Metal Toxicity on Phosphate Removal in Pure Culture and in Activated Sludge Systems

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Abstract
Environmental factors, operational conditions, and wastewater characteristics may aifect phosphate removal capability without impairing organic substrate utilization. Thus, these factors must be considered for successful biological phosphate removal from wastewater. Metal toxicity on phosphate removal in chemostat studies of Acinetobacter species, in batch activated sludge, and sequencing batch systems was investigated in this study. At a Zn(II) concentration of 10 mg/L, phosphorus content in cell mass was reduced from 3.2‐4.8% of the control system to 2.0‐2.8%, depending on the dilution rate in Acinetobacter continuous culture studies. In a batch activated sludge system, 20 mg/L Zn reduced phosphorus uptake from 23‐16 mg/L. In a sequencing batch system, addition of 10 mg/L Zn inhibited phosphate removal after 14 days of continuous Zn addition. In all cases, COD utilization was not affected. Thus, in comparison with oxidative enzymes, the enzymes responsible for the formation of polyphosphate granules are more sensitive to Zn toxicity. Since they exhibit high phosphate uptake during the log‐growth stage, the use of Acinetobacter species to detect compound toxicity on phosphate uptake is recommended.