Phototrophic periphyton techniques combine phosphorous removal and recovery for sustainable salt-soil zone

The P (P-i as KH2PO4 and P-o as ATP) removal processes by phototrophic periphyton were investigated by determining the removal kinetics, metal content (Ca, Mg, Al, Fe, Cu, and Zn) of the solution and P fractions (Labile-P, Fe/Al-P, Ca-P, and Res-P) within the periphyton. Results showed that the periphyton was able to remove completely both P-i and P-o after 48 h when periphyton content was greater than 0.2 g L-1 (dry weight). The difference between P-i and P-o removal was the conversion of P-o into P-i by the periphyton, after that the removal mechanism was similar. The P removal mechanism was mainly due to the adsorption on the surfaces of the periphyton, including two aspects: i) the adsorption of PO43- onto metal salts such as calcium carbonate (similar to 50%) and ii) complexation between PO43- and metal cations such as Ca2+ (similar to 40%). However, this bio-adsorptional process was significantly influenced by the extracellular polymeric substance (EPS) of periphyton, water hardness, initial P concentration, temperature and light intensity. This study not only deepens the understanding of P biogeochemical process in aquatic ecosystem, but provides a potential biomaterial for combining phosphorous removal and recovery from non-point source wastewaters, especially around salt-soil zone. (C) 2016 Elsevier B.V. All rights reserved