Treatment of partially hydrolyzed polyacrylamide by mixed bacteria isolated from wastewater

In this work, a mixed strain which could degrade hydrolyzed polyacrylamide (HPAM) was constructed based on SS5 and SS6 isolated from two wastewater samples. SS5 is a globular gram-negative bacterium, and SS6 is a rod-shaped gram-negative bacterium. Moreover, SS5 and SS6 were identified as Acinetobacter sp. and Pseudomonas sp., respectively. The removal performance of the mixed strain was optimized using single-factor experiment and response surface methodology. The maximal HPAM removal efficiency 29.78% was observed at pH 7.5, 35 degrees C, 170 rpm rotation speed, and inoculum loading 3% (v/v) for 7 days. The optimal concentrations of nutrients were 0.32 g/L glucose, 0.21 g/L NaNO3, 2.10 g/L KH2PO4-K2HPO4, and the HPAM removal efficiency reached 45.82%. Finally, the optimal HPAM concentration and the HPAM removal efficiency were 300 mg/L and 45.82%, respectively. The results indicate that the mixed strain was a potential candidate for dealing with oil- or gas-field sewage with high hydrolyzed polyacrylamide concentration.