Evaluating and identifying key parameters influencing biomass production and wastewater treatment in algal-membrane photobioreactors using multivariate analysis

Abstract

This study evaluates biomass production, wastewater treatment efficiency, and membrane fouling behavior in Algal Membrane Photobioreactors (AMPBRs) operated under varying conditions. Six lab-scale AMPBRs were operated continuously under different organic loading rates (OLRs) and hydraulic retention times (HRTs), with a constant flux of 100 L/m²/day and a 12-h light/dark cycle. Performance was assessed in terms of biomass yield, contaminant removal efficiency, and membrane fouling characteristics. Principal Component Analysis (PCA) was employed to identify the most critical parameters influencing AMPBR performance and efficiency. Experimental results showed that the highest biomass production rate (40 mg/L d) occurred under lower OLR conditions. BOD and COD removal efficiencies exceeded 85–95%, while total nitrogen (TN) and total phosphorus (TP) removal rates ranged from 55 to 60% and 20 to 35%, respectively, under different OLR and HRT conditions. Five principal components (PCs) with eigenvalues higher than ‘1’ were extracted. PC1 reflected variability associated with influent organic content, photosynthetic activity, and membrane fouling rates. PC2 was influenced by HRT, effluent organic content, and phosphorus levels, while PC3 represented nutrient variability in the effluent. Factor loading analysis revealed that OLR and HRT strongly influenced biomass production. In contrast, organic matter (BOD and COD) removal was largely independent of these parameters. TN removal was primarily driven by algal assimilation at lower OLR, but shifted toward nitrification and denitrification under higher OLR conditions. TP removal was significantly affected by HRT, with minimal dependence on OLR. Membrane fouling rates increased at higher OLRs due to elevated production of extracellular polymeric substances (EPS).