Enhanced MPBR with polyvinylpyrrolidone-graphene oxide/PVDF hollow fiber membrane for efficient ammonia nitrogen wastewater treatment and high-density Chlorella cultivation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2020-01, Vol.379, p.122368, Article 122368
• Main Authors: Wu, Wei, Zhang, Xu, Qin, Lei, Li, Xiong, Meng, Qin, Shen, Chong, Zhang, Guoliang
• Format: Article
• Language: English
• Subjects: Antifouling; Chlorella cultivation; High ammonia-nitrogen wastewater treatment; Hollow fiber membrane; Membrane photo-bioreactor (MPBR); PVP-GO nanocomposites
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.122368

[Display omitted] •High efficient algae-MPBR with novel PVP-GO/PVDF hollow fiber membrane was first built.•Surface modification of PVDF membrane was first taken by GO-based composites grafting.•Degradation efficiency were greatly enhanced in high NH3-N+ wastewater treatment.•Modified PVDF membrane held superior water transport and attractive antifouling ability.•Average algal biomass production rate in algae-MPBR reached as high as 45 mg/L d. Membrane fouling always as the main obstacle hinders wide application of membrane bioreactor (MBR). Development of antifouling membranes is a promising strategy to overcome this issue. In this study, novel polyvinylpyrrolidone (PVP)-graphene oxide (GO)/PVDF hollow fiber membrane with enhanced hydrophilicity and antifouling property was synthesized by assembling PVP-GO nanocomposites via chemical grafting method. The PVP-GO/PVDF membrane was successfully applied into algae-membrane photo-bioreactor (MPBR) with solids retention times (SRTs) of 30 d for high ammonia-nitrogen wastewater treatment at hydraulic retention times (HRTs) of 24 h. The permeability, removal performance and influence on extracellular polymeric substance (EPS) of algae-MPBR with modified PVDF membrane were compared to a control traditional system operated in parallel. Compared with pristine PVDF membrane, PVP-GO/PVDF membrane exhibited improved hydrophilicity (contact angle decreased from 97 to 62°), better permeability (1.7 times) and attractive flux recover rate (96%) in MPBR filtration, which was attributed to uniformly dispersed PVP-GO nanocomposites as spatial brushes for mitigating foulants on membrane surface. In terms of contaminants degradation, COD, NH4-N+ and NO3-N removal efficiency of algae-MPBR with modified membranes were kept above 97.8, 93.1 and 68.7%, much higher than traditional MBR. Moreover, remarkable reduction in hydrophobic proteins amount of EPS on fouling layer was observed for PVP-GO/PVDF membrane. The biomass concentration was maintained around 780 mg/L after 16 days and average biomass production rate reached as high as 45 mg/L d. These results indicated that PVP-GO/PVDF membrane exhibited superior antifouling performance for high-density microbes harvesting and efficient treatment for high ammonia-nitrogen wastewater.