| The land use of sludge is a good resource utilization method to solve its problem of huge production.The sludge needs to be harmlessly treated to meet the standards for disposal of sludge from municipal wastewater treatment plant-quality of sludge used in land improvement.The effect of sludge as soil improvement is remarkable,which can solve the problem of sludge digestion and improve the structure of barren soil.The addition of harmless sludge will affect the soil quality and aggregate structure in many aspects.First,soil samples A and B were selected for modification and the properties of soil aggregate stability under different soil sample types were studied.Different types of compound soil samples were obtained by controlling four representative influence factors,including particle grading,p H,inorganic salts and organic matter.Experimental results showed that: The stability of aggregate was related to the particle size distribution.The water stability aggregate of 5.0-2.0mm particle was as high as 70.0%,and the cohesion of fine-grained group was larger,the maximum value was 20.14 k Pa.The p H value of soil samples polluted by acid and alkali ranged from 5.5 to 9.9.The p H value of soil would change under strong pollution environment,which would lead to the loss of inorganic salt nutrients and the weakening of adhesion between particles.The content of soil water stability aggregates reduced,and the maximum reduction was 8.34%.As the soil samples became fragile and easy to compress,the measured cohesion increased.Inorganic salt and its hydration made the content of water stable aggregates decrease,and the maximum reduction was 7.86%.Aggregates were easy to be broken and the cementation of soil particles were weakened.Polyacrylamide(PAM)and organic liquid fertilizer were two good organic cements,which could improve the structure of soil aggregates.When the concentration of organic liquid fertilizer was 1.0%,water stability aggregates of soil sample A could be increased from 10.84% to 48.28%.The maximum cohesion of soil samples A and B under the action of organic cement were 18.81 k Pa and 19.12 k Pa respectively.Considering both effect and cost,the improvement effect of organic liquid fertilizer was better,but the application amount should not be too large.Through multiple linear regression analysis of the aggregate stability of soil samples,the mathematical model between the aggregate stability indexes and four influence factors were obtained.The results showed that the order of the effect on the water stability of large aggregates was non-uniform coefficient > organic matter >inorganic salt > p H.The order of the effect on cohesion was p H > organic matter >inorganic salt > non-uniform coefficient.The indexes of soil water stability and mechanical stability could be predicted by detecting the easily measured physical and chemical indexes of soil.The mathematical model was used to guide the experiment of sludge mixed with sandy soil.Mixed compost sludge,dried sludge and carbonized sludge with sandy soil at 5%-30% respectively.The results showed that with the increase of sludge addition,the p H value decreased obviously.The conductivity and organic matter increased.The content of water stable aggregates increased and the water stability came from the solid particle size and the agglomeration of sludge.The cohesion of soil sample increased.When the sludge addition was 30%,the cohesion of the compost sludge compound soil was 10.97 k Pa,which was the closest sample to the planting soil level.Comparing the measured values of water stable aggregates and cohesion with the predicted values of the model,the absolute value of error was between 0.55% and 29.57%,the prediction of mathematical models was relatively accurate. |
PDF Full Text Request