Immobilization Of Heavy Metals And Flue Gas Control For The Process Of Bricks-making Using Wastewater Sludge

With the development of urbanization, huge amount of sludge is produced in municipal sewage treatment. Currently, sludge is disposed by incineration in most developed countries while developing countries mainly use the methods such as landfill and composting which may cause secondary pollutions. Nowadays, sludge utilization into the construction field is widely researched. Plenty of investigations showed that building materials with sewage sludge could still conform to the required standard and the heavy metals were solidified. However, different content of sludge may result in the change of waste gas components and solidification rate of heavy metals.This project focused on the content of the heavy metal in sludge, leaching rate of heavy metals in sintering bricks and the control of waste gas in process of bricks-making mixed with sludge of a brick company in Xiaoshan.After filter pressing, the moisture content of sludge decreased from80%to50%, and the arsenic concentration exceeded42.1%-, showing that the sewage sludge can’t be discharged directly. Leaching experiments of porous sintered bricks in neutral, acidic and alkaline solution respectively showed that Cr, Cu, Zn, As and Pb had been solidified into bricks stably.With large amount of water vapor, dust and some inorganic and organic gas, the waste gas was passed through washing spray, the plasma treatment and bases-oxidant absorption treatment. More than90%of inorganic contaminants had been removed after two alkaline washing processes. The terminal concentration of VOCs was only40.73mg/m3, which met the national discharge standards. Meanwhile, more water in waste gas resulted in a lower organics removal efficiency of plasma treatment (2.6%) than that by washing (4.41%). After adding hydrogen peroxide to remove organics in washing process, the organics removal efficiency increased from3.83%to16.29%. Meanwhile, the odour met the national discharge standards with a decrease from7413to1318. As the waste gas with complex composition and difficult processing has never been successfully controlled in the country, it can be a beneficial exploration of waste gas control for this research.