Performance of a novel rotating membrane photobioreactor based on indigenous microalgae-bacteria consortia for wastewater reclamation

Abstract

Performance of a novel a rotating membrane photobioreactor (R-MPBR) for wastewater reclamation under photosynthetic oxygenation was investigated. The unit was operated in dead-end mode with an alternative physical cleaning strategy based in membrane module rotation. It was found that the carbon loading rate applied (CLR) (9.1–36.6 g DOC·m−3·d-1) determined the dissolved oxygen concentration, affecting nutrient removal, bioflocculation and membrane fouling. Indigenous microalgae-bacteria consortia were effectively developed under each condition. At high CLR values, the dissolved inorganic nitrogen removal was significantly enhanced (81.2 ± 13.9 %), probably due to a simultaneous nitrification–denitrification process as a result of the negligible dissolved oxygen concentration. Decreasing CLR from 36.6 to 9.1 g DOC·m−3·d-1, increased particle size (D(0.5) from 61.9 to 92.8 μm) and decreased biopolymer clusters content (from 50.0 to 2.3 mg DOC·L-1). It also revealed that membrane rotation does not compromise bioflocculation. Cake filtration model showed that fouling was associated to the supernatant fraction, particularly to the biopolymer clusters. Sustainable long-term operation was achieved at a permeate flux of 10 L·h−1·m−2 and CLR ≤ 11.4 g DOC·m−3·d-1. The proposed configuration effectively controlled membrane fouling, allowing to further process optimization.