Study On The Utilization Of Urban Sewage Sludge As Ceramic Tiles Material And Waste Landfill Liner

Refer to processes of common ceramic tile production, outdoor ground tiles made from dehydrated wastewater treatment sludge were produced on bench scale, and the feasibility was explored through measuring their compressive strength and evaluating main strength influencing factors. The results showed that the compressive strength of the sintered tiles decreased as the sludge contents increased, and the optimum recipe was suggested as kaolin: sludge: feldspar powder = 4:1:2. It was found that tiles made from sludge with fine particles (diameter is less than 0.15mm) were denser and its compressive strength was greater than the tiles made from sludge with coarse particles (diameter is between 0.15mm and 0.63mm). Molding condition of had great influence on compressive strength of sintered tiles whose compressive strength increased as the water content and shape-forming pressure increased. Suitable water content and shape-forming pressure ranged 9%-15% and 24MPa-45MPa, respectively, holding 2h to benefit fully physicochemical reaction of stock was suggested. Further, the sandwich structure was better than single structure in enhance tile's compressive strength: the compressive strength of tiles with the sandwich structure and final particle sludge was 27.38MPa while the strength of tiles with the sandwich structure and coarse particle sludge was 23.70MP. The strength of the two kinds of tiles respectively meet the strength grade of MU25 and MU20 in"Sintered Brick Strength Grade(GB5101-93)".The flexural strength and influencing factors were tested to further explore and confirm the component recipe and processing parameter of the sludge tiles. The composition analysis, water absorption, compressive strength, flexural strength, abrasion-resistance strength, corrosion resistance were examined to comprehensively evaluate the nature of sludge tiles. Corrosiveness of leaching liquid from the tile and the efficiency of heavy metal sealing in the tiles were also tested to estimate the environmental impacts if applied practically. The results showed that the optimum water content and sintered temperature were 11% and 1200℃, respectively. With the sludge content increased, the compressive strength of the sludge-tile dropped rapidly though flexural strength increased slightly, the optimum sludge content was proposed as 14.3%. The tiles made from fine particle sludge were denser and overall nature was better than that made from coarse particle sludge, indicating decrease of the sludge particle size could enhance the strength of tiles. With the 14.3% sludge content, the compressive strength of tiles made of fine particle sludge and coarse particle sludge meet the strength grade of MU30 and MU20, respectively. The flexural strength of the sludge tiles was much greater than that of common bricks. The mineral compositions of tiles body were greatly changed after sintering. The sintered tiles can be classified as clay-pottery, and it was found that abrasion-resistance property of the sludge tiles was better than common bricks and the tiles could meet the requirements to resistant chemical attack. The leaching liquid from sludge tiles was almost no corrosive for it's pH varied between 6.4 and 6.9, and the heavy metals Cu and Mn containing in sludge could be well sealed up in the tiles.Anti-permeate experiments had been performed to evaluate the possibility of using urban sewage sludge to substitute the compound clay as the major constituent for liner material in waste landfill. It was found that anti-permeability could strengthen with the dry density increasing, and the optimal content of the sludge was 40%. At the optimal content and 1.08 g/cm3 dry density, the permeating coefficient of compound clay reaches 10-7cm/s level which meets the criterion of liner material in waste landfill. The property of permeating liquid could greatly affect the permeating coefficient of the sludge liner, the permeating coefficient of the liner increased with as the concentration of electrolyte increased. The sludge liner clay could also absorb its bearing Cu2+,Zn2+ effectively.Permeability resisting experiments had been performed for composite of urban sewage sludge and Kaolin with addition of solidifying enzyme TZ. It was found that though the enzyme TZ had little effect on the optimum moisture content of the composite which was about 20%, the initial permeability resistance of the composite was well improved. Comparing permeating coefficient of the enzyme added composite (0.4mL/10kg composite) pre-molded at 300kPa with that of the non-enzyme added composite, the permeating coefficient of the enzyme added composite decreased by 36% after adding enzyme for 24h, and reached 10-7cm/s level which meet the criterion for the anti-permeable liner material of landfill.The make use of urban sewage sludge as tiles and liner material in waste landfill was feasible.