Effects of powdered activated carbon addition on filtration performance and dynamic membrane layer properties in a hybrid DMBR process

- PAC-DMBR showed better filterability and removal of organics, ammonia and color.
- Biological PAC formation changed the structure of the DM layer.
- The diversity of microbial communities increased in the PAC-DMBR.
- Several specific genera were enriched in the PAC-DMBR.
- PAC addition modified the properties of activated sludge and the DM layer.

A powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) was developed and used to treat domestic wastewater by dosing with 3 g/L PAC. The experimental results were compared with those of a control DMBR to investigate the filtration performance and various properties of the dynamic membrane (DM) layer. One flat-sheet DM module made of nylon mesh (pore size 75 μm) was used for effluent production at a high stable flux (50-100 L/m2 h) under a 10 cm water head by gravity flow, resulting in continuous operation cycles of 60-120 h. During the operation period, the PAC-DMBR showed enhanced removal efficiency of pollutants, higher stable membrane flux (10 L/m2 h more), lower filtration resistance (6.0-8.0 × 1010 m−1), quicker formation of the DM layer (within 5 min), and better DM layer regeneration after air backwashing. The DM layer in the PAC-DMBR showed a more porous and incompressible structure, because less extracellular polymeric substance and a portion of the biological PAC were incorporated into the DM layer formed as verified by the analytical results. Using high-throughput pyrosequencing technology, it was revealed that at the genus level the diversity of bacterial communities increased from 18 to 23 genera, while several genera that were favored in the PAC-assisted environment or were responsible for degrading complex organics were enriched. Moreover, the abundance of phylum Proteobacteria, which served as pioneer surface colonizers, was reduced in the PAC-DMBR. It was concluded that PAC addition could modify various aspects of the activated sludge and the DM layer properties, which affected the filtration behavior of the DM layer in the PAC-DMBR.

98