(594c) Development of Waste Water Treatment Process with Sorbents Derived From Waste Concrete Sludge

Sorbents for ion removal in waste water derived from waste concrete were developed and their ion removal performances were investigated. The waste concrete sludge is a slurry mixture of cement, aggregate and an industrial waste generated from concrete-using industry such as building. Because waste concrete sludge is rich in calcium components, it can be used as a low-cost material for preparing sorbents potentially applicable to waste water treatment processes

After adding or removal some components in the concrete sludge, the slurry was dehydrate and dried to form solid sorbents. The ion removal performances of the sorbents were examined with simulated waste water. A sorbent with partially extraction of calcium component showed an excellent capture performance for phosphorous ions in water. This result indicates that the sorbent can be applied for the recovery of phosphorus from waste water effluents. The obtained product is composed of hydroxyapatite (HAP), and it showed an excellent sorption performance with heavy metal ions such as lead, cadmium.  The sorbent itself also showed an excellent removal performance for boric ions: in this case boric ions can be captured with the formation of ettringite crystal in the sorbent upon mixing with water. The ettringite-containing sorbent can be prepared from the waste concrete sludge by adding aluminum sulfate. The obtained sorbent showed a high removal performance for anions such as boric ions and fluoride ions. Furthermore, the calcium content could be used for fixation of carbon dioxide in the form of calcoum carbonate: an altanate process of carbon sequestration.