N and P removal from pond effluent with three hydrophytes.

In order to investigate hydrophyte role on the purification of pond effluent which was eutrophic,three hydrophytes(Phragmites communis Trin.,Ceratophyllum demersum and Trapa quadrispinosa Roxb.) were grown in treated water and as a none-plant to compare effectiveness of nutrient removal.It can be concluded that all the hydrophytes had a good performance on removal nutrients from treated water rather than without hydrophyte.After growing the three hydrophytes 50 days,the total nitrogen(TN) was removed by P.communis Trin.(80.8%)T.quadrispinosa Roxb.(62.6%)C.demersum(34.4%).The total phosphorus(TP) was removed by P.communis Trin.(73.2%)C.demersum(27.1%)T.quadrispinosa Roxb.(17.2%).P.communis Trin.and C.demersum grew better in pond effluent than that of T.quadrispinosa Roxb.during experiment period.The average livability of P.communis Trin.and C.demersum reached up to 85% and 60%,respectively.However,T.quadrispinosa Roxb.only kept under 45%.For the three hydrophytes growing under the same condition,P.communis Trin.was the most effective hydrophyte for TN and TP removal,T.quadrispinosa Roxb.was next for TN removal.However,C.demersum was better than T.quadrispinosa Roxb.for TP removal.