Experimental Study On Nitrogen Removal From Farmland Drainage Water Using A Rice Husk Bioreactor

Excessive application of chemical fertilizers in agricultural production activities,discharged into the surface and underground water bodies by precipitation or irrigation,become an important source of agricultural nitrogen pollution and cause harm to regional ecological environment.How to reduce the nitrogen pollution of farmland drainage through ecological engineering measures is of great significance for ensuring agricultural production and protecting ecological environment.In this paper,the effect of nitrogen removal in a biological reactor filled with lice husk was studied by laboratory experiments.According to the characteristics of the bioreactor treatment system,an experimental device was constructed to simulate the nitrogen removal capacity of the system by using rice husk as the filling material and a water distribution tank to simulate the outflow in the field.The experiment involves static and dynamic flow processes.During the experiment ambient temperature stability between 20?30?,three concentration levels were set up as high(20 mg/l),medium(10 mg/1),low(3 mg/1),hydraulic process and the change of the inflow concentration were monitored,main findings are:(1)During the static water test,the nitrate reduction rate has nothing to do with the inflow nitrate concentration.The average nitrate reduction rate and the nitrate reduction concentration in the static reaction under the three conditions of water concentration less than 20mg/l are 77.1%and 0.11mg/(l·h)respectively.In the dynamic water test with the increase of the inflow rate,the nitrate reduction rate decreased.When the inflow concentration was less than 22mg/l,the nitrate rate of the bioreactor system ranged from 51.8%to 87.62%,and the average nitrate reduction concentration was 1.03 to 1.82mg/(1·h).(2)During the whole experiment,the dissolved oxygen showed a decreasing trend during the reaction,and the concentration of dissolved oxygen after the reaction ranged from 0.03 to 0.8mg/l.The REDOX potential changed from positive to negative,ana the reaction range was-132.6?-269.5mv.PH decreased slightly,and the reaction range was 5.06?6.92,showing weak acidity.2)during the whole experiment,the dissolved oxygen showed a decreasing trend during the reaction,and the concentration of dissolved oxygen after the reaction ranged from 0.03 to 0.8mg/l.The REDOX potential changed from positive to negative,and the reaction range was-132.6?-269.5mv.pH decreased slightly,and the reaction range was 5.06?6.92,showing weak acidity.(3)The nitrate-nitrogen degradation process of the rice husk bioreactor system was analyzed in this experiment,and the denitrification reaction kinetics of the system was simulated on the basis of the first-order kinetic model.Reaction kinetics simulation was applied to the experimental field along the canal irrigation area in Jiangdu district,Yangzhou city.The simulation results showed that the rice husk bioreactor could reduce the nitrate nitrogen in the outlet by 80%,and the nitrate nitrogen concentration in the experimental field ranged from 0 to 1.81mg/l after the reduction.It has certain reference significance for the further research of bioreactor system.