Research On Tannery Sludge Solidification,pollutant Release Inhibition And Building Materials Technology

The treatment and disposal of tannery sludge is difficult because it contains a large amount of pollutants such as organic matter,heavy metals,ammonia nitrogen and salts.The use of tannery sludge as building materials can not only achieve the purpose of sludge treatment,but also enable sludge to be utilized as a resource.This is an ideal method for treating tannery sludge.In this research,sludge unburned aggregates were prepared by adding such as cement,sodium silicate,quicklime,plaster of paris,calcium magnesium phosphate fertilizer and zeolite powder to tannery sludge,and then they could replace gravel to produce concrete unburned bricks,which solves the problems of low strength and a large amount of pollutant leaching when tannery sludge is directly mixed with solidified materials.This provides a new idea and a feasible method for the utilization of sludge as a building material.The main conclusions are as follows:(1)Through single mixing experiment,orthogonal experiment and range analysis,it is preliminarily determined that the proportion(percentage of the mass of tannery sludge)of solidified tannery sludge to prepare sludge unburned aggregates is: cement,15%;sodium silicate,4%;quicklime,5% and plaster of paris,4%.(2)On the basis of the preliminarily determined ratio,calcium magnesium phosphate fertilizer and zeolite powder were separately chosen to replace 20% and30% of cement as the improved ratio.The strength and pollutant release inhibition ability of the modified sludge unburned aggregates can be improved.The improved ratio with the utilization of zeolite powder can significantly reduce the leaching concentration of total chromium,ensuring it is lower than the limit value of“Integrated Wastewater Discharge Standard”(GB 8978-1996).XRD pattern analysis shows that the main crystal phases of sludge unburned aggregates prepared with different ratios are ettringite,calcite and quartz.Struvite was found in the sludge unburned aggregates sample prepared with improved ratio of calcium magnesium phosphate fertilizer.(3)Sludge unburned aggregates which prepared with improved ratio of zeolite powder were used to replace gravel to prepare concrete unburned bricks.The increase of the replacement ratio of sludge unburned aggregates could reduce the density and compressive strength of concrete unburned bricks,and increase the water absorption,moisture content and pollutant leaching concentration.When the replacement ratio of sludge unburned aggregates does not exceed 50%,the physical properties of concrete unburned bricks can meet the requirements of “Concrete Solid Bricks”(GB/T 21144-2007).(4)The soaking of concrete unburned bricks in simulated acid rain for 35 days could reduce its strength.The higher the replacement ratio of sludge unburned aggregates is,the more the strength decreases.Simulated acid rain could increase the leaching concentration of pollutants such as chemical oxygen demand(COD),total chromium,ammonia nitrogen,total nitrogen and total phosphorus in concrete unburned bricks,but the leaching concentration is not significantly increased compared with the blank groups.When the replacement ratio of sludge unburned aggregates does not exceed 50%,the leaching concentration of pollutants in concrete unburned bricks can meet the corresponding standards.