| Swine wastewater is an important aspect of agricultural non-point source pollution.Ecological wetland treatment of high load swine wastewater has the outstanding advantages of low cost and resource utilization.Because of the high concentration of swine wastewater,it is easy to cause wetland plant death if swine wastewater is discharged into ecological wetland directly.Therefore,taking appropriate measures to reduce the concentration of wastewater before discharged into ecological wetlands is of great significance to ensure the normal operation of wetlands.Based on this,the straw of wheat,corn and rice were selected as the experimental materials to construct the biological matrix treatment system.The removal effect of the main pollutant indexes such as ammonia and nitrous oxide emission was studied by field control experiment for one year.The removal effect and composition characteristics of nitrogen in different forms were investigated.The main conclusions of the experiment are as follows:1)matrix pool with straw material was significantly effective in removing COD and Nitrogen in different forms,but there was no significant difference in removal effect between different straw materials?P>0.05?.The effluent concentration of COD decreased from 1196.49-2962.28 mg·L-1 to 775.9-2167.03 mg·L-1.The effluent concentration of TN decreased from 419.47-877.65 mg·L-11 to 330.72-613.99mg·L-1.The effluent concentration of NH4+-N decreased from 189.73-683.89 mg·L-1to 148.25-437.60mg·L-1.The removal rates of COD,TN and NH4+-N reached25.1%,26.76%and 27.58%,respectively.For comparison of the three stalks,The removal effect of wheat straw on COD,TN and PN was relatively good,and the removal effect of straw on NH4+-N,NO3--N and DON was better,but the statistical difference of three kinds of straw materials did not reach the statistical significant level?P>0.05?.The change trend of total nitrogen and ammonia nitrogen removal rate was first increased,then fluctuation decreased and finally decreased steadily,and the removal rate decreased obviously after 5 months.2)the addition time of straw material can inhibit ammonia emission within 8months.after 8 months,the inhibition effect of straw material on ammonia emission is weakened,and the ammonia emission of matrix pool after 10 months is even higher than that of control group,but the difference of ammonia emission between different straw materials is not significant?P>0.05?.Ammonia volatilization is not the main nitrogen removal mode in the matrix pool of straw materials.Nitrogen removed in the form of ammonia volatilization during the period of validity of straw is 6%-31%of the system nitrogen removal,while the nitrogen lost in the form of ammonia volatilization in the control group accounts for about 65%of the system nitrogen removal during the whole period of the trial.3)Compared with the control?P<0.05?,the nitrogen oxide emissions of the three straw-treated matrix pools varied significantly.but the trend of the emissions was consistent.At the initial stage of straw material addition,the nitrous oxide emissions were higher at 263.17 mg·?m2·d?-1,and the emissions decreased after the first month and then slowly increased within the next 7 months,the emissions were significantly lower than the first month,and the nitrous oxide emissions increased significantly after 8 months.From the point of view of nitrous oxide emissions,the straw material supplement period shall not exceed 8 months.4)The removal rate of nitrogen decreased with the decomposition of hemicellulose,cellulose and lignin.The nitrogen removal rate,ammonia gas and nitrous oxide of different forms were obviously affected by water environment factors.5)The effect of straw material on nitrogen removal in water body and the effect of straw material on nitrous oxide and ammonia emission were synthesized.we can determine the supplement period of straw material is 4 and 5 months. |
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