Abstract <p>Heavy metals are obnoxious pollutants that are detrimental to humans and other species and constitute a menace to the ecosystem’s stability. The present study unravels the bioaccumulation efficacy of five microalgae, i.e., R1, H2, F1, Mg1, and M1 isolated from different agroclimatic zones of Punjab, India, for the heavy metal reduction in untreated domestic wastewater. Physicochemical analysis revealed that maximum reduction efficiency in BOD, COD, TDS, and electrical conductivity (EC) was obtained for the H2 consortium followed by R1 and Mg1. The isolation and physiological characterization of dominating photosynthetic organisms from each consortium unraveled their morphological and biochemical constitution. Furthermore, they were evaluated for heavy metal detoxification potential from untreated domestic wastewater by ICP-OES. The eukaryotic aseptate cylindrical filamentous isolate H2 (PP621793) has the highest capacity for remediating heavy metals. It showed a 50%, 50%, 40%, and 75% reduction in As, Cd, Ni, and Pb, respectively. A simultaneous study on heavy metal bioaccumulation recorded maximum biosorption in the biomass of the H2 isolate. Hence, this investigation reports the isolation of a novel microalga H2 from the Hoshiarpur district of the sub-mountain undulating zone of Punjab and underscores its potential for heavy metal detoxification from untreated domestic wastewater.</p> Graphical abstract <p></p>