Electrically enhanced microalgae-bacteria systems for wastewater treatment under low-temperature conditions

Low temperatures suppress microbial growth and metabolism activity and pollutant removal in wastewater treatment systems. This study systematically compared shaping effect of micro electric fields (MEF) and pulsed electric fields (PEF) on municipal wastewater treatment by a microalgae-bacteria system (MBS) at 5 °C, 10 °C, and 15 °C. Both electric field modes showed significant improvement in cell biomass accumulation, photosynthetic pigment synthesis, and nutrient and COD removals compared to non-electrified controls. Under identical operating conditions, MEF and PEF exhibited distinct electrobiological modulation behaviors, MEF promoted more stable cell biomass-pollutant coupling under cold stress, whereas PEF provided stronger short-term stimulation at moderately low temperatures. Energy analysis showed that PEF reduced volumetric energy consumption by 20–50% compared with MEF. Overall, a coupled process of microalgal-bacterial consortia and PEF offers an energy-efficient, non-thermal complementary strategy to conventional thermal approaches for wastewater management under low-temperature conditions.