Performance of a pilot split-type anaerobic membrane bioreactor (AnMBR) treating antibiotics solvent wastewater at low temperatures

- Antibiotics solvent wastewater was treated by an AnMBR at low temperatures.
- High COD and THF removal efficiency can be found at 15 ± 3 °C in this study.
- Performance of the reactor showed that it can be well adapted to temperature shocks.
- Methanosarcinaceae and Methanobacteriales were dominant at low temperatures.
- The physical removal played an important role at lower temperatures.

The performance of a new pilot split-type anaerobic membrane bioreactor (AnMBR) configuration for treating antibiotics solvent wastewater at low temperatures was evaluated in this study. The AnMBR system comprised an internal circulation (IC) and ultrafiltration membrane modules, working as the biological removal and physical retention, respectively. The whole process was divided into four stages in terms of the variation of temperatures (35 ± 3 °C, 25 ± 3 °C, 15 ± 3 °C, 25 ± 3 °C). Total chemical oxygen demand (CODtotal) and tetrahydrofuran (THFtotal) removal efficiency at temperatures as low as 15 ± 3 °C were similar to mesophilic conditions (35 ± 3 °C, 25 ± 3 °C), which achieved over 95% and 96%, respectively. While different mechanism of removal was obtained at different temperatures. The excellent removal efficiency was maintained via the combination of biological and physical removal, biological removal was the major reason of removal efficiency (>83.3%) at mesophilic temperatures and physical removal (>38.6%) dominated the effect at lower temperatures. As temperature decreased, permeate volatile fatty acids (VFA) in the bioreactor accumulated suggesting a reduction of methanogens activity and pH had a minimum value of 6.5. However, neither of them showed significant sign of water degradation towards the end of experiment. The examination of alkalinity, α value, and end-products of anaerobic fermentation, MLSS, MLVSS and MLVSS/MLSS suggested a negative effect slightly on microbial activity and no negative effect on the effluent quality at low temperatures due to the retention of membrane.