Optimization of algal-based membrane bioreactor for greywater treatment

Abstract

For bioreactors, hydraulic retention time plays a very important role in biomass production. The effectiveness of Algal-based Membrane Bioreactor (AMBR) has not been adequately explored for domestic greywater treatment. The present study aims to assess AMBR’s efficiency for treating domestic greywater operating at four hydraulic retention times (HRTs) of 1–7 d. Microalgal biomass production, removal efficiency, fouling characteristics, and net energy efficiency of the AMBR were optimized. The experimental study showed that algal biomass productivity increased with decreasing HRT, and the highest productivity (48 mg/L/d) was achieved at 2 d of HRT. Independent of HRT, 94 % BOD and 96 % anionic surfactant (AS) removals were achieved, while the highest TN and TP removals (59.5 % and 34.5 %) were achieved at HRT of 7 d. Effluent monitoring revealed that microalgae assimilation was the primary pathway of TN and TP removals. Membrane fouling frequency decreased with increasing HRT, and the lowest fouling was found at 7d of HRT. The highest methane yield (0.332 m3/d) and the net energy return NER (1.04) were estimated at HRT of 2 d. Overall, HRT of 2 d would be optimum for AMBR operation and can be modeled as a self-sustainable greywater treatment system with zero power requirements. The present study provides the basis for establishing the guidelines for AMBR design for the treatment and recycling of greywater.