加气对水肥混合液细小泥沙絮凝沉降的影响

Effect of aeration on flocculation and sedimentation of finesediment in water fertilizer mixture

为探明加气对水肥一体化滴灌管网中泥沙沉降能力的影响,配置6种粒径泥沙和3种类型肥料(硫酸钾肥、复合肥、尿素,质量分数均为1.0%)组合的浑水,测定3种水流剪切强度(0,1.38和4.67 s^(-1))条件下加气前后的浑水浊度、泥沙中值沉速和沉降泥沙中值粒径.结果表明:加气加速水肥混合液中细小泥沙的絮凝沉降,尿素水肥混合液加气后泥沙中值沉速增幅最大,硫酸钾肥次之,复合肥最小,分别比未加气处理最高增加89.27%,52.74%和45.63%;加气加速泥沙絮凝沉降的作用随泥沙粒径的减小而增大,加气显著促进中值粒径D≤31μm泥沙的絮凝(P<0.05),沉降泥沙粒径较未加气处理增大3.22%~21.99%,加气显著加速中值粒径D≤53μm泥沙的沉降(P<0.05),中值沉速较未加气处理提高23.96%~89.27%;水流剪切强度越大,加气促进泥沙沉降的作用越小,当水流剪切强度小于4.67 s^(-1)时,加气处理的泥沙中值沉速比未加气处理显著提高9.38%~89.27%(P<0.05).泥沙粒径、肥料种类、水流剪切强度和加气处理相互作用,显著影响浑水泥沙的絮凝沉降,建议水肥气混合液滴灌时应定期冲洗灌溉管网,以减少沉降泥沙.

In order to explore the influence of aeration on the sediment sedimentation capacity in the water and fertilizer integrated drip irrigation pipe network,muddy water with a combination of sediment of six particle sizes and three types of fertilizers(potassium sulfate fertilizer,compound fertilizer and urea,mass fraction of 1.0%)was configured.The turbidity of muddy water,the median settling velocity of sediment and the median particle size of settled sediment before and after aeration were measured under three kinds of flow shear strengths(0,1.38 and 4.67 s^(-1)).The results show that aeration acce-lerates the flocculation and sedimentation of fine sediment in water fertilizer mixture.After aeration of urea water fertilizer mixture,the increase of median settling velocity of sediment is the largest,followed by potassium sulfate fertilizer,and the compound fertilizer is the smallest,which increase by 89.27%,52.74%and 45.63%respectively compared with non-aeration treatment.The effect of aeration on flocculation and sedimentation of sediment increases with the decrease of particle size of sediment.Aeration significantly promotes the flocculation of sediment with median particle size less than 31μm(P<0.05),and the particle size of settled sediment increases by 3.22%-21.99%compared with that of non-aerated treatment.Aeration significantly promotes the sedimentation of sediment with median particle size less than 53μm(P<0.05),and median settling velocity is 23.96%-89.27%higher than that of non-aerated treatment.The greater the flow shear strength,the smaller the effect of aeration on sediment settlement.When the flow shear strength is less than 4.67 s^(-1),the median settling velocity of aerated treatment is significantly higher than that of non-aerated treatment by 9.38%-89.27%(P<0.05).The interaction of sediment particle size,fertilizer type,flow shear strength and aeration treatment significantly affects the flocculation and sedimentation of muddy cement sand.It is suggested that the irrigation pipe network should be washed regularly during drip irrigation of water fertilizer gas mixture to reduce the sedimentation sediment in the pipe network.