0.04mg/L.且出水中的TP和TN主要为有机态,存在一个TP和TN背景浓度.TN去除率与负荷之间具有很好的相关性(R2=0.9968),但是TP去除率与负荷之间相关性较差(R²=0.5987).以HRT为2d计算,1m²的芦苇床处理该农业灌溉径流的能力为0.1m³/d,出水TN和TP浓度可控制在0.50mg/L和0.154mg/L以下.

Removal of nitrogen and phosphorus from agricultural irrigation runoff in subsurface horizontal-flow wetland

The subsurface horizontal-flow wetland planted Phragmites communis was constructed to study the long-term performance nitrogen and phosphorus removal from agricultural irrigation runoff (TN was about 7mg/L, TP was about 0.5mg/L). TP and TN removal rates were above 87% and 68% at the hydraulic remain time (HRT) of 2, 4, 6d. The influence of HRT on the removal of TN, NH4 -N and TP by wetland was relatively great (P<0.05) and less for PO43--P removal. Under all HRT conditions the removal rates of NH4 -N, NO2--N, NO3--N and PO43--P were all higher than 93%, with their concentrations generally below 0.04mg/L. The TP and TN in the wetland effluent were mainly of organic from, due to the release of organic nitrogen and organic phosphorus induced by internal circulation of nitrogen and phosphorus in wetland system. There existed TP and TN background levels in the wetland effluent. Wetland possessed very good relativity with TN removal rate and load (R2=0.9968); but relatively poor with TP (R2=0.5987). Based on 2d HRT, the Phragmites communis bed with surface area 1m2 had 0.1m3/d ability of treating the agriculture irrigation runoff and the effluent TN and TP concentration could be controlled below 0.50mg/L and 0.154mg/L.