Eliminating Nitrogen Load From The Ancient Canal In Yangzhou City By Active Zeolite Capping Technique

Sediment deposition is the deterioration of the major sources to cause pollution ofancient canal in Yangzhou City. Capping activite zeolite can not only inhibit the releaseammonia from sediment to overlying waterbody, but can eliminate part of the nitrogenload in the sediment. So, it is an effective way of control of internal pollution sources.In this study ancient canal in Yangzhou City acts as object of research, and activezeolite act as cover material, the feasibility of reducing nitrogen (N) load of ancientcanal in Yangzhou by active zeolite capping technique was investigated. This researchare mainly monitoring and discussing the water quality characteristic and regular ofancient canal in Yangzhou City. Meanwhile, analyze influence factors such as grainsize, ammonium concentration, temperature and pH on ammonia nitrogen adsorptionby zeolites; discuss the effect of bacterial strain, zeolite dosing, DO and nitrogen loadon eliminating sediment nitrogen pollution load. Finally, the optium conditionsincluding bacterial strain, zeolite dosing, DO, nitrogen load were obtained. Based onthe optium conditions, a field experiment was carried out in ancient canal in YangzhouCity to investigate elimination nitrogen load by active zeolite capping layer. The mainexperimental results are as follows:1) The result shows that concentration of chlorophyll is varying from4μg/Lto41μg/L of ancient canal in Yangzhou. The result indicated the water quality ofancient canal presents the trend of eutrophication.The average concentration of totalnitrogen (TN) is1.67mg/L in winter, autumn and spring (total160days), and nitrogenretention is0.05g/(m~2.d). However, total nitrogen concentration reachs to5.38mg/L in summer (total90days). The corresponding nitrogen retention is0.32g/(m~2.d).This data of ancient canal is at the same range as the Rzeszów Reservoir in Poland(0.18g/(m~2.d)-0.5g/(m~2.d)). In addition, the results indicate that85.8%of totalnitrogen comes from release of sediment.2) The ammonia adsorption of zeolite is effect by zeolite size and initialconcentration of ammonia nitrogen. The smaller zeolite particle size is，the faster rateto absorb ammonia nitrogen. The adsorption can quickly attent to balance. Whendosing of zeolite was set constant, the higher concentration of ammonia nitrogen, theadsorption capacity of zeolite is greater. The relationship between adsorptive capacityand ammonia nitrogen concentration is linearity, equation is y=0.0122x+4.5291, R~2is0.9733. When ammonia nitrogen concentration was set constant, the less zeolite is, themore adsorption capacity of zeolite does. Adsorption capacity of zeolite has arelationship with zeolite number in water body, the relation formula is y=-3.50790ln(x)+4.5291, R~2is0.9929.3) After capping active zeolite inoculated strain A separated from lake sediment,the eliminating efficiency of TN load of the overlying water, TN load of sediment andammonium concentration of pore water in sediment reach to75.2%、16.4%and21.6%.However, after capping active zeolite inoculated strain B, the correspondingeliminating efficiency are75.2%、16.4%and21.6%. The results indicated that strain Ais superior bacterial strain to remove nitrogen load.4) When active zeolite dosing increased at the range from1kg/m~2to3kg/m~2,removal efficiency of nitrogen load is at the range from22.0%to7.9%in the overlyingwater, and the corresponding data is at the range from22.6%to31.0%in the sedments.The eliminating nitrogen loads (from0.32g/(m~2.d) increased to0.44g/(m~2.d))are higher than the nitrogen retention load (0.32g/(m~2.d)). It shows that nitrogenpollution can effectively control when the coverage density of activite zeolite aregreater than1kg/m~2. In addition, we found that85%~96%of TN were eliminatedthrough the biological way, and the biological transform is the main way of eilimatingnitrogen load in active zeolite layer.5) When DO concentration is below1mg/L, the removal efficiency of totalnitrogen is50.5%in the overlying water. When DO concentration is up to1.5mg/L ~5mg/L, the removal efficiency of total nitrogen is75.2%in the overlying water. Theremoval efficiency of nitrogen load enhanged24.7%.6) When nitrogen retention load increased from0.04g/(m~2.d) to0.66g/(m~2.d), the eliminating nitrogen load decreased from0.44g/(m~2.d) to0.09g/(m~2.d) after capping active zeolite.The results indicate active zeolite layer is noteffective to eliminate nitrogen load under high nitrogen retention load.7) A field experiment, the test area is0.785m~2, water volume is1413liters, wascarried out in ancient canal in Yangzhou City to investigate elimination nitrogen loadby2kg/m~2active zeolite capping layer. The results indicated that the eliminatingefficiency of nitrogen load in overlying water and sediment and reach to35.2%,11.33%, respectively.