Effects of ions and phosphates on alkaline phosphatase activity in aerobic activated sludge system

The influence of metal ions, anions, ortho-phosphate, polyphosphate and organic phosphorus on the activity and kinetics of alkaline phosphatase in aerobic activated sludge taken from a local municipal wastewater treatment plant was investigated. Results suggested that there were three impact models of heavy metals on alkaline phosphatase activity (APA) and most inorganic anions were relatively innocuous at concentrations from 0 to 5.0 mM. However, phosphorus especially pyrophosphate had an inhibitory effect on APA, since the residual activity of alkaline phosphatase dramatically decreased to 34.8% of the control at the pyrophosphate concentration of 5.0 mM. The inhibition of Cu2+ on alkaline phosphatase was described satisfactorily by an uncompetitive type at low concentrations, but a mixed of noncompetitive–uncompetitive type at high concentrations. The inhibition of ortho-phosphate was found to be of the competitive type. Vmax/Km ratio is a good indicator for the catalytic efficiency of alkaline phosphatases in wastewater.