External-loop split-type dynamic membrane photobioreactor for the treatment of high-strength pyridine wastewater: Improved photosynthetic oxygenation and mitigated membrane fouling

In order to avoid pyridine volatilization in the conventional aerobic system based on bubble aeration, an algal-bacterial symbiotic system based on photosynthetic oxygenation was developed. Nonetheless, pyridine at high concentration would inhibit algal growth and photosynthetic activity, and thus decrease oxygen production efficiency. An external-loop split-type dynamic membrane photobioreactor system was proposed for treating high-strength pyridine wastewater, which consisted of a pyridine degrading reactor (R1–1), and an algal-bacterial dynamic membrane bioreactor (R1–2) for the photosynthetic oxygenation. The results showed that pyridine could be effectively removed at the influent concentration as high as 500 mg·L−1 at the hydraulic retention time of 48 h. Preferable algal growth and photosynthetic activity were retained in R1–2, with Fv/Fm maintained at 0.502 ± 0.013 at the influent pyridine concentration of 500 mg·L−1. The decreased reactive oxygen species and malondialdehyde level as well as the relative low catalase and superoxide dismutase activities also revealed the alleviation of oxidative stress in algae. The mitigated membrane fouling was due to reduced protein/polysaccharide ratio in the extracellular polymeric substances in the mixed liquor and fouling layer in R1–2. Rhodobacter and Rhodococcus were the dominant genus in R1–1 and R1–2, and Chlorella was enriched in R1–2, responsible for pyridine degradation and oxygen production. [Display omitted] •ESDMPBR was developed to alleviate the inhibitory effects of pyridine to algae.•Pyridine removal, nitrogen removal and oxygen production were enhanced in ESDMPBR.•Membrane fouling could be alleviated at high PS concentration and low PN/PS ratio.•Mechanism for enhanced pyridine removal involved in ESDMPBR was proposed.•Algal-bacterial symbiotic system was promising in treating high-strength pyridine.