Abstract

Microalgae/bacteria consortia (MBC) are considered a promising platform for wastewater treatment. Biomass retention based on membrane filtration represents an effective alternative to enhance organic matter and nutrient removal. This study investigated the effects of uncoupling solid from hydraulic retention time (SRT and HRT, respectively) when treating synthetic municipal wastewater. For that purpose, 50L high-rate algal pond was coupled with a membrane filtration step and operated at different conditions. The performance of the system was evaluated in terms of its load and concomitant removal of organic matter and nutrients. Organic matter removal exceeded 90%. Nitrogen removal efficiencies were in the range 46-68%, with the highest nitrogen removal rate exceeding 40gN m 1at HRT of 1day. Phosphorus removal efficiencies varied between 39% and 70%. High loads resulting from low HRTs caused low oxygen levels in the reactor, allowing favourable conditions for the occurrence of denitrification. Experimental data supported the possibility of having in the same treatment unit different nitrogen removal mechanisms: assimilation, nitrification, and denitrification