Performance of a novel multiple draft tubes airlift loop membrane bioreactor to treat ampicillin pharmaceutical wastewater under different temperatures

In this study, the performance and removal mechanisms of a novel lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) for treating high-strength ampicillin pharmaceutical wastewater under different temperatures (7 °C, 16 °C, 24 °C, 36 °C, 48 °C) were investigated. During 150 days operation, the optimal average chemical oxygen demand (COD) and ampicillin removal rates were 98.2 ± 0.2% (36 °C) and 63.2 ± 5.6% (7 °C), respectively. The main mechanisms of pollutants removal were membrane removal (7 ~ 16 °C) and bioreactor removal (16 ~ 48 °C). Adsorption and membrane rejection were main pathways at low temperature, as temperature increased, hydrolysis and biodegradation gradually occupied a dominant position. Meanwhile, the optimum temperature ranges for activated sludge microorganisms were 16 °C ~ 36 °C, the corresponding β-lactamase at 36 °C was the highest activity value among all the set temperature values. Experimental results showed that temperature had a significant impact on the removal rate, the optimum temperature range was proposed to be at 24 ~ 36 °C. The half-life [Formula presented] of ampicillin drastically decreased from 330.0 d to 2.1 d when the temperature was increased from 7 °C to 48 °C. And the maximum adsorption capacity K_f at the adsorption temperatures of 7, 16, 24, 36 and 48 °C was 0.1284, 0.2169, 0.0645, 0.1502 and 0.1524 mg/g, respectively. The values of ΔG° were all negative, proving that the adsorption process of the ampicillin belonged to a spontaneous physical adsorption. In addition, autoregressive integrated moving average (ARIMA) and mathematical fitting models were developed and well simulated the performance of Mt-ALMBR to treat the ampicillin wastewater. These results suggest that Mt-ALMBR holds great potential for application in ampicillin pharmaceutical wastewater treatment.