Optimisation of membrane photobioractors (MPBRs) for enhanced biomass productivity and effective wastewater treatment

Given the numerous challenges faced by conventional algae culturing techniques, such as biomass washout and harvesting limitations, a recent evolution of algal system has seen the incorporation of membrane in the reactor, which has resulted in the membrane photobioreactor (MPBR) concept. The major goal of this study was to examine the biomass growth and nutrient removal in MPBRs operated at different hydraulic retention times (HRTs) of 1 and 4 days. Chlorella vulgaris was used as the inoculant in the rigs fed with synthetic secondary effluent. This work comprised two phases, the acclimatisation phase (prior to membrane addition into the PBRs) and the MPBR phase. The concentrations of total organic carbon (TOC), nitrate, nitrite, ammonia and phosphate in the systems were monitored regularly. The biomass growth and characterisation were also analysed through cell counting, measurement of mixed liquor suspended solids (MLSS), microscopic observation and flow cytometry. The results showed that nutrient removal reduced slightly as the HRT decreased from 4 days to 1 day, but operating the MPBR at the shorter HRT achieved higher biomass growth. In addition, it was observed that longer HRT led to a more heterogeneous system with increased bacterial counts, as demonstrated by flow cytometry analysis. The outcomes of this study suggest that the MPBR has the potential to operate at shorter HRTs (1 day) as compared to PBRs (2 – 5 days), while offering enhanced wastewater treatment efficiency and biomass growth.status: publishe