Study On The Law Of Water Transport And Evaporation In Composite Medium During The Process Of Sludge Improves Sand

Up to now,sludge of municipal wastewater treatment plants in our country can not be treated reasonably,sludge utilization ratio is low,and the secondary pollution problem of environment is becoming more and more serious.At the same time,China is one of the countries with serious desertification,which brings up to 5 billion economic losses every year.In recent years,more and more attention has been paid to sludge treatment and desertification soil control.This study is based on the concept of environmental protection,which is "Treating waste with waste and treating sediment together".In order to investigate the effect of centrifugal dewatering sludge as a soil modifier in municipal domestic sewage treatment plant on the restoration of wind-eroded sandy soil,taking the water infiltration ability,soil saturated moisture content,soil water retention capacity and soil moisture evaporation as the indexes,the best "sludge-sand" mixing ratio and the best water-retaining layer were selected.And simulated by Hydrus-1D soil moisture simulation software,contrast analysis with laboratory data.It provides a theoretical basis for the optimal selection and accurate control of the mixing ratio,mixing depth and plant irrigation cycle in the application of sludge control engineering,and also provides technical guidance for the soil remediation project of the same type of desertification.Therefore,this study has certain theoretical significance and engineering demonstration value.(1)In the experiment of rainfall leaching,it is found that the infiltration time is the shortest,the maximum infiltration time is 30%and 50%,and the infiltration rate is slow when the mixing ratio is 10%.The water wetting front curve and power function S=atb degree of each blending ratio are higher than that of time,and the determining parameter R2 is larger than 0.99.The order of soil water accumulation infiltration was:10%(54.15cm)>15%(47.12cm)>20%(40.80cm)>sandy soil(34.97cm)>30%(23.10cm)>50%(12.68cm).The empircal formula of Kostiakov infiltration has the best fit for the results.In the experiment of soil moisture content and water redistribution in different mixing ratio of sludge and sandy soil,the saturated water content and soil water retention performance are analyzed.The best choice is the mixed soil with 20%ratio of sludge to sandy soil.The soil layer with the best water retention is 4#and 5#(40-60cm).(2)In the evaporation experiment of mixed soil with different mixing ratio of "sludge-sand",it is found that the proportion of sludge is the larger,the decrease of moisture content is the smaller.In the process of cumulative evaporation changing with time,the order of cumulative evaporation from large to small was:50%(0.580kg)>30%(0.540kg)>0(0.530kg)>10%(0.475kg)>15%(0.465kg)>20%(0.450kg);In the experiment,the relationship between cumulative evaporation E(kg)and test time t(h)was fitted.It accords with the power function E=atb;Among the three parameters of ?E?R and Ri,the composite soil with 20%sludge and sand mixing ratio had the smallest value,indicating that the composite soil could inhibit soil water evaporation more effectively and retain water best.(3)With known soil particle composition,the soil water characteristic curve can be predicted by Hydrus-1D software,and the basic soil properties parameters such as residual water content(?r),saturated water content(0s),reciprocal air intake value(a),pore size distribution index(n),hydraulic conductivity(Ks)can be obtained,Which provide a theoretical parameter basis for the subsequent simulation of soil water infiltration and redistribution.According to the comparison between the measured and simulated water infiltration curves in 0-30min,the Hydrus-1D software is feasible in simulating the water infiltration in sandy soil and 20%mixed soil.According to the comparison between the measured and simulated curves of soil moisture redistribution after 60min,the Hydrus-ID software for simulating soil water redistribution neglects the marginal effect of the device and the capillary action of each soil layer.