Biomass production and nutrient removal by using micoalgal submerged membrane photobioreactor

In this study, nutrient removal and biomass productivity from wastewater with mixed microalgae culture and 0.45 µm hollow fiber (HF) membrane were investigated at microalgae submerged membrane photobioreactor (msMpBR). 24 hours of hydraulic retention time (HRT) was kept constant and 3, 6, 12 and 24 days of sludge retention time (SRT) were studied and optimum SRT was determined by synthetic wastewater and also 48, 60 and 72 hours of HRT were studied in this SRT to determine the optimum HRT. The real wastewater has been studied with the optimum conditions. Volumetric microalgae production efficiency and nutrient removal rates were determined in all studies. In addition, the lipid and protein content of the produced biomass was determined and the predominant cultures at set times of each study were determined. According to this, the optimum values in synthetic wastewater were determined as 3 days of SRT and 24 hours of HRT. In this study, mixed liquid suspended solids (MLSS) and Chlorophyll-a concentrations in stable conditions were measured as 354 mg/L and 11.54 mg/L, respectively, and the volumetric microalgae production rate was calculated as 0.118 gr/L-day. Removal rates were found to be 5.55 mg/L-day in total nitrogen (TN) and 0.40 mg/L-day in phosphate phosphorus (PO4-P). In addition, in stable conditions approximately 45-50% Chaetophora sp. and 45-50% Navicula sp. were observed and lipid ratio was 8.90% and protein ratio was 30% in dry biomass. In real treated domestic wastewater, nutrient removal rates were found to be 1.37 mg/L-day and 0.40 mg/L-day in TN and PO4-P, respectively. The volumetric microalgae production rate was found to as 0.037 gr/L-day and %14.33 lipid and 32.20% protein were measured in dry biomass. According to all these results, in this study, high concentrations were achieved by preventing the escape of biomass in the reactor. In addition, obtained biomass yields and nutrient removal rates by mixed microalgae culture were found to be acceptable compared to one type culture. On the other hand, the potential of mixed microalgae culture for dry biomass protein and oil analysis and raw food or alternative biofuel products (biodiesel, ethanol, bioelectric, hydrogen, methane etc.) will be a source of information for future researchers.