Nitrogen and Phosphorus Removal Efficiency and Mechanism of Immobilized Bacteria Algae/aluminum Sludge

In aluminum sludge treatment, solid powder adsorbent is easily to be lost and difficult to be separated from the liquid wastewater. In this study, nitrogen and phosphorus removal efficiency from wastewater were investigated with simulated aluminum sludge, immobilized bacteria, immobilized algae/aluminum sludge, and immobilized bacteria algae/aluminum sludge. The results show that the combination of algae powder and aluminum sludge increased the specific surface area of the adsorbent and provided more adsorption sites for nitrogen and phosphorus. The maximum adsorption capacities for phosphorus by the algae/aluminum sludge in the ratios of 1∶10, 1∶5, and 1∶2 were 8.45, 10.06, and 6.68 mg·g^-1, respectively; these values were 2.41, 2.87, and 1.91 times higher, respectively, than those of aluminum sludge alone. The purifying effect of the immobilized bacteria algae/aluminum sludge (1∶5) on wastewater was better than that of aluminum sludge, immobilized bacteria, and immobilized algae/aluminum sludge (1∶5). The removal rates of chemical oxygen demand, total phosphorus, ammonia nitrogen, and total nitrogen by immobilized bacteria algae/aluminum sludge were 80.35%, 91.88%, 90.92%, and 92.51%, respectively. The removal of phosphorus by immobilized bacteria algae/aluminum sludge (1∶5) adsorbent mainly depends on the ion exchange and electrostatic interaction between the aluminum sludge and phosphate. The mass transfer of the immobilized rubber ball adsorbent provides excellent conditions for simultaneous nitrification and denitrification.