Microalgal-Bacterial membrane photobioreactor (MBMPBR) for wastewater treatment and membrane fouling characterization

Abstract

This thesis investigated the effects of combined hydraulic retention time (HRT) and nitrogen/phosphorus (N/P) ratio variation, and solo solids retention time (SRT) variation on the biological performance and membrane fouling of microalgal-bacterial membrane photobioreactor (MB-MPBR) for wastewater treatment. The results showed that both HRT and N/P ratio significantly affected biomass production, nutrient removal, and biological micromorphology. The reason was attributed to the different nutrient loading rates resulted from the various combinations of HRT and N/P ratio. Controlling nutrient loading rate below the nutrients removal capacity threshold was critical to achieving superior effluent quality meeting the discharge standards. A lower N/P ratio of 3.9:1 led to a more quickly transmembrane pressure increase under the same HRT and total influent nitrogen concentration. Characterization of mixed liquor showed that smaller particle size under the lower N/P ratio was the primary contributor to the faster increase in membrane fouling. X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and microscopic analysis demonstrated that the underlying reason for the decreased floc size was attributed to the strengthened competitiveness and overgrowth of microalgae at P-rich conditions. [...]