Research On The Behavior And Removal Mechanism Of Phosphorus In Wetland

The constructed wetland has a high removal efficiency of phosphorus. But the researches of this technology were not embedded and systemic. Particularly, the researches has just begun in our country, the present condition affect the application and expansion of this technology in our country.Two vertical flow constructed wetland unit were build in order to research the removing effect of phosphorus from laboratory domestic wastewater in this article. One plant reed, another plant nothing at the earlier stage of the experiment, the high removal efficiency of phosphorus from the reed unit was studied. Then the two unit plant Grassleaf Sweetfalg Rhizome and Canna generalis for each other, the effect of hydraulic load, inflow water TP and COD concentration, hydraulic retention time, dry and wet changes, season changes, pH value on TP removal efficiency were investigated. The behavior and removal mechanism of phosphorus in wetland had also studied.When the hydraulic load is 0.15m~3/m~2·d, the reed unit achieved the best TP removal efficiency 92%, TP concentration of outflow was 0.39 mg/L, the blank unit TP removal efficiency and TP concentration of outflow was 0.96 mg/L and 78.81%, 67.35% and 31.13% of total phosphorus were removed depend on the upper filler for reed and blank unit, respectively.The TP removal efficiency became worse with the hydraulic load increase for both Grassleaf Sweetfalg Rhizome and Canna generalis unit when the inflow TP concentration was 3-7mg/L. When the hydraulic load was 0.15m~3/m~2·d, both unit TP removal efficiency can get 90%, outflow TP concentration <0.6mg/L, but The TP removal efficiency would drop to 73.3% and 77% or 57% and 63.3% for TP concentration of inflow was 4mg/L or 7mg/L at the hydraulic load 0.3m~3/m~2·d,the outflow TP concentration would increase fast and TP removal efficiency would drop fast when the hydraulic load 0.20 -0.30m~3/m~2·d compared to 0.10-0.20m~3/m~2·d.The outflow TP concentration of the two units were<1mg/L on the condition that inflow TP concentration<4mg/L. The highest TP removal efficiency attained at the inflow TP concentration was 6mg/L or 4mg/L on the condition that hydraulic load <0.2m~3/m~2·d or >0.2m~3/m~2·d.When hydraulic load 0.2m~3/m~2·d, inflow TP concentration 6mg/L,the TP removal efficiency can get 85% for both unit.The TP removal efficiency became worse with the consecution circulate. After consecution circulate a week, the two unit's TP removal efficiency descend from 89.4% to 85.2% and 91.3% to 83.0%,but after two days cease work, TP removal efficiency recover to 89.2% and 88.6% ,respectively. More and more TP would removed by the upper filler, but less for the lower filler when the unit consecution circulate.The two unit's TP removal efficiency were 88.3% and 92.0% in the middle of August, but 81.5% and 82.3% the lowest in the middle of December, respectively, motion range <10%.The two unit's outflow TP concentration were 0.73-1.58mg/L and 0.62 -1.47mg/L when the inflow TP concentration and pH value were 5.87-6.13mg/L and 5-9.The best pH value for TP removal efficiency was 7-8.When pH value 8, the best TP removal efficiency were 87.9% and 89.7% for the two unit, respectively.