Artificial Agricultural Runoff Treatment Using Novel Regulated Ottelia Acuminata Constructed Wetlands

Erhai Lake is the typical eutrophication of the early lakes,the western and northern watershed are the main source of pollutants.Dali is typical agricultural state which agricultural planting patterns are mainly garlic-rice,beans-rice and vegetablesvegetables.Lots of nitrogen and phosphorus resided in the farmland is washed into Erhai in rainy season,which causing serious pollution.In this study,the low-level contaminated water and rainfall runoff from the farmland of Erhai Lake were treated.The treatment efficiency of low-polluted water and the growth of Ottelia acuminate were studied when the nitrate concentration???NO₃^-N??was 1,5 and 10 mg/L,respectively.And four groups of Regulated Ottelia Acuminata Constructed Wetlands?ROCWs?were established by changing the wetland water level of the impact process.Removal of nitrogen and phosphorus from artificial low polluted water and agricultureal runoff by Non-Regulated Ottelia Acuminata Constructed Wetlands?NROCWs?and ROCWs were studied at hydraulic load impacting 0.50,0.75 and 1.00 m3/?m2·d?.The main results were as follows:?1?When the influent ??NO₃^--N??mean ± variance,n=12?was 1.52 ± 0.48,5.62 ±0.41 and 9.78 ± 0.24 mg/L,the effluent ??NO₃^--N?were 0.24,0.30 and 0.55 mg/L after Ottelia wetlands reach stable state,and the removal rates were 87.26%,94.98% and94.48% respectively.Nitrate in low pollution water can be removed by Ottelia wetland effectively.?2?When the influent nitrate concentration???NO₃^--N??was 1.52±0.48 mg/L and5.62±0.41 mg/L,Ottelia acuminate can grow normally in the wetland.But the growthof Ottelia acuminate was inhibited when ??NO₃^--N?was 9.78±0.24 mg/L.Ottelia acuminate can be planted as a wetland plant to treat wastewater cause the ??NO₃^--N?in low polluted water of Erhai watershed is less than 5 mg/L.?3?When hydraulic load impacting was 0.50 m3/?m2·d?,ROCWs effluent ??TN?and ??TP?can reach stable state within 10 days.And the time needed for ROCWs to reach stable state was less than NROCWs.When hydraulic load impacting was 0.75m3/?m2·d?and 1.00 m3/?m2·d?,the time had no different between NROCWs and ROCWs.?4?while the impacting last 1 d,the rejection rates of ROCWs to nitrogen and phosphorus were above 50% and 57% when hydraulic load impacting were 0.50m3/?m2·d?and 0.75 m3/?m2·d?,and rejection rates of nitrogen and phosphorus in ROCWs was 3²8% higher than NROCWs.The reduction of nitrogen and phosphorus in ROCWs was higher than that in NROCWs within 10 days after impacting.In summary,when regulated volume of ROCWs was 1/3 the volume of the effective volume of wetland,the impact load generated by rainfall runoff was less than 0.75m3/?m2·d?,and the impact time is less than one day,the removeal rate of nitrogen and phosphorus by ROCWs was more than 50%.?5?The economic generated by Ottelia acuminate during the experiment was3.95×104 yuan/?hm2·a?,Ottelia acuminate had good economic benefit.And rainfall impact process has little effect on the growth of the sea cauliflower,Ottelia acuminate can been chosen as wetland plant when treating low pollution water,but the maintenance of Ottelia acuminate during the wetland operation was necessary to make Ottelia acuminate occupy the absolute advantage in the wetland.