Secondary wastewater effluent treatment by microalgal-bacterial membrane photobioreactor at long solid retention times

• Published in: Journal of water process engineering 2022-10, Vol.49, p.103200, Article 103200
• Main Authors: Segredo-Morales, E., González, E., González-Martín, C., Vera, L.
• Format: Article
• Language: English
• Subjects: Biopolymer clusters; Membrane fouling; Membrane photobioreactor; Microalgae-bacteria consortia; Nutrient removal
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2022.103200

Microalgal-bacterial membrane photobioreactors (MPBRs) have recently emerged as a new sustainable technology in wastewater treatment. For advanced treatment of domestic secondary effluents, selecting long solids retention times (SRTs) may be crucial to achieve optimal community structure and therefore, process performance. This study assesses the effects of operating conditions on nutrient removal, biomass productivity, suspension characteristics and membrane fouling. A lab-scale MPBR was run during long-term tests to assess process stability. Indigenous microalgae-bacteria consortia were developed for each condition. Conventional membrane bioreactor was used for tested control condition. Experimental results showed the crucial role of extending SRT to 80 d to enhance bioflocculation, avoid biopolymer clusters accumulation and minimize membrane fouling rates. Despite influent fluctuations, optimal hydraulic retention time value between 2 and 5 d was necessary to achieve moderate nutrient removal (40.6–48.7 % and 18.5–34.7 % for nitrogen and phosphorus, respectively). A mixed microalgal structure of green microalgae, cyanobacteria and diatoms was also achieved. [Display omitted] •Long solid retention times avoid biopolymer clusters accumulation.•Moderate nutrient removal affected by influent fluctuations was reported.•Reversible and residual fouling are related to biopolymer clusters.•Membrane fouling has been effectively controlled at long solid retention times.