Use of Microalgae in MBR

Abstract

Membrane photobioreactor is a system that integrates microalage growth with membrane separations for nutrient (N and P) removal from wastewater and algal biomass production for biofuels, as shown in Fig. 1. Commercial use of algal cultures for wastewater treatment and mass production of algal biomass has a history over one century. Biological wastewater treatment with microalgae is particularly attractive due to their photosynthetic capabilities in converting solar energy and CO2 into useful biomass and uptaking nutrients (nitrogen and phosphorus) into microalgae biomass (Rawat et al. 2011). The use of membrane bioreactors for microalgae wastewater treatment simplifies the operation of microalgae harvesting and produces effluent with superior quality. Membrane bioreactor (MBR) has been widely used for municipal and industrial wastewater treatment, due to the advantages of small footprint, high productivity, and superior quality of effluent for water reuse and system closure. However, nutrient (N and P) removal has been a challenge for both aerobic MBR and anaerobic MBR. The capability of microalgae for nutrient uptake and CO2 as carbon source for growth makes it an ideal candidate for sustainable wastewater treatment. The integrated MBR-microalgae processes have received much attention in recent years as a next-generation technology for sustainable wastewater treatment. There are three types of microalgae membrane bioreactor processes: (1) an integration of conventional activated sludge process with membrane photobioreactor, (2) an integration of MBRs (aerobic MBR or anaerobic MBR) with conventional microalgae photobioreactor, and (3) an integration of MBRs (aerobic MBR or anaerobic MBRs) with a membrane photobioreactor. For the second scenarios, a microalgae photobioreactor was used to treat the effluent of an anaerobic MBR for municipal wastewater treatment (Ruiz-Martinez et al. 2012). At a solid retention time of 2 days, the microalgae photobioreactor achieved a mean biomass productivity of 234 mg/d and a nutrient removal efficiency of 67.2 % for ammonium (NH4 –N) and 97.8 % for phosphate (PO4 3 P) (Ruiz-Martinez et al. 2012). In the third scenarios, an aerobic MBR-membrane photobioreactor system was tested for domestic wastewater treatment (Singh and Thomas 2012). Similarly, a comparative study between the second and third scenarios found that the use of membrane photobioreactor significantly increased the microalgae biomass concentration and volumetric productivity by 3.5 and 2 times, respectively, in addition to the elimination of microalgae washout and superior effluent quality (Marbelia et al. 2014). The membrane photobioreactor was