Performance of an outdoor membrane photobioreactor for resource recovery from anaerobically treated sewage

Abstract

[EN] The objective of this work was to evaluate the performance of a pilot scale membrane photobioreactor (MPBR) for treating the effluent of an anaerobic membrane bioreactor (AnMBR) system. In particular, new experimental data on microalgae productivity, nutrient recovery, CO2 biofixation and energy recovery potential was obtained under different operating conditions, which would facilitate moving towards cost-effective microalgae cultivation on wastewater. To this aim, a 2.2-m(3) MPBR equipped with two commercial-scale hollow-fibre ultrafiltration membrane modules was operated treating the nutrient-loaded effluent from an AnMBR for sewage treatment. The influence of several design, environmental and operating parameters on MPBR performance was studied. Among the conditions evaluated, variations in solar irradiance significantly affected the nutrient recovery rate (NRR). Operating at temperatures above 25 degrees C and high biomass concentrations, which increased light shading effect, negatively affected biomass production and NRR. Maximum biomass productivity of 66 mg VSS L-1 d(-1) (areal productivity of 15.78 g VSS m(-2) d(-1)) and NRR of 7.68 mg N L-1 d(-1) and 1.17 mg P L-1 d(-1) were achieved when operating at 4.5 days of biomass retention time. These results would outcome maximum theoretical energy recoveries and CO2 biofixations of about 0.43 kWh and 0.51 kg CO2 per m(3) of treated water, respectively. Moreover, the excellent quality permeate that was produced (i.e. negligible levels of pathogens and suspended solids) represents a reclaimed water source. (C) 2017 Elsevier Ltd. All rights reserved.