Study on Intercepting Method for Nitrogen and Phosphorus in Ecological Ditches and Pond

[Objective] The research aimed to reduce emission load of the farmland runoff by using ecological ditches and pond. [Method] N and P intercepting project construction of the ecological ditches and pond in Zhaiji Village, Xiangcheng District, Suzhou City as research object, by repairing 1 834 m3 of original drainage ditches, newly excavating 6 800 m2 of ecological main ditches and 6 000 m2 of artificial purification ecological pond, etc., runoff emission load in real control area of the project was counted. [Result] Annual net loads of the runoff emission for TN and TP were respectively 2 552.22 and 95.00 kg in 33.3 hm2 of farmland. Annual runoff intercepting loads of TN and TP were respectively 1 225.07 and 50.35 kg in ditches. Annual runoff intercepting loads of TN and TP were respectively 1 327.15 and 44.65 kg in ecological pond. In effluent, TN concentration was 6.32 mg/L and was smaller than 15 mg/L. TP concentration was 0.25 mg/L and was smaller than 0.5 mg/L. They both reached level-one A discharge standard. [Conclusion] The research provided theoretical basis for effective control of the agricultural non-point source pollution in Taihu Lake basin.

Study on the Effects of Nitrogen and Phosphorus Absorptionby Ecological Ditches

By using the simulated ditch experiment,the differences of nitrogen and phosphorus absorption capacities of 9 aquatic plants were studied,and the better varieties of nitrogen and phosphorus absorption capacity were selected to construct the ecological ditch and oxidation pond to study the nitrogen and phosphorus absorption effect.The results showed that the nitrogen and phosphorus residues in the simulated ditch water were signi ficantly reduced after planting aquatic plants.The biomass of Canna glauca,Myriophyllum elatinoides,Sorbaria sorbifolia,Pontederia cordata and Zizania was high,and the uptakes of nitrogen and phosphorus were high.Among them,the effect of planting Canna glauca and Myriophyllum elatinoides was the best.The concentration of nitrogen and phosphorus in farmland drainage decreased signi ficantly after being absorbed by aquatic plants in ecological ditches;the concentration of total nitrogen,soluble nitrogen and total phosphorus in main ditches decreased by 39.6%,40.1% and 36.9% respectively on average;the concentration of total nitrogen,soluble nitrogen and total phosphorus in branch ditches decreased by 6.6%,10.3% and 13.6% on average.The concentration of total nitrogen and total phosphorus in the oxidation pond could be further reduced by 17.7%and 13.3%.Ecological ditches can effectively intercept nitrogen and phosphorus in water,and have good ecological benefits of purifying water to obtain improved water quality.

Nitrogen and Phosphorus Pollutants Removal from Rice Field Drainage with Ecological Agriculture Ditch: A Field Case

Excessive nitrogen and phosphorus in agricultural drainage can cause a series of water environmental problems such as eutrophication of water bodies and non-point source pollution.By monitoring the water purification effect of a paddy ditch wetland in Gaochun,Nanjing,Jiangsu Province,we investigated the spatial and temporal distribution patterns of N and P pollutants in paddy drains during the whole reproductive period of rice.Then,the dynamic changes of nitrogen and phosphorus in time and space during the two processes of rainfall after basal fertilization and topdressing were analyzed after comparison.At last,the effect of the ditch wetland on nutrient purification and treatment mechanism,along with changing flow and concentration in paddy drains,was clarified.The results of this study showed that the concentrations of various nitrogen and phosphorus in the ditch basically reached the peak on the second and third days after the rainfall(5.98 mg/L for TN and 0.21 mg/L for TP),which provided a response time for effective control of nitrogen and phosphorus loss.The drainage can be purified by the ecological ditch,about 89.61%,89.03%,89.61%,98.14%,and 79.05%of TN,NH4+-N,NO3−-N,NO2−-N,and TP decline.It is more effective than natural ditches for water purification with 80.59%,40%,12.07%,91.06%and 18.42%removal rates,respectively.The results of the study can provide a theoretical basis for controlling agricultural non-point source pollution and improving the water environment of rivers and lakes scientifically.